Re: [LAD] what does "full range" mean with regard to ambisonics and speakers?

On 07/31/2010 04:40 AM, "Bearcat M. Şandor" wrote:
> Folks,
>
> I'm a recovering audiophile.

:-]

> I have read that speakers in an ambisonic set up should be "full range".
> I'd like to set up a ambisonic speaker system (8 channel to start), and
> the prospect of 8 full range channels is daunting. Since it seems they
> would be stand or wall mounted (at least some of them) that means
> monitors and subwoofers. Since all channels must be the same, that means
> 8 subwoofers...somewhere in the room.
>
> So what does "full range" mean usually and what does it mean in terms of
> talk on this list?

first, as initial shock therapy to the (ex-?) audiophile: ambisonics is
not full-range in the usual sense. its localisation mechanism only works
in a very limited frequency range. the idea is to use that small range
to produce such good cues to the brain that it conveniently ignores that
the rest is garbage ;)
i'm taking localisation only - timbre reproduction must of course happen
from 20 to 20k...

if you want eight speakers, that would fix you up for up to third order.
since i assume you're not much into computer-generated music (which
would provide some source material), and since i know that higher-than
1st-order recordings are rare (because i've personally made at least 1%
of them...), it could make sense to go for 6 speakers initially. very
good for first-order replay, very good for "super-stereo", easily
accommodates 5.1 content with only minor placement errors, easier to
place, and 25% cheaper. unless you choose a very exotic brand and model,
it should be no problem to extend this setup to eight or more later.

it's no problem (and in fact customary) to use subwoofers with
ambisonics for low-range extension. you can either forego localisation
in that band and just use a mono sub (perfectly ok), use 2 and have some
l/r signal in ithem, or you can use 4 subs in the corners of the room
and drive them with a special horizontal decode. that's pretty awesome,
because you can do a decode such that one speaker pushes while the
opposite speaker pulls. of course that wastes quite some amp power, but
it makes your room effectively infinite volume, which means you can fit
very long waves into it without weird effects, and you will win a nice
trouser-flapping effect without boominess and that obnoxious pressure on
the ears.

if you're going to use ambdec for decoding, i can show you how to create
two separate configurations for the full-range speakers and the subs,
and to combine them into a single matrix (that's assuming that the subs
themselves do their own low-pass filtering - if not, you'd need to do
that with a plugin, but that means you will have to use another
application in addition to ambdec).

best,

jörn

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Received on Sat Jul 31 12:15:02 2010