>My filter has 2 poles and 1 zero. Unlike the Cookbook filter, which >has 2 poles and 2 zeros. >I think that automatically assumes, the transfer function cannot be equivalent.
No, that does not follow. A filter with two zeros can produce all of the transfer functions that a filter with one zero can, and many more besides. You just stick the extra zero(s) off at z=infinity. >That also means, that my filter is also faster to process. First order filters are typically cheaper to process than second order filters. I wouldn't say that is a good argument that they are preferable to second order filters, though. E On Wed, Feb 4, 2015 at 5:25 PM, Peter S <peter.schoffhau...@gmail.com> wrote: > On 04/02/2015, robert bristow-johnson <r...@audioimagination.com> wrote: > > i'm only saying that > > with a 2nd-order filter, there are only 5 degrees of freedom. only 5 > > knobs. so when someone says they came up with a different or better > > method of computing coefficients for *whatever* 2nd-order filter, my > > first curiosity will be what is the transfer function and from that, we > > usually find out it is equivalent to the Cookbook transfer function > > except Q or bandwidth is defined differently. > > My filter has 2 poles and 1 zero. Unlike the Cookbook filter, which > has 2 poles and 2 zeros. > I think that automatically assumes, the transfer function cannot be > equivalent. > (And strictly speaking, the transfer curve of my filter is not > biquadratic, just BLT.) > That also means, that my filter is also faster to process. > > Best regards, > Peter > -- > 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 > -- 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
