[PD] biquad~ with elementary filters [was: Re: dinosaurs ...]

[Frank Barknecht]

Hallo,
martin brinkmann hat gesagt: // martin brinkmann wrote:

> Claude Heiland-Allen wrote:
> 
> > cpole~ czero~ rpole~ rzero~ have signal inlets for filter control, so i 
> > assume sufficiently smooth changes will not cause clicks
> 
> that is true, but it looks like no one has made a (usual lp,hp,etc.)
> filter with these objects until now.

Except Miller. [1]

Though I agree that some more of these would be handy. I tried to make
a biquad~ clone with the elementary filters, but failed so far. I
assume from [2] that the transfer function of two rzero~ and two
rpole~ in series should be the same as a biquad~, however I don't know
how to convert the ff1, ff2, ff3, fb1 and fb2 coefficients of biquad~
into the coefficients to use at the second inlets of the elemetary
filters. Can anyone help?

[1] http://crca.ucsd.edu/~msp/techniques/latest/book-html/node160.html
[2] http://crca.ucsd.edu/~msp/techniques/latest/book-html/node136.html 

Ciao
-- 
 Frank Barknecht                                     _ ______footils.org__