Hallo, Vreahli the Audio Bandit hat gesagt: // Vreahli the Audio Bandit wrote:
Hiya. Okay - so here's the skinny. I set out about a half hour ago to figure out how to set up a 2 pole low pass filter with resonance in Puredata. Looks like that's apparently set up with a biquad~ filter. I read through the rather handy looking information over here at http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt. I came out of that a bit more confused than when I went in. I also bumped in to http://www.creativesynth.com/MAXMSP/001-SynthBuildingMSP/sbm_03.html - which left me drooling quite a bit more than when I went in. Is there any way to set up a LPF with a live-tweakable audio rate resonance and frequency setting while avoiding doing the biquad math by hand? I can't even figure out how to get my computer to crunch those numbers for me. Thanks in advance for helping me out with this seemingly simple yet convoluted question.
The biquad~ math isn't extremely hard, but of course it's still hard if you have no experience/knowledge about filter theory yet. Actually there was a long discussion about biquad two or three weeks ago, you may want to check the archive.
The quickest route to getting useful biquad~ coefficients without going through the math would be the filter objects in the ggee-library (CVS at /externals/ggee/filters). They implement the equations from the Audio-cookbook.
However [biquad~] doesn't have audio inputs to set the coeffs. Alternatively you could use the elementary filters [rpole~], [rzero~] etc. They accept signals for their parameters. Maybe I should sit down and build a 2plp now ...
Ciao
Frank Barknecht _ ______footils.org_ __goto10.org__