Hi Martin (and Eric!),
One very simple thing I would do, before doing anything else, with any
system that's playing, as we say, silly bu..ers, is just to play a well
localisable sound out of each speaker (on its own) in turn and check that
(a) it's coming out of the speaker it should (all connections are correct)
and that it sounds like it's coming from the direction you think it should
(acoustics not too disruptive). If you really want to be picky, stick a
soundfield type mic at the nominal centre point and check correct B format
signals are produced for each speaker location at the same time. Only then
start worrying about decoders, plugin connections and the rest. I once
worked out that in a simple 1st order system driving a cube of speakers,
there are 16 million ways of it going wrong, without counting individual
component failures in amps, etc. Of course, lots of these ways of going
wrong are self cancelling (*both* ends of speaker cable can be connected
wrongly, cancelling out the polarity inversion, for instance) which is a
darn good job otherwise our job would be near impossible. So, checking the
simple things first is a good way to avoid delving around the complex..
Good luck
Dave
On 23 March 2016 at 18:13, Eric Benjamin <eb...@pacbell.net> wrote:
> "In both cases the sound was coming from seemingly random places, and a
> number of positions went practically silent."
> What is needed, not just for you, but for everyone, is a comprehensive set
> of test files. It may be that your loudspeakers aren't where the system
> thinks they are (wrong speaker assignments), or it may be that that the
> decoder is doing the wrong thing. I have more extensive versions of test
> files, including "with height" like the eight directions files on
> Ambisonia., featuring the voice of the lovely Haley Jo. I could upload
> those if anyone would like them.
> You can then use metering to determine if the specific sounds light up the
> speaker(s) that they should.
>
> Sent from Yahoo Mail on Android
>
> On Tue, Mar 22, 2016 at 1:18 PM, Jörn Nettingsmeier<
> netti...@stackingdwarves.net> wrote: On 03/22/2016 07:49 PM, Martin
> Dupras wrote:
> > Today I tried playback sources in third order Ambisonics on a 8+6+1
> > hemispheric speaker array using Reaper. It didn't quite work as
> > intended so I'm trying to figure out where I've gone wrong.
> >
> > I was using the Blue Ripple TOA-Core panner plugin to position the
> > sound. I understand that Blue Rippler plugins use the Furse-Malham
> > convention.
> >
> > The only decoders that I could find to decode to my specific array
> > (using coefficients that I calculated using the Ambisonics Decoder
> > Toolkit) were the Ambix Plug-ins and AmbDec.
> >
> > I tried Ambix first, which I understand uses the ACN ordering
> > convention. I tried re-ordering the channels based on information that
> > I found here:
> https://en.wikipedia.org/wiki/Ambisonic_data_exchange_formats#ACN.
> > But that didn't really work.
> >
> > I then tried to run 16 outputs out of Reaper into Jack, and from Jack
> > into AmbDec, again using my ADT-calculated coefficients. I understand
> > that AmbDec uses the Furse-Malham convention, so I would have thought
> > it was compatible with the output of the Blue Rippler plugins. But
> > again, that didn't really work well at all.
> >
> > In both cases the sound was coming from seemingly random places, and a
> > number of positions went practically silent.
>
> To debug erratic panning behaviour, start with first order, verify, and
> work your way up from there. To make sure the error is not in your
> calculated coefficients, try to use a known-good decoding matrix that
> approximates what you have, before feeding in your optimized one.
>
> With Ambdec, weird things can happen if you connect several ins at the
> same time using some graphical client, because the order shown in for
> example qjackctl is lexical, whereas the internal order is different. So
> you will end up with garbled connections. You can feed an ACN signal
> into ambdec succesfully if you choose SN3D input scaling _and_ manually
> connect the inputs correctly.
> This wikipedia article
> https://en.wikipedia.org/wiki/Ambisonic_data_exchange_formats
> has some information on that, and other pitfalls when interfacing
> different formats.
>
>
> All best,
>
>
> Jörn
>
>
>
> --
> Jörn Nettingsmeier
> Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
>
> Meister für Veranstaltungstechnik (Bühne/Studio)
> Tonmeister VDT
>
> http://stackingdwarves.net
>
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--
As of 1st October 2012, I have retired from the University.
These are my own views and may or may not be shared by the University
Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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