[LAD] Leslie and convolution

[Gene Heskett]

On Thursday 26 July 2012 13:37:45 Julien Claassen did opine:

> Hello again!
>    So the very short answer would be: It's not been done inany Linux
> software yet.
>    Thanks for the explanations. I have thought a little too simple it
> seems and the outcome is what I originally expected. No go. :-)
>    Kindly yours
>            Julien

Speaking as a bit of an engineer, to do a Leslie simulation would require 
that something like a bucket brigade be done with the digital data once 
decoded, then setup a pair of taps that would sample the digital from the 
brigade , advancing the signal in time for the speaker nearest the 
listener, and delaying the other half of the mix equally. Then combine it, 
and send it on down the path to the speakers, or perhaps to 2 separate 
speakers, but the 2 speaker approach would add its own artifacts.  What you 
are then building is in essence similar to a comb filter with a variable 
clock speed.

And this effect would only be valid for a stationary listener, because the 
bucket-brigade would have to get longer for the angle being synthesized 
according to where the listener is.  The farther off the centerline, the 
longer the brigade, up to the time lag representing the maximum separation 
of the actual speakers on the Leslies rotating board.  I'm sure some 
curious coder could work out the math, but the bucket-brigade would 
probably have to be done in hardware.  Such IC's are (or were a decade ago) 
available.

Cheers, Gene
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