[sdiy] 3 Pole state-variable filters

[Magnus Danielson]

From: "jhaible" <jhaible at debitel.net>
Subject: Re: [sdiy] 3 Pole state-variable filters
Date: Sun, 10 Feb 2002 23:14:59 +0100

> > I'm currently working on an 18dB state-variable filter (LP/BP/HP at the
> > SAME time, unlike the Formant).  The maths gets a bit hairy,
> 
> >Its not too bad if you're familiar with s-plane math.
> 
> 3 poles for HP and LP make sense. I think 3 poles on BP would mean
> you spend one pair for the BP function, and then decide whether to
> steepen the upper or the lower slope (i.e. adding a real pole LPF or HPF).
> Or is there a way to "distribute" 3 poles equally on both slopes of a
> BPF function ?

You do not actually place the poles out for the slopes, that's what the
zero's do. If you want to place out the resonances you muck about with
the poles.

Cheers,
Magnus