subject:"\[Sursound\] Distance perception"


On 07/26/2011 02:18 AM, Marc Lavallée wrote:


Imagine two rooms with proper acoustic characteristics and treatments
for ambisonics reproduction: the first is 3mX4m and the other is four
times larger in surface (9mX12m). In both rooms there's a
horizontal hexagon of speakers, and 5 speakers are against a wall.


regardless of room size, they will require a bit of equalisation. if the 
speakers are designed to be close to a boundary surface, the one that's 
not against a wall needs (gentle) bass boost. vice versa, if your 
speakers are designed to be free-standing, the five speakers need some 
attenuation at LF.


if you're still shopping for speakers, i found that the genelec 8030 
have a nice built-in bass eq which can be used to deal with this issue. 
i was able to even out the bass response of a rig where most speakers 
are next to two boundary surfaces and a few only next to one. of course, 
you could also do this in software.



When NFC is applied in both rooms, do they sound the same in terms of
distance perception when playing the same recording?


NFC is not a constant. the amount of NFC depends on the distance to the 
speaker.



Or is the same
"sound object" appear to be twice as far in the largest room?


actually, if you hope to get distance perception so good that the notion 
of "twice as far" begins to make sense, then you're in for some heartache.


that's why i said "distance cues are gimmickry" earlier. the actual 
curvature of the soundfield (which is all that NFC does for you) is not 
a very robust distance cue. the delay of the (reproduced) floor 
reflection is a lot more helpful, as is the ratio of direct to 
reverberated sound (but the latter doesn't help soundman john with his 
spitfires).
so why get gung-ho about a cue of secondary importance, for a perception 
apparatus that doesn't care much anyways...


the problem is that your listening room floor reflection will always be 
different from and stronger than the recorded floor reflection, which 
pulls the image towards the speaker circle.


if you close your eyes and find yourself able to suspend your disbelief 
long enough to actually imagine yourself in a cathedral listening to an 
organ, then rejoice and be happy. don't spoil the magic by gauging the 
distance. it's not going to happen.


the sad and simple fact is that _no_ surround rig can get the distance 
unambiguously right in any but anechoic conditions.
and before you run off to shop for styrofoam, be warned that most 
recordings would sound utter crap in anechoic conditions, because nobody 
mixes for that.
moreover, the phasing problems of our beloved ambisonic technique would 
become very obnoxious indeed.


the deader you make your room, the more hope you have to get precise 
distance information. at the same time, the rig will sound less pleasant 
and artefacts will become more obvious. since humans suck at absolute 
distance perception anyways, your best bet is to be content with some 
degree of distance discriminination. that is, you want to hear the 
woodwinds _somewhere_behind_ the strings. you wouldn't normally care how 
many metres. this usually works well if the recording is ok.



Apart from widening the listening sweet spot, are larger rooms "better"
at reproducing distance cues when using the same speaker configuration?
Is distance perception directly related to speaker distances?


as mentioned before, the floor reflection is a very strong distance cue 
at close range under semi-anechoic conditions (i.e. if you want to gauge 
the distance of that sabre-toothed tiger or the potential mating 
candidate). if you're right next to the sound source, the floor 
reflection will have the longest delay. far away, the delay will be 
negligible.

the general case is
  dly = 340 / (sqrt(ear_height^2 + half_distance^2) * 2)

when a listening room first reflection is strong and early, it will 
dominate your sense of distance. in that sense, larger rigs have the 
potential to be less intrusive wrt distance perception.


--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT

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Re: [Sursound] Distance perception


sorry, itchy trigger finger...

On 07/26/2011 10:14 AM, Jörn Nettingsmeier wrote:


as mentioned before, the floor reflection is a very strong distance cue
at close range under semi-anechoic conditions (i.e. if you want to gauge
the distance of that sabre-toothed tiger or the potential mating
candidate).


uhm, i realise that the latter example is a bit dated - who meets 
significant others in the great outdoors, these days. for clubbing, the 
dominant cue should be direct-to-reverb ratio, unless you have to fall 
back to olfactory and visual cues entirely because of the extremely loud 
music.



if you're right next to the sound source, the floor
reflection will have the longest delay. far away, the delay will be
negligible.
the general case is
dly = 340 / (sqrt(ear_height^2 + half_distance^2) * 2)


minus the straight-path delay of course:

dly = 340 / (sqrt(ear_height^2 + (distance/2)^2) * 2 - distance)


--
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Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT

http://stackingdwarves.net

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Re: [Sursound] Distance perception

2011-07-26 Thread Marc Lavallée

Tue, 26 Jul 2011 10:14:50 +0200,
Jörn Nettingsmeier  wrote :

> regardless of room size, they will require a bit of equalisation. if
> the speakers are designed to be close to a boundary surface, the one
> that's not against a wall needs (gentle) bass boost. vice versa, if
> your speakers are designed to be free-standing, the five speakers
> need some attenuation at LF.

The smallest KEF "eggs" should be fine against the walls, as you
already wrote me. Two will be free-standing (front and back) and will
need a bit more electronic correction.

> if you're still shopping for speakers, i found that the genelec 8030 
> have a nice built-in bass eq which can be used to deal with this
> issue. i was able to even out the bass response of a rig where most
> speakers are next to two boundary surfaces and a few only next to
> one. of course, you could also do this in software.

I will do it in software. It's a domestic setup, so I don't need
expensive active speakers and cabling; I prefer to use very small
speakers with lamp cords.

> the problem is that your listening room floor reflection will always
> be different from and stronger than the recorded floor reflection,
> which pulls the image towards the speaker circle.

Then less reflections means less localization of the speakers?

> the sad and simple fact is that _no_ surround rig can get the
> distance unambiguously right in any but anechoic conditions.
> and before you run off to shop for styrofoam, be warned that most 
> recordings would sound utter crap in anechoic conditions, because
> nobody mixes for that.

What follows is just my opinion. 

We are free to record and mix in any imaginable ways, so recordings
sound "imperfect" in most situations. There's little a listening room
can do to beautify recordings and reproduction systems, unless the room
is considered as a musical instrument. Even in a small room with too
much acoustic treatment, I may be pleasantly surprised by some very good
recordings, and find some qualities in some very bad recordings;
anything can happen in the middle, and low expectations is the key to
happiness.

What I expect from listening to ambisonic recordings is a better
envelopment and a sense of realism not found in stereo recordings. I
also expect some new experiences from field recordings and
electroacoustic music for ambisonics. I also want to compare ambisonics
to other reproduction methods; maybe stereo and 5.1 are not so bad...
The other use for all those speakers is to add a bit of hall
reverberation to some dry stereo recordings.

> moreover, the phasing problems of our beloved ambisonic technique
> would become very obnoxious indeed.

Obnoxious phasing problems? Now I'm afraid! ;-)
Maybe I spent decades listening to obnoxious problems I never noticed...
I'll do my best to control phasing problems at the sweet spot.

> the deader you make your room, the more hope you have to get precise 
> distance information. at the same time, the rig will sound less
> pleasant and artefacts will become more obvious. since humans suck at
> absolute distance perception anyways, your best bet is to be content
> with some degree of distance discriminination. that is, you want to
> hear the woodwinds _somewhere_behind_ the strings. you wouldn't
> normally care how many metres. this usually works well if the
> recording is ok.

I found good acoustic panels, and I have to decide how much surface to
cover. I once built large and thick panels to cover half of the walls
and 2/3 of the ceiling. There was also a wool carpet with foam under
it. The room was so dead that I was able to listen to my heart beat. I
remember how sharp the stereo image was and how the speakers were not
easy to localize with good recordings. Of course the room was a bit
oppressive, almost like a recording booth... I hope to find a better
compromise between analytic listening and listening for enjoyment.

> when a listening room first reflection is strong and early, it will 
> dominate your sense of distance. in that sense, larger rigs have the 
> potential to be less intrusive wrt distance perception.

Right: first reflections should be better controlled in a small room.

> > if you're right next to the sound source, the floor
> > reflection will have the longest delay. far away, the delay will be
> > negligible.
> > the general case is
> > dly = 340 / (sqrt(ear_height^2 + half_distance^2) * 2)
> 
> minus the straight-path delay of course:
> 
> dly = 340 / (sqrt(ear_height^2 + (distance/2)^2) * 2 - distance)

So floor and ceiling reflections also need to be controlled, even more
in a small room. The difficulty is how to leave some harmless
and lively reflections. Maybe that adding a few small diffusors would be
a good compromise.

Thanks!

--
Marc


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Re: [Sursound] Distance perception

2011-07-26 Thread Aaron Heller

Some papers that may be of interest:

Takahashi, "A Novel View of Hearing in Reverberation," Neuron, Volume
62, Issue 1, 6-7, 16 April 2009
doi:10.1016/j.neuron.2009.04.004

Devore, et al., "Accurate Sound Localization in Reverberant
Environments Is Mediated by Robust Encoding of Spatial Cues in the
Auditory Midbrain," Neuron, Volume 62, Issue 1, 123-134, 16 April 2009
doi:10.1016/j.neuron.2009.02.018

Antje Ihlefeld and Barbara G. Shinn-Cunningham, "Effect of source
spectrum on sound localization in an everyday reverberant room,"  J.
Acoust. Soc. Am. Volume 130, Issue 1, pp. 324-333 (2011)
http://dx.doi.org/10.1121/1.3596476

--
Aaron Heller (hel...@ai.sri.com)
Menlo Park, CA  US
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Re: [Sursound] Distance perception

2011-07-26 Thread Fons Adriaensen

On Tue, Jul 26, 2011 at 04:35:39PM -0400, Marc Lavallée wrote:

> I will do it in software. It's a domestic setup, so I don't need
> expensive active speakers and cabling; I prefer to use very small
> speakers with lamp cords.

Lamp cords ? Use at least 2.5 mm^2 ! 

> > the problem is that your listening room floor reflection will always
> > be different from and stronger than the recorded floor reflection,
> > which pulls the image towards the speaker circle.
> 
> Then less reflections means less localization of the speakers?

Yes, in general this is true, and it's quite logical - we use
reflections to build up an 'acoustic picture' of a space, and
in turn that is used to aid localisation. If the cues provided
by room reflections dominate those reproduced from the recording
you can't but identify the speakers as the source.

> > the sad and simple fact is that _no_ surround rig can get the
> > distance unambiguously right in any but anechoic conditions.
> > and before you run off to shop for styrofoam, be warned that most 
> > recordings would sound utter crap in anechoic conditions, because
> > nobody mixes for that.

That is really a very valid observation. Almost all recordings rely
on the listener's room acoustics to do part of the work. And studio
control rooms usually have well controlled acoustics, but they are
by no means anechoic. Which means that something similar is expected
of the listening environment.

> What I expect from listening to ambisonic recordings is a better
> envelopment and a sense of realism not found in stereo recordings. I
> also expect some new experiences from field recordings and
> electroacoustic music for ambisonics. I also want to compare ambisonics
> to other reproduction methods; maybe stereo and 5.1 are not so bad...

They are not. Very nice results can be achieved with either.

> The other use for all those speakers is to add a bit of hall
> reverberation to some dry stereo recordings.

Depends a bit on the type of music you are listening to, but in
general that is a good idea for any type of music that is normally
played in concert hall like environments. 

There is another thing which I can't explain ATM. I've been working
lately most of the time in a studio that has a regular octagon of
speakers for Ambisonic monitoring. But half of the work done there
is just stereo. The thing is that I very much prefer listening to
stereo using two virtual speakers panned into 3rd order AMB rather
than sending L,R directly to two of the speakers. But I can't ATM
explain why.

> So floor and ceiling reflections also need to be controlled, even more
> in a small room.

Yes. I recently moved home, and my new working environment is a rather
small and boxy room. Its only redeeming feature is that the ceiling is
not horizontal but inclined by 15 degress or so. The floor is hardwood,
nice for recording but in this case it doesn't help for listening.
When I first listened to some reference recordings in this place I was
'not amused' at all. But putting a thick carpet in front of the speakers
changed the picture quite dramatically. The room is still a disaster for
good LF response, but otherwise it has become acceptable by reducing a
very strong floor reflection.

> The difficulty is how to leave some harmless
> and lively reflections. Maybe that adding a few small diffusors would be
> a good compromise.

Diffusers are almost never a bad idea.

Ciao,

-- 
FA

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Re: [Sursound] Distance perception


On 07/26/2011 10:58 PM, Aaron Heller wrote:

Some papers that may be of interest:


<..>

Antje Ihlefeld and Barbara G. Shinn-Cunningham, "Effect of source
spectrum on sound localization in an everyday reverberant room,"  J.
Acoust. Soc. Am. Volume 130, Issue 1, pp. 324-333 (2011)
http://dx.doi.org/10.1121/1.3596476


cheers!

here's a result that surprised me (i had assumed otherwise when trying 
to predict localisation performance before):


"
In Experiment 2, simultaneous presentation of low- and high-frequency 
noises yielded performance that was less accurate than that for 
high-frequency noise, but equal to or better than for low-frequency 
noise. Results suggest that listeners perceptually weight low-frequency 
information heavily, even in reverberant conditions where high-frequency 
stimuli are localized more accurately.

"

my gut feeling had always been that in the presence of HF cues, you can 
get away with sloppy LF cues (as in, drive all your subs in mono for 
maximum ooomph, but the kick sound of the kick drum will make sure it's 
localised properly). maybe i was wrong. or maybe their band-limited 
noise is just too artificial...


--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister (VDT)

http://stackingdwarves.net
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Re: [Sursound] Distance perception

2011-07-26 Thread Sampo Syreeni


On 2011-07-26, Fons Adriaensen wrote:


Lamp cords ? Use at least 2.5 mm^2 !


Where does this come from? I've never though cable geometry matters much 
at all, unless your pumping so much power through a cable over such a 
long distance that you have to worry about ohmic heating and the like. 
And even there, I've always thought changing resistance would mostly 
affect a tube end stage, which we've almost done away with already in 
favour of the A/B class solid state one. And at audio frequencies, 
shouldn't even feedback oscillation and its kin be well below perceptual 
thresholds?


True, my cables are multistrand ones with approximately that 
cross-sectional area per polarity. But not because of some esoteric, 
audiophile reason. It's because that's what they sell the cheapest as 
"speaker cable" in my local shop.

--
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Re: [Sursound] Distance perception

2011-07-26 Thread Fons Adriaensen

On Wed, Jul 27, 2011 at 01:16:59AM +0300, Sampo Syreeni wrote:
> On 2011-07-26, Fons Adriaensen wrote:
>
>> Lamp cords ? Use at least 2.5 mm^2 !
>
> Where does this come from? I've never though cable geometry matters much  
> at all, unless your pumping so much power through a cable over such a  
> long distance that you have to worry about ohmic heating and the like.  
> And even there, I've always thought changing resistance would mostly  
> affect a tube end stage, which we've almost done away with already in  
> favour of the A/B class solid state one. And at audio frequencies,  
> shouldn't even feedback oscillation and its kin be well below perceptual  
> thresholds?
>
> True, my cables are multistrand ones with approximately that  
> cross-sectional area per polarity. But not because of some esoteric,  
> audiophile reason. It's because that's what they sell the cheapest as  
> "speaker cable" in my local shop.

I certainly don't want you to waste your money on fancy speaker
cables. Just ordinary mains cable is perfectly OK. But resistance
does matter, so a good cross section such as 2.5 mm^2 puts you on
the safe side.

Ciao,

-- 
FA


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Re: [Sursound] Distance perception

2011-07-26 Thread Sampo Syreeni


On 2011-07-27, Jörn Nettingsmeier wrote:

my gut feeling had always been that in the presence of HF cues, you 
can get away with sloppy LF cues (as in, drive all your subs in mono 
for maximum ooomph, but the kick sound of the kick drum will make sure 
it's localised properly). maybe i was wrong. or maybe their 
band-limited noise is just too artificial...


That's my thought as well, but perhaps for a different reason.

This goes back to the debates over whether ultrasonics can actually be 
heard, and so whether high sampling rates are beneficial beyond double 
the frequency cutoff of human hearing. Everybody can already agree that 
sustained ultrasonic sinusoids cannot be heard even unconsciously above 
some threshold, which lies around 30kHz or a bit over it. But at least 
to my knowledge, nobody's really settled the question of whether they 
might be heard in combination with lower frequencies. That is, nobody's 
ever ruled out the possibility that in addition to linear, frequency 
sensitive analysis, our ears/brains might be doing something nonlinear 
that isn't being as consciously heard as a clear pitch, but which still 
affects, say, spatial hearing. (There is even some evidence in support 
of this, and certainly we know the auditory system as a whole is very 
nonlinear at each and every stage.)


The best alternative/nut theory I've heard is that we might do 
independent, time-domain analysis and between-the-ears correlation for 
transients, quite regardless of frequency, while in parallel doing 
frequency sensitive analysis for sustained, spectrally sharp stuff. 
(There is some evidence for this in early dichotic listening experiments 
utilizing analog hardware and synthetic impulses reaching beyond 150kHz. 
They yield directional uncertainty intervals well below what is 
attainable when utililizing bandlimited waveforms; a telltale sign of 
nonlinear processing.)


So, is it sure that such processes, if in fact real, couldn't be at play 
within the audible band as well? That'd for instance mean that frequency 
dependent phase delays which cannot be heard in steady state would 
suddenly still show up with transients, in particular in a 
dichotic/binaural setting.

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Re: [Sursound] Distance perception

2011-07-26 Thread Sampo Syreeni


On 2011-07-26, Fons Adriaensen wrote:

I certainly don't want you to waste your money on fancy speaker 
cables.


Never thought otherwise. That's obviously never been what we do here. ;)

But resistance does matter, so a good cross section such as 2.5 mm^2 
puts you on the safe side.


What I was trying to ask is, what's the real problem with resistance, 
especially with regard to a passive speaker and a modern, A/B class 
solid state end stage? I mean, I don't really see cable resistance 
shifting their operating point much, even with feedback, within the 
audible range.


What is it that I'm missing?
--
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Re: [Sursound] Distance perception


On 07/27/2011 12:41 AM, Sampo Syreeni wrote:

On 2011-07-26, Fons Adriaensen wrote:


I certainly don't want you to waste your money on fancy speaker cables.


Never thought otherwise. That's obviously never been what we do here. ;)


But resistance does matter, so a good cross section such as 2.5 mm^2
puts you on the safe side.


What I was trying to ask is, what's the real problem with resistance,
especially with regard to a passive speaker and a modern, A/B class
solid state end stage? I mean, I don't really see cable resistance
shifting their operating point much, even with feedback, within the
audible range.

What is it that I'm missing?


power transmission impedance matching.
if you look at the spec sheet of a commercial p.a. amplifier, 9 times 
out of 10 you will see twice the power rating for 4 ohm loads than for 8 
ohms. usually this means you connect two 8 ohm enclosures in parallel 
for an optimum load. but obviously any resistance of the wire will limit 
the power you can draw from the amp.
say you're using the really cheap NYM 3G1.5 wire, which has about 14 
ohms per km. for a practical speaker line length of 20m, that's 0.3 
ohms. i won't make a fool of myself here by giving precise numbers after 
a day of mixing and three bottles of beer, but it's easy to see that 0.3 
compared to 4 ohms is a significant fraction.



--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT

http://stackingdwarves.net

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Re: [Sursound] Distance perception

2011-07-26 Thread Marc Lavallée

Tue, 26 Jul 2011 21:32:26 +,
Fons Adriaensen  wrote :

> Lamp cords ? Use at least 2.5 mm^2 ! 

I'll use less than 10 meters of cabling to drive 10W max in each tiny 6
ohms speaker. So I'm not worried at all. Gauge 14 or 16 should be fine:
http://www.roger-russell.com/wire/wire.htm

> The thing is that I very much prefer listening to
> stereo using two virtual speakers panned into 3rd order AMB rather
> than sending L,R directly to two of the speakers.

It's very interesting!
How large is the resulting stereo image?
Is your technique documented somewhere? 
Can it work with a horizontal hexagon?
With 2rd order AMB?

--
Marc
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Re: [Sursound] Distance perception

2011-07-26 Thread Bill de Garis


On 26/07/11 3:41 p.m., Sampo Syreeni wrote:

On 2011-07-26, Fons Adriaensen wrote:

I certainly don't want you to waste your money on fancy speaker cables.

Never thought otherwise. That's obviously never been what we do here. ;)

But resistance does matter, so a good cross section such as 2.5 mm^2 puts you 
on the
safe side.


What I was trying to ask is, what's the real problem with resistance, 
especially with
regard to a passive speaker and a modern, A/B class solid state end stage? I 
mean, I
don't really see cable resistance shifting their operating point much, even with
feedback, within the audible range.

What is it that I'm missing?
I swapped out some lamp cable on the speakers of a stereo setup some years back with 
some cheap stranded speaker cable I bought at Costco. Each core of the cable was about 3 
times the cross sectional area of the lamp cord (each core of the speaker cable was 
about 3/16" in dia). The distances were not great, 5 or 6 feet.

The improvement in stereo imaging was huge.
Previously the image had wandered around between the speakers seemingly at random, now 
it was rock solid at the point wherever it was when I recorded it.

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Re: [Sursound] Distance perception

On Wed, Jul 27, 2011 at 01:41:51AM +0300, Sampo Syreeni wrote:
> On 2011-07-26, Fons Adriaensen wrote:
>
>> I certainly don't want you to waste your money on fancy speaker  
>> cables.
>
> Never thought otherwise. That's obviously never been what we do here. ;)
>
>> But resistance does matter, so a good cross section such as 2.5 mm^2  
>> puts you on the safe side.
>
> What I was trying to ask is, what's the real problem with resistance,  
> especially with regard to a passive speaker and a modern, A/B class  
> solid state end stage? I mean, I don't really see cable resistance  
> shifting their operating point much, even with feedback, within the  
> audible range.
>
> What is it that I'm missing?

When the voice coil of speaker moves in the magnetic field it
is surrounded by it generates a voltage proportional to its
velocity. Ideally that voltage should be equal to the one
produced by the amplifier: in that case the amplifier has
complete control over the movement.

You can easily test this: disconnect the speaker and gently
push the cone of the woofer. You will see it moves quite
easily. Now connect the speaker and switch on the amplifier,
OR just short-circuit the speaker terminals. In both cases
the speaker sees a very low impedance, and it will resist
movement.

In practice there is a problem: any resistance in series
with the 'ideal' voice coil means that those two voltages
are not equal and the amplifier is not fully in control.

The resistance that appears in series is the the sum of the
DC resistance of the voice coil itself, cable resistance and
the output impedance of the amplifier. This sum should be as
small as possible, and cable resistance can be a significant
part of it.

One advantage of integrated amps/speakers is that the amplifier
can be designed to compensate for this resistance by giving
it a negative impedance. This has to be controlled very
carefully - overdoing it makes the whole thing unstable and
ready to auto-destruct. Which is why it can't be done with
separate amps and speakers.

Ciao,

-- 
FA

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Re: [Sursound] Distance perception

On Tue, Jul 26, 2011 at 10:26:49PM -0400, Marc Lavallée wrote:

> How large is the resulting stereo image?

As large as you make it, see below.

> Is your technique documented somewhere? 
> Can it work with a horizontal hexagon?
> With 2rd order AMB?

Sure. There isn't much to document, just
set up your AMB system and use two AMB
panners for the L and R signals.

Ciao,

-- 
FA

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Re: [Sursound] Distance perception

2011-07-27 Thread Dave Malham

Apart from the damping problem which has been very well laid out by Fons, there is another factor
which can come into play and which I documented in an article in Hi-Fi for Pleasure many years ago.
The fact is that many poorly constructed cables, when hit with a bit of power, will actually produce
sound themselves. Those of us who are ancient, like me, will remember that in the days before
printed circuit board construction - so things were point-to-point wired - oscilloscopes (in
particular but not exclusively), were very prone to this and would often "sing" quite happily when
hit with an audio signal. So, when I first heard the sound from the cables I though it was the scope
I was using and it took me a while to realise it wasn't. The produced sound suffers from extreme
variations in frequency response and is very 'hysteric', in that there is often a level below which
it doesn't happen at all and over which it suddenly starts to sing. It's to long ago to quote
figures, the experimental approach I used was not terrible rigorous and the whole subject needs
(properly) reinvestigating but it's still something to be aware of. Fortunately, as Fons says,
decent mains cable would be fine - at least it was then. The one I really liked when I was testing
speaker cables was ordinary flat ribbon cable with alternate conductors paralleled up. Low
resistance, low inductance, didn't produce its own noises and fitted nicely under carpets (or you
could use the colour coded variety and use it as a feature in the room - not sure if it would
necessarily improve the SAF, though :-)

Dave

On 27/07/2011 05:57, Bill de Garis wrote:

On 26/07/11 3:41 p.m., Sampo Syreeni wrote:

On 2011-07-26, Fons Adriaensen wrote:

I certainly don't want you to waste your money on fancy speaker cables.

Never thought otherwise. That's obviously never been what we do here. ;)

But resistance does matter, so a good cross section such as 2.5 mm^2 puts you
on the
safe side.

What I was trying to ask is, what's the real problem with resistance,
especially with
regard to a passive speaker and a modern, A/B class solid state end stage? I
mean, I
don't really see cable resistance shifting their operating point much, even with
feedback, within the audible range.

What is it that I'm missing?
I swapped out some lamp cable on the speakers of a stereo setup some years back with some cheap
stranded speaker cable I bought at Costco. Each core of the cable was about 3 times the cross
sectional area of the lamp cord (each core of the speaker cable was about 3/16" in dia). The
distances were not great, 5 or 6 feet.

The improvement in stereo imaging was huge.
Previously the image had wandered around between the speakers seemingly at random, now it was rock
solid at the point wherever it was when I recorded it.

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These are my own views and may or may not be shared by my employer
/*/
/* Dave Malham http://music.york.ac.uk/staff/research/dave-malham/ */
/* Music Research Centre */
/* Department of Music"http://music.york.ac.uk/"; */
/* The University of York Phone 01904 432448*/
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Re: [Sursound] Distance perception

2011-07-27 Thread Dave Malham

I think this has a lot to do with the fact that there is never just one speaker on in the panned to 
ambi rig, unlike the stero case, at least for amplitude panned material. This makes the imaging less 
susceptible to acoustic differences between the speakers.


  Dave

On 27/07/2011 03:26, Marc Lavallée wrote:

Tue, 26 Jul 2011 21:32:26 +,
Fons Adriaensen  wrote :



The thing is that I very much prefer listening to
stereo using two virtual speakers panned into 3rd order AMB rather
than sending L,R directly to two of the speakers.

It's very interesting!
How large is the resulting stereo image?
Is your technique documented somewhere?
Can it work with a horizontal hexagon?
With 2rd order AMB?

--
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 These are my own views and may or may not be shared by my employer
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/* Music Research Centre */
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/* The University of York  Phone 01904 432448*/
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/* York YO10 5DD */
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Re: [Sursound] Distance perception

2011-07-27 Thread Dave Hunt

On 26 Jul 2011, at 17:00, sursound-requ...@music.vt.edu wrote:

Date: Mon, 25 Jul 2011 20:18:42 -0400
From: Marc Lavall?e 

After reading this difficult thread (I'm replying with a new title),
I have simple questions about room sizes and speaker distances.

Imagine two rooms with proper acoustic characteristics and treatments
for ambisonics reproduction: the first is 3mX4m and the other is four
times larger in surface (9mX12m). In both rooms there's a
horizontal hexagon of speakers, and 5 speakers are against a wall.

When NFC is applied in both rooms, do they sound the same in terms of
distance perception when playing the same recording? Or is the same
"sound object" appear to be twice as far in the largest room?

As J?rn has pointed out, the effect of the different acoustics of the  
rooms is hard to eliminate, and speaker placement relative to walls  
and other surfaces also has audible consequences. Anechoic rooms are  
hard to achieve, and are rather unpleasant and disturbing to be in.  
It is would be difficult to do an A/B comparison.

So, it is a rather hypothetical, if relevant, question. A better test  
would be two identical or similar outdoor rigs at different distances  
matched in level, with the ability to switch between them.

The "40' geese" phenomenon has been mentioned many times. John  
Leonard's recording, obviously fairly close perspective, when played  
on large systems gives the impression of very large geese. No-one  
seems to have an explanation for this. Possibly it is due to  
conflicting perceptual cues, visual as well as aural. Even without  
any visual aspect close sound sources seem 'bigger'. Aural  
perspective is not the same as visual perspective, though there are  
some similarities. Visual distance acuity is probably not much better  
than aural distance acuity. Both rely on comparison, experience and  
supposition.

My hunch, which I cannot back up with formal theory, is that distance  
perception is  relative rather than absolute. So, I would expect the  
two 'rooms' to sound broadly similar though not identical, assuming   
'proper acoustic characteristics' and appropriate NFC. Distance  
perception would be consistent, though different, in each 'room'.

Apart from widening the listening sweet spot, are larger rooms  
"better"
at reproducing distance cues when using the same speaker  
configuration?

It has been said several times on this list that the size of the  
sweet spot is related to wavelength and not the size of the speaker  
rig, and I'm not knowledgeable enough to disagree.

Certainly larger rooms have later and lower level reflections, with  
lower frequency resonant nodes and a more even frequency distribution  
of the harmonics of those nodes. Speakers can be more easily located  
away from walls and corners, resulting in direct sound sound from  
them arriving earlier and being louder than reflected sound.

Is distance perception directly related to speaker distances?

I suspect that that it is related in the case of ambisonics, though  
not directly. This is more psychoacoustics than just physics or  
acoustics.

Ciao,

Dave Hunt
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Re: [Sursound] Distance perception


years ago (no decades ago) i found what a huge difference it made if the wires 
were reasonably thick, and cut to be exactly same length. cutting them to same 
length is problematic with eight loudspeakers (unless the amp sits in the sweet 
spot) but my next rig, in my own house, in bangalore next year, will have same 
length wires to all the speakers. umashankar

i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
 > Date: Tue, 26 Jul 2011 21:57:49 -0700
> From: d...@dgvo.net
> To: sursound@music.vt.edu
> Subject: Re: [Sursound] Distance perception
> 
> On 26/07/11 3:41 p.m., Sampo Syreeni wrote:
> > On 2011-07-26, Fons Adriaensen wrote:
> >> I certainly don't want you to waste your money on fancy speaker cables.
> > Never thought otherwise. That's obviously never been what we do here. ;)
> >> But resistance does matter, so a good cross section such as 2.5 mm^2 puts 
> >> you on the
> >> safe side.
> >
> > What I was trying to ask is, what's the real problem with resistance, 
> > especially with
> > regard to a passive speaker and a modern, A/B class solid state end stage? 
> > I mean, I
> > don't really see cable resistance shifting their operating point much, even 
> > with
> > feedback, within the audible range.
> >
> > What is it that I'm missing?
> I swapped out some lamp cable on the speakers of a stereo setup some years 
> back with 
> some cheap stranded speaker cable I bought at Costco. Each core of the cable 
> was about 3 
> times the cross sectional area of the lamp cord (each core of the speaker 
> cable was 
> about 3/16" in dia). The distances were not great, 5 or 6 feet.
> The improvement in stereo imaging was huge.
> Previously the image had wandered around between the speakers seemingly at 
> random, now 
> it was rock solid at the point wherever it was when I recorded it.
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Re: [Sursound] Distance perception


my favourite visual image is of a boeing 747. it always  seems to fly so slow. 
we seem to have, in our brains, a 'size' for aircraft, so we can use that to 
compute speed from angular momentum. so small aircraft wiz by and big ones 
lumber. what models do we create for sound objects? umashankar
i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
 > From: davehuntau...@btinternet.com
> Date: Wed, 27 Jul 2011 11:01:32 +0100
> To: sursound@music.vt.edu
> Subject: Re: [Sursound] Distance perception
> 
> 
> On 26 Jul 2011, at 17:00, sursound-requ...@music.vt.edu wrote:
> 
> > Date: Mon, 25 Jul 2011 20:18:42 -0400
> > From: Marc Lavall?e 
> >
> > After reading this difficult thread (I'm replying with a new title),
> > I have simple questions about room sizes and speaker distances.
> >
> > Imagine two rooms with proper acoustic characteristics and treatments
> > for ambisonics reproduction: the first is 3mX4m and the other is four
> > times larger in surface (9mX12m). In both rooms there's a
> > horizontal hexagon of speakers, and 5 speakers are against a wall.
> >
> > When NFC is applied in both rooms, do they sound the same in terms of
> > distance perception when playing the same recording? Or is the same
> > "sound object" appear to be twice as far in the largest room?
> 
> As J?rn has pointed out, the effect of the different acoustics of the  
> rooms is hard to eliminate, and speaker placement relative to walls  
> and other surfaces also has audible consequences. Anechoic rooms are  
> hard to achieve, and are rather unpleasant and disturbing to be in.  
> It is would be difficult to do an A/B comparison.
> 
> So, it is a rather hypothetical, if relevant, question. A better test  
> would be two identical or similar outdoor rigs at different distances  
> matched in level, with the ability to switch between them.
> 
> The "40' geese" phenomenon has been mentioned many times. John  
> Leonard's recording, obviously fairly close perspective, when played  
> on large systems gives the impression of very large geese. No-one  
> seems to have an explanation for this. Possibly it is due to  
> conflicting perceptual cues, visual as well as aural. Even without  
> any visual aspect close sound sources seem 'bigger'. Aural  
> perspective is not the same as visual perspective, though there are  
> some similarities. Visual distance acuity is probably not much better  
> than aural distance acuity. Both rely on comparison, experience and  
> supposition.
> 
> My hunch, which I cannot back up with formal theory, is that distance  
> perception is  relative rather than absolute. So, I would expect the  
> two 'rooms' to sound broadly similar though not identical, assuming   
> 'proper acoustic characteristics' and appropriate NFC. Distance  
> perception would be consistent, though different, in each 'room'.
> 
> > Apart from widening the listening sweet spot, are larger rooms  
> > "better"
> > at reproducing distance cues when using the same speaker  
> > configuration?
> 
> It has been said several times on this list that the size of the  
> sweet spot is related to wavelength and not the size of the speaker  
> rig, and I'm not knowledgeable enough to disagree.
> 
> Certainly larger rooms have later and lower level reflections, with  
> lower frequency resonant nodes and a more even frequency distribution  
> of the harmonics of those nodes. Speakers can be more easily located  
> away from walls and corners, resulting in direct sound sound from  
> them arriving earlier and being louder than reflected sound.
> 
> > Is distance perception directly related to speaker distances?
> 
> I suspect that that it is related in the case of ambisonics, though  
> not directly. This is more psychoacoustics than just physics or  
> acoustics.
> 
> Ciao,
> 
> Dave Hunt
> ___
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> https://mail.music.vt.edu/mailman/listinfo/sursound
  
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Re: [Sursound] Distance perception

2011-07-27 Thread Marc Lavallée


Speaker wiring really is a hot topic on all audio related forums.
Next time I'll use the term "speaker wire" instead of "lamp cord". :-)

For a small and inefficient Kef satellite speaker (3" with a
tiny coaxial tweeter and internal crossover circuit), unable to
reproduce frequencies lower that 120Hz, driven by a dirt cheap 10W
class-T amp, for listening at a maximum distance of 2.5 meters, I doubt
that using short lamp cords will be my worst problem; sleeping well,
for example, is a better investment to improve my listening
experience than getting better cables or amplified speakers. For lower
frequencies I use small subs with integrated amps; I have no idea if
Kef used some negative impedance trick in their cheapest sub.

Wed, 27 Jul 2011 07:43:37 +,
Fons Adriaensen  a écrit :

> On Wed, Jul 27, 2011 at 01:41:51AM +0300, Sampo Syreeni wrote:
> > On 2011-07-26, Fons Adriaensen wrote:
> >
> >> I certainly don't want you to waste your money on fancy speaker  
> >> cables.
> >
> > Never thought otherwise. That's obviously never been what we do
> > here. ;)
> >
> >> But resistance does matter, so a good cross section such as 2.5
> >> mm^2 puts you on the safe side.
> >
> > What I was trying to ask is, what's the real problem with
> > resistance, especially with regard to a passive speaker and a
> > modern, A/B class solid state end stage? I mean, I don't really see
> > cable resistance shifting their operating point much, even with
> > feedback, within the audible range.
> >
> > What is it that I'm missing?
> 
> When the voice coil of speaker moves in the magnetic field it
> is surrounded by it generates a voltage proportional to its
> velocity. Ideally that voltage should be equal to the one
> produced by the amplifier: in that case the amplifier has
> complete control over the movement.
> 
> You can easily test this: disconnect the speaker and gently
> push the cone of the woofer. You will see it moves quite
> easily. Now connect the speaker and switch on the amplifier,
> OR just short-circuit the speaker terminals. In both cases
> the speaker sees a very low impedance, and it will resist
> movement.
> 
> In practice there is a problem: any resistance in series
> with the 'ideal' voice coil means that those two voltages
> are not equal and the amplifier is not fully in control.
> 
> The resistance that appears in series is the the sum of the
> DC resistance of the voice coil itself, cable resistance and
> the output impedance of the amplifier. This sum should be as
> small as possible, and cable resistance can be a significant
> part of it.
> 
> One advantage of integrated amps/speakers is that the amplifier
> can be designed to compensate for this resistance by giving
> it a negative impedance. This has to be controlled very
> carefully - overdoing it makes the whole thing unstable and
> ready to auto-destruct. Which is why it can't be done with
> separate amps and speakers.
> 
> Ciao,
> 

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Re: [Sursound] Distance perception

2011-07-27 Thread Marc Lavallée

Wed, 27 Jul 2011 07:53:18 +,
Fons Adriaensen  wrote :

> On Tue, Jul 26, 2011 at 10:26:49PM -0400, Marc Lavallée wrote:
> 
> > How large is the resulting stereo image?
> 
> As large as you make it, see below.

In your earlier post you mentioned that you can't explain why you like
virtual speakers better than using real speakers. Can you describe some
perceived differences? For example, how are rendered mono signals; are
they right in the middle or smeared between the two virtual speakers?
In other words, is localization better when using virtual speakers?

> > Is your technique documented somewhere? 
> > Can it work with a horizontal hexagon?
> > With 2rd order AMB?
> 
> Sure. There isn't much to document, just
> set up your AMB system and use two AMB
> panners for the L and R signals.

Easy!

--
Marc

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Re: [Sursound] Distance perception

2011-07-27 Thread Jörn Nettingsmeier

On 07/27/2011 04:26 AM, Marc Lavallée wrote:

Tue, 26 Jul 2011 21:32:26 +,
Fons Adriaensen wrote :

The thing is that I very much prefer listening to
stereo using two virtual speakers panned into 3rd order AMB rather
than sending L,R directly to two of the speakers.

It's very interesting!
How large is the resulting stereo image?
Is your technique documented somewhere?

as fons said, it's just panning. at lac 2010, i presented a paper on
using this technique to play back arbitrary discrete multichannel works
on an ambisonic rig, with some listening tests:
http://stackingdwarves.net/public_stuff/linux_audio/lac2010/day2_1130_General_purpose_Ambisonic_playback_systems_for_electroacoustic_concerts.ogv

executive summary: in the general case, it's very nice. for some signals
and some expectations, it does not work that well.
but fons' preference for the "bastardized stereo" sound over native
reproduction is not shared by most people i talked to, unless you make
the triangle significantly wider than 60°, at which point the "wow!"
effect takes over :)

Can it work with a horizontal hexagon?
With 2rd order AMB?

easily. my own tests were all on 3rd order rigs, but i've done it on a
hexagon at home, and it was ok.

--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT

http://stackingdwarves.net

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Re: [Sursound] Distance perception

On Wed, Jul 27, 2011 at 01:19:50PM -0400, Marc Lavallée wrote:

> In your earlier post you mentioned that you can't explain why you like
> virtual speakers better than using real speakers. Can you describe some
> perceived differences? For example, how are rendered mono signals; are
> they right in the middle or smeared between the two virtual speakers?
> In other words, is localization better when using virtual speakers?

This is very subjective, but yes, I have the impression it is better.
Also the speakers tend to disappear as being the sources of the sound
and there is less interaction from the room - the sensation that the
sound is 'just there' is stronger than for straight stereo.  But again,
this is quite subjective and may be particular for my setup. 

If you have the required hardware I'd say: just try it !

Ciao,

-- 
FA

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Re: [Sursound] Distance perception

2011-07-27 Thread Scott Wilson

On 27 Jul 2011, at 18:33, Fons Adriaensen  wrote:

> On Wed, Jul 27, 2011 at 01:19:50PM -0400, Marc Lavallée wrote:
> 
>> In your earlier post you mentioned that you can't explain why you like
>> virtual speakers better than using real speakers. Can you describe some
>> perceived differences? For example, how are rendered mono signals; are
>> they right in the middle or smeared between the two virtual speakers?
>> In other words, is localization better when using virtual speakers?
> 
> This is very subjective, but yes, I have the impression it is better.
> Also the speakers tend to disappear as being the sources of the sound
> and there is less interaction from the room - the sensation that the
> sound is 'just there' is stronger than for straight stereo.  But again,
> this is quite subjective and may be particular for my setup. 
> 
> If you have the required hardware I'd say: just try it !

Do you find it varies with material? People don't always say it this way, but 
sometimes increased localisation blur is nice!

S.
> 
> Ciao,
> 
> -- 
> FA
> 
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Re: [Sursound] Distance perception

On Wed, Jul 27, 2011 at 06:50:03PM +0100, Scott Wilson wrote:

> Do you find it varies with material? People don't always say
> it this way, but sometimes increased localisation blur is nice!

Good question, but I can't give a definite answer. 
Most of the material I've been working on there is
contemporary (2nd half of 20th century) music for
small ensembles, and recorded by myself in a place
I know very well. One exception is a concert with
madrigals by Adriano Banchieri (late 16th cent.).
For that one I could use for the first time (in
that place) a suspended ORTF pair, but it was just
a bit too far from the stage (practical constraints)
and I'm not 100% happy with the result.

I'll try to listen to some more diverse material and
report my impressions.

Ciao,

-- 
FA

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Re: [Sursound] Distance perception

2011-07-28 Thread Justin Bennett





On Wed, Jul 27, 2011 at 01:19:50PM -0400, Marc Lavall?e wrote:

In your earlier post you mentioned that you can't explain why you  
like
virtual speakers better than using real speakers. Can you describe  
some
perceived differences? For example, how are rendered mono signals;  
are

they right in the middle or smeared between the two virtual speakers?
In other words, is localization better when using virtual speakers?


This is very subjective, but yes, I have the impression it is better.
Also the speakers tend to disappear as being the sources of the sound
and there is less interaction from the room - the sensation that the
sound is 'just there' is stronger than for straight stereo.  But  
again,

this is quite subjective and may be particular for my setup.

If you have the required hardware I'd say: just try it !

Ciao,

--
FA



Maybe a similar effect to the Bloomline speakers

http://www.bloomline.nl/

not a very useful website if you don't speak dutch - but
these speakers create a virtual image between 2
vertically positioned drivers - indeed the speakers "disappear"
I heard a concert with amplified instruments and electronic
sources and it was very impressive - or rather unimpressive
because the sound seemed so "natural".  I think these have
been discussed before on the list. The demo I heard
was on a large theatre stage with speakers on the floor
and hung from the lighting grid. The sound seems to
come from the stage - in between. All the audio
was panpotted stereo or mics in stereo pairs as far as I know.

best, Justin.

Justin Bennett

van der Duijnstraat 61A
2515 NG Den Haag NL
+3170-3893912

j...@bmbcon.demon.nl
http://this.is/justin
http://this.is/bmbcon

NEW RELEASES AND FREE DOWNLOADS FROM http://spore.soundscaper.com






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Re: [Sursound] Distance perception

2011-07-28 Thread Fons Adriaensen

On Thu, Jul 28, 2011 at 10:43:33PM +0200, Justin Bennett wrote:

> Maybe a similar effect to the Bloomline speakers
>
> http://www.bloomline.nl/
>
> not a very useful website if you don't speak dutch - but
> these speakers create a virtual image between 2
> vertically positioned drivers - indeed the speakers "disappear"
> I heard a concert with amplified instruments and electronic
> sources and it was very impressive - or rather unimpressive
> because the sound seemed so "natural".  I think these have
> been discussed before on the list. The demo I heard
> was on a large theatre stage with speakers on the floor
> and hung from the lighting grid. The sound seems to
> come from the stage - in between. All the audio
> was panpotted stereo or mics in stereo pairs as far as I know.

Interesting. But the website is pretty useless even if
you speak dutch as I do. Until they explain how this works
I'll take it with an unhealthy dose of salt.

BTW, one must be either Ferengi or Dutch to turn 'Blumlein'
into 'Bloomline'.

Ciao,

-- 
FA


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Re: [Sursound] Distance perception

2011-07-28 Thread Sampo Syreeni


On 2011-07-27, Jörn Nettingsmeier wrote:


power transmission impedance matching.


That I've understood for the longest time. But then, when you learn it 
from a power electronics book -- which only talks about power 
transmission efficiency at a single frequency -- and then somebody tells 
you that's all bunk with audio circuits since there the ideal is to have 
total input-output control by always going from minimum output impedance 
to maximum input impedance... You can sort of lose track.


When I reread Robert's idiot-guide, I literally blushed.

if you look at the spec sheet of a commercial p.a. amplifier, 9 times 
out of 10 you will see twice the power rating for 4 ohm loads than for 
8 ohms.


How is this possible, given that the intrinsic ohmic load of the source 
ought to stay the same? Yielding more current, and as such not just more 
(linear) distortion from the reactive components, but also more power 
lost within the amp instead of within the wiring and/or the speaker?


Then the real question is, why can't this sort of a problem be corrected 
across the board with adaptive feedback? Even in the endstage? I mean, 
it shouldn't be too difficult to measure both the current and the 
voltage going out, and to feed them back via some mock-reactances over 
to the input side of the final amp. Over a narrow band that should be 
doable even in analog hardware. And over the whole audio band, why not 
just go with adaptive zero latency convolution and be done with the 
speaker impedance matching problem, once and for all? I.e. even if you 
don't have real variable reactances on the amp side which could be 
brought to bear, you could always go with the smallest common 
denominator you *can* handle by brute force, achieving a flat matching 
to an arbitrary speaker.


Or is it that this is patent protected already? Somehow I seem to 
remember reading a research paper or somesuch from Meridian, which could 
have suggested they did something like this at least for their flag-line 
DSP speakers' bass section, in order to get optimum power transfer, and 
as such high SPL's. Do we perchance have Bob Stuart online to verify or 
dispute my hunch?

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Re: [Sursound] Distance perception

2011-07-28 Thread Robert Greene



I am not sure I understand the question here. My impression
of why power doubles into 4 ohms compared to 8 ohms is
that most amps are voltage limited, not current limired
(until the impedance gets super-low).
And for a given voltage limit V , the power(which is nominally
VI= V(V/R)= Vsquared /R) will double when R is halved.
Of course, it depends on what makes the amp run out of steam!
Low current amps like the Quad current dumpers do not double into
half impedance loads very far down--they start to current limit.

But big current amps do do this,double into hald impedance,  down to 
fairly far down.


I am not an electronics designer but I think the causes of
current limiting and voltage limiting are in effect different.
Of course the one actually happens when the other happens:
an amp cannot maintain  voltage without maintaining  current too
(and vice versa). But I think the causes of limiting into high 
impedance and low impedance are different.
Current strength(which is what gives out in this informal sense into low 
impedances)  is attached to big power supply storage and (I think) lots 
of output devices paralleled , and voltage(which is 
what limits when the speaker impedance is high, again in this informal 
sense) is attached  to the rail levels or the voltage limits of the output 
devices.


Anyway, the little Quad 306 say , which has a dumpy(no pun intended) 
little power supply,

works really well into high impedance, but ask it to put out much current
on account of low speaker impedance, and it cries uncle. Power rating is
50 watts into 8 ohms, only 70 into 4 ohms. (Quad was and is very up front
about such things)

Please forgive, you electronics designers out there, this no doubt 
over-simplified view.


Am I missing the point here? I do not see how feedback could fix these 
limitations, though feedback surely does lower the output impedance--

one of the things it is for!

Robert

On Fri, 29 Jul 2011, Sampo Syreeni wrote:


On 2011-07-27, J?rn Nettingsmeier wrote:


power transmission impedance matchin>
That I've understood for the longest time. But then, when you learn it from a 
power electronics book -- which only talks about power transmission 
efficiency at a single frequency -- and then somebody tells you that's all 
bunk with audio circuits since there the ideal is to have total input-output 
control by always going from minimum output impedance to maximum input 
impedance... You can sort of lose track.


When I reread Robert's idiot-guide, I literally blushed.

if you look at the spec sheet of a commercial p.a. amplifier, 9 times out 
of 10 you will see twice the power rating for 4 ohm loads than for 8 ohms.


How is this possible, given that the intrinsic ohmic load of the source ought 
to stay the same? Yielding more current, and as such not just more (linear) 
distortion from the reactive components, but also more power lost within the 
amp instead of within the wiring and/or the speaker?


Then the real question is, why can't this sort of a problem be corrected 
across the board with adaptive feedback? Even in the endstage? I mean, it 
shouldn't be too difficult to measure both the current and the voltage going 
out, and to feed them back via some mock-reactances over to the input side of 
the final amp. Over a narrow band that should be doable even in analog 
hardware. And over the whole audio band, why not just go with adaptive zero 
latency convolution and be done with the speaker impedance matching problem, 
once and for all? I.e. even if you don't have real variable reactances on the 
amp side which could be brought to bear, you could always go with the 
smallest common denominator you *can* handle by brute force, achieving a flat 
matching to an arbitrary speaker.


Or is it that this is patent protected already? Somehow I seem to remember 
reading a research paper or somesuch from Meridian, which could have 
suggested they did something like this at least for their flag-line DSP 
speakers' bass section, in order to get optimum power transfer, and as such 
high SPL's. Do we perchance have Bob Stuart online to verify or dispute my 
hunch?

--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-50-5756111, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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Re: [Sursound] Distance perception

2011-07-29 Thread Fons Adriaensen

On Thu, Jul 28, 2011 at 05:30:55PM -0700, Robert Greene wrote:

> I am not an electronics designer but I think the causes of
> current limiting and voltage limiting are in effect different.
> Of course the one actually happens when the other happens:
> an amp cannot maintain  voltage without maintaining  current too
> (and vice versa). But I think the causes of limiting into high impedance 
> and low impedance are different.
> Current strength(which is what gives out in this informal sense into low  
> impedances)  is attached to big power supply storage and (I think) lots  
> of output devices paralleled , and voltage(which is what limits when the 
> speaker impedance is high, again in this informal sense) is attached  to 
> the rail levels or the voltage limits of the output devices.

Correct. Output voltage is limited by the voltage of the power
supply and any voltage lost in circuit elements. If you try to
go above it the signal will simply be clipped. More sophisticated
amps will monitor this and stop you from driving their high power
parts into saturation by limiting the input voltage.

Current is limited by what the power supply can deliver, and in
almost all amps is *actively* limited regardless of that to protect
the amp itself, both against excessive current AND excessive
internal power dissipation. For the latter, the current limiting
is usually made dependent on output voltage: more current is
allowed when the momentary output voltage gets higher (and voltage
drop over the output devices delivering the current gets lower).
This can lead to an amp having problems driving a reactive load.

Very high power amps as used in PA do monitor all of this, they
are well aware of the impedance they are driving and have data
interfaces reporting a variety of performance data to a centralised
monitoring and control application.

But in all cases, as long as they are working within their normal
limits, they are supposed to be voltage sources, with the resulting
current being whatever it takes.

Ciao,

-- 
FA

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Re: [Sursound] Distance perception

2011-07-31 Thread Sampo Syreeni


On 2011-07-27, Fons Adriaensen wrote:


This is very subjective, but yes, I have the impression it is better.
Also the speakers tend to disappear as being the sources of the sound
and there is less interaction from the room - the sensation that the
sound is 'just there' is stronger than for straight stereo.


I wonder... Has anybody tried calculating the traditional ambisonic 
localisation measurables for this sort of playback? For UHJ super stereo 
we already know what they are. But for ambisonically panned stereo?


At least for Blumlein stereo it would stand to reason that we'd be 
getting many of the same benefits we get when going with TriField, or 
any of the multichannel frontal stereo setups Gerzon at al's work for 
HDTV compatibility stereo hinted at. Then, some of that benefit would 
leach onto pairwise panned, staged material as well -- it does retain 
phase just as coincident Blumlein does, and the main psychoacoustics 
happen on the decoder side, so that the only thing which really is 
mismatched is the encoding locus over the Scheiber sphere.


With intensity panned stereo, it isn't that far off if you look at it...
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[Sursound] distance perception in virtual environments

2011-04-16 Thread Junfeng Li

Dear list,

I am now wondering how to subjectively evaluate distance perception in
virtual environments which might be synthesized using WFS or HOA (high-order
ambisonics). In my experiments, the sounds were synthesized at different
distances and presented to listeners for distance discrimination. However,
the listener cannot easily perceive the difference in distance between these
sounds.

Anyone can share some ideas or experiences in distance perception
experiments? or share some references on this issue?

Thank you so much.

Best regards,
Junfeng
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[Sursound] distance perception in virtual environments

2011-04-17 Thread Richard Lee

You must simulate at least 2 things.

At close range, you must simulate the curvature of the soundfield.  This is 
simply proximity for 1st order and the effect is, if anything, exaggerated.  
see the Appendix of

"Is My Decoder Ambisonic", Heller et al, AES San Francisco 1980 aka BLaH3

See Daniel for HOA

You have to simulate early reflections and a reverb pattern appropriate to 
source distance.  MAG has a paper on this under "Distance Panners" from an idea 
by Peter Craven.

Real Life Distance Perception is TERRIBLE under (near) anechoic conditions.  I 
recorded Paul Robinson's band at the IMAX theatre in Bradford.  They were 
providing music for a festival of silent movies.  Even after 5 days, we still 
found it disconcerting in that very dead environment.  Someone would call you 
from the door 20m away and you thought they were beside you.


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[Sursound] distance perception in virtual environments

2011-04-17 Thread Richard Lee

I hope you have a control where you measure "real" distance perception too.

Not having a "real" control is a fault in many localisation experiments.
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Re: [Sursound] distance perception in virtual environments

2011-04-17 Thread Dave Hunt

Hi,

Date: Sun, 17 Apr 2011 09:28:28 +0800
From: Junfeng Li 
Subject: [Sursound] distance perception in virtual environments

Dear list,

I am now wondering how to subjectively evaluate distance perception in
virtual environments which might be synthesized using WFS or HOA  
(high-order
ambisonics). In my experiments, the sounds were synthesized at  
different
distances and presented to listeners for distance discrimination.  
However,
the listener cannot easily perceive the difference in distance  
between these

sounds.

Anyone can share some ideas or experiences in distance perception
experiments? or share some references on this issue?

Thank you so much.

Best regards,
Junfeng

Change in amplitude with distance should be perceptible fairly  
easily, but on its own would just sound the same but quieter, or  
louder. High frequency absorption by the air is only really  
perceptible when the distance is fairly large, though this effect  
could be exaggerated for artistic purposes. The lateness of arrival  
of sound from distant objects is not directly perceptible unless  
there is something visible (e.g. lightning and thunder).

Reverberation definitely gives perceptible distance effects. More  
distant sources are more reverberant. The amplitude of the direct  
signal should decrease with distance (inverse square law, or some  
similar law), while the amplitude of the reflected and reverberant  
signal would remain fairly constant or decrease less rapidly with  
distance than that of the direct signal. It is the ratio of direct to  
reverberant sound that is important.

John Chowning's 1971 paper "The Simulation of Moving Sound Sources"  
is a good early consideration of how to synthesise distance.

Of course the reported result will depend on the listener, who may  
not be used to analysing sound for these effects.

Ciao,

Dave

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Re: [Sursound] distance perception in virtual environments

2011-04-17 Thread Markus Noisternig

Hi, 

Gavin Kearney et al have presented their work on "Depth perception in 
interactive virtual acoustic environments using higher order ambisonic 
soundfields" at the Ambisonics'11 symposium in Paris; the article is available 
online at http://ambisonics10.ircam.fr/drupal/?q=proceedings/o6

Best, 
Markus

On 17 avr. 2011, at 19:38, Dave Hunt wrote:

> Hi,
> 
>> Date: Sun, 17 Apr 2011 09:28:28 +0800
>> From: Junfeng Li 
>> Subject: [Sursound] distance perception in virtual environments
>> 
>> Dear list,
>> 
>> I am now wondering how to subjectively evaluate distance perception in
>> virtual environments which might be synthesized using WFS or HOA (high-order
>> ambisonics). In my experiments, the sounds were synthesized at different
>> distances and presented to listeners for distance discrimination. However,
>> the listener cannot easily perceive the difference in distance between these
>> sounds.
>> 
>> Anyone can share some ideas or experiences in distance perception
>> experiments? or share some references on this issue?
>> 
>> Thank you so much.
>> 
>> Best regards,
>> Junfeng
> 
> Change in amplitude with distance should be perceptible fairly easily, but on 
> its own would just sound the same but quieter, or louder. High frequency 
> absorption by the air is only really perceptible when the distance is fairly 
> large, though this effect could be exaggerated for artistic purposes. The 
> lateness of arrival of sound from distant objects is not directly perceptible 
> unless there is something visible (e.g. lightning and thunder).
> 
> Reverberation definitely gives perceptible distance effects. More distant 
> sources are more reverberant. The amplitude of the direct signal should 
> decrease with distance (inverse square law, or some similar law), while the 
> amplitude of the reflected and reverberant signal would remain fairly 
> constant or decrease less rapidly with distance than that of the direct 
> signal. It is the ratio of direct to reverberant sound that is important.
> 
> John Chowning's 1971 paper "The Simulation of Moving Sound Sources" is a good 
> early consideration of how to synthesise distance.
> 
> Of course the reported result will depend on the listener, who may not be 
> used to analysing sound for these effects.
> 
> Ciao,
> 
> Dave
> 
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Re: [Sursound] distance perception in virtual environments

2011-04-17 Thread jim moses

That's an interesting question. The environment you're working in for
synthesis could matter quite a bit. That is, if your working in, or
simulating, an environment with little reverberation it is harder to judge
distance since direct-to-reflected energy ratio is an important cue. The
other important cue is timbre detail - especially high frequencies. But this
requires the listener be familiar with the sound source to be able to
discriminate. Try testing with spoken voice.

I can't think of any research of the top of my head (especially for
multi-channel environments). It is certainly well known that controlling
high frequencies and direct/reflected ratio is important for distance
perception in stereo mixing - but even there that's usually a relative, or
comparative judgment, of one sound source appear vaguely 'behind' another.
Not so much an absolute judgment that you might want for a virtual
environment.

jim

On Sat, Apr 16, 2011 at 9:28 PM, Junfeng Li wrote:

> Dear list,
>
> I am now wondering how to subjectively evaluate distance perception in
> virtual environments which might be synthesized using WFS or HOA
> (high-order
> ambisonics). In my experiments, the sounds were synthesized at different
> distances and presented to listeners for distance discrimination. However,
> the listener cannot easily perceive the difference in distance between
> these
> sounds.
>
> Anyone can share some ideas or experiences in distance perception
> experiments? or share some references on this issue?
>
> Thank you so much.
>
> Best regards,
> Junfeng
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-- 
Jim Moses
Technical Director/Lecturer
Brown University Music Department and M.E.M.E. (Multimedia and Electronic
Music Experiments)
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Re: [Sursound] distance perception in virtual environments

2011-04-17 Thread Fons Adriaensen

On Sun, Apr 17, 2011 at 09:28:28AM +0800, Junfeng Li wrote:

> I am now wondering how to subjectively evaluate distance perception in
> virtual environments which might be synthesized using WFS or HOA (high-order
> ambisonics). In my experiments, the sounds were synthesized at different
> distances and presented to listeners for distance discrimination. However,
> the listener cannot easily perceive the difference in distance between these
> sounds.

No surprise really. 

There is very little difference between the _direct_ sound of a source
at e.g. 2 m distance, and one at 20 m. Except for *very* close sources
a static receiver having the size of a human head has almost no
information to detect the curvature of the wavefront and hence the
distance of the source. In anechoic conditions it's near impossible to
detect distance, except again for very close sources, or by implicitly
assuming some standard loudness for the source, e.g. a human voice 
which has a strong correlation between loudness and timbre.

As others have already pointed out, distance perception depends in
practice almost entirely on interaction of the sound source with the
environment: the relative level of reverberation and direct sound,
and the delays and levels of early reflections. In a virtual environment
created by HOA or WFS you have to artificially recreate those as well,
otherwise the acoustics of the listening space will dominate and the
apparent distance of any reproduced sound will be the distance to the
speaker.

Ciao,

-- 
FA

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Re: [Sursound] distance perception in virtual environments

2011-04-17 Thread Ralph Glasgal

For relatively nearby distance detection such as the buzzing bee or whispering 
or conversation (versus more distant sources such as in a concert hall), one 
needs to deliver interaural level differences on the order of 10 ot 20 dB with 
the corresponding ITD of up to 700 microseconds.  (If the sources and speakers 
are relatively centered then we can ignore the pinna distance detection 
problem.)  At the moment I believe only the Choueiri BACCH dummy head recording 
and crosstalk cancellation method can routinely deliver this magnitude of ILD 
over the full range of frequencies.  If you are synthesizing the ILD in 
your virtual signals then you don't need to use a dummy head or an Ambiophone.  
Of course, this ILD seems to apply only for distances to sources at the sides 
of the head but in practice extreme XTC and thus real binaural ITD provides for 
proximity at all frontal angles in the horizontal plane as in everyday 
hearing.    
 
RACE, if carefully implemented with directional nearfield speakers, can get up 
to about 10 dB or more ILD and you might try this since it is easier (cheaper) 
than using any of the other crosstalk cancelling or WFS or HOA methods.  There 
is no question that Ambiophonic users report enhanced depth perception when 
listening to ordinary music or the commercially available earphone type 
binaural recordings but you may want more than this for what you are doing so 
you should tweak the normal Ambiophonic methodology to optimize ILD capture and 
reproduction.
 
Ralph Glasgal
www.ambiophonics.org    

From: Junfeng Li 
To: Surround Sound discussion group 
Sent: Saturday, April 16, 2011 9:28 PM
Subject: [Sursound] distance perception in virtual environments

Dear list,

I am now wondering how to subjectively evaluate distance perception in
virtual environments which might be synthesized using WFS or HOA (high-order
ambisonics). In my experiments, the sounds were synthesized at different
distances and presented to listeners for distance discrimination. However,
the listener cannot easily perceive the difference in distance between these
sounds.

Anyone can share some ideas or experiences in distance perception
experiments? or share some references on this issue?

Thank you so much.

Best regards,
Junfeng
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Re: [Sursound] distance perception in virtual environments

2011-04-18 Thread Helmut Oellers

Hello Junfeng

We cannot perceive the distance regarding the sound source directly. The
both receptors for sound, differently the eyes, are dedicated for perceiving
the direction regarding the source, not the distance. Thus, we must rely
upon natural Stimul, stored by listening experience in our mind.

Unfortunately, that detection is very difficulty. Especially, if we don't
know the genuine sound of the source, we can estimate the distance only very
crude.

Moreover, if the playback room spends considerably own reflections at the
signal, the correct estimation regarding source distance becomes nearly
impossible, especially for proximate sound sources. Thus, the description of
the formidable deep impression of any loudspeaker reproduction seems
doubtful in my view.


Regards, Helmut
www.holophony.net





2011/4/17 Junfeng Li 

> Dear list,
>
> I am now wondering how to subjectively evaluate distance perception in
> virtual environments which might be synthesized using WFS or HOA
> (high-order
> ambisonics). In my experiments, the sounds were synthesized at different
> distances and presented to listeners for distance discrimination. However,
> the listener cannot easily perceive the difference in distance between
> these
> sounds.
>
> Anyone can share some ideas or experiences in distance perception
> experiments? or share some references on this issue?
>
> Thank you so much.
>
> Best regards,
> Junfeng
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Re: [Sursound] distance perception in virtual environments

2011-04-18 Thread Martin Leese

Richard Lee  wrote:

> You must simulate at least 2 things.
...
> You have to simulate early reflections and a reverb pattern appropriate to
> source distance.  MAG has a paper on this under "Distance Panners" from an
> idea by Peter Craven.

MAG's paper is:
M.A. Gerzon, "The Design of Distance Panpots",
Preprint 3308 of the 92nd Audio Engineering Society Convention, Vienna
(1992 Mar.)
(Simulating distance effects in directional reproduction.)

A commercialisation of this was the TrueVerb
product from Waves.

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] distance perception in virtual environments

2011-04-19 Thread dw


On 17/04/2011 02:28, Junfeng Li wrote:

Dear list,

I am now wondering how to subjectively evaluate distance perception in
virtual environments which might be synthesized using WFS or HOA (high-order
ambisonics). In my experiments, the sounds were synthesized at different
distances and presented to listeners for distance discrimination. However,
the listener cannot easily perceive the difference in distance between these
sounds.

Anyone can share some ideas or experiences in distance perception
experiments? or share some references on this issue?

Thank you so much.

Best regards,
Junfeng
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Hi List,
Just popped in.. It's been a while!

IMO it is a combination of time-of-flight and the inverse square law, 
where t=0 is a virtual point in time determined by the brain as an 
intercept by "plotting" a function of the intensity of (primarily) 
transverse reflections against time.  Fortunately it is not necessary to 
work out how the brain might do this. One needs to concentrate 
maximising the availability, and accuracy of the information that would 
be needed to make such a calculation possible, without making too much 
muddy reverb. in the process.  Mono reverb does not seem to play much, 
or possibly any, part in this. It seems to be extracted in some way from 
larger ITDs and ILDs ie. transverse discrete reflections. It took me 
several years to work all this out, and nobody seems to have 
independently come  to the same conclusion in the last decade or so.. so 
it must be wrong. At least it is free and in the public domain now! My 
Heli.wav on "Audio and Three Dimensional Sound Links* (long gone) was a 
product of precisely this method of distance synthesis.


Regards,
David Wareing.
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Re: [Sursound] distance perception in virtual environments

2011-04-20 Thread Helmut Oellers

Hi David,

you are not alone in your insigthes. Some single discrete reflections are
the most important fact for estimation of source distance.
There exist research from Helmut Wittek, who was proven, play the
reverberation from four different directions is absolutely sufficient. We
cannot use the direction of the wave fronts in the reverberation tail for
determine the position of the source. Also in the recording room, the
reverberation arrives from all possible directions.

Another case are the first reflections. Her  delay time and direction are
the most important fact for approve the source position, what inclusdes its
distance and the size impression of the recording room. Such single
reflections causing deep comb filter effects and change the perception
considerably. On the other hand, for reverberation is valid, what floyd
Toole says sometimes: As more reflections esxist as less disturbing there
are. ( as far as I remember well his words ).

All we need for correct distance reproduction is restore some ingle
reflections from her correct starting points and the correct relation
between direct wave and  reverberation.

Regards Helmut
www.holophony.net





2011/4/19 dw 

>
> Hi List,
> Just popped in.. It's been a while!
>
> IMO it is a combination of time-of-flight and the inverse square law, where
> t=0 is a virtual point in time determined by the brain as an intercept by
> "plotting" a function of the intensity of (primarily) transverse reflections
> against time.  Fortunately it is not necessary to work out how the brain
> might do this. One needs to concentrate maximising the availability, and
> accuracy of the information that would be needed to make such a calculation
> possible, without making too much muddy reverb. in the process.  Mono reverb
> does not seem to play much, or possibly any, part in this. It seems to be
> extracted in some way from larger ITDs and ILDs ie. transverse discrete
> reflections. It took me several years to work all this out, and nobody seems
> to have independently come  to the same conclusion in the last decade or
> so.. so it must be wrong. At least it is free and in the public domain now!
> My Heli.wav on "Audio and Three Dimensional Sound Links* (long gone) was a
> product of precisely this method of distance synthesis.
>
> Regards,
> David Wareing.
>
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Re: [Sursound] distance perception in virtual environments

2011-04-20 Thread dw


On 20/04/2011 22:04, Helmut Oellers wrote:

Hi David,

you are not alone in your insigthes. Some single discrete reflections are
the most important fact for estimation of source distance.
There exist research from Helmut Wittek, who was proven, play the
reverberation from four different directions is absolutely sufficient. We
cannot use the direction of the wave fronts in the reverberation tail for
determine the position of the source. Also in the recording room, the
reverberation arrives from all possible directions.

Another case are the first reflections. Her  delay time and direction are
the most important fact for approve the source position, what inclusdes its
distance and the size impression of the recording room. Such single
reflections causing deep comb filter effects and change the perception
considerably. On the other hand, for reverberation is valid, what floyd
Toole says sometimes: As more reflections esxist as less disturbing there
are. ( as far as I remember well his words ).

All we need for correct distance reproduction is restore some ingle
reflections from her correct starting points and the correct relation
between direct wave and  reverberation.

Regards Helmut
www.holophony.net
I think rooms are poor substitute, and very recent on evolutionary 
timescales, for the predictable reflections one gets in a forest. You 
need the simulated  forest (sort of both uniform but also random )for an 
accurate guess of the "start time". Then you delay the direct sound 
arrival time from there as well as decreasing its amplitude proportional 
to 1/t (where t is the time-of-flight from "start time" to arrival at 
the listener).. if I remember what I tried to do. If you live in a room 
then expect errors but the same principle applies!
We can't and don't determine the direction and distance of a sound with 
only two ears. We use an infinite 3d array. We just don't know the 
precise details of the ever-changing array. It is a very clever trick 
that evolution has come up with!


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Re: [Sursound] distance perception in virtual environments

2011-04-24 Thread Helmut Oellers

   ...modern computers are also clever. Today nothing is unaccountable if we
know the formula and all variables. Audio is no mysterious. The complete
sonic field would be calculatable. The only problem is the huge amount of
variables. In principle, yet, we are able to calculate any wave front of the
source and any of her reflections in the recording room. The Wave Field
Synthesis provides the approach for handling the problem. The procedure can
synthesize the complete spatial distribution of all wave fronts. In
principle, also all reflections become to restore correct in time, level and
direction, at least in the horizontal level of the loudspeaker rows. The
really disturbing component always remained, as like at all other audio
playback, the additional playback room acoustics, which deliver unwanted
reflections.

However, at WFS we have a chance for avoiding that problem. All we need is
including the playback room properties into the synthesis. By this way
becomes possible, subtract the additional detours of single wave fronts in
the playback room. Never conventional procedure will be able to that,
because direct wave, first reflections and reverberation inseparably merge
together in the transmitting channels. Thus, the playback room unavoidably
remains the disturbing component in transmitting chain. No chance exists for
true spatial audio by that way, thereby. And no chance exists for
reproducing the source distance correctly in the traditional way.


Regards Helmut
www.holophony.net





>  I think rooms are poor substitute, and very recent on evolutionary
>> timescales, for the predictable reflections one gets in a forest. You need
>> the simulated  forest (sort of both uniform but also random )for an accurate
>> guess of the "start time". Then you delay the direct sound arrival time from
>> there as well as decreasing its amplitude proportional to 1/t (where t is
>> the time-of-flight from "start time" to arrival at the listener).. if I
>> remember what I tried to do. If you live in a room then expect errors but
>> the same principle applies!
>> We can't and don't determine the direction and distance of a sound with
>> only two ears. We use an infinite 3d array. We just don't know the precise
>> details of the ever-changing array. It is a very clever trick that evolution
>> has come up with!
>
>
>
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Re: [Sursound] distance perception in virtual environments

2011-04-26 Thread Dave Malham


Hi

On 24/04/2011 19:11, Helmut Oellers wrote:

...modern computers are also clever. Today nothing is unaccountable if we
know the formula and all variables.


That's a BIG assumption - and given the essentially chaotic (in the mathematical sense) nature of 
the Universe, wrong. We are now pretty certain that nothing is that predictable and that that idea's 
basically (old) Science Fiction - we have moved from  E. E. "Doc" Smith's "Lensman" universe ( where 
ultimately intelligent beings could predict everything because they knew the complete starting 
conditions and laws of the Universe) to the Discworld universe of Terry Pratchett where one flap of 
a Quantum Weather Butterfly's *** wings can change the course of the entire Universe (and confound 
even the Gods).



However, at WFS we have a chance for avoiding that problem. All we need is
including the playback room properties into the synthesis. By this way
becomes possible, subtract the additional detours of single wave fronts in
the playback room.


Even in theory, this can only be done to a limited extent as you don't have sufficient foreknowledge 
of the state of the room acoustics, only that of a model with significant simplifications on things 
like surface properties of materials and, perhaps more importantly, air movements in the space - 
which cannot be predicted given the chaotic nature of the system. In practice, the limitations 
caused by finite speaker separation and the two dimensional nature of most extant WFS systems mean 
that the cancellation would only be valid at low frequencies. The perceptual effects of having the 
disruptive effects of playback space reflections cancelled at low frequencies and not at higher ones 
would need to be subject to listening tests, as would the 2D/3D conflict before we could give any 
kind of definitive answers - there might well be situations (or source materials) for which 
attempting cancellation of playback space acoustics could actually be worse than the effects of the 
playback space acoustics themselves.



Never conventional procedure will be able to that,
because direct wave, first reflections and reverberation inseparably merge
together in the transmitting channels. Thus, the playback room unavoidably
remains the disturbing component in transmitting chain. No chance exists for
true spatial audio by that way, thereby. And no chance exists for
reproducing the source distance correctly in the traditional way.


I think this is unnecessarily pessimistic and ignores the capabilities of the human brain to fill in 
missing details and/or ignore incorrect/inconsistent cues just so long as a sufficient subset of the 
cues presented are both (adequately) correct and consistent.


On the other hand, if  "true spatial audio" is intended to mean the recreation of an original real 
acoustic acoustic event (concert, airshow recording, whatever...) as it would have existed as a 
percept by a human attending that event, well, that's not going to happen with any of our systems 
until (and if) we can do direct brain recording and stimulation to a level of detail that current 
fMRI working is only barely beginning to hint at. That's because that percept does not just consist 
of the stimulation of our ear drums by the sound waves but also all the inputs from the other senses 
and, moreover, not just at that point in time but also previous to that.


  Dave

*** 
http://en.wikipedia.org/wiki/Quantum_Weather_Butterfly#Quantum_Weather_Butterfly

--
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Re: [Sursound] distance perception in virtual environments

2011-04-28 Thread Helmut Oellers

2011/4/26 Dave Malham 

>
>
  On 24/04/2011 19:11, Helmut Oellers wrote:

   ...modern computers are also clever. Today nothing is unaccountable if we
know the formula and all variables.

That's a BIG assumption - and given the essentially chaotic (in the
mathematical sense) nature of the Universe, wrong. We are now pretty certain
that nothing is that predictable and that that idea's basically (old)
Science Fiction - we have moved from  E. E. "Doc" Smith's "Lensman" universe
( where ultimately intelligent beings could predict everything because they
knew the complete starting conditions and laws of the Universe) to the
Discworld universe of Terry Pratchett where one flap of a Quantum Weather
Butterfly's *** wings can change the course of the entire Universe (and
confound even the Gods).

Hello Dave,

what you are describing, I would consider as the “Heisenberg uncertainty
principle”, which  disclosures, as closer we look at the things, as less we
can discover.  Accordingly, in the quantum world the random exist, really
not computable. However, in the macro world of whole air molecules, the
conditions are describable.

On 24/04/2011 19:11, Helmut Oellers wrote: However, at WFS we have a chance
for avoiding that problem. All we need is including the playback room
properties into the synthesis. By this way becomes possible, subtract the
additional detours of single wave fronts in the playback room.

You wrote: Even in theory, this can only be done to a limited extent as you
don't have sufficient foreknowledge of the state of the room acoustics, only
that of a model with significant simplifications on things like surface
properties of materials and, perhaps more importantly, air movements in the
space - which cannot be predicted given the chaotic nature of the system.

I agree we have to simplify. However, at least for direct wave and her first
order reflections an model calculation would be sufficiently. The first
reflections are causing deep comb filter effects with the direct wave,
especially at lower frequencies. That is simply calculable, so simple that
we are able for construct a common model from recording and playback room.
By that way, we can really subtract the additional detours and level changes
from the playback room regarding the first reflections. The playback wall
reflection become able for faking the first recording room reflection in
time, level and direction, at this way.
The timbre of the recording room, caused at the fine structure of the
reflecting surfaces, is mainly include in the reverberation. That complex
reflection pattern is really not calculable in simple model. However, there
is no need for restore the correct starting point of any reflection in the
reverberation tail. We need only enveloping distribution. Convolution in a
simple impulse response is reliable way in this matter.

Nevertheless, true spatial distribution of the starting points,
independently the listener position, is indespensable for the direct wave
and her first reflections. An air movement, i admit, is hardly predictable.
That will cause some gaps in the perfect recreation of the first
reflections. Nevertheless, as you have written, fortunately exist
“capabilities of the human brain to fill in missing details and/or ignore
incorrect/inconsistent cues just so long as a sufficient subset of the cues
presented are both (adequately) correct and consistent.” Obviously, we can
fill out the gaps.
However, from physically point of view, in the conventional procedures we
haven’t to fill out some gaps; we are constrained to recreating the audio
event from a very crude fragment!

You wrote: In practice, the limitations caused by finite speaker separation
and the two dimensional nature of most extant WFS systems mean that the
cancellation would only be valid at low frequencies. The perceptual effects
of having the disruptive effects of playback space reflections cancelled at
low frequencies and not at higher ones would need to be subject to listening
tests, as would the 2D/3D conflict before we could give any kind of
definitive answers - there might well be situations (or source materials)
for which attempting cancellation of playback space acoustics could actually
be worse than the effects of the playback space acoustics themselves.

In theory, the Wave field synthesis principle is not limited at the
horizontal plane. The attempt, to raze the playback room reflection by means
of the differently shaped cylinder waves of the loudspeaker rows, seem
really dilettantish. As you know, problems cannot become solved from the
same reasoning, by which they were created. Much more clever as figthing
against the reflections is including those playback room reflections
purposefully into the synthesis.

You wrote: On the other hand, if "true spatial audio" is intended to mean
the recreation of an original real acoustic event (concert, airshow
recording, whatever...) as it would have existed as a percept by a human
attending tha

Re: [Sursound] distance perception in virtual environments

2011-04-28 Thread Helmut Wittek

Hello Junfeng,

it's no easy task to evaluate distance perception under anechoic conditions 
(which obviously hardly exists).
We did this during my PhD research on WFS.
Have a look at our paper:

Wittek, H., Kerber, S., Rumsey, F. and Theile, G.
Spatial perception in Wave Field Synthesis rendered sound fields: Distance of 
real and virtual nearby sources
Preprint #6000, AES 116th Convention, Berlin, 2004

or my thesis on my website:
http://www.hauptmikrofon.de/

Good luck,
best regards,
Helmut Wittek


>>>-Ursprüngliche Nachricht-
>>>Von: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu]
>>>Im Auftrag von Junfeng Li
>>>Gesendet: Sonntag, 17. April 2011 03:28
>>>An: Surround Sound discussion group
>>>Betreff: [Sursound] distance perception in virtual environments
>>>
>>>Dear list,
>>>
>>>I am now wondering how to subjectively evaluate distance perception in
>>>virtual environments which might be synthesized using WFS or HOA (high-
>>>order
>>>ambisonics). In my experiments, the sounds were synthesized at different
>>>distances and presented to listeners for distance discrimination. However,
>>>the listener cannot easily perceive the difference in distance between
>>>these
>>>sounds.
>>>
>>>Anyone can share some ideas or experiences in distance perception
>>>experiments? or share some references on this issue?
>>>
>>>Thank you so much.
>>>
>>>Best regards,
>>>Junfeng
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>>>4a7d936/attachment.html>
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Re: [Sursound] distance perception in virtual environments

2011-04-28 Thread Sampo Syreeni


On 2011-04-28, Helmut Wittek wrote:

it's no easy task to evaluate distance perception under anechoic 
conditions (which obviously hardly exists).


By the way, I think that is one of the reasons anechoic rooms are 
perceptually so overwhelming and induce the kind of anxiety they do: in 
the absence of pretty much all meaningful distance cues, sound sources 
sort of crawl up onto you skin, and the distance perception also becomes 
rather unstable. I'm reasonably sure at least half of the "pushing", 
"suffocating" or "anxious" feeling they give you comes from the illusion 
that any and every sound source is violating your sphere of 
privacy/autonomy. That's also why I've never really been happy when 
people describe the sensation as being "sterile" -- to me it seems 
rather the opposite.



We did this during my PhD research on WFS.


With the above in mind, do you know of any research into the purely 
psychological and/or emotive aspects of anechoic conditions, and/or 
other spatial distortions? Including at least WFS's spatial aliasing, 
HOA's angular blurring, or, say, binaural/XTC related externalisation 
effects ("in your head" and all that)?



Wittek, H., Kerber, S., Rumsey, F. and Theile, G.
Spatial perception in Wave Field Synthesis rendered sound fields: Distance of 
real and virtual nearby sources
Preprint #6000, AES 116th Convention, Berlin, 2004


Ooh, I don't think I have this one yet. Care to share a preprint?

Also, if people want, I could probably assume the risk over another 
collection of papers in addition to the Ambisonic Motherlode, this time 
pertaining to WFS. Perhaps even a third one, with discrete systems in 
mind. If ya'll're game, private and/or anonymous submissions are 
welcome.


Finally, right now I'm at least a year or so behind current Ambisonic 
research as well. Any recent contributions to the Ambisonic 'lode would 
be greatly appreciated; eventhough I still don't have the time or the 
energy to organize it neatly.

--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-50-5756111, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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Re: [Sursound] distance perception in virtual environments

2011-04-28 Thread Martin Leese

Helmut Oellers  wrote:

> 2011/4/26 Dave Malham 

>>   On 24/04/2011 19:11, Helmut Oellers wrote:
>>>...modern computers are also clever. Today nothing is unaccountable if we
>>> know the formula and all variables.
>>
>> That's a BIG assumption - and given the essentially chaotic (in the
>> mathematical sense) nature of the Universe, wrong. We are now pretty certain
>> that nothing is that predictable and that that idea's basically (old)
>> Science Fiction - we have moved from  E. E. "Doc" Smith's "Lensman" universe
>> ( where ultimately intelligent beings could predict everything because they
>> knew the complete starting conditions and laws of the Universe) to the
>> Discworld universe of Terry Pratchett where one flap of a Quantum Weather
>> Butterfly's *** wings can change the course of the entire Universe (and
>> confound even the Gods).

> Hello Dave,
>
> what you are describing, I would consider as the ?Heisenberg uncertainty
> principle?, which  disclosures, as closer we look at the things, as less we
> can discover.  Accordingly, in the quantum world the random exist, really
> not computable. However, in the macro world of whole air molecules, the
> conditions are describable.

No, not the Heisenberg uncertainty principle
just, as Dave stated, chaos.  At times, the
weather system gets itself into a chaotic state.
The motion of the planets is also thought to be
chaotic.  These are macro.

This example of the weather system gave rise
to the (unsubstantiated) claim that the flap of a
butterfly’s wings in Brazil can set off a tornado
in Texas.  (The location of the butterfly and its
effects vary.)  This very nice example was then
purloined and mangled by Terry Prachett who
introduced a spurious reference to Quantum
Theory.

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] distance perception in virtual environments

2011-04-28 Thread Robert Greene



Actually, the butterfly flap thing is not really good either.
In chaos, things do not cause other things. The system is
essentially noncausal.
This is a trick point. But if a system depends unstably
on its initial state, it makes no real sense to say that it
depends on its initial state at all in any detail.

The weather has large scale stable aspects--it is almost always warmer in 
the summer  than in the winter for example. But the details of the weather 
are(it is currently believed) unstable. They are not really caused by

anything in any reasonable sense.

This is in fact not completely detached from quantum uncertainty
because if a system is unstable then it can obviously be knocked about
by quantum level changes--since it can be knocked about by arbitrarily
small changes of any sort. One merges into the other.

Also, there is no reason at all why a quantum uncertainty cannot
have macro effects, cf. Schrodinger's cat and many other examples.


Time for work. More on this later(if anyone cares)

Robert

On Thu, 28 Apr 2011, Martin Leese wrote:


Helmut Oellers  wrote:


2011/4/26 Dave Malham 



  On 24/04/2011 19:11, Helmut Oellers wrote:

   ...modern computers are also clever. Today nothing is unaccountable if we
know the formula and all variables.


That's a BIG assumption - and given the essentially chaotic (in the
mathematical sense) nature of the Universe, wrong. We are now pretty certain
that nothing is that predictable and that that idea's basically (old)
Science Fiction - we have moved from  E. E. "Doc" Smith's "Lensman" universe
( where ultimately intelligent beings could predict everything because they
knew the complete starting conditions and laws of the Universe) to the
Discworld universe of Terry Pratchett where one flap of a Quantum Weather
Butterfly's *** wings can change the course of the entire Universe (and
confound even the Gods).



Hello Dave,

what you are describing, I would consider as the ?Heisenberg uncertainty
principle?, which  disclosures, as closer we look at the things, as less we
can discover.  Accordingly, in the quantum world the random exist, really
not computable. However, in the macro world of whole air molecules, the
conditions are describable.


No, not the Heisenberg uncertainty principle
just, as Dave stated, chaos.  At times, the
weather system gets itself into a chaotic state.
The motion of the planets is also thought to be
chaotic.  These are macro.

This example of the weather system gave rise
to the (unsubstantiated) claim that the flap of a
butterfly?s wings in Brazil can set off a tornado
in Texas.  (The location of the butterfly and its
effects vary.)  This very nice example was then
purloined and mangled by Terry Prachett who
introduced a spurious reference to Quantum
Theory.

Regards,
Martin
--
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] distance perception in virtual environments(OT)

2011-04-28 Thread Robert Greene



The deterministic universe idea departed from serious science
almost 100 years ago since qunatum mechanics is by nature 
nondeterministic. (More precisely,  80 some years ago if you want to wait 
for people to have realized exactly how intrinsic the nondeterminacy

was--Heisenberg formulated his uncertainty principle in 1927 as I recall).
On the other hand, it is not clear to me that this really affects
computers directly.
They do freeze up at what appear to be random times and for unknown 
reasons. But I would be prepared to believe that they are not truly

random if one could look down in the works as it were.
But no one scientific seriously doubts that the universe is 
nondeterministic.


Robert

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Re: [Sursound] distance perception in virtual environments(OT)

2011-04-28 Thread umashankar mantravadi


i always thought that it is impossible to actually know the state of every gate 
and shift register in a cpu. so it is not deterministic
 
umashankar

i have published my poems. read (or buy) at http://stores.lulu.com/umashankar


 
> Date: Thu, 28 Apr 2011 07:48:22 -0700
> From: gre...@math.ucla.edu
> To: sursound@music.vt.edu
> Subject: Re: [Sursound] distance perception in virtual environments(OT)
> 
> 
> The deterministic universe idea departed from serious science
> almost 100 years ago since qunatum mechanics is by nature 
> nondeterministic. (More precisely, 80 some years ago if you want to wait 
> for people to have realized exactly how intrinsic the nondeterminacy
> was--Heisenberg formulated his uncertainty principle in 1927 as I recall).
> On the other hand, it is not clear to me that this really affects
> computers directly.
> They do freeze up at what appear to be random times and for unknown 
> reasons. But I would be prepared to believe that they are not truly
> random if one could look down in the works as it were.
> But no one scientific seriously doubts that the universe is 
> nondeterministic.
> 
> Robert
> 
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Re: [Sursound] Distance perception (really speaker wire discussion!)

2011-07-27 Thread Neil Waterman

I wrote the following as a guide for internal use at my work-place a few years 
back:

One "don't" that I hold close is this: Don't be mislead by the many "snake oil 
and, smoke and mirrors" cable vendors that seem to imbue speaker cables with 
magical (and astronomically expensive) properties. No matter what Monster 
Cable, Audioquest, or Cardas claim (or any other esoteric speaker wire 
manufacturer for that matter), there has never been any proof in any unbiased 
listen test that there is any benefit from using these "snake oil, and smoke 
and mirrors" inventions. [I still stand absolutely by this statement... if you 
are one of the sad souls that believe they can hear a difference, then you 
deserve to waste ALL your money on magical items - I have some acoustic candles 
for sale > they cost $1000 each and you must use one per speaker in your 
listening room the benefits are "when lit, you can find each speaker when 
you turn the lights off").

The most amusing claim is that some speaker wires are directional... yes, some 
manufacturers have decided that their cables must be installed in a particular 
orientation (usually indicated by an arrow printed on the outer jacket of the 
cable indicating the direction from the amp to the speaker that the wire is 
"designed" to be used. All sorts of claims are made trying to justify this. 
However speakers are inherently AC (Alternating Current) devices, and hence the 
electrons in a speaker wire spend just as much time traveling in one direction, 
as they do the other, so there is no fathomable reasoning that explains just 
how a speaker cable can possibly be directional, well excepting possibly being 
able to charge 10 times more to cover the cost of printing the arrows...  In 
fact if you consider this claim further, the more you realize the "wacko" 
aspect to this - if the cable truly did work better in one direction versus the 
other, then the resultant sound cannot possibly be anyt
 hing other than distorted when the electrons are flowing in the reverse 
direction!

Another odd claim heard for some of the astoundingly expensive speaker connects 
on the market* is that 'normal' speaker cables exhibit some resonance in the 
audio band, due to their claimed transmission line properties (since it is 
common to model a cable as an RLC network). While the RLC model is not invalid, 
the (usually unsubstantiated) claim that the resonance occurs in the audio band 
(most often mentioned is 1.5kHz), is very easily proven through basic 
electronic math to be hopelessly incorrect, and even for a long 50 foot 10AWG 
cable of quite humble specification, the resonant frequency calculates out to 
be 2.02MHz (some 2 magnitudes beyond human hearing)! In reality cables  DO NOT  
resonate at all! The model represented here is single RLC lumped circuit for 
simplicity and is only accurate at audio frequencies for circuit analysis. A 
speaker cable is actually a distributed element and should be represented as 
infinite number of lumped RLC models. As an infinite number o
 f lumped RLC circuits are modeled becoming its true distributed form factor, 
we see the resonance frequency go to infinity. 

In order to shorten this discussion the most basic don't is, don't buy any 
cable that claims anything other than the simple design goal of connecting an 
amplifier to a speaker.

So what does matter? 

The bottom line is that the speaker cable DC resistance should by rule 
-of-thumb present no more than  5% of the impedance load presented by the 
speaker, and hence the ONLY real issue of concern is the resistance of the 
selected wire per foot. The speakers I use most often have a rated impedance of 
4 Ohms, hence we do not want to see a DC resistance greater than 0.2 Ohms for 
the cable run. 

In general the distance run per wire gauge recommendations I use are as follows:

Up to 40 feet : 14AWG
40-60 feet: 12 AWG
60-100 feet: 10 AWG

- Neil

On Jul 27, 2011, at 8:03 AM, umashankar mantravadi wrote:

> 
> years ago (no decades ago) i found what a huge difference it made if the 
> wires were reasonably thick, and cut to be exactly same length. cutting them 
> to same length is problematic with eight loudspeakers (unless the amp sits in 
> the sweet spot) but my next rig, in my own house, in bangalore next year, 
> will have same length wires to all the speakers. umashankar
> 
> i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
>> Date: Tue, 26 Jul 2011 21:57:49 -0700
>> From: d...@dgvo.net
>> To: sursound@music.vt.edu
>> Subject: Re: [Sursound] Distance perception
>> 
>> On 26/07/11 3:41 p.m., Sampo Syreeni wrote:
>>> On 2011-07-26, Fons Adriaensen wrote:
>>>> I certainly don't want you to waste your money on fancy speaker cables.
>>> Never thought otherwise. T

Re: [Sursound] Distance perception (really speaker wire discussion!)


havent you heard of tired electron distortion ? (TID). the electrons in speaker 
wire get tired moving back and forth and not going anywhere. the solution is to 
disconnect the speaker every few hours connect a battery one side and short the 
other, so all the old electrons can be flushed out (i think i read this in the 
wireless world) umashankar

i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
 > From: neil.water...@asti-usa.com
> Date: Wed, 27 Jul 2011 08:20:02 -0400
> To: sursound@music.vt.edu
> Subject: Re: [Sursound] Distance perception (really speaker wire discussion!)
> 
> I wrote the following as a guide for internal use at my work-place a few 
> years back:
> 
> One "don't" that I hold close is this: Don't be mislead by the many "snake 
> oil and, smoke and mirrors" cable vendors that seem to imbue speaker cables 
> with magical (and astronomically expensive) properties. No matter what 
> Monster Cable, Audioquest, or Cardas claim (or any other esoteric speaker 
> wire manufacturer for that matter), there has never been any proof in any 
> unbiased listen test that there is any benefit from using these "snake oil, 
> and smoke and mirrors" inventions. [I still stand absolutely by this 
> statement... if you are one of the sad souls that believe they can hear a 
> difference, then you deserve to waste ALL your money on magical items - I 
> have some acoustic candles for sale > they cost $1000 each and you must use 
> one per speaker in your listening room the benefits are "when lit, you 
> can find each speaker when you turn the lights off").
> 
> The most amusing claim is that some speaker wires are directional... yes, 
> some manufacturers have decided that their cables must be installed in a 
> particular orientation (usually indicated by an arrow printed on the outer 
> jacket of the cable indicating the direction from the amp to the speaker that 
> the wire is "designed" to be used. All sorts of claims are made trying to 
> justify this. However speakers are inherently AC (Alternating Current) 
> devices, and hence the electrons in a speaker wire spend just as much time 
> traveling in one direction, as they do the other, so there is no fathomable 
> reasoning that explains just how a speaker cable can possibly be directional, 
> well excepting possibly being able to charge 10 times more to cover the cost 
> of printing the arrows...  In fact if you consider this claim further, the 
> more you realize the "wacko" aspect to this - if the cable truly did work 
> better in one direction versus the other, then the resultant sound cannot 
> possibly be an
 yt
>  hing other than distorted when the electrons are flowing in the reverse 
> direction!
> 
> Another odd claim heard for some of the astoundingly expensive speaker 
> connects on the market* is that 'normal' speaker cables exhibit some 
> resonance in the audio band, due to their claimed transmission line 
> properties (since it is common to model a cable as an RLC network). While the 
> RLC model is not invalid, the (usually unsubstantiated) claim that the 
> resonance occurs in the audio band (most often mentioned is 1.5kHz), is very 
> easily proven through basic electronic math to be hopelessly incorrect, and 
> even for a long 50 foot 10AWG cable of quite humble specification, the 
> resonant frequency calculates out to be 2.02MHz (some 2 magnitudes beyond 
> human hearing)! In reality cables  DO NOT  resonate at all! The model 
> represented here is single RLC lumped circuit for simplicity and is only 
> accurate at audio frequencies for circuit analysis. A speaker cable is 
> actually a distributed element and should be represented as infinite number 
> of lumped RLC models. As an infinite number
  o
>  f lumped RLC circuits are modeled becoming its true distributed form factor, 
> we see the resonance frequency go to infinity. 
> 
> In order to shorten this discussion the most basic don't is, don't buy any 
> cable that claims anything other than the simple design goal of connecting an 
> amplifier to a speaker.
> 
> So what does matter? 
> 
> The bottom line is that the speaker cable DC resistance should by rule 
> -of-thumb present no more than  5% of the impedance load presented by the 
> speaker, and hence the ONLY real issue of concern is the resistance of the 
> selected wire per foot. The speakers I use most often have a rated impedance 
> of 4 Ohms, hence we do not want to see a DC resistance greater than 0.2 Ohms 
> for the cable run. 
> 
> In general the distance run per wire gauge recommendations I use are as 
> follows:
> 
> Up to 40 feet : 14AWG
> 40-60 feet: 12 AWG
>

Re: [Sursound] Distance perception (really speaker wire discussion!)

2011-07-27 Thread Richard

Oh dear.  LOL

April edition was it?   LOL


  havent you heard of tired electron distortion ? (TID). the electrons in 
speaker wire get tired moving back and forth and not going anywhere. the 
solution is to disconnect the speaker every few hours connect a battery one 
side and short the other, so all the old electrons can be flushed out (i think 
i read this in the wireless world) umashankar

  i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
   > From: neil.water...@asti-usa.com
  > Date: Wed, 27 Jul 2011 08:20:02 -0400
  > To: sursound@music.vt.edu
  > Subject: Re: [Sursound] Distance perception (really speaker wire 
discussion!)
  > 
  > I wrote the following as a guide for internal use at my work-place a few 
years back:
  > 
  > One "don't" that I hold close is this: Don't be mislead by the many "snake 
oil and, smoke and mirrors" cable vendors that seem to imbue speaker cables 
with magical (and astronomically expensive) properties. No matter what Monster 
Cable, Audioquest, or Cardas claim (or any other esoteric speaker wire 
manufacturer for that matter), there has never been any proof in any unbiased 
listen test that there is any benefit from using these "snake oil, and smoke 
and mirrors" inventions. [I still stand absolutely by this statement... if you 
are one of the sad souls that believe they can hear a difference, then you 
deserve to waste ALL your money on magical items - I have some acoustic candles 
for sale > they cost $1000 each and you must use one per speaker in your 
listening room the benefits are "when lit, you can find each speaker when 
you turn the lights off").
  > 
  > The most amusing claim is that some speaker wires are directional... yes, 
some manufacturers have decided that their cables must be installed in a 
particular orientation (usually indicated by an arrow printed on the outer 
jacket of the cable indicating the direction from the amp to the speaker that 
the wire is "designed" to be used. All sorts of claims are made trying to 
justify this. However speakers are inherently AC (Alternating Current) devices, 
and hence the electrons in a speaker wire spend just as much time traveling in 
one direction, as they do the other, so there is no fathomable reasoning that 
explains just how a speaker cable can possibly be directional, well excepting 
possibly being able to charge 10 times more to cover the cost of printing the 
arrows...  In fact if you consider this claim further, the more you realize the 
"wacko" aspect to this - if the cable truly did work better in one direction 
versus the other, then the resultant sound cannot possibly be 
 an
   yt
  >  hing other than distorted when the electrons are flowing in the reverse 
direction!
  > 
  > Another odd claim heard for some of the astoundingly expensive speaker 
connects on the market* is that 'normal' speaker cables exhibit some resonance 
in the audio band, due to their claimed transmission line properties (since it 
is common to model a cable as an RLC network). While the RLC model is not 
invalid, the (usually unsubstantiated) claim that the resonance occurs in the 
audio band (most often mentioned is 1.5kHz), is very easily proven through 
basic electronic math to be hopelessly incorrect, and even for a long 50 foot 
10AWG cable of quite humble specification, the resonant frequency calculates 
out to be 2.02MHz (some 2 magnitudes beyond human hearing)! In reality cables  
DO NOT  resonate at all! The model represented here is single RLC lumped 
circuit for simplicity and is only accurate at audio frequencies for circuit 
analysis. A speaker cable is actually a distributed element and should be 
represented as infinite number of lumped RLC models. As an infinite numb
 er
o
  >  f lumped RLC circuits are modeled becoming its true distributed form 
factor, we see the resonance frequency go to infinity. 
  > 
  > In order to shorten this discussion the most basic don't is, don't buy any 
cable that claims anything other than the simple design goal of connecting an 
amplifier to a speaker.
  > 
  > So what does matter? 
  > 
  > The bottom line is that the speaker cable DC resistance should by rule 
-of-thumb present no more than  5% of the impedance load presented by the 
speaker, and hence the ONLY real issue of concern is the resistance of the 
selected wire per foot. The speakers I use most often have a rated impedance of 
4 Ohms, hence we do not want to see a DC resistance greater than 0.2 Ohms for 
the cable run. 
  > 
  > In general the distance run per wire gauge recommendations I use are as 
follows:
  > 
  > Up to 40 feet : 14AWG
  > 40-60 feet: 12 AWG
  > 60-100 feet: 10 AWG
  > 
  > - Neil
  > 
  > 
  > 
  > On Jul 27, 2011, at 8:03 AM, umashankar mantra

Re: [Sursound] Distance perception (really speaker wire discussion!)


but of course ! umashankar

i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
 > From: zoanne...@yahoo.co.uk
> To: sursound@music.vt.edu
> Date: Wed, 27 Jul 2011 13:26:47 +0100
> Subject: Re: [Sursound] Distance perception (really speaker wire discussion!)
> 
> Oh dear.  LOL
> 
> April edition was it?   LOL
> 
> 
>   havent you heard of tired electron distortion ? (TID). the electrons in 
> speaker wire get tired moving back and forth and not going anywhere. the 
> solution is to disconnect the speaker every few hours connect a battery one 
> side and short the other, so all the old electrons can be flushed out (i 
> think i read this in the wireless world) umashankar
> 
>   i have published my poems. read (or buy) at 
> http://stores.lulu.com/umashankar
>> From: neil.water...@asti-usa.com
>   > Date: Wed, 27 Jul 2011 08:20:02 -0400
>   > To: sursound@music.vt.edu
>   > Subject: Re: [Sursound] Distance perception (really speaker wire 
> discussion!)
>   > 
>   > I wrote the following as a guide for internal use at my work-place a few 
> years back:
>   > 
>   > One "don't" that I hold close is this: Don't be mislead by the many 
> "snake oil and, smoke and mirrors" cable vendors that seem to imbue speaker 
> cables with magical (and astronomically expensive) properties. No matter what 
> Monster Cable, Audioquest, or Cardas claim (or any other esoteric speaker 
> wire manufacturer for that matter), there has never been any proof in any 
> unbiased listen test that there is any benefit from using these "snake oil, 
> and smoke and mirrors" inventions. [I still stand absolutely by this 
> statement... if you are one of the sad souls that believe they can hear a 
> difference, then you deserve to waste ALL your money on magical items - I 
> have some acoustic candles for sale > they cost $1000 each and you must use 
> one per speaker in your listening room the benefits are "when lit, you 
> can find each speaker when you turn the lights off").
>   > 
>   > The most amusing claim is that some speaker wires are directional... yes, 
> some manufacturers have decided that their cables must be installed in a 
> particular orientation (usually indicated by an arrow printed on the outer 
> jacket of the cable indicating the direction from the amp to the speaker that 
> the wire is "designed" to be used. All sorts of claims are made trying to 
> justify this. However speakers are inherently AC (Alternating Current) 
> devices, and hence the electrons in a speaker wire spend just as much time 
> traveling in one direction, as they do the other, so there is no fathomable 
> reasoning that explains just how a speaker cable can possibly be directional, 
> well excepting possibly being able to charge 10 times more to cover the cost 
> of printing the arrows...  In fact if you consider this claim further, the 
> more you realize the "wacko" aspect to this - if the cable truly did work 
> better in one direction versus the other, then the resultant sound cannot 
> possibly b
 e 
>  an
>yt
>   >  hing other than distorted when the electrons are flowing in the reverse 
> direction!
>   > 
>   > Another odd claim heard for some of the astoundingly expensive speaker 
> connects on the market* is that 'normal' speaker cables exhibit some 
> resonance in the audio band, due to their claimed transmission line 
> properties (since it is common to model a cable as an RLC network). While the 
> RLC model is not invalid, the (usually unsubstantiated) claim that the 
> resonance occurs in the audio band (most often mentioned is 1.5kHz), is very 
> easily proven through basic electronic math to be hopelessly incorrect, and 
> even for a long 50 foot 10AWG cable of quite humble specification, the 
> resonant frequency calculates out to be 2.02MHz (some 2 magnitudes beyond 
> human hearing)! In reality cables  DO NOT  resonate at all! The model 
> represented here is single RLC lumped circuit for simplicity and is only 
> accurate at audio frequencies for circuit analysis. A speaker cable is 
> actually a distributed element and should be represented as infinite number 
> of lumped RLC models. As an infinite nu
 mb
>  er
> o
>   >  f lumped RLC circuits are modeled becoming its true distributed form 
> factor, we see the resonance frequency go to infinity. 
>   > 
>   > In order to shorten this discussion the most basic don't is, don't buy 
> any cable that claims anything other than the simple design goal of 
> connecting an amplifier to a speaker.
>   > 
>   > So what does matter

Re: [Sursound] Distance perception (really speaker wire discussion!)