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Re: spacial sound



At 08:55 PM 11/3/99 +0000, you wrote:
>....2 I've not tried this one. It involves placing a full range speaker
>behind the audience and wiring it up to the two live terminals on a
>stereo amp....

Yeah, that's the setup Brian Eno described on the back of one of his albums
(I've forgotten which). It does mess with the impedance, though, so be
careful of your output transistors! The way it works is by phase
cancellation; since the third speaker is connected to the positive
terminals of the two stereo channels, any sound common to both channels
(i.e. in or near the center of the stereo field) cancels itself out and
does not come out of the third speaker. Sounds that are panned hard left or
right do come out of the third speaker, sounds appearing at intermediate
points in the stereo image show up at different relative volumes due to
their particular phase relationship. The effect is that, instead of a
clearly defineable third sound source, certain sounds appear to come from
points along the triangle formed by the three speakers, thus widening the
stereo image and causing the illusion that the stereo field curves back
around the listener inside the triangle. It makes the listening environment
seem bigger, especially for sounds that pan around. I had my stereo set up
this way for most of the early '80's, although the effect is probably too
subtle to be of much use in a live-performance situation, unless there's a
very low level of ambient noise. It would probably work well on a quiet,
ambient art gallery-type gig, but would be pointless in most clubs or 
bars. 

Tim