n-channel matrix panning

[Tim Boykett]

Hi Bill,

this dynamic sound placement is something that I have
been working with on and off for a while. I presume
you would like to be able to place sound arbitrarily
inside the surface that the speakers enclose. This
is a bit harder than placement around the ring
of speakers.

The ring placement is basically a pan between the
two speakers, a linear fade as opposed to a log
fade used for levels. This little note is trivial when
you know it, which you probably do, but vital
if you dont, so I thought it good to make sure you do.

This is easy and fast, we have done a bunch of work with
some equipment and sound movement using rotation
as a main theme.

The placement on a surface is more dependent upon the
precise arrangement in space of the
surrounding triangle of speakers. I have done calculations
for speakers on a regular square grid, to place a sound anywhere
on that grid, but I dont have them with me. It's a bit
of trigonometry and a bit complex, but nothing too
much.

The sound sources we found had to have certain properties,
most importantly was a lack of resonance. Most effective
was some pure noise, Japanese stuff or John Duncan sort of
noise tracks. Pure tones resonate too well and envelop
the space. Percussivity was also a little distracting,
depending upon the speed of movement relative to the
beat rate. One has to ensure that
the sound source doesn't disappear at one point and reappear
elsewhere, unless that is the desired effect.

This is, of course, all work very much in progress, so I
would love to hear about your and other people's experiences
with other techniques.

Cheers,

 tim

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