Generally, over the years, I've reckoned on 2 * (M + 1) for horizontal rigs and 2 * (m + 1) * (m +
1) for with height rigs, as practical, rather than theoretical, minima, at least for lower orders (m
<= 3). The theoretical minima are, in my experience, incredibly unstable in practise, especially for
first order (3 and 4 respectively). Note that this is for regular arrays. If you have too many
speakers, as others have pointed out, you run into problems with comb filtering, though the "spatial
dithering" caused by local reflections and other inaccuracies in placement can ameliorate this. I
keep meaning to try Angelo's idea of convolution with a short, exponentially decaying, noise burst
to see if this helps - one of these days...
Dave
On 09/07/2012 14:50, Richard Furse wrote:
IMHO it depends on how you're generating your decoder - using a fairly
"evenly" spaced speaker layout that's roughly consistent with the order
means that all the matrices in the maths end up well-behaved if you do a
fairly simple matrix inversion. HOWEVER, it isn't obvious that this is the
best way to do things in general, and can break quite badly for irregular
rigs, e.g. if you have too few or many speakers for the order you're using,
or if your speakers aren't spread "evenly".
... so, if you're generating your decoder with relatively simple approaches
(e.g. lightly conditioned pseudo-inverse), you'll probably get best results
with a rig and order that are at least roughly in line in channel count. But
I consider this to be a limitation introduced by the decoder method, rather
than an intrinsic necessity. (Obviously, this is a lightly veiled plug for
the Rapture3D decoder ;-)
Best wishes,
--Richard
-----Original Message-----
From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu]
On Behalf Of Augustine Leudar
Sent: 09 July 2012 12:32
To: Surround Sound discussion group
Subject: Re: [Sursound] higher order ambisonics over 8 to 10 loudspeakers
I cant remember the formula off hand but it important ,I am told, to use
the correct number of speakers for the order you are using - so if you use
too many speakers for the order that can also muddy up the localisation.
Someone will enlighten us Im sure but is it :
the order number + 1 squared ?
If thats correct you should use 9 speakers for second order ?
cheers,
Gus
On 9 July 2012 12:17, Garth Paine <ga...@activatedspace.com> wrote:
Hi everyone
I have been gathering lots of ambient field recordings in A-Format for a
few years using my SPS200 Soundfiled mike and a 788T. I have experimented
with playback over an 8 channel circle, and also with 3 circles of 8 at
different heights (roof, 3M, 1M), and some other arrangements. I am
currently working on 2 dance works where I want to use some of this
material and also spatialise other synthesized material. I have 8 Meyer
UPJ-1 to use in the space and may be able to get 2 more for height (not
certain adn these may not be available at all venues).
I would like to achieve better localization than I have found easy to do
using lower order playback and wonder if it is possible to undertake
higher
order playback with only 8 speakers? ALso would it make sense to have the
speakers in the circle at different heights - would that allow a hint of
the height information (I would tell the plugin where they are), or just
distort the render?
Thanks in advance for your advice
Cheers,
Garth Paine
ga...@activatedspace.com
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