On 07/26/2012 07:04 PM, Julien Claassen wrote: 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

On Thursday 26 July 2012 13:37:45 Julien Claassen did opine: 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 -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Most of our lives are about proving something, either to ourselves or to someone else.

On Thu, 2012-07-26 at 13:49 -0400, Gene Heskett wrote: Analog bucket brigade reminds me to ugly delay circuits, we build as children, with an entertaining noise performance :D. At all events, when building such a thing use a perfboard to ensure to get as much bad audio quality as possible. To be serious, there are some old professional delays based on analog bucket brigade, but using it today IMO isn't worth the hassle.

On Thu, 2012-07-26 at 17:13 -0400, Gene Heskett wrote: Apologize Gene, after sending my mail I already googeld for digital versions :). However, we agree that analog bucket brigade were a PITA :). Best, Ralf

I can't resist: http://www.youtube.com/watch?v=Y5KaeCZ_AaY

On Thu, Jul 26, 2012 at 08:14:26PM +0200, Robin Gareus wrote: Crossfading between IRs will not reproduce the Doppler effect unless the phase response of the two IR that are being cross- faded is within 90 degrees or so at all frequencies of interest. Which means you'll need a lot of IRs. So it's more efficient to separate the filtering and the delay. Once that's done, you can probably find a parametric description of the filtering in function of the angle of the driver. It doesn't need to be exact - a lot of what a Leslie produces is there not by design but by accident. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow)

On 07/26/2012 07:00 PM, Florian Paul Schmidt wrote: You'll want angular dependent convolution https://ccrma.stanford.edu/~jos/doppler/dafx02.pdf CCRMA has more publications on that matter.