SV: [sdiy] Filter Musings

[John Alex Hvidlykke]

Indeed, bare filter slope is far from everything!

Though not DIY, the ancient E-mu romplers, starting with Morpheus, did boast
50 different "Z-plane" filter characteristics!

http://www.soundonsound.com/sos/jun98/articles/synthschool.html

\John


> -----Oprindelig meddelelse-----
> Fra: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl]På vegne af Scott Nordlund
> Sendt: 30. januar 2010 14:45
> Til: synth-diy at dropmix.xs4all.nl
> Emne: RE: [sdiy] Filter Musings
>
>
>
> Stop band slope isn't everything.  The arrangement of poles and
> zeros can give higher order filters more interesting responses
> than simple lowpass.  Compare the outputs of a state variable
> filter (2 pole) to those of the Expander/Matrix 12 filter (4
> pole).  All of the different filter types (in both cases) are the
> result of different arrangements of poles and zeros. 
>
> A high order allpass filter doesn't have a "stop band" at all,
> but it's still interesting.
>
> > Date: Sat, 30 Jan 2010 09:45:27 +0100
> > From: dixon at interchange.ubc.ca
> > Subject: RE: [sdiy] Filter Musings
> > To: jhaible at debitel.net; taciturn_unquiet at hotmail.com;
> synth-diy at dropmix.xs4all.nl
> > CC:
> >
> >> Excepting the trivial case of two identical filters, you will
> get a more
> >> complex behaviour than with a single filter.
> >> Two 4-pole LPFs in parallel form an 8-pole filter indeed. But
> you also get
> >> zeroes, so there will be no 48dB/Oct slope.
> >
> > But what good is an 8-pole filter if you don't get the 48dB/oct
> slope?  It's
> > a bit like having an 8-cylinder engine in your car that's just
> as gutless as
> > a four-banger!
> >
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