[PD] reson~ from max in pd

[Björn Lindig]

Hi,

a friend asked me, wether there is a object similar to the [fffb~] in max/msp 
(a "fast fixed filter bank") in pd. I did not find it instantly so I started 
to build one after the formula posted in [reson~]s help in max:

y[n] = gain * (x[n] - r * x[n-2]) + c1 * y[n-1] + c2 * y[n-2]

I appended a patch, that I created after this formula. The Problem is, that I 
would love to klone the max-object, but at the moment I have only inlets for 
r, c1, c2 and gain. What I need is the math to calculate the values for r, c1, 
c2 and gain for given center frequency, Q/Bandwith, and gain. 

I started reading the chapters on time shifts and delays and filters in 
miller-puckettes book and the book of J. O. Smith. But to be honest, I did not 
yet understand much of what is writen there. So I thought, there might be 
someone arround here, who can give me a fast answer, or who can point me into 
the right direction. 

If it is the best to try resonz and resonr (I'm on train building pd-extended, 
used vanilla before), I'll accept that. On the other hand, I would be realy 
curious about the math that is used to solve this problem.

Thank you very much!

Bjoern



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