[PD] multichannel reverb?

Rory Walsh rorytheroar at yahoo.com
Fri Jul 12 12:14:52 CEST 2002

Most standard reverbs involve the use of a network of
comb and allpass filters. The Schroeder model uses 4
comb filter in parallel and two cascading allpass
filters like this,


I have included a comb filter and allpass filter in
the attached patch, in a comb filter the input signal
is fed into a delay which is then feedback into the
delay after being mmultipliedby a gain factor less
than 1, anything over one will cause the filter to be
An allpass filter is ssimilarbut there is no initial
delay between the incoming and outputted signal, the
signal goes straight through the filter but splits
into two before being outputted, one of the signals is
multiplied by -gain and sent straight to the output
and the other goes into a delay line which is then
ffed backinto the delay line after being multiplied by
a +gain, the product of the -gain and +gain are added
together then to form your ooutputsignal, this is why
the allpass filter is unique in that it passes all
frequencies equally, if that makes sense, anyway the
patch will make it clearer, hopefully! 


 --- David Sabine <dave at davesabine.com> wrote: > Hello
> Has anybody designed a multichannel reverb
> abstraction or external for PD (Windows version). 
> To be honest, I'd like to build a 4-channel reverb
> myself but I'm having some difficulty understanding
> how such a thing is accomplished.  Can anybody lend
> some help?
> the multiverb~ (ala freeverb~ external) crashes my
> Windows XP.
> Regards,
> Dave Sabine

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