Odp: [sdiy] moog high pass flter

[Roman Sowa]

I'm just a humble player of only one VCF, and it's state
variable, so you may
think it's no good. My filter uses 2 SVFs and couples them
in various
topologies with rotary switch. Most of the time that switch
is in LH or LB
position (Low-High, and Low-Band respectively). The sound is
sweet.
That little filter is talking to me then :)
I'm saying HighPass is cool, but I rarely use it only as HP.

Just my 0.03PLN on this

Roman

----- Original Message -----
From: harrybissell <harrybissell at prodigy.net>
To: Gavin <elmystico at earthlink.net>
Cc: Ian Fritz <ijfritz at earthlink.net>; benno
<benj at iinet.net.au>; <synth-diy at dropmix.xs4all.nl>
Sent: Monday, December 09, 2002 5:38 AM
Subject: Re: [sdiy] moog high pass flter


> Have not tried that one. Do you know what the topology of
that one is ???
>
> I've tried HPF using the State Variable and Sallen Key
methods. (both are
> 12dB/oct).  I just finished the EFM  MS-20 clone and the
HPF has some
> appeal.  I guess time will tell how often I patch the HPF
in.  I used toggles so
> I can switch real fast if I want to.
>
> Like I said earlied... I wanted to try the "Moog Filter
Coupler" which is why I
> used the MS-20 filters (because I have them, I 'can'...
and they would go to waste
> in my box of half finished stuff... otoh they are now
finished and will probably be
> underused...)
>
> H^) harry
>
> TO clear the air... I really do not think HPFs 'suck'.  I
reserve that word for
> BBDs....
>
> Gavin wrote:
>
> > i think High Pass is incredible.  particularly on the
Yamaha CS synths.  The
> > reason someone who's experience with the Moog High Pass
might not be so into
> > high pass is most likely because the moog ladder or the
ssm2040, basically
> > the same filter, is extremely rich in the low end, but
very weak in the high
> > end.  I think the fault is in the filter, not the
mode... check it out
> > ----------
> > >From: Ian Fritz <ijfritz at earthlink.net>
> > >To: harrybissell <harrybissell at prodigy.net>, benno
<benj at iinet.net.au>
> > >Cc: synth-diy at dropmix.xs4all.nl
> > >Subject: Re: [sdiy] moog high pass flter
> > >Date: Sun, Dec 8, 2002, 9:56 PM
> > >
> >
> > >Actually, I've been thinking lately that HPFs are
underappreciated and
> > >underutilized.
> > >
> > >Many acoustic instrument sounds have frequency spectra
whose fundamentals
> > >are weaker than several of the higher harmonics.
> > >
> > >The reason for this is that the low frequencies need to
be well trapped
> > >inside the acoustic waveguide structure in order for
the non-linear engine
> > >that drives the sound production to operate
efficiently.  What we hear is
> > >more like the exhaust!
> > >
> > >A pretty example of this is shown in the recent book on
mathematical
> > >modeling of acoustic instruments edited by Hirschberg,
Kergomard and
> > >Weinreich (Mechanics of Musical Instruments,
Springer-Verlag,
> > >1995).  Figure 1 of the Introduction  shows internal
and external waveforms
> > >of a clarinet.  The internal wave is a rounded square
wave, whereas the
> > >external waveform is extremely spikey, obviously
dominated by high  harmonics.
> > >
> > >As an other example, look at the simple digital
waveguide models developed,
> > >for example, by  J. O. Smith at Stanford.  The wave
reflected from the end
> > >of the waveguide (back to the excitation source) is LP
filtered, whereas
> > >the transmitted (output) wave is HP filtered.
> > >
> > >Of course, acoustic instruments have HF cutoffs, also,
so LP filtering is
> > >indeed a natural part of music.  But HP filtering is
every bit as important.
> > >
> > >It is impossible to obtain spectra with higher
harmonics dominating the
> > >fundamental by using standard synth waveforms plus LP
filtering. So unless
> > >you have a cool waveshaper like the Wavolver, you will
definitely need to
> > >include HP filtering in your acoustic arsenal.
> > >
> > >As an interesting sidenote, the research done by H.
Benade showed that the
> > >HF cutoff frequency of woodwinds is independent of
pitch (in the lowest
> > >register).  An amazing result!  He and a student
actually designed and
> > >built an isospectral clarinet (cutoff following pitch)
and found that it
> > >was too dark and muffeled at low frequencies and too
bright at high
> > >frequencies.  So non-tracking LP filtering is also an
interesting synth
> > >programming option.
> > >
> > >At 12:20 PM 12/8/2002, harrybissell wrote:
> > >
> > >>and Hipass filters suck. oops did I say that outloud.
Thats bad.. thats
> > >>flamebait ;^P
> > >>maybe blasphemy...
> > >
> > >Ignorance is what sucks, IMO.
> > >
> > >Best regards,
> > >
> > >   Ian
> > >
>