Physical modelling... SV: Re: [sdiy] standard filters from ladder topology?

[Magnus Danielson]

From: karl dalen <dalenkarl at yahoo.se>
Subject: Physical modelling... SV: Re: [sdiy] standard filters from ladder topology?
Date: Mon, 5 Sep 2005 03:11:18 +0200 (CEST)
Message-ID: <20050905011118.10279.qmail at web25502.mail.ukl.yahoo.com>

> I agree with Magus in that for ordinary filtering purpose
> (filtering coposite wave forms)the effect is quite marginal
> to be worth the effort wheter its butterwort,chebyshew ,cauer
> etc.
> 
> But you say, subtle changes of phases in passband
> for physical modelling with a BBD, so why use a 
> filter in the first place?
> 
> What is the BBD supposed to do? Resonator?

For delay-line work in a physical model you have resonant behaviour from the
delay itself and the surrounding circuit. In such an environment I think that
a maximal flat group-delay is really the only interesting choice for a filter.
Other group-delay responces can make the device harder to control, but then
again, that *might* do it more interesting so maybe I should just shut up.

> If you are using it as a delay line to do lin FM (Phase)
> then phases will cause differences, as so are feedback
> in delay line, but why not try out accurate phase stages
> instead of a filter! Phases could make major differences
> in a resonating tube for instance, if thats the use of 
> the BBD!

I think we have seen too little of polyphase filters in creative designs.

Cheers,
Magnus