Charles Henry wrote:
wow - this is a bit above my head at the moment. i can go from equations in C to pd, but only if i have the equations themselves to look at...
It's easy. I've done it half a dozen times. For example, http://lists.puredata.info/pipermail/pd-list/2007-01/046315.html
Look at the help file for biquad~ in Pd. The equations are there.
last time i looked at the equations in biquad~'s help patch, my brain melted.
Here's the transfer function: Y/X=(ff1 + ff2*z^(-1) + ff3*z^(-2))/(1 - fb1*z^(-1) - fb2*z^(-2))
or
Y/X=(ff1*z^2 + ff2*z^1 + ff3)/(1*z^2 - fb1*z^1 - fb2)
All that you need to do to find the complex zeros is to use quadratic formula on the numerator (ff1*z^2 + ff2*z^1 + ff3)
and do the same to find the complex poles on (1*z^2 - fb1*z^1 - fb2)
dude, that's not 'easy'. i can barely remember how the quadratic formula works with pen and paper, let alone in C, and let alone to the point where i could confidently transfer from C to Pd. i'd have no idea where the bugs were... and indeed, no idea
and once i've got these 'complex zeros' and 'complex poles' i don't have any idea how to plug them into czero~ and cpole~ (or is it rzero~ and rpole~?) objects.