If you just want to mess with biquads, this is a really good applet
for playing around with them:
http://www.earlevel.com/Digital%20Audio/PoleZero.html .. it'll show
freq. response, but unfortunately won't show impulse response or
phase. But, I've found biquads to be a good starting point for
filters because there is so much information available on their
mathematics and you can create so many different types of filters with
them (btw have you checked out Julius O. Smith's site or
There's also Pure Data, which is a free Max/MSP clone. It supplies
both real and complex pole/zero functions, and has an FFT function as
well. There's a learning curve there, but it's pretty flexible.
You'll probably want something to help you solve for gain though if
you end up using Pd.
On Thu, May 6, 2010 at 10:41 AM, Mark Knecht wrote: