[LAU] more than 4 channels for listening? Really?

fons at kokkinizita.net fons at kokkinizita.net
Thu Feb 25 18:08:39 EST 2010


On Thu, Feb 25, 2010 at 05:53:15PM -0500, Monty Montgomery wrote:
> > I am currently in the process of building an eight-channel ambisonics setup in
> > my home-office. Size is about 3x3x2.5 meters.
> 
> To be clear---
> 
> You do mean a three channel first-order setup with eight speakers, correct?
> 
> To answer questions a few others asked, It's not that a bunch of
> channels are needed, rather that more speakers are needed to fill gaps
> in the wavefront imaging.  quad/5.1/7.1/etc takes an ad-hoc approach
> to this by adding more and more fully discrete channels to 'plug
> holes' while Ambisonics takes a methodical approach that simply adds
> more speakers to the already constructed/encoded model.
> 
> ("Why didn't Ambisonics win then?" you ask... well, it requires signal
> processing that was hideously expensive at the time of its
> introduction, and the 'add another full channel for each speaker
> approach' was far cheaper and more practical at the time.  Today, the
> average cereal box contains more computing power than used to land on
> the Moon, so I think the Ambisonics approach is suddenly the
> easier/cheaper way to do things. Excepting of course that the discrete
> channel method has a huge installed base.  For that reason, Ambisonics
> is still 'weird' and 'fringe',)

With four speakers AMB can give good - and in particular
musically pleasant - results, but using six improves things. 
What does not work in my experience is 5.1 transcoded to 1st
order AMB, in that case just using the original signals with
C distributed to L and R works better. But 5.1 recoded to 2nd 
order AMB over six speakers seems to work well. I'd start with
at least six, given the choice.

Ciao,

-- 
FA

O tu, che porte, correndo si ?
E guerra e morte !


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