I think they are completely different. Biquad~ at least is not really good if you want to control in the signal domain. The lowpass etc externals implement the filters from here:
http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt written by Robert Bristow-Johnson
i'll have a look at it...
Then the last time I saw them they were written by me, and not part of the iemlib, but how knows, ... in reality the hard work was done by Robert Bristow-Johnson.
sorry for that ... i must have mixed them up with iemlib's filter abstractions ...
cheers...
Tim mailto:TimBlechmann@gmx.de ICQ: 96771783 -- The only people for me are the mad ones, the ones who are mad to live, mad to talk, mad to be saved, desirous of everything at the same time, the ones who never yawn or say a commonplace thing, but burn, burn, burn, like fabulous yellow roman candles exploding like spiders across the stars and in the middle you see the blue centerlight pop and everybody goes "Awww!" Jack Kerouac