GIC String Filter - first experiments (was: [sdiy] Filter Banks & CSound)

[Cynthia Webster]

on 2/7/04 4:35 PM, Michael Baxter at mab at cruzio.com wrote:

> JH,
> 
> Way cool sound, amazing!
> 
> On the second sample, after the 40-bank GIC filter was turned on along
> with the parametric, a little while in, the sound to me was distinctly
> like a hammered dulcimer. Very nice rings and percussive timbres.

> Best,
> Michael

Great Job Jurgen!

Delightful, those same "rings and percussive timbres"!

Cynthia


> 
> On Sat, 7 Feb 2004, jhaible wrote:
> 
>> Hi,
>> 
>> I've finally made my own version of a String Filter Bank.
>> Samples from some first experiments are avaiable at
>> http://home.debitel.net/user/jhaible/jh_string_filter.html
>> 
>> I think the peak/valley ratio of the main filter bank is ok,
>> but the air/wood/bridge resonance needs some more
>> adjustments. Any hints how to improove this are welcome.
>> (Benade gives detailed information about the frequency -
>> 125Hz, 175Hz, 1.5kHz and 2kHz for Cello -, but not
>> about Q and Gain.)
>> 
>> JH.
>> 
>> 
>> 
>> 
>> 
>> -----Ursprüngliche Nachricht-----
>> Von: Ian Fritz <ijfritz at earthlink.net>
>> An: Tim Ressel <madhun2001 at yahoo.com>
>> Cc: <synth-diy at dropmix.xs4all.nl>
>> Gesendet: Mittwoch, 11. Dezember 2002 04:26
>> Betreff: Re: [sdiy] Filter Banks & CSound
>> 
>> 
>>> Tim --
>>> 
>>> Filter bank references:
>>> 
>>> "Electronic simulation of violin resonances," JV Mathews and J Kohut, J.
>>> Acoust. Soc. Am., vol. 53, 1620 (1973).
>>> 
>>> "Audio engineering improvements for clavichords," RW Burhans, J. Aud. Eng.
>>> Soc., vol. 23, 635 (1975).
>>> 
>>> "Filter bank design," IJ Fritz, Electronotes, #107, 16 (1979).
>>> 
>>> "A 39-channel variable-Q filter bank," BA Hutchens, Electronotes, #115, 3
>>> and #116, 3 (1980).
>>> 
>>> It's the peak-to-valley ratio that mainly characterizes the overall
>>> sound.  This ratio is strongly influenced by the shape of the resonance
>>> curves and the number of resonators, since many long tails can add up to
>> an
>>> appreciable contribution.
>>> 
>>> I used a single transistor circuit for my resonators -- just a phase-shift
>>> oscillator with a bit of degeneration to set the Q.  I started with
>> nominal
>>> Q values around 20, but had to increase this somewhat to get 10 dB
>> contrast
>>> with all the bands turned up.  My design has variable amplitude on each
>>> filter and variable Q in sub-banks of six frequencies.  That way I can --
>>> for example -- do some formant shaping at low frequencies and timber
>>> enrichment at high frequencies at the same time.
>>> 
>>> The hollow, echoey sound you describe is from too large a peak-to-valley
>>> ratio.  Several people have remarked on this before.
>>> 
>>> Ian
>>> 
>>> 
>>> At 07:50 PM 12/10/2002, Tim Ressel wrote:
>>>> Ian,
>>>> 
>>>> Yes, in fact Dr. Matthews was mentioned in the
>>>> article. I'd love to see the article if you can lay
>>>> your paws on it.  What kind of filters are in your
>>>> filter bank? What frequencies and Qs??
>>>> 
>>>> By the by, the CSound filters I used did not seem to
>>>> parallel well. I didn't get that timbre change for
>>>> slight frequency changes. Also the bank had a hollow,
>>>> echo like sound. If I knew the real filters used I
>>>> might be able to get it working better.
>>>> 
>>>> --tr
>>> 
>>> 
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