[LAU] ambisonics: fons ambdec and muse.demon.co.uk ambidec

Arnold Krille arnold at arnoldarts.de
Fri Jan 7 11:44:24 UTC 2011

On Friday 07 January 2011 11:10:41 Jörn Nettingsmeier wrote:
> On 01/07/2011 10:01 AM, Arnold Krille wrote:
> > On Friday 07 January 2011 09:10:41 Giso Grimm wrote:
> > Finally, one of the main advantages of ambisonics compared to that
> > 5.1/7.1- crap is that your setup doesn't have to be perfect. Different
> > distances and even different irregularities in shape can be compensated
> > and still reproduce the signal as intended.
> well, yes and no. the failure modes are different, too. depending on how
> 5.1 and 7.1 are mixed, you can usually place the speakers any old way
> and still get something out of it, only the source positions will be
> displaced. heck, ever seen those setups with all 5 speakers below the
> screen, sitting on top of the vcr? not much surround, but you still get
> the idea of the mix.
> in ambi, it tends to work well for minor displacements (which you can of
> course also correct in the decoder, but i'm assuming user errror here),
> but for large uncompensated placement errors, the whole reconstruction
> will fail. in this latter case, ambi will behave far less predictable
> than any discrete speaker technique.
> and people should not expect wonders from ambi rigs. the ITU 5.1 setup
> is the most irregular you should try - anything worse than that, and
> ambisonics won't be much fun.
> maybe when franz zotter and his friends from graz get their partial
> spheres decoder into a usable shape (right now it's pd magic only).
> it basically enables you to build only parts of a loudspeaker sphere and
> discard all direct sound coming from the wrong directions.

Hm, my experience is limited, my setup was only once working with 5 speakers. 
It aim to be a 6 speaker deformed hexagon but for the sixth speaker I don't 
yet have the cable and stand in place. So one position was empty that 
afternoon I tested. But it didn't sound too bad. Of course sound from the 
missing direction was very thin to say the least and sound from the opposite 
was to strong as the counterpart was missing. I tried to match levels but then 
I ended with the four speaker square:-) But when I rotated the playback so the 
single speaker wasn't to my right side but to the front, results became 
better. (*)
Just me memory glossing over the past or is it some valid loop-hole?

Have fun,


(*) Of course then the bass was different and only from my left. Thats what you 
get with two full-range active speakers for the front pair and the rest small 
jbl-monitors without enough volume (as in space, not loudness) to reproduce 
anything <100HZ to satisfaction. But the frequency-split in ambdec and DRC for 
each speaker help there. I just don't know what this does to phase response of 
the final setup. And I don't have the ears to determine that...
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