[LAD] Leslie and convolution

[Florian Paul Schmidt]

On 07/26/2012 07:04 PM, Julien Claassen wrote:
> Hello Flo!
>   OK, I'm with you so far. So I suppose, that it is possible to 
> process the IR of a time-variant system. The question is: Is it done 
> in any library already optimised for the audio domain?
>   Thanks and best wishes
>            Julien
>

I sense a misunderstanding. With a single constant kernel you can only 
model time-invariant systems. A Leslie is NOT time-invariant. I.e. the 
response changes with time (the speaker rotates). So what you could do 
as a workaround would be to get IRs from the Leslie at various 
positions. Then convolve your input signal with each of them and mix the 
outputs together with the mixing coefficients being a periodic function 
of time.. You could probably get away with calculating only a few of the 
convolutions if your mixing coefficients are sparse, i.e. you only 
crossfade between two consecutive (in time) output signals.. (keep in 
mind the window length of the convolution kernel, though)..

It's of course a tradeoff - You need quite a few IRs to make the 
transitions smooth.. But then it's just a matter of hacking some code 
around an existing convolution engine..

But this could be done with shelf solutions

Flo

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