On Sun, Nov 3, 2013 at 2:26 PM, robert bristow-johnson <r...@audioimagination.com> wrote: > On 11/3/13 10:21 AM, Chris Townsend wrote: >> >> Thanks guys. I was also thinking a Moog style filter with first order >> sections inside a feedback loop might work me, since it performs well >> under high rates of coefficient changes. >> >> It seems like you could make a fully general 2nd order filter by using >> two first order shelf filters. > > no. unless you implement complex coefficients.
I just mean two first order filters within a feedback loop. This would be similar in style to a Moog VCF, but would have 2 poles and 2 zeros. Are you saying this cannot be a fully general second order filter? > > BTW, to do a general 2nd-order filter with either Hal's SVF or the Lattice > or the normalized Ladder, you need to generalize those designs a little and > pull out 3 taps with coefficients to implement general zeros in the transfer > function. > Like I mentioned the Kingsbury filter seems to be a general version of the SVF, although the references I've found show it with poles only. If you don't need to share state then it's trivial to tack on the zeros. The AES paper "Roundoff Error Analysis of Digital Filters" by Udo Zolzer seemed to have the best info I could find. -Chris -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
