[sdiy] Filter slopes

[Ian Fritz]

And also there has been a lot of work done in Reaktor, eg Steampipe by Martijn Zwartes, Silverwood by Chet Singer, and all their descendants and variations.

Ian

> On Jun 11, 2018, at 5:29 PM, Ian Fritz <ijfritz at comcast.net> wrote:
> 
> Doesn’t Dieter do that with his delay units?  
> 
> Ian
> 
>> On Jun 11, 2018, at 5:17 PM, Scott Gravenhorst <music.maker at gte.net> wrote:
>> 
>> 
>> Also, a friend of mine, Les Hall on electro-music.com, came up with an analog way to do
>> Karplus-Strong using a BBD and a single pole low pass analog filter (just RC) in the loop. 
>> This works and might also be applicable to the flute model described on ccrma.standford.com. 
>> That might be tricky to get working, but probably not impossible.  If I were to try it (I'm not
>> really an analog guy now), I'd start with Les Hall's BBD KS circuit and see what the problems
>> are with it.  Another friend implemented it (BBD KS) and he said it suffers the same problem
>> that the digital model has - the low pass filter adds a bit of extra delay so it detunes a bit
>> as the delay is shortened.  Delay time is controlled by using a VCO as a clock to drive the BBD.
>> 
>> music.maker at gte.net wrote:
>>> 
>>> 
>>> 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
>>> 
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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
>> 
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