I would definitely second Jörn. We had a 16 speaker array (4-8-4) in a room
which was hexagonal (with a pitched roof) that comes out as near a
hemisphere as far as audio is concerned. It had an awful focusing effect at
the centre until a brilliant guy in our estates department came up with a
relatively low cost solution which was to get a large (~3-4 metre diameter)
end dish from a beer brewing vessel and suspend it, concave side facing
down, below the centre of the ceiling, near its focal point, to break up
the main modes. The difference was amazing.- the room was still not really
good but it was usable and was far better for it's main use as a rehearsal
room, as well. No digital room correction as it was back in the day -
analog decoder design by Dylan Menzies, installation of the rig by various
masters Music Technology students (were you one, Richard F?, Can't remember
now...). Was in use for a decade until the Rymer Auditorium was built and
we transferred the speakers and amps over, retired the decoder and replaced
it with a digital one.
Dave
On 12 March 2014 12:19, Jörn Nettingsmeier <netti...@stackingdwarves.net>wrote:
> On 03/10/2014 11:50 PM, Steve Boardman wrote:
>
>> Hi J?rn (not sure what the character '?' is as it always displays
>> that way)
>>
>
> an o with double dot.
>
> the way i approach it is: * keep the early reflection paths clean
>>> for every speaker, like you would for stereo. no reflections < 10
>>> ms is a good thing, if possible. * keep the diffuse field under
>>> control. off-axis mud adds up as you add more speakers, so proper
>>> bass absorption and diffuse reflection in the treble and upper
>>> midrange are important. * use mild digital room correction in
>>> addition to acoustic treatment, it can do wonders for bass
>>> problems, where mechanical measures are difficult. * if you have to
>>> make compromises, keep the frontal direction as perfect as
>>> possible, and use it as a "magnifying glass" to work on details
>>> even if the respective sound later moves elsewhere.
>>>
>>
>> This is interesting, as I have had various opinions on this. Some
>> people say that spheres are the best as they have no parallel sides,
>> so reflections are reduced.
>>
>
> the center of a sphere is absolutely unusuable. all kinds of weird stuff
> from in-head localisation to total collapse of localisation, changing
> rapidly and erratically with just a few inches of head movement.
>
> the curvature of the walls does not mean that reflections are reduced,
> only that they are focused towards the center.
> there can even be a flutter echo.
>
> They also only have one room mode, that
>> can be predicted and treated. Or not excited (depending on the size).
>>
>
> i'd love to hear a spherical room that is not totally abysmal, and be
> proven wrong. but i won't buy shares of your studio when you go for a
> sphere :)
>
> I do know of speaker box technology that uses this thought to it's
>> advantage, but I have never considered it for studio construction,
>> due to complexity and space. It would also have to be very large for
>> the lowest fundament not to excite it!
>>
>
> think whisper gallery. do you want that in your control room?
>
> I must say, I like dead rooms, although I do agree that they are not
>> the best places to work. In fact quite disorientating. Listening to
>> ones own body internally is very off putting. As a consequence I
>> generally make the front complete dead with absorb-tion materials and
>> then have the back handle for reflections via random breakup
>> reflectors. Is this still a good idea?
>>
>
> i guess so. my (modest) experience tells me that overly dead rooms often
> call for "freshening up" by thin layers of HF-diffusing surface on top of
> the bass absorbers...
>
> A little room correction will of course be needed, especially for
>> bass.
>>
>> an off-the-cuff suggestion: * four subs in the corners. * the
>>> fullrange speakers on a horizontal ring, with one speaker in
>>> front, for a decent approximation of ITU 5.1 and 7.1, if
>>> necessary. * the satellites in a lower ring-of-eight, an upper
>>> ring-of-eight, another ring of six, one zenith speaker. then you
>>> have two spares, and they will come in handy some day.
>>>
>>> the bass management will be tricky. first of all, each speaker
>>> needs to be perfectly delay-compensated to the listening spot. then
>>> i'd try to create different layers of decoding:
>>>
>>> * separate first-order decode for the subs, low-passed at 60,
>>> 24dB/oct * fourth-order decode for everything else * horizontal
>>> speakers high-passed at 120/24 * satellites high-passed at 120/24 *
>>> a separate horizontal-only decode (of the same full-sphere input
>>> signal) for the range from 60 to 120 hz, again at 24dB/oct
>>>
>>> this lets you drive all speakers to the best of their abilities,
>>> and puts the missing bass frequencies in the correct direction.
>>> $DEITY help you if anything is not perfectly phase-aligned,
>>> though.
>>>
>>> disclaimer: i've toyed with such hacked-up multiband setups, but
>>> none of them ever went to production (or had to), so there may be
>>> pitfalls i've overlooked.
>>>
>>
>> First order decode for the four subs in the corners was what I was
>> thinking. Didn't think about going to fourth order on everything else
>> though, as I didn't think the increase in channel count was worth the
>> little improvement. I also want to leave some processing power for
>> mixing plugs (I use a lot) :)
>>
>
> well, i started from the number of speakers you said you had available.
>
> Agreed on the full range horizontal ring. I was more thinking of a
>> dodecahedron for the satellites, either only 20 on the vertices, or
>> get 5 more, and would it be possible to use the edges?
>>
>
> you mean you want to create entirely separate horizontal and full-sphere
> systems?
>
> Is it better
>> to use platonic solids, or doesn't it matter?
>>
>
> with the recent advances in optimizing for irregular layouts by zotter et
> al and heller et al, there is no longer a compelling reason to go for
> platonic solids, except that they are kind of pretty :)
> layouts based on a horizontal ring have the big advantage of better
> horizontal-only performance, without much degradation in the 3d case.
>
> Thanks again, and needless to say I will be asking a few more
>> questions as I progress. The build won't start for another month, and
>> when it's finished I would love for all you ambisonic heads to have a
>> listen.
>>
>
> can't wait to. where is your studio located?
>
>
>
> --
> Jörn Nettingsmeier
> Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
>
> Meister für Veranstaltungstechnik (Bühne/Studio)
> Tonmeister VDT
>
> http://stackingdwarves.net
>
> _______________________________________________
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound
>
--
As of 1st October 2012, I have retired from the University.
These are my own views and may or may not be shared by the University
Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<https://mail.music.vt.edu/mailman/private/sursound/attachments/20140313/7cd2edff/attachment.html>
_______________________________________________
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound
