Ambisonics

[umläute]

"sfogar at libero.it" wrote:
> 
> Wonderful !
> 
> Dear Iohannes, Can you please explain better what is needed on the
> hardware side ?
> 
> The patch needs 16 outputs, you said, so a rme9652 hammerfall soundcard
> is needed.
> 
> OK, I have an Rme Hammerfall, a Swissonic 8 ch. DAC, a Behringer 2004
> mixer.
> 
> But I think I need an additional 8 ch ADAT DAC.

yes
the patch is designed for 16 outputs, so you have to get 16 channels out
of the computer somehow; since the hammerfall card does so, the only
problem is to convert the 16 digital channels to 16 analogue. therefore
you'll need 2 8ch-ADAT-DACs.

> 
> These 16 ch. have to be mixed ? How ?
> 

the outputs are designed as direct to speaker channels (in fact, in
vienna we do not even use a mixer:: hammerfall => 2* fostex vc-8 DAC =>
amplifiers => speakers 

on the other hand, you certainly can use your mixer to route through
your signals...

> Which kind of speaker are required ? Which ones did you use in Wien ?
> 
we use 16 jbl Control-1C; but that's just our personal choice and if you
cannot afford such high-end, any other hifi-speakers will do


> Is it possible to have some ambisonics with only 8 channels, changing
> the patchers a little bit  ?
> 

speakers 1..4 are up, spk 13..16 are down, while spk 5..12 are vertical
only; 
so the easiest way to get an 8-channel version would be to map the
output channels 5..12 of the current patch somehow to the dac~ 1..8;
since both ouput-channel "LS<n>" and dac-channel "<m>" are passed to the
speaker~ object as creation arguments it should be fairly easy:: instead
of "speaker~ LS1 1" this should read then "speaker~ LS5 1" and so on;

so you lose the 3rd dimension (no z-axis) and have 3rd-order ambisonic
in the horizontal plane; be sure to keep the elevation theta of all
virtual sources at 0 (so do not make 3dimensional moves in a
2dimensional room)

mfg.dfa.r
iohannes

> Please let me know, I'm really interested about this !
> 
> Cheers
> 
> Alessandro Fogar
> 
> forum::für::umläute wrote:
> >
> > i have put a spatialization-engine that uses ambisonic on our
> > ftp-server:: ftp://iem.mhsg.ac.at/pd/Patches/ambisonic
> >
> > features :
> > 3d-ambisonic (horizontal plane :: 3rd order ambisonic; vertical plane
> > 1st order ambisonic)
> > modular architecture :: for easy implementation of any number of
> virtual
> > sound-sources
> > 3d-reverberator
> > 16 channels out (so you'll need a hammerfall-card)
> >
> > have fun
> > mfg.fds.ar
> > iohannes