[LAU] ssr and alternatives

Peter P. peterparker at fastmail.com
Mon Mar 1 16:12:20 CET 2021


* Brandon Hale <bthaleproductions at gmail.com> [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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