Re: ssr and alternatives

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* Brandon Hale <bthaleproductions@xxxxxxxxx> [2021-03-01 16:53]:
> Thanks for all of this good info Peter. I didn't know about the sursound
> mailing list, and will experiment with that pd library you told me about.
> This is all a learning experience for me.
> 
> When you say 5th order 3d, wouldn't that only be 36 loudspeakers?

The basic relation you have to consider is this classic one:

In order to reproduce a 2D soundfield (planar, loudspeaker ring) of
order N you need at least L loundspeakers
(N+1)^2 =< L
so for 5th order it would be 6^2 = 36 as you mention, but thanks to the
greater-equal sign you can always use more speakers. You will not
exploit a possibly higher order, but as Fons remarked, there might not
be much spatial resolution to gain.

Give it a try, perhaps subscribe to the pd list for more help with the
objects if needed, and take a listen.

cheers, P

> 
> Brandon Hale
> 
> On 3/1/21 10:12 AM, Peter P. wrote:
> > Hi,
> > 
> > * Brandon Hale <bthaleproductions@xxxxxxxxx> [2021-03-01 15:37]:
> > > > 1. Computing decoders for arbitrary speaker positions is still some
> > > > sort of 'black art' unless the postions form a more or less regular
> > > > grid. Don't believe everything about automated methods claiming to
> > > > do this.
> > > This is good to keep in mind. Have you ever seen the ICST plugins for max
> > > msp? Those objects have a method of putting in xyz coordinates for its
> > > ambisonic decoders.
> > I think Fons means that building "good" decoders is some sort of a black
> > art for a given (non-regular) layout. All technical solutions allow xyz
> > coordinate entry and come up with a static decoder matrix (this is
> > really just a matrix of static floating point numbers, you could write
> > this on a beer mat if pubs were open).
> > 
> > > Where I work at, we use this to output ambisonics to all
> > > of our spaces at ICAT, including the Cube
> > > <https://icat.vt.edu/studios/the-cube.html>. It does work well, but I do
> > > know of colleagues who complain about how "fuzzy" the spatialization is. Do
> > > these kinds of decoders fudge the decoding to achieve output? I really want
> > > to find something like this for Linux.
> > If you want to get the full craze of kinds of decoder discussions you
> > might want to sign up to the sursound mailing list.
> > 
> > > > 3. I really can't imagine anything done with speakers that would
> > > > require 7th order. Even with 4th or 5th order, if you have enough
> > > > speakers to use that, the angles between the speakers are so small
> > > > that even phantom images in between speakers are for all practical
> > > > purposes perfect.
> > > The reason I ask is because I want to find a Linux-based system for the
> > > Cube, which has 138 speakers arranged in a rectangular prism. I am
> > > constantly looking for a way to decode ambisonics to it without having to
> > > use max msp.
> > Use the Pd objects I mentioned and go for 5th order 3D which will create
> > output signals for all 138 speakers. Also correct the
> > speaker distances with short delays and compensate for level differences
> > by ear or by using a SPL meter.
> > 
> > > I have not had much luck finding something standalone or in pd.
> > > Maybe I should learn supercollider? It can be hard to find decoders that go
> > > to 10th or 11th order.
> > Again, its not a question of max vs pd vs sc3 vs csound, but of the
> > usefulness of doing it. If you already have these 138 speakers mounted,
> > then configure one of the mentioned solutions to use the corresponding
> > order and have a listen.
> > 
> > > > 4. To do anything similar to WFS 'internal sources' (i.e. in front
> > > > of the speakers) in any practical frequency range, you'd need the
> > > > same amount of speakers as WFS would, and of course the required
> > > > very high order input.
> > > At work, I may be getting hold of 64 AVB speakers that I can arrange in a
> > > line to experiment with WFS. The great thing about this is the speakers are
> > > AVB, and not Dante. I may be able to play with these speakers on Linux. Of
> > > course, there is at least one WFS processor (is that the right term?) that I
> > > know of in max. But, I find max too annoying and locked down for real use,
> > > and of course I want to do it on Linux!
> > I managed to get ssr~ to run as a pd external a few years ago.
> > Furthermore be aware that the distance between the speakers determines
> > the upper frequency limit. I don't know if AVB introduces some latency
> > between speakers. Fons might know something about this perhaps?
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