[sdiy] ot: rotating speaker simulation or stupid approach

[Richard Wentk]

At 16:34 02/07/2003 +0200, Czech Martin wrote:
>I can record the transfer charactericstic of a loudspeaker with some
>microphone in some room (the impulse response, if you like).
>I can repeat that, turning the speaker a few degrees of axis.
>I can do this , say for 23 steps of 15 deg to make a full circle.
>I must be carefull in order to get the right time shift for
>each impulse response vs. all the others.
>I think the impulse response will be not too long, perhaps
>some 10ms.

I doubt this will work, because an essential part of the rotating speaker 
effect is the way the sound dopplers as the horns move. If you record the 
impulse response you'll just get the effect of the room/horn-as-filter 
sound, with a different frequency response available as the horn points in 
different directions. But the dopplering won't be present, and 
interpolating between different impulse responses won't create it.

The rotating speaker effect is *not* the same effect as simple panning. You 
can pan (in theory) a sound at the speed of light and you won't get any 
dopplering. But if you start physically moving the sound source, the effect 
is completely different because you'll get the compression/expansion of the 
audio wavefronts as the sound zips past.

Richard