[PD] EQs - FIR or Biquad or others

[c]

> looking to build a couple of parametric EQs with 4
> to 6 poles.  At the moment I'm looking at the biquad
> equations in the help file and can't make heads or
> tails of them.  I can't find anything helpful on the
> internet either on how those equations relate to the
> frequency response of the filter.

assuming youve used RBJ's variables, as in
http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
 the response for a particular frequency is
sqrt(pow(($b0+$b1*cos($w)+$b2*cos(2*$w)),2)+pow(($b1*sin($w)+$b2*sin(2*$w)),2))/sqrt(pow(($a0+$a1*cos($w)+$a2*cos(2*$w)),2)+pow(($a1*sin($w)+$a2*sin(2*$w)),2))


>  Has anyone else built parametric EQ modules for me to
> tinker with?

for pd, theres a Tk version at
http://cvs.sourceforge.net/viewcvs.py/pure-data/extensions/gui/ix/filter.wid?rev=1.2&view=markup
and C versions at
http://cvs.sourceforge.net/viewcvs.py/pure-data/externals/ggee/filters/
. if you make an abstraction-based version of biquad param generators,
let us know!