Hello,

Theoretically, with Ambisonics any configuration of loudspeaker outside a
listening spot, with speaker in distance which Produce a kind of plane
wavefield is suitable for Ambisonics. The better the speaker sound, the
better the whole system, but it is robust for individual speaker differences
as long you calibrate it and has a way better energy distribution than vbap
for small speaker. Of course, if speaker missing on some side there can be no
sound from there, but placing virtual speaker for decoder makes smoother
transistions to this direction and so on, best follow the advices in
Ambisonics Decoder Toolbox [ADT] by Aaron J. Heller [1] to calculate a
decoder.

Anyhow we are on the way for a Pd Ambisonics library for "Imperfect Ambisonics
Systems". Which also means in rooms with "bad acoustics" or any other odd
places, mixed speaker setup and so on. You are invited to join to extend this
simple abstraction lib.

https://git.iem.at/pd/acre-amb

By the way it supports multichannel patching with names as buses and so on, to
reduce Pd-cabling. (Note it is in development and should be stable end of
summer).

Next week we want to finalize the new Ambisonics domeplayer [2] for AAAS
(affordable autonomous Ambisonics system) for the workshop in September (and
publish it on git).

[1] https://bitbucket.org/ambidecodertoolbox/adt.git )
[2] https://iaem.at/kurse/projekte/aaas2/iemkit_6ch.jpg

rfc
winfried

Am Samstag, 24. Juni 2017, 11:26:59 schrieb Pierre Guillot:

Hi Jesse,

With Ambisonics, ideally your loudspeakers should discretize perfectly a
sphere, you should have your head at the exact center of this sphere, etc.
and perhaps if you forget that your head interferes and the loudspeakers
don't generate plane waves you'll be able to reconstruct a coherent sound
field... But to avoid these restrictions (because very few people have a
full sphere of loudspeakers - or want to ask the audience to be completely
crushed at the center of the sphere) there are several techniques :
optimizations of the energy and/or velocity vectors, optimizations of the
decoding, etc. The problem is that none of the solutions are completely
generic. Your choice must be driven by your approach and your goal.The
advantage of Ambisonics lies in its intermediary representation of the
sound field that allows to apply transformations (rotation or whatever) and
to decode for different loudspeakers configurations. But if you just want
to spatialize individuals point sources, you can also use VBAP that is
perhaps much more accessible. Nevertheless yes, you can surely find a way
to decode the sound field for two ring of loudspeakers with Ambisonics (we
can discuss it if you want). And one good rule is just to avoid placing
sources where the loudspeakers are missing. I don't know if I really answer
the question, I hope a bit :)

Cheers,

Pierre

Date: Fri, 23 Jun 2017 16:19:29 -0600
From: jmejia@anestheticaudio.com
To: pd-list@lists.iem.at
Subject: [PD] HOA / spatialization approaches for a hemisphere
Message-ID: <3149263781acf8439b762eef943d60e5@anestheticaudio.com>
Content-Type: text/plain; charset="utf-8"

Hi List,

I'm putting together a 32 channel HDLA and looking for spatialization
advice. The configuration will be two rings, one higher than the other,
and I've been thinking a bit smaller/closer to approximate a hemisphere.
But that's flexible - they could be parallel rings if it simplifies
things.

I have some (limited) experience using HoaLibrary + PD for 2D ambisonics
- so my initial thought was to try the 3d externals there - however I'm
not sure if it actually makes sense to build an abstraction setup for a
sphere of twice as many channels while limiting access to the upper
hemisphere only. I'm assuming there would be some problems with that
approach.

I found a few papers on mixed-order ambisonics - by Chris Travis and
also the AmbiX crew - but I'm not sure if there's away to implement that
stuff with HoaLibrary. I'm also open to using different software if
something else is recommended instead.

Thanks for any advice!

-Jesse