Re: [Sursound] More Capsules - More Self-Noise Or Less?

[Rudy Chalupa]

 But isn't that only true if all the capsules are picking up the full signal? 
In the case of an Ambisonic mike, where the directional capsules are pointed in 
various directions, you won't get the full advantage.
Cordially,
Rudy ChalupaPleiades Audio + Electronics
On Wednesday, November 8, 2023 at 08:37:52 PM EST, 
lenmoskow...@optonline.net  wrote:  
 
 Do Many Small Capsules Mean More Self-Noise Or Less? Less!


As we've discussed before, the more capsules an array microphone has, 
the lower its self-noise. That's because as you double the number of 
capsules, the combined output voltage goes up 6 dB, but the self-noise 
only goes up 3 dB.

The noise increases only 3 dB  because it's uncorrelated across 
capsules. So each time you double the number of capsules, self-noise 
drops 3 dB. OctoMic's combined eight capsules have 9 dB lower self-noise 
than a single capsule.

That results in a low self-noise specification.  We specify it 
conservatively as 15 dBA. That's the same as DPA's wonderful 4003, or 
only 1 dB more than Schoeps' Mk 4.



Len Moskowitz (mosko...@core-sound.com)
Core Sound LLC
www.core-sound.com
Home of OctoMic and TetraMic
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Re: [Sursound] Death Spiral

[Rudy Chalupa]

Hi Stefan,
The layperson's explanation: If you are flying by visual flight rules 
(typically a small plane with no instruments)(or you ignore your instruments) 
and you cannot see the horizon (clouds, night), you can get into a situation 
where the plane begins to bank (turn) but you don't know it (due to gravity 
plus centrifugal force still pulling you toward the floor). In this case the 
plane will spiral ever tighter and lower until it reaches the ground while you 
are all the while convinced you are flying straight and level.
Hope this helps!
Rudy ChalupaPleiades Audio + Electronics


-Original Message-
From: Stefan Schreiber 
To: Surround Sound discussion group 
Sent: Tue, Feb 21, 2023 7:50 pm
Subject: Re: [Sursound] So long CIPIC HRTF?

Maybe it is me who now really would need some crash course in aviation, but:

Is flying in a spiral not something you would do in some intentional way?

(Opposite to the spin situation, because this is kind of uncontrolled.  
Or you "have to do something".)

So in which sense would you have to "recover" from the spiral?

I read this before, btw:

"But whoever cares, really? We all know what we're talking about.  
Especially when you have to use the instrument in order to deliver  
yourself and your passengers from a death spiral."

So what is this spiral? A situation when the plane is spinning, even a  
stall (interruption of air flow), or what else?

(Please enlighten me, and then I will ask Anders H. "what to do". ;-)

Best,

Stefan

- Mensagem de Fons Adriaensen  -

  Data: Tue, 21 Feb 2023 21:45:38 +0100

  De: Fons Adriaensen 

  Assunto: Re: [Sursound] So long CIPIC HRTF?

  Para: sursound@music.vt.edu

> On Tue, Feb 21, 2023 at 07:08:51PM +, Stefan Schreiber wrote:
>
>> I am just “sharing” what a Swedish pilot and aviation engineer wrote to me,
>>
>>  discussing and clarifying your problem(s)... ;-)
>
> We were not discussing spins, either upright or inverted.
>
>
>
>  A 'spiral', very different from any spin, was mentioned,
>
>  and Sampo seemed to think that recovery from that would
>
>  require regaining speed. The opposite is true, as in a
>
>  spiral your airspeed will increase [1]. Unless you recover,
>
>  there are two ways in which it can end: by smashing into
>
>  the ground, by or structural breakdown as the result of
>
>  excessive speed.
>
>
>
>  So as part of spiral recovery, you need to reduce speed.
>
>
>
>  [1] As it will during any turn, unless you compensate
>
>  by pulling the stick to maintain altitude.
>
>
>
>  Ciao,
>
>
>
>  --
>
>  FA
>
>
>
>  ___
>
>  Sursound mailing list
>
>  
> surso...@music.vt.eduhttps://mail.music.vt.edu/mailman/listinfo/sursound -  
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- Fim da mensagem de Fons Adriaensen  -
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Re: [Sursound] Level difference between A-format and B-format (Ambix and FuMa)

[Rudy Chalupa]

The Mixpre recorders had a similar issue with MS encoding when they first came 
out - it took a few revisions before that got sorted out. So it wouldn't 
surprise me that something similar is happening here.
Cordially,
Rudy ChalupaPleiades Audio + Electronics


-Original Message-
From: Arthur Sauer 
To: sursound@music.vt.edu
Sent: Tue, Jun 22, 2021 5:17 pm
Subject: [Sursound] Level difference between A-format and B-format (Ambix and 
FuMa)

I'm having an issue with a Sound Devices recorder (MixPre 10 II), where there 
is a level difference between the A-format and the simultaneously recorded 
B-format (Ambix and FuMa).
The level difference is 16 dB.
This is a first order ambisonic recording (with a Core Sound Tetramic).

Someone from Sound Devices assumed that this level difference may be due to the 
conversion.

Now I know normalizations are used for the conversion from A to B-format (SN3D, 
maxN), but I can't work out the mathematics behind it.
Anyway, looking at it does in no way seem to explain a level difference of 16 
dB.

Now I was wondering: is there any level difference to be expected between 
A-format and B-format Ambix or FuMa?
How much?

I do not like to make wrong statements to someone who should be helping me 
fixing a bug.
So, could someone enlighten me on this subject?

Best regards,

Arthur Sauer


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Re: [Sursound] Analogue 3D / surround sound panners?

[Rudy Chalupa]

There's the 360 degree pot on the Soundfield Mk V that lets you spin a first 
order Ambisonic image; it was/is accessible via the monitor path.
Cordially,
Rudy ChalupaPleiades Audio + Electronics


-Original Message-
From: Augustine Leudar 
To: Sursound 
Sent: Mon, Feb 17, 2020 9:34 pm
Subject: [Sursound] Analogue 3D / surround sound panners?

What was/is around in terms of analogue physical 3D or horizontal only
panners? I've seen the little joystick things on desks. Was wondering what
else?

-- 
Dr. Augustine Leudar
Artistic Director Magik Door
www.magikdoor.net
+44(0)7555784775
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Re: [Sursound] Ambix to FuMa conversion

[Rudy Chalupa]

https://xkcd.com/927/ 



-Original Message-
From: Jon Honeyball 
To: Surround Sound discussion group 
Sent: Mon, Apr 16, 2018 4:19 am
Subject: Re: [Sursound] Ambix to FuMa conversion

The wonderful thing about standards is the opportunity to have lots of them

jon

> On 14 Apr 2018, at 09:55, Jack Reynolds  wrote:
> 
> FuMa is WXYZ and ambiX is WYZX with SN3D normalisation. 
> I forget the gains off the top of my head, but will have a look and get back 
> if no one else has chipped in. 
> J
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Re: [Sursound] Soundfield mic disintegrating foam

[Rudy Chalupa]

Michael,


I've had to "de-foam" a couple of Mk IVs in the last few years. Remove the four 
screws holding the cage and you can get most of the foam out while safely 
remote from the capsules. I took the foam out of the leather case; I just place 
the microphone in a USPS Priority Mail padded envelope which is a conveniently 
perfect fit. The microphone seems to do acceptably well wind-wise without the 
foam. though I imagine it's attracting significantly more dust. I have yet to 
find a source of acoustic foam that's thin enough to replace the original.


The foam in the cases in both mikes I've serviced has held up well, so I can't 
advise on that. Sorry!


Cordially,


Rudy Chalupa
Pleiades Audio + Electronics



-Original Message-
From: Michael Dunn 
To: Surround Sound discussion group 
Sent: Thu, Oct 26, 2017 11:24 am
Subject: [Sursound] Soundfield mic disintegrating foam

The foam in my MkIV “suitcase” has turned to horrid mush. Argh. Any ideas for 
dealing with it?  I am incredibly scared to open the mic lest I find foam gunk 
all over those beautiful capsules!!!   Michael  -- next part 
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Re: [Sursound] Making something of faulty A-format recording

[Rudy Chalupa]

Did you record A or B format? If the former, two possibilities come to mind 
(assuming stereo out is the goal):
-Use the two back-to back capsules of the remaining three;
-Use the two back-to back capsules, one reverse polarity, for a difference 
signal and add the center capsule as the mono signal in an MS configuration.
 
If B format, you could dematrix to A, then proceed as above.
 
In all cases, significant EQ will probably be needed.
 
Cordially,

Rudy Chalupa
Pleiades Audio + Electronics
 
 
-Original Message-
From: Tom Hall 
To: Surround Sound discussion group 
Sent: Thu, Jun 8, 2017 10:24 am
Subject: [Sursound] Making something of faulty A-format recording

I've got a SPS200 recording with a unusable 3rd channel (possibly an electrical 
problem in the recorder). The recording was of general ambience and extracting 
a detailed/realistic soundstage isn't important. I thought I might be able to 
extract something in Harpex, but even using the mono shotgun setting, couldn't 
locate a direction that omitted signal from the ruined 3rd channel. Likewise in 
Surround Zone 2, adjusting the mic orientation with 0 width stereo still 
contained channel 3 signal.

I'd like to create a 2-channel output that is less arbitrary than simply using 
two of the three usable channels, and have got some 'interesting' results using 
with azimuth / level matching tool in Izotope RX.

I wonder if the group has any other suggestions for experimentation with the 3 
usable channels.

Tom 


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Re: [Sursound] Storage - how do you do yours?

[Rudy Chalupa]

I've been using Blu-ray. You can store the discs in jewel boxes and they don't 
take up too much space.You could fit as much as 100GB (two double-layer discs) 
in one jewel box.
 
Cordially,
 
Rudy Chalupa
Pleiades Audio + Electronics
 
 
-Original Message-
From: John Leonard 
To: Surround Sound discussion group 
Sent: Fri, Apr 15, 2016 1:09 pm
Subject: [Sursound] Storage - how do you do yours?

A question:Most of my recording is now 4 four or six channel 96/24 and 
currently, I back up from the recorders to bare hard drives via an eSATA 
docking station, which means that I have an every-increasing pile of hard 
drives, as I back up every thing important twice. I’ve pretty much standardised 
on 2TB drives; a mixture of Seagate and Western Digital  (I keep telling myself 
that it’s cheaper than a reel of 1” Ampex 456, but at the rate that I’m piling 
the drives up, it’s still a bit daunting.) Although this system works pretty 
well, and I use DiskTracker to keep a record of what’s where, It does mean that 
I just have a shelf full of 3.5” hard drives, which is a) a bit messy and b) a 
bit of a risk. The cloud is an option - or at least it will be once I get my 
super-duper-whizzy even faster Virgin upgrade, but even at the current upload 
rate of 10 MB, a full drive takes days to upload and then it’s not exactly 
quick to get it back.Given that I don’t have an educational establishment with 
huge servers, anyone got any reasonably-priced suggestions for 
storage?Ta,JohnPlease note new email address & direct line phone numberemail: 
john@johnleonard.ukphone +44 (0)20 3286 
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Re: [Sursound] Are mems a good choice for ambisonic microphones?

[Rudy Chalupa]

Note the equivalent input noise of 31dBA. It's going to take a fairly large 
array of these to get the noise to an acceptable level.
 
Cordially,
 
Rudy Chalupa
Pleiades Audio + Electronics
 
 
-Original Message-
From: Marc Lavallee 
To: Surround Sound discussion group 
Sent: Wed, Apr 13, 2016 10:27 am
Subject: [Sursound] Are mems a good choice for ambisonic microphones?


I'm looking at this product here:
http://www.invensense.com/products/analog/ics-40300-3/

I wonder if mems are good for building an ambisonic microphone... The
document named "Low-Noise Directional Studio Microphone Reference
Design" shows an array of 32 mems.

--
Marc
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Re: [Sursound] Soundfield MK IV Disassembly

[Rudy Chalupa]

Mr. Lee,
 
Thanks! The key turned out to be the Allen head cap screw at the wide end of 
the "cone" - I unscrewed that and the whole assembly came apart. I must admit 
it was a challenge lining up all the pieces for reassembly; I assume that in 
"production" this stage occurred before the side rails and printed circuit 
assembly were added.
 
You had asked for details of my modifications; here's the first installment. 
The first page shows the regulator I added to my own microphone; the second 
details the changes to the one that's currently under the knife. My goal is to 
avoid cutting the foil at the cathode of the LED; I'll let you know how it 
works out. I'll try to send a picture of the regulator installed; the 
Surf-Board I use requires some surgery to fit into the available space. Pardon 
the hand-scrawled schematics!

BTW, it turned out the resistor was fine; a solder joint had given way due to 
the resistor leads being inserted an insufficient distance. Reminds one of 
working on old British sports cars! ("Why do the British drink warm beer?")
 
Cordially,

Rudy Chalupa
Pleiades Audio + Electronics
 
-Original Message-
From: Richard Lee 
To: 'Surround Sound discussion group' 
Sent: Tue, Mar 29, 2016 8:04 pm
Subject: Re: [Sursound] Soundfield MK IV Disassembly

> I have a question for the keepers of ancient wisdom: how does one remove 
the capsule assembly from a Soundfield MK IV microphone? I have one on 
which the 1 kilohm "capsule heater" resistor has gone open circuit. The 
cone on the MK V and newer is split and comes apart pretty readily, but the 
MK IV cone is solid and it's not apparent how to reach the resistor.

Rudy, It's more than 30 yrs since I took a Mk4 capsule assembly apart so 
bear with me I'm pontificating from the wrong orifice.

1   Unsolder the leads from capsule to PCB.
Can't remember if you can reach this from inside as the connections may 
be 
in the cone section.
If so (!!#*??), you'll have to disassemble the capsule assembly, remove 
at 
least 2 capsules on their tetrahedron sections and unsolder from the tags 
behind the capsule.

Keep the capsules in their little holder to provide some measure of 
protection but this is still a brain surgery type operation.

2   The tetrahedron stalk is screwed to a brass block on the PCB.  The 1k 
resistor is sandwiched to the block/stalk in some way which I've long 
forgotten.  IIRC, there was another small PCB whose sole purpose was to 
clamp the resistor.

3   Removing the tetrahedron allows the cone to come off.

I you have the set of dwgs which were supplied with early Mk4s, there 
should be one that makes this clearer (or not).

My apologies for this Heath Robinson design from my mispent youth.
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[Sursound] Soundfield MK IV Disassembly

[Rudy Chalupa]

I have a question for the keepers of ancient wisdom: how does one remove the 
capsule assembly from a Soundfield MK IV microphone? I have one on which the 1 
kilohm "capsule heater" resistor has gone open circuit. The cone on the MK V 
and newer is split and comes apart pretty readily, but the MK IV cone is solid 
and it's not apparent how to reach the resistor.


Cordially,


Rudy Chalupa
Pleiades Audio + Electronics
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Re: [Sursound] Servicing a Soundfield MK V in the United States.

[Rudy Chalupa]

Due to necessity, I've learned to service pretty much every piece of my MK IV. 
(I'm the guy who did this: 
https://www.gearslutz.com/board/11410162-post650.html.)If you have a schematic, 
I'd be willing to take a look at your Mk V. I'm in the Philadelphia area.


Cordially,


Rudy Chalupa
Pleiades Audio + Electronics



-Original Message-
From: bbowling 
To: sursound 
Sent: Sun, Mar 20, 2016 6:02 pm
Subject: [Sursound] Servicing a Soundfield MK V in the United States.

Hello All,From reading the subjects that have been posted over the past year, I 
can see many of us have issues with our Soundfield equipment. I have been able 
to make contact with the U.S. based sales rep in Los Angeles, Ca, and I have 
spoken to TSL support twice in regards to having our Soundfield MK V serviced. 
The conclusion from every angle is that I will have to send it to them in 
Marlow, U.K. to have it serviced.Have any of you found any companies in the 
U.S. that can, or are willing to service Soundfield products? We believe there 
is a power issue at hand and would like to avoid sending it to Europe if at all 
possible.Here is a description of the problem from the Professor. "Actually the 
problem is that it does not always turn on.  There appears to be a problem with 
its power supply that causes it to chirp/click repeatedly while attempting to 
power on, and often even when it does finally turn on (after letting it try and 
“chirp” for a while, the display lights up without the usual channel indicators 
and level meters being displayed.  Sometimes if you let it sit (on) long 
enough, or try cycling the power a number of times in succesion, the unit 
starts up correctly and works as expected."Thank you in advance, and all the 
best to you all!"Barry 
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[Sursound] ST250 Schematic?

[Rudy Chalupa]

Hello everyone! I'm new to this list, but not to Ambisonics - I had the 
firstCalrec MK IV microphone in North America. (Apparently my modifications to 
the MK IV got mentioned here in October.) Anyway, I just purchased a used ST250 
which sounds like it might be a little dodgy. I understand the internals are 
quite different from the MK IV or MK V. I've located a pdf of the user's 
manual, but a schematic would be most welcome. Does anyone have one? Do you 
think TSL would be forthcoming with such a thing?

Cordially,

Rudy Chalupa
Pleiades Audio + Electronics
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