[sdiy] Resonator type filters

Tue Jul 4 06:54:25 CEST 2017

Some of the models of Dave Rossum’s 14 pole Z-plane filters attempt this.
They have been made availble again recently:

http://www.rossum-electro.com/products/morpheus/

> 
> When I hear "Resonator type filters", I'm thinking of "Body modelling
> filters" - e.g. filters that allow you to model the body (and other)
> resonances in acoustic instruments to either synthesise them more
> accurately, or to add another dimension to other synth sounds that may not
> be a copy of a particular acoustic instrument, but which might have a
> particular character ("woodwind" say).
> 
> What is required for this varies a fair bit. What I knew already was about
> brass, woodwind, and vocal resonances, which are fairly few in number (5
> would cover it - 4 is ok, even 3 does a reasonable job, as Elhardt's
> PolyMoog video demonstrates). You need less for brass and woodwind and more
> for vocals.
> 
> What I've learned from the paper posted above is that for strings this is
> not sufficient, although there might be a couple of major resonances lower
> down that you could copy fairly easily. But the "lush", "rich" quality which
> we're after seems to come from the amplitude modulation of the harmonics
> caused by many narrow bands coupled with a limited vibrato. So we need lots
> of peaks (20-30 seems like the best, from their results) and the peaks need
> to not match any *particular* note's harmonics so all notes are similarly
> affected. Finally, the peaks need to be spaced enough that's there's roughly
> a -12dB trough between them. Much more than than that, and you get a "hole"
> and dead notes, less than that and you don't get enough movement in the
> notes.
> 
> So there are really two basic types of resonator bank you could build. One
> would be basically a sophisticated parametric EQ with several bands (say, 3,
> 4 or 5) with variable frequency, Q, and gain. The other would be a much
> larger bank of fixed filters. This would have individually variable gain,
> and could potentially have overall variable Q by wrapping feedback round the
> whole lot, as described in Bernie's Electronotes posting.
> 
> The first style is probably good for woodwinds, brass, and vocal sounds. The
> second is what you need for strings, at least according to that paper.
> 
> Ok, that's the results of my researches on the subject, and my understanding
> of what's been discussed here so far! I hope it helps.
> 
> Tom
> 
> ==================
>        Electric Druid
> Synth & Stompbox DIY
> ==================
> 
> 
> 
> 
> On 3 Jul 2017, at 16:43, ezion <ezion67 at gmail.com <mailto:ezion67 at gmail.com>> wrote:
> 
> > Think the Elektor Formant resonator module might also be of interest to
> > you.
> > Sorry no link, but the Formant schematics (a DIY modular from the late
> > '70) are on the net for sure.
> > Basically its a 3 band boost only parametric EQ.
> > Personally now days when working with VSTs I just abuse a EQ plug-in.
> >
> > Groetjes Theo
> >
> > On Thu, Jun 29, 2017 at 12:43 PM, Elaine Klopke <functionofform at gmail.com <mailto:functionofform at gmail.com>>
> > wrote:
> > Hey list,
> >
> > So I'm sure that I'm not aware of all of the variations, but....
> >
> > I've run across the Scott Stites triple Wilson SVVCF (and still plan on
> > building it!), and the Cwejman QMMF, and was thinking of cooking up my
> > own. But how many filters is overkill? Above are examples of three and
> > four filters in parallel with independent controls and a master section to
> > alter them all together. What about five filters? Six? 40?
> >
> > Just another silly question going through my brain..
> >
> > Sent from my iPhone
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