[sdiy] Filter slopes

[Scott Gravenhorst]

Look at Perry Cook's flute model:

https://ccrma.stanford.edu/software/clm/compmus/clm-tutorials/pm.html#s-f

It's an extension of Karplus-Strong string models.  There are two delay lines, one is exactly
1/2 the length of the other.  The short one models the mouthpiece and it energizes the long
one.  I've gotten it to work and it sounds VERY flute-like, however, I still need to work on
it because it comes to full amplitude very slowly with whatever mistake I made.  I'm sure
another look at my code and I'll see a doofus thing I did.

Tom Wiltshire <tom at electricdruid.net> wrote:
>Ok, I don’t know anything about “coupled resonators”. What 
>would I look up to find out more (aside from that obvious term ), 
>and how would I implement such a thing for analogue audio? Making 
>“resonators” is easy enough. How do I “couple” them? 
>
>I’m looking for a practical implementation with details of how 
>that was arrived at, rather than a highly abstract splurge of 
>math that I won't understand and which could probably be 
>explained in words of two syllables or less if anyone took the 
>time to bother. 
>
>Thanks,
>Tom
>
>==================
>       Electric Druid
>Synth & Stompbox DIY
>==================
>
>> On 11 Jun 2018, at 20:50, ASSI <Stromeko at nexgo.de> wrote:
>> 
>> On Monday, June 11, 2018 7:43:22 AM CEST Elain Klopke wrote:
>>> I was reading an article about the spectral content of various instruments
>>> (woodwinds and strings) and while they didn't have any circuits, there were
>>> some tables showing cutoff frequencies and high and low slopes. Several of
>>> the pictures looked like bandpass filter responses with different slopes on
>>> each side. How would I go about doing that? Is the slope determined by the
>>> gain of the op amp in an active filter? If it's that easy, would it be a
>>> highpass filter followed by a lowpass filter each with their own gain
>>> settings?
>> 
>> Both woodwinds and string instruments (among others) can be modeled with 
>> coupled resonators.  The characteristic timbre of each is related to the modes 
>> of these resonators and the transfer of energy between them.  The slopes of 
>> the bandpass skirts depend on both the quality factor of the resonator and the 
>> coupling strength to other resonators or resonator modes.  Generally speaking, 
>> losing energy (e.g. into another mode) is a reduction in Q and hence shows up 
>> as a flattening of the slope.  If you just want to approximate the magnitude 
>> response, a filter bank with a high enough number of filter bands is as good 
>> as any other method and relatively easy to implement, it just uses many de-
>> coupled resonators instead of few(er) coupled ones.
>> 
>> 
>> Regards,
>> Achim.
>> -- 
>> +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
>> 
>> Wavetables for the Terratec KOMPLEXER:
>> http://Synth.Stromeko.net/Downloads.html#KomplexerWaves
>> 
>> 
>> 
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-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- http://scott.joviansynth.com/
-- When the going gets tough, the tough use the command line.
-- Matt 21:22