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... 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!