Re: [Sursound] Ambisonics on the cheap?

[Hugh Pyle]

I have one of these, and it's cheap and works well.  The biggest issue is
the sample rate limitation;  with 8 channels you can only run at 44.1 kHz.

On Sat, Jul 30, 2011 at 12:07 AM, Ben Bloomberg  wrote:

> Has anyone tried anything from ESI audio? It looks too good to be true.
>
> http://www.esi-audio.com/products/gigaporthd/
> It seems like they can be had for around $100.
>
> ben
>
> On Fri, Jul 29, 2011 at 9:41 AM, Dave Malham 
> wrote:
>
> >
> >
> > On 29/07/2011 11:30, Michael Chapman wrote:
> >
> >> Now I would like to construct a higher-order sound system, ideally with
> >>> consumer-level (and consumer-priced) components. I don't need a big
> >>> dynamic range, high power, or the best sound fidelity possible, I just
> >>> need a working prototype. This is the part I have found very little
> >>> information on in my research�
> >>>
> >>> My understanding is that 8 channels is the minimum needed for stable
> 3-D
> >>> Ambisonics (rather than planar surround).
> >>>
> >> There was a recent reminder, on this list, within the last month, that
> >> one could use 6 channels (the mid points of the faces of a cube).
> >> I've never heard anyone say they've done it, let alone say it was
> 'nice'.
> >> (The engineering would, also, not be fun ... though you are not obliged
> >> to place speakers mid-wall/ceiling/floor ... you can tilt the cube!)
> >> So I'd stick to eight unless you are really adventurous.
> >>
> >>  We've used it in the dim and distant past and it's not to be
> recommended
> > as it is right at the limits of usability (very unstable image,
> incredibly
> > tiny sweet spot and so on). I would compromise on the quality of the
> > speakers so that I could buy eight, rather than buy only six better ones
> > (ditto for the audio interface and amps)
> >
> >  Dave (signing off for now as I'm off on vacation, hurrah!)
> >
> >
> > --
> >  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/<
> 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*/
> > /* Heslington  Fax   01904 432450*/
> > /* York YO10 5DD */
> > /* UK   'Ambisonics - Component Imaging for Audio'   */
> > /*"http://www.york.ac.uk/inst/**mustech/3d_audio/<
> http://www.york.ac.uk/inst/mustech/3d_audio/>"
> > */
> > /***
> > **/
> >
> > __**_
> > Sursound mailing list
> > Sursound@music.vt.edu
> > https://mail.music.vt.edu/**mailman/listinfo/sursound<
> https://mail.music.vt.edu/mailman/listinfo/sursound>
> >
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Re: [Sursound] Ambisonics on the cheap?

[Michael Chapman]

One should buy any equipment that does _not_ use
1/8 inch stereo jacks ... that is a big plus!

The minus would seem to be one is (for a cube)
stuck with 44.1 KHz ...
"different playback modes:
44.1kHz with 16-bit and 8 channels,
44.1kHz with 24-bit and 6 channels,
48kHz with 24-bit and 6 channels,
96kHz with 24-bit and 2 channels"
... pity
>
> going to order one and see.  umashankar
>
It sounds as if it should work with Linux ... if you get a chance to try it
can you 'report', thanks,

Michael

>  > From: b...@mit.edu
>> Date: Sat, 30 Jul 2011 00:07:12 -0400
>> To: sursound@music.vt.edu
>> Subject: Re: [Sursound] Ambisonics on the cheap?
>>
>> Has anyone tried anything from ESI audio? It looks too good to be true.
>>
>> http://www.esi-audio.com/products/gigaporthd/
>> It seems like they can be had for around $100.
>>
>> ben
>>


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Re: [Sursound] Ambisonics on the cheap?

[umashankar mantravadi]

going to order one and see.  umashankar

i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
 > From: b...@mit.edu
> Date: Sat, 30 Jul 2011 00:07:12 -0400
> To: sursound@music.vt.edu
> Subject: Re: [Sursound] Ambisonics on the cheap?
> 
> Has anyone tried anything from ESI audio? It looks too good to be true.
> 
> http://www.esi-audio.com/products/gigaporthd/
> It seems like they can be had for around $100.
> 
> ben
> 
> On Fri, Jul 29, 2011 at 9:41 AM, Dave Malham  wrote:
> 
> >
> >
> > On 29/07/2011 11:30, Michael Chapman wrote:
> >
> >> Now I would like to construct a higher-order sound system, ideally with
> >>> consumer-level (and consumer-priced) components. I don't need a big
> >>> dynamic range, high power, or the best sound fidelity possible, I just
> >>> need a working prototype. This is the part I have found very little
> >>> information on in my research�
> >>>
> >>> My understanding is that 8 channels is the minimum needed for stable 3-D
> >>> Ambisonics (rather than planar surround).
> >>>
> >> There was a recent reminder, on this list, within the last month, that
> >> one could use 6 channels (the mid points of the faces of a cube).
> >> I've never heard anyone say they've done it, let alone say it was 'nice'.
> >> (The engineering would, also, not be fun ... though you are not obliged
> >> to place speakers mid-wall/ceiling/floor ... you can tilt the cube!)
> >> So I'd stick to eight unless you are really adventurous.
> >>
> >>  We've used it in the dim and distant past and it's not to be recommended
> > as it is right at the limits of usability (very unstable image, incredibly
> > tiny sweet spot and so on). I would compromise on the quality of the
> > speakers so that I could buy eight, rather than buy only six better ones
> > (ditto for the audio interface and amps)
> >
> >  Dave (signing off for now as I'm off on vacation, hurrah!)
> >
> >
> > --
> >  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*/
> > /* Heslington  Fax   01904 432450*/
> > /* York YO10 5DD */
> > /* UK   'Ambisonics - Component Imaging for Audio'   */
> > /*
> > "http://www.york.ac.uk/inst/**mustech/3d_audio/"
> > */
> > /***
> > **/
> >
> > __**_
> > Sursound mailing list
> > Sursound@music.vt.edu
> > https://mail.music.vt.edu/**mailman/listinfo/sursound
> >
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Re: [Sursound] Ambisonics on the cheap?

[Ben Bloomberg]

Has anyone tried anything from ESI audio? It looks too good to be true.

http://www.esi-audio.com/products/gigaporthd/
It seems like they can be had for around $100.

ben

On Fri, Jul 29, 2011 at 9:41 AM, Dave Malham  wrote:

>
>
> On 29/07/2011 11:30, Michael Chapman wrote:
>
>> Now I would like to construct a higher-order sound system, ideally with
>>> consumer-level (and consumer-priced) components. I don't need a big
>>> dynamic range, high power, or the best sound fidelity possible, I just
>>> need a working prototype. This is the part I have found very little
>>> information on in my research�
>>>
>>> My understanding is that 8 channels is the minimum needed for stable 3-D
>>> Ambisonics (rather than planar surround).
>>>
>> There was a recent reminder, on this list, within the last month, that
>> one could use 6 channels (the mid points of the faces of a cube).
>> I've never heard anyone say they've done it, let alone say it was 'nice'.
>> (The engineering would, also, not be fun ... though you are not obliged
>> to place speakers mid-wall/ceiling/floor ... you can tilt the cube!)
>> So I'd stick to eight unless you are really adventurous.
>>
>>  We've used it in the dim and distant past and it's not to be recommended
> as it is right at the limits of usability (very unstable image, incredibly
> tiny sweet spot and so on). I would compromise on the quality of the
> speakers so that I could buy eight, rather than buy only six better ones
> (ditto for the audio interface and amps)
>
>  Dave (signing off for now as I'm off on vacation, hurrah!)
>
>
> --
>  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*/
> /* Heslington  Fax   01904 432450*/
> /* York YO10 5DD */
> /* UK   'Ambisonics - Component Imaging for Audio'   */
> /*
> "http://www.york.ac.uk/inst/**mustech/3d_audio/"
> */
> /***
> **/
>
> __**_
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/**mailman/listinfo/sursound
>
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Re: [Sursound] Ambisonics not on the cheap

[Ben Bloomberg]

Ok, at the behest of Jörn, I am going to send some links to various things.
Feel free to tear them apart! Also for what it's worth, the setup pictured
in the first article is about the worst sounding rig we've put together. The
speakers are really not that bad, though. I wish we had given them some
other photos.

http://blog.bowers-wilkins.com/sound-lab/the-future-of-surround-sound-from-mit/
http://bot23.com/tag/ambisonics/

We also had a paper in NIME this year that has a description of our current
project:
http://www.nime2011.org/proceedings/papers/J01-Jessop.pdf

Ben



On Fri, Jul 29, 2011 at 12:05 PM, Ben Bloomberg  wrote:

> Hi Everyone,
>
> Well, now that Sarang has spoken up, he's given me the courage as well.
>  I've been lurking on this list for several months now. Just to be clear, I
> think you're all high-priestesses!! It's been incredible to read the
> discussion (most of which has been way over my head, but I try to slog
> through) and hear what people have to say.
>
> My experience with ambisonics is odd, having sort of jumped into the deep
> end after suggesting ambisonics as a solution for a school project 3 years
> ago (with little knowledge of math, let-alone spherical harmonics). We ended
> up piecing together an 8 channel system for a 1700 seat hall that was not
> accurate in the slightest. However, my professor and the sound designer were
> both blown away by the precision of what was essentially glorified panning,
> despite the large hall. We used the ICST Max 4.5 externals.
>
> Since then, we've implemented our own parallel processing audiounit/OSC
> based system and we use ambisonics as an abstracted panning system for
> synthetic sound environments on most of the performances we put together. My
> professor loves the idea that we can encode something and play it back on
> any speaker configuration with relatively consistent results (given the
> halls we play are vastly different anyway, usually the ambisonic
> configuration is the least of our concerns).
>
> So my experience is almost purely empirical/trial-and-error. We've done
> systems for 3 people and systems for 2000 people, some very high density and
> some very low density. Mostly we just put up speakers and listen to see what
> we think, or take the live-sound fudging approach of blurring multiple
> systems together for different seating areas. Having taken some more math
> classes, things are starting to become a bit clearer now, but I'm still
> learning (that never stops!). Some of our equipment sponsors have asked me
> to write things about the projects for them, which have ended up on the
> internet and probably contain some mis-information.
>
> That said, I have a two questions and an offer.
>
> First, I'm really interested in ambisonic decoder and encoder weightings.
> From what I read, they provide a means to used fixed-point processing.
> However, playing with them results in vastly different sounding results. I
> made a really simple script to visualize the phase of a signal at the output
> of decoders with different weightings, but I'm not sure I understand what
> I'm seeing or how that has an effect on what we hear. I will try to make a
> comped image of all the plots and send it out.
>
> Second, we will be putting up a fairly large ambisonic system hanging from
> a 20 by 20 foot truss in the next month. I have heard that the more speakers
> you can add to a system, the better it will sound. Is that true? With higher
> speaker counts >20, we've had the best results by removing decoder
> weightings. We seem to hear a better sense of localization for our synthetic
> recordings. I had an idea that this changes the decay rate of "cosines" in
> what is essentially a vector projection, so each speaker occupies a smaller
> slice of the surround field "pie". Is that anything close to correct?  What
> would be the optimum number and configuration of speakers for a 20' dome?
> (assuming equipment is not an issue)
>
> Ok, now the offer! Being at a place that has a lot of resources, but little
> time and man-power, I wanted to offer up our inventory of equipment to the
> community. We have about 90 speakers that we keep around for projects or
> touring. If anyone is working on a project that could benefit from extra
> speakers, drop me a line. If we've got the gear free, you're welcome to it.
> It's a mish-mash of Bowers and Wilkins, Duran Audio Axys, and Mackie 824s.
> We drive our systems with MOTU, RME, and SSL MADI interfaces. Also, if
> people are interested in testing things on this 20x20 dome and want to come
> down to Boston (it'll be up in September and October), we'd be honored to
> have you 

Re: [Sursound] Subject: Re: Distance perception

[Robert Greene]

Talk about mumbo jumbo!

Sounds to me as though all this(that is described)  would do is to create 
confusion.

If people  like it, fine. But it is surely not suppressing HRTFs--
it is just presenting a sort of diffuse effect. The HRTFs
are still there--they are just operating on a confused and confusing 
situation.


So what?  Bose (and widely spaced omni recording peopple!)latched on to 
something a long time ago--a lot
of people apparently  do not like direct radiation stereo and prefer a lot 
of sound arriving in odd ball ways. Fine by me."If that's your pleasure, 
go on, live that way".
 But no mumbo jumbo  explaining 
why some people like confusion is needed.


Incidentally, turning the cones inside out probably  makes them work
badly  but it does 
not actually change their radiation pattern

all that much except in very  high frequencies(where
they should not be being used anyway).

Robert

On Fri, 29 Jul 2011, Justin Bennett wrote:



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.


the cones of the speakers are turned inside out so that they
become "omni" (ish) sources. Each side has two drivers. As far as I
remember they are twisted at 90 degrees with respect to each
other - e.g. one is pointing sideways towards the centre stage, one
is pointing downwards towards the floor. According to the inventor
this supresses our brain's use of HRTFs to locate the source, thereby
managing to create a virtual image between two vertically spaced speakers.

(I apologise if I'm quoting him wrongly, but it was something like that)



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


ja, verschrikkelijk, toch? En dan ook nog de Ambisonic / Calrec Logo 
inpikken!


groeten, Justin.


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[Sursound] Subject: Re: Distance perception

[Justin Bennett]

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.


the cones of the speakers are turned inside out so that they
become "omni" (ish) sources. Each side has two drivers. As far as I
remember they are twisted at 90 degrees with respect to each
other - e.g. one is pointing sideways towards the centre stage, one
is pointing downwards towards the floor. According to the inventor
this supresses our brain's use of HRTFs to locate the source, thereby
managing to create a virtual image between two vertically spaced  
speakers.


(I apologise if I'm quoting him wrongly, but it was something like that)



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


ja, verschrikkelijk, toch? En dan ook nog de Ambisonic / Calrec Logo  
inpikken!


groeten, Justin.


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[Sursound] Ambisonics not on the cheap

[Ben Bloomberg]

Hi Everyone,

Well, now that Sarang has spoken up, he's given me the courage as well.
 I've been lurking on this list for several months now. Just to be clear, I
think you're all high-priestesses!! It's been incredible to read the
discussion (most of which has been way over my head, but I try to slog
through) and hear what people have to say.

My experience with ambisonics is odd, having sort of jumped into the deep
end after suggesting ambisonics as a solution for a school project 3 years
ago (with little knowledge of math, let-alone spherical harmonics). We ended
up piecing together an 8 channel system for a 1700 seat hall that was not
accurate in the slightest. However, my professor and the sound designer were
both blown away by the precision of what was essentially glorified panning,
despite the large hall. We used the ICST Max 4.5 externals.

Since then, we've implemented our own parallel processing audiounit/OSC
based system and we use ambisonics as an abstracted panning system for
synthetic sound environments on most of the performances we put together. My
professor loves the idea that we can encode something and play it back on
any speaker configuration with relatively consistent results (given the
halls we play are vastly different anyway, usually the ambisonic
configuration is the least of our concerns).

So my experience is almost purely empirical/trial-and-error. We've done
systems for 3 people and systems for 2000 people, some very high density and
some very low density. Mostly we just put up speakers and listen to see what
we think, or take the live-sound fudging approach of blurring multiple
systems together for different seating areas. Having taken some more math
classes, things are starting to become a bit clearer now, but I'm still
learning (that never stops!). Some of our equipment sponsors have asked me
to write things about the projects for them, which have ended up on the
internet and probably contain some mis-information.

That said, I have a two questions and an offer.

First, I'm really interested in ambisonic decoder and encoder weightings.
>From what I read, they provide a means to used fixed-point processing.
However, playing with them results in vastly different sounding results. I
made a really simple script to visualize the phase of a signal at the output
of decoders with different weightings, but I'm not sure I understand what
I'm seeing or how that has an effect on what we hear. I will try to make a
comped image of all the plots and send it out.

Second, we will be putting up a fairly large ambisonic system hanging from a
20 by 20 foot truss in the next month. I have heard that the more speakers
you can add to a system, the better it will sound. Is that true? With higher
speaker counts >20, we've had the best results by removing decoder
weightings. We seem to hear a better sense of localization for our synthetic
recordings. I had an idea that this changes the decay rate of "cosines" in
what is essentially a vector projection, so each speaker occupies a smaller
slice of the surround field "pie". Is that anything close to correct?  What
would be the optimum number and configuration of speakers for a 20' dome?
(assuming equipment is not an issue)

Ok, now the offer! Being at a place that has a lot of resources, but little
time and man-power, I wanted to offer up our inventory of equipment to the
community. We have about 90 speakers that we keep around for projects or
touring. If anyone is working on a project that could benefit from extra
speakers, drop me a line. If we've got the gear free, you're welcome to it.
It's a mish-mash of Bowers and Wilkins, Duran Audio Axys, and Mackie 824s.
We drive our systems with MOTU, RME, and SSL MADI interfaces. Also, if
people are interested in testing things on this 20x20 dome and want to come
down to Boston (it'll be up in September and October), we'd be honored to
have you as guests!

Best wishes,
Ben
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Re: [Sursound] Ambisonics on the cheap?

[Dave Malham]

On 29/07/2011 11:30, Michael Chapman wrote:

Now I would like to construct a higher-order sound system, ideally with
consumer-level (and consumer-priced) components. I don't need a big
dynamic range, high power, or the best sound fidelity possible, I just
need a working prototype. This is the part I have found very little
information on in my research�

My understanding is that 8 channels is the minimum needed for stable 3-D
Ambisonics (rather than planar surround).

There was a recent reminder, on this list, within the last month, that
one could use 6 channels (the mid points of the faces of a cube).
I've never heard anyone say they've done it, let alone say it was 'nice'.
(The engineering would, also, not be fun ... though you are not obliged
to place speakers mid-wall/ceiling/floor ... you can tilt the cube!)
So I'd stick to eight unless you are really adventurous.

We've used it in the dim and distant past and it's not to be recommended as it is right at the 
limits of usability (very unstable image, incredibly tiny sweet spot and so on). I would compromise 
on the quality of the speakers so that I could buy eight, rather than buy only six better ones 
(ditto for the audio interface and amps)


  Dave (signing off for now as I'm off on vacation, hurrah!)

--
 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*/
/* Heslington  Fax   01904 432450*/
/* York YO10 5DD */
/* UK   'Ambisonics - Component Imaging for Audio'   */
/*"http://www.york.ac.uk/inst/mustech/3d_audio/"; */
/*/

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Re: [Sursound] Ambisonics on the cheap?

[Michael Chapman]

> Hi everyone,
>
> I've been lurking for only a day, but Sampo's note gives me the courage to
> go ahead and ask the first question I was hoping this group might help me
> answer.
>
See you've already had some good replies.
But, I'll throw in my experiences ... some of which have been
at the really cheap end of things ;-(>

> I am interested in experimenting with periphonic sound synthesis using
> Ambisonics and (likely) Matlab, for research purposes. I've got a grasp on
> the software side of things to do this, and already can pipe multichannel
> sounds generated in Matlab to a standard 5.1 receiver.
>
Beware Condon-Shortley Phase and Matlab.
Ambisonics doesn't use it, quantum physics does. (You get some of
the rotations oing backwards ...)

> Now I would like to construct a higher-order sound system, ideally with
> consumer-level (and consumer-priced) components. I don't need a big
> dynamic range, high power, or the best sound fidelity possible, I just
> need a working prototype. This is the part I have found very little
> information on in my research�
>
> My understanding is that 8 channels is the minimum needed for stable 3-D
> Ambisonics (rather than planar surround).

There was a recent reminder, on this list, within the last month, that
one could use 6 channels (the mid points of the faces of a cube).
I've never heard anyone say they've done it, let alone say it was 'nice'.
(The engineering would, also, not be fun ... though you are not obliged
to place speakers mid-wall/ceiling/floor ... you can tilt the cube!)
So I'd stick to eight unless you are really adventurous.

> From my Mac, I can easily output
> up to 8 channels of lossless PCM audio over HDMI or optical Toslink. So it
> seems like it should be possible, in principle, to assemble a budget
> system -- the question is what kind of affordable receiver/amp would be
> appropriate?
>
> The home cinema/gaming market offers several 7.1 systems these days, but I
> imagine the subwoofer channel would likely be band-limited with different
> amplifier circuitry than the other channels.

In my early days I used a USB 5.1 card.
Subjectively I concluded all six channels were identical ... but never
measured them.


> There are also some 9.2
> receivers available. I'm not clear how to input more than 8 channels to
> these receivers, given that they all take HDMI/Toslink inputs, Dolby
> TrueHD etc are all 7.1, as far as I know, and they don't normally have
> discrete analog inputs. So I'm not sure if an 8-channel digital input
> would imply one channel is destined for a subwoofer as expected for a 7.1
> system. And, otherwise, if these systems do funky in-receiver processing
> to generate 9.2 sound from 8 input channels, then that certainly seems
> incompatible with Ambisonics�
>
> Are any of these receivers an option? Any other suggestions? Of course, I
> don't care about the video switching capabilities, etc., the multiplexed
> digital input just needs to be decoded and sent to 8+ speakers somehow.
>
> Otherwise, if there's a Firewire or USB solution, I'd be happy to hear
> more about those as well.

I use a MOTU Traveller. An expensive firewire solution.
(The reason is that it is good for TetraMic recordings ...).
That gives 8 analogue outs, with another 8 by ADAT (you need
a cheap (dare I say Behringer?) AdAT->-analogue box).

If I was staring again, just for playback, I'd probably grit my teeth
and buy a 24 channel ?Hammerfall card to use on Linux ... but
that just proves the point that so many of the answers depend
on what Operating System you put in the question ;-)>

___

My first set-up was ... just to show how naff one can be ...
four pairs of computer monitors.
The results were pleasant (pleasant enough, that i was
disappointed when I heard some of the same pieces
on a professional/research system;-)>

But that did iliustrate the 'infrastructure' expense ... I
decided to install a mains socket in each corner of the
ceiling: I did that myself, but the materials cost more
than the speakers.

Recently, with a student, we created a whole variety of
rigs.
The bottom end one was a 'kiosk':
A free-standing set of tubes, that gives a 1.1 metre cube
(on legs) that you can 'walk into'. The idea is not original,
was on this list some long time back (apologies to
inventor, I've forgotten who!).
Again, using computer speaker pairs.

We tried DRC techniques on that to 'improve'
performance, but the corrections were worse than
au naturel.
Still it gives a interesting experience.
Certainly for non-music (non classical music)
such as jet planes buzzing about, firework displays
--where the listener expectation is not of delicate
harpsichord playing-- it is very good.


If you want to play --sorry, do preliminary studies-- then
computer speakers are 'fun'.

After that, I think you hav two big questions to answer:

- What OS am I wiling to use.
(I think there is only one answer to that, but I won't start
an OS-war on this thread;-)

Re: [Sursound] Ambisonics on the cheap?

[Dave Malham]

On a mac it is very easy to create an aggregate audio device from several different units, even if 
you can't physically lock their clocks together - which is, of course, the ideal way to do it. You 
chose one of them as the master device which supplies the clock and OSX itself automatically handles 
any needed sample rate conversion. Ok, it's not ideal but it does mean it is possible to use several 
el cheapo USB soundcards together to make a multichannel output device.


 Dave

On 29/07/2011 04:35, Marc Lavallée wrote:

Sarang,

Here's my non-professional solution for 16 channels:

- One recent PC with 2 free PCI slots
- Two 7.1 PCI sound cards (16bit / 48KHz is enough)
- Linux (or OSX) with Jackd
- Basic soldering skills
- A bit of lecture and some luck :
http://quicktoots.linuxaudio.org/toots/el-cheapo/
http://www.jrigg.co.uk/linuxaudio/ice1712multi.html

An easier (but more expensive) solution is to use M-Audio Delta 1010
PCI cards and interconnect their external sync, for up to 4 cards (and
32 channels).

For the amplifiers you can use D-class (or T-class) stereo (or quad) amp
modules and one (or more) big switching PSU with a few big filtering
capacitors (for a cleaner supply).

--
Marc


Fri, 29 Jul 2011 02:23:22 +0200,
"Sarang S. Dalal"  wrote :


Hi everyone,

I've been lurking for only a day, but Sampo's note gives me the
courage to go ahead and ask the first question I was hoping this
group might help me answer.

I am interested in experimenting with periphonic sound synthesis
using Ambisonics and (likely) Matlab, for research purposes. I've got
a grasp on the software side of things to do this, and already can
pipe multichannel sounds generated in Matlab to a standard 5.1
receiver.

Now I would like to construct a higher-order sound system, ideally
with consumer-level (and consumer-priced) components. I don't need a
big dynamic range, high power, or the best sound fidelity possible, I
just need a working prototype. This is the part I have found very
little information on in my research…

My understanding is that 8 channels is the minimum needed for stable
3-D Ambisonics (rather than planar surround). From my Mac, I can
easily output up to 8 channels of lossless PCM audio over HDMI or
optical Toslink. So it seems like it should be possible, in
principle, to assemble a budget system -- the question is what kind
of affordable receiver/amp would be appropriate?

The home cinema/gaming market offers several 7.1 systems these days,
but I imagine the subwoofer channel would likely be band-limited with
different amplifier circuitry than the other channels.  There are
also some 9.2 receivers available. I'm not clear how to input more
than 8 channels to these receivers, given that they all take
HDMI/Toslink inputs, Dolby TrueHD etc are all 7.1, as far as I know,
and they don't normally have discrete analog inputs. So I'm not sure
if an 8-channel digital input would imply one channel is destined for
a subwoofer as expected for a 7.1 system. And, otherwise, if these
systems do funky in-receiver processing to generate 9.2 sound from 8
input channels, then that certainly seems incompatible with
Ambisonics…

Are any of these receivers an option? Any other suggestions? Of
course, I don't care about the video switching capabilities, etc.,
the multiplexed digital input just needs to be decoded and sent to 8+
speakers somehow.

Otherwise, if there's a Firewire or USB solution, I'd be happy to
hear more about those as well.

Thanks in advance!

Sarang


On Jul 29, 2011, at 1:06 AM, Sampo Syreeni wrote:


On 2011-07-28, Carsten Bohn wrote:


I usually don't comment very often cause most threads are "out of
my league knowledge-wise" ;-) [...]

It just came to my mind, I've been seing these kinds of comments
alot on-list. All too many, in fact. On most lists I've been on,
they are a sure sign that the list is less accessible than it could
be. And usually not because of the technical level of discussion,
but because for one reason or another, "it's difficult to get into
the discussion". Because of the perception that there's an
established in-crowd that doesn't really want you, or somesuch
other sociological reason.

So I hope I'm not too much out of line if I say, that's not how it
works around here. Please don't hesitate to participate, even by
just asking about what the hell all that ambisonic high priestess
shit is about. I mean, I at least didn't, and that's pretty much
the only reason I ever got even this far in understanding surround,
or that high priestess shit. If you look a few years back, you'll
see I've made a total ass of myself over and over again, often
without even realizing it, before I finally started to grasp what
this stuff is about. And I've never seen a list more accommodating
of such newbie stuff (or the not-so-newbie) than this one.

Surround sound is a broad and variegated subject, with altogether
too little easily accessed reference material lieing around.
Ambisonic as part of it is 

Re: [Sursound] [meta] about the level of discussion, and accessibility

[Dave Malham]

Can I ask a question? Where are the ambisonic high priestesses? Where have you 
hidden then? :-)

 Dave

On 29/07/2011 00:06, Sampo Syreeni wrote:

On 2011-07-28, Carsten Bohn wrote:

I usually don't comment very often cause most threads are "out of my league knowledge-wise" ;-) 
[...]


It just came to my mind, I've been seing these kinds of comments alot on-list. All too many, in 
fact. On most lists I've been on, they are a sure sign that the list is less accessible than it 
could be. And usually not because of the technical level of discussion, but because for one reason 
or another, "it's difficult to get into the discussion". Because of the perception that there's an 
established in-crowd that doesn't really want you, or somesuch other sociological reason.


So I hope I'm not too much out of line if I say, that's not how it works around here. Please don't 
hesitate to participate, even by just asking about what the hell all that ambisonic high priestess 
shit is about. I mean, I at least didn't, and that's pretty much the only reason I ever got even 
this far in understanding surround, or that high priestess shit. If you look a few years back, 
you'll see I've made a total ass of myself over and over again, often without even realizing it, 
before I finally started to grasp what this stuff is about. And I've never seen a list more 
accommodating of such newbie stuff (or the not-so-newbie) than this one.


Surround sound is a broad and variegated subject, with altogether too little easily accessed 
reference material lieing around. Ambisonic as part of it is doubly so, since it's so poorly 
known. That's then precisely why these kinds of lists are there: not only to discuss esoterica 
between those already in the know, but also to keep up the culture. Not least by inducting new 
folks into it.


So again, and with due reference to the Real Practitioners and the Tenured Gurus around here, I 
think people shouldn't apologize unless they royally fucked up. Instead they should use those two 
lines to pose an interesting question. And of course the next half a decade to become the guru in 
the guru's place. ;)


--
 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*/
/* Heslington  Fax   01904 432450*/
/* York YO10 5DD */
/* UK   'Ambisonics - Component Imaging for Audio'   */
/*"http://www.york.ac.uk/inst/mustech/3d_audio/"; */
/*/

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Re: [Sursound] Distance perception

[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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