Re: [music-dsp] What is resonance?

[Mehdi Touzani]

Hello !

Thanks a lot everyone. Thanks for the book info Vadim.
I was not notified that this thread was going on, so I forgot it.
I managed to make something work, but sonically speaking, it was far from a
moog filter :-)

The appearance/disappearnce of the resonance effect was pretty brutal, and
with a kind of veil on the higher frequencies.
I should have taken a screen shot of the "circuit" (the interconnected
modules, mix, feedback, and may be gain). But I think I was too ashamed of
my first attempt  :)
I had to do something else (much much easier = a 4*32 step sequencer with
many modulators and triggers)  that controls eurorack, using a scope dsp
card, and a exprt sleepers converters, no sound magic involved . :-)
I've also been educated to dsp cards with development kits, for pretty
cheap prices (compared to when I last checked 10 years ago).
but right now i will try native tools to try to translate what i've build
recently.

To be continued 

Mehdi
(for examples of what i've been "building" or putting together)
https://spacef-devices.com





Le lun. 23 juil. 2018 à 11:42, Vadim Zavalishin <
vadim.zavalis...@native-instruments.de> a écrit :

> On 20-Jul-18 18:13, Mehdi Touzani wrote:
> > So... how do you do a resonance in a lowpass circuit?   :-)   not the
> > math, not the code, just the architecture.
>
> There are many different ways to create resonance in a lowpass circuit
> (esp. if the order is larger than 2). The higher is the order of the
> filter, the more different answers there are.
>
> Making a feedback loop around a lowpass chain is one way, but AFAIK it
> works perfectly (or close to that) only for the 4th order filter (the so
> called Moog ladder). I'm not aware of any standard generic structure (or
> even a transfer function to begin with) which could be referred to as a
> generic Nth order resonating filter. Recently I tried to propose one way
> of generalizing the 2nd order resonance to an arbitrary order by what I
> called "Butterworth filters of the 2nd kind", but this involves just the
> transfer function, whereas you still have lots of freedom in the
> implementation structure. You could look into the latest revision of my
> book for more details (where I also explain the problems with the
> lowpass feedback).
>
> Regards,
> Vadim
>
>
> --
> Vadim Zavalishin
> Reaktor Application Architect
> Native Instruments GmbH
> +49-30-611035-0
>
> www.native-instruments.com
>
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Re: [music-dsp] What is resonance?

[Vadim Zavalishin]

On 20-Jul-18 18:13, Mehdi Touzani wrote:

So... how do you do a resonance in a lowpass circuit?   :-)   not the
math, not the code, just the architecture.


There are many different ways to create resonance in a lowpass circuit
(esp. if the order is larger than 2). The higher is the order of the
filter, the more different answers there are.

Making a feedback loop around a lowpass chain is one way, but AFAIK it
works perfectly (or close to that) only for the 4th order filter (the so
called Moog ladder). I'm not aware of any standard generic structure (or
even a transfer function to begin with) which could be referred to as a
generic Nth order resonating filter. Recently I tried to propose one way
of generalizing the 2nd order resonance to an arbitrary order by what I
called "Butterworth filters of the 2nd kind", but this involves just the
transfer function, whereas you still have lots of freedom in the
implementation structure. You could look into the latest revision of my
book for more details (where I also explain the problems with the
lowpass feedback).

Regards,
Vadim


--
Vadim Zavalishin
Reaktor Application Architect
Native Instruments GmbH
+49-30-611035-0

www.native-instruments.com

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Re: [music-dsp] What is resonance?

[David Reaves]

In the physical world, resonance can generally be observed as the 
frequency-dependent cyclic exchanging of energy between potential (stored) and 
kinetic (active) forms. A pendulum is a basic example: at either end of its 
swing a pendulum exhibits purely its maximal stored potential energy while 
momentarily there is zero (kinetic) motion; at mid-swing there is no storage 
(potential) and all energy is kinetic, in motion. Each form of energy has two 
opposing modes: potential has the two opposite extremes of the swing; kinetic, 
the two different directions of swing. The amplitudes of the two forms of 
energy are in quadrature, a 90° cyclic relationship; when charted, the two 
energy levels trace out sine and cosine forms. 

In the real world, when continually given new energy with proper timing, a 
pendulum will swing indefinitely. If the outside source of energy is taken 
away, the resonance will decay: friction (resistance; damping) will slow and 
eventually stop the swinging. Within the limits of swing amplitude, the 
frequency of the pendulum's motion remains the same.

If you see such a back-and-forth, energy-trading relationship, there is likely 
resonance going on. Freezing can possibly be seen as energy storage and 
stretching can possibly be seen as activity, but unless one ‘feeds' the other 
and vice-versa, it’s probably not resonance.

(I will be pleased if someone corrects any false assumption I have made.)

David Reaves


On Sun, 22 Jul 2018 22:05:48 -0400 charles morrow mailto:c...@cmorrow.com>> wrote:
> 
> How about freezing and stretching moments. Is this resonance?

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Re: [music-dsp] What is resonance?

[robert bristow-johnson]

Any textbook study of resonant circuits and, using bilinear mapping a 
discrete-time counterpart, 3 dB bandwidths and Q is about a 2nd-order system.
A hemholtz resonator or a comb filter have resonance at many frequencies and 
they are much higher order tHan 2.  The are also tuned to harmonics.
The 2nd-order section, or "biquad" (with Q greater than 1/2) is resonant to 
only one non-negative frequency.
--r b-j                     r...@audioimagination.com
"Imagination is more important than knowledge."




 Original message 
From: Stefan Sullivan  
Date: 7/22/2018  9:55 PM  (GMT-08:00) 
To: A discussion list for music-related DSP  
Subject: Re: [music-dsp] What is resonance? 

Oh interest challenge of the definition of resonance. The typical textbook 
diagram shows a little local bump at some frequency in a bode diagram, but if 
you consider dc the resonant frequency, then the only way to show a bump is by 
being higher than all the other frequencies (i.e. monotonically decreasing).
Hmm, I wonder. One common definition of resonance bandwidth is also the "3dB" 
point. But I guess resonating at dc is probably not a common use case.
Stefan

On Sun, Jul 22, 2018, 18:11 robert bristow-johnson  
wrote:



I've been wondering about the connection that resonance and filter orders at 
least 2.  That's 2 delays (and feedback).
But if you're limiting the resonant frequencies to DC and Nyquist, then with a 
one-sample delay digital filter, you can have something like "resonance".
 Even if the single delay is two samples long (but no tap in the middle), that 
allows only DC, Nyquist, or half-Nyquist as tunable frequencies. 
So just sayin, in another sense of the word, that "resonance" can be had with a 
single *long* delay and one feedback path or with two arbitrarily short delays 
and two feedback paths.


--r b-j                     r...@audioimagination.com
"Imagination is more important than knowledge."




 Original message 
From: Stefan Sullivan  
Date: 7/22/2018  2:20 PM  (GMT-08:00) 
To: A discussion list for music-related DSP  
Subject: Re: [music-dsp] What is resonance? 

Yes. The term helmholz resonator should be a hint ;) Basically when a sounds 
gets added to itself after a delay you end up adding energy to the frequency 
that corresponds to that delay amount. For very long echos we don't hear it as 
a resonance, but for shorter delays it will boost higher and higher frequencies 
into the audible range.
Stefan
On Sun, Jul 22, 2018, 08:10   wrote:

Hello all

 

Is "feedback with delay" really resonance? I recognize many people describe the 
effects of "room resonanes this way", but to my understanding these are no 
resonances in the basic meaning but reflections. A resonance is a self standing 
oscillating system like a guitar string or an air mass in a Helmholtz resonator.

 

 Rolf

 

Gesendet: Samstag, 21. Juli 2018 um 04:33 Uhr

Von: "Andrew Simper" 

An: "A discussion list for music-related DSP" 

Cc: audit...@lists.mcgill.ca, local-us...@ccrma.stanford.edu, 
surso...@music.vt.edu

Betreff: Re: [music-dsp] What is resonance?





Resonance is just delay with feedback. Resonance occurs when you delay a signal 
and then feed it back with some gain to the input of the delay "in phase"

 





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Re: [music-dsp] What is resonance?

[Stefan Sullivan]

Oh interest challenge of the definition of resonance. The typical textbook
diagram shows a little local bump at some frequency in a bode diagram, but
if you consider dc the resonant frequency, then the only way to show a bump
is by being higher than all the other frequencies (i.e. monotonically
decreasing).

Hmm, I wonder. One common definition of resonance bandwidth is also the
"3dB" point. But I guess resonating at dc is probably not a common use case.

Stefan


On Sun, Jul 22, 2018, 18:11 robert bristow-johnson 
wrote:

>
> I've been wondering about the connection that resonance and filter orders
> at least 2.  That's 2 delays (and feedback).
>
> But if you're limiting the resonant frequencies to DC and Nyquist, then
> with a one-sample delay digital filter, you can have something like
> "resonance".
>
>  Even if the single delay is two samples long (but no tap in the middle),
> that allows only DC, Nyquist, or half-Nyquist as tunable frequencies.
>
> So just sayin, in another sense of the word, that "resonance" can be had
> with a single *long* delay and one feedback path or with two arbitrarily
> short delays and two feedback paths.
>
>
>
> --
> r b-j r...@audioimagination.com
>
> "Imagination is more important than knowledge."
>
>
>
>
>
>  Original message 
> From: Stefan Sullivan 
> Date: 7/22/2018 2:20 PM (GMT-08:00)
> To: A discussion list for music-related DSP 
>
> Subject: Re: [music-dsp] What is resonance?
>
> Yes. The term helmholz resonator should be a hint ;) Basically when a
> sounds gets added to itself after a delay you end up adding energy to the
> frequency that corresponds to that delay amount. For very long echos we
> don't hear it as a resonance, but for shorter delays it will boost higher
> and higher frequencies into the audible range.
>
> Stefan
>
> On Sun, Jul 22, 2018, 08:10  wrote:
>
>> Hello all
>>
>> Is "feedback with delay" really resonance? I recognize many people
>> describe the effects of "room resonanes this way", but to my understanding
>> these are no resonances in the basic meaning but reflections. A resonance
>> is a self standing oscillating system like a guitar string or an air mass
>> in a Helmholtz resonator.
>>
>>  Rolf
>>
>> *Gesendet:* Samstag, 21. Juli 2018 um 04:33 Uhr
>> *Von:* "Andrew Simper" 
>> *An:* "A discussion list for music-related DSP" <
>> music-dsp@music.columbia.edu>
>> *Cc:* audit...@lists.mcgill.ca, local-us...@ccrma.stanford.edu,
>> surso...@music.vt.edu
>> *Betreff:* Re: [music-dsp] What is resonance?
>> Resonance is just delay with feedback. Resonance occurs when you delay a
>> signal and then feed it back with some gain to the input of the delay "in
>> phase"
>>
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Re: [music-dsp] What is resonance?

[Sound of L.A. Music and Audio]

A HHR performes both simple reflection and self oscillation. At the 
beginning of the triggering phase the sound runs into it and is 
reflected at the inner walls. A little part of the sound comes out 
through the hole while a larger part is reflected creating steady waves 
as known in all rooms as modes. These partly again come out. So far this 
is just reflection.


But the little hole causes losses and local over pressure so it is also 
an obstacle for the air inside which will start to pump. This way a 
continous wave in beneath the HH-frequency is so to speak "loading" the 
HHR which will become louder and louder. This causes a shift of the 
phase difference between the incoming and outgoing waves coming to zero 
finally when the feeding signal reaches the losses.


Therefore the HH might emphasize but also eliminate certain frequencies 
in the room depending on the phase and volume difference and the length 
of the signal. It might happen that a triggering sound is thus limited 
and does not overload the room with modes but after the sound is over, 
the HHR resonator will continue to feed the room with sound when 
unloading his energy, unless damping material is used inside to limit this:


http://96khz.org/files/2003/helmholtz-resonator-damped-silenced.jpg


A classical HHR built as a heavy iron sphere will have only one dominant 
frequency and low losses, while a wooden case might have up to three. A 
light wooden case might even pick up energy from the moving air inside 
starting to emit sound on it's own resonance freqs.


So does the guitar: it picks up energy from the stings and performs both 
energy storage in the wood and direct reflections inside the corpus. In 
theory a guitar even has little HHR capabilites :-)


To distinguish both effects in the meaning of signal processing, one 
could describe the reflections as a FIR behaviour while the energy 
storing is an IIR. Real time simulation of loudspeaker cases can be done 
this way, e.g. bass reflection tubes. In a very simple model the 
reflections can also be replaced by IIR since the reflection of a sine 
wave with a smoothed volume curve will also add to something like a II 
response.


gtx

Dipl.-Ing. Jürgen Schuhmacher


Am 22.07.2018 um 23:20 schrieb Stefan Sullivan:
Yes. The term helmholz resonator should be a hint ;) Basically when a 
sounds gets added to itself after a delay you end up adding energy to 
the frequency that corresponds to that delay amount. For very long echos 
we don't hear it as a resonance, but for shorter delays it will boost 
higher and higher frequencies into the audible range.


Stefan

On Sun, Jul 22, 2018, 08:10 > wrote:


Hello all
Is "feedback with delay" really resonance? I recognize many people
describe the effects of "room resonanes this way", but to my
understanding these are no resonances in the basic meaning but
reflections. A resonance is a self standing oscillating system like
a guitar string or an air mass in a Helmholtz resonator.
  Rolf

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Re: [music-dsp] What is resonance?

[charles morrow]

How about freezing and stretching moments. Is this resonance?

> On Jul 22, 2018, at 21:10, robert bristow-johnson  
> wrote:
> 
> 
> I've been wondering about the connection that resonance and filter orders at 
> least 2.  That's 2 delays (and feedback).
> 
> But if you're limiting the resonant frequencies to DC and Nyquist, then with 
> a one-sample delay digital filter, you can have something like "resonance".
> 
>  Even if the single delay is two samples long (but no tap in the middle), 
> that allows only DC, Nyquist, or half-Nyquist as tunable frequencies. 
> 
> So just sayin, in another sense of the word, that "resonance" can be had with 
> a single *long* delay and one feedback path or with two arbitrarily short 
> delays and two feedback paths.
> 
> 
> 
> --
> r b-j r...@audioimagination.com
> 
> "Imagination is more important than knowledge."
> 
> 
> 
> 
> 
>  Original message 
> From: Stefan Sullivan  
> Date: 7/22/2018 2:20 PM (GMT-08:00) 
> To: A discussion list for music-related DSP  
> Subject: Re: [music-dsp] What is resonance? 
> 
> Yes. The term helmholz resonator should be a hint ;) Basically when a sounds 
> gets added to itself after a delay you end up adding energy to the frequency 
> that corresponds to that delay amount. For very long echos we don't hear it 
> as a resonance, but for shorter delays it will boost higher and higher 
> frequencies into the audible range.
> 
> Stefan
> 
> On Sun, Jul 22, 2018, 08:10  <mailto:rolfsassin...@web.de>> wrote:
> Hello all
>  
> Is "feedback with delay" really resonance? I recognize many people describe 
> the effects of "room resonanes this way", but to my understanding these are 
> no resonances in the basic meaning but reflections. A resonance is a self 
> standing oscillating system like a guitar string or an air mass in a 
> Helmholtz resonator.
>  
>  Rolf
>  
> Gesendet: Samstag, 21. Juli 2018 um 04:33 Uhr
> Von: "Andrew Simper" mailto:a...@cytomic.com>>
> An: "A discussion list for music-related DSP"  <mailto:music-dsp@music.columbia.edu>>
> Cc: audit...@lists.mcgill.ca <mailto:audit...@lists.mcgill.ca>, 
> local-us...@ccrma.stanford.edu <mailto:local-us...@ccrma.stanford.edu>, 
> surso...@music.vt.edu <mailto:surso...@music.vt.edu>
> Betreff: Re: [music-dsp] What is resonance?
> Resonance is just delay with feedback. Resonance occurs when you delay a 
> signal and then feed it back with some gain to the input of the delay "in 
> phase"
>  
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Re: [music-dsp] What is resonance?

[robert bristow-johnson]

I've been wondering about the connection that resonance and filter orders at 
least 2.  That's 2 delays (and feedback).
But if you're limiting the resonant frequencies to DC and Nyquist, then with a 
one-sample delay digital filter, you can have something like "resonance".
 Even if the single delay is two samples long (but no tap in the middle), that 
allows only DC, Nyquist, or half-Nyquist as tunable frequencies. 
So just sayin, in another sense of the word, that "resonance" can be had with a 
single *long* delay and one feedback path or with two arbitrarily short delays 
and two feedback paths.


--r b-j                     r...@audioimagination.com
"Imagination is more important than knowledge."




 Original message 
From: Stefan Sullivan  
Date: 7/22/2018  2:20 PM  (GMT-08:00) 
To: A discussion list for music-related DSP  
Subject: Re: [music-dsp] What is resonance? 

Yes. The term helmholz resonator should be a hint ;) Basically when a sounds 
gets added to itself after a delay you end up adding energy to the frequency 
that corresponds to that delay amount. For very long echos we don't hear it as 
a resonance, but for shorter delays it will boost higher and higher frequencies 
into the audible range.
Stefan
On Sun, Jul 22, 2018, 08:10   wrote:

Hello all

 

Is "feedback with delay" really resonance? I recognize many people describe the 
effects of "room resonanes this way", but to my understanding these are no 
resonances in the basic meaning but reflections. A resonance is a self standing 
oscillating system like a guitar string or an air mass in a Helmholtz resonator.

 

 Rolf

 

Gesendet: Samstag, 21. Juli 2018 um 04:33 Uhr

Von: "Andrew Simper" 

An: "A discussion list for music-related DSP" 

Cc: audit...@lists.mcgill.ca, local-us...@ccrma.stanford.edu, 
surso...@music.vt.edu

Betreff: Re: [music-dsp] What is resonance?





Resonance is just delay with feedback. Resonance occurs when you delay a signal 
and then feed it back with some gain to the input of the delay "in phase"

 





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Re: [music-dsp] What is resonance?

[Stefan Sullivan]

Yes. The term helmholz resonator should be a hint ;) Basically when a
sounds gets added to itself after a delay you end up adding energy to the
frequency that corresponds to that delay amount. For very long echos we
don't hear it as a resonance, but for shorter delays it will boost higher
and higher frequencies into the audible range.

Stefan

On Sun, Jul 22, 2018, 08:10  wrote:

> Hello all
>
> Is "feedback with delay" really resonance? I recognize many people
> describe the effects of "room resonanes this way", but to my understanding
> these are no resonances in the basic meaning but reflections. A resonance
> is a self standing oscillating system like a guitar string or an air mass
> in a Helmholtz resonator.
>
>  Rolf
>
> *Gesendet:* Samstag, 21. Juli 2018 um 04:33 Uhr
> *Von:* "Andrew Simper" 
> *An:* "A discussion list for music-related DSP" <
> music-dsp@music.columbia.edu>
> *Cc:* audit...@lists.mcgill.ca, local-us...@ccrma.stanford.edu,
> surso...@music.vt.edu
> *Betreff:* Re: [music-dsp] What is resonance?
> Resonance is just delay with feedback. Resonance occurs when you delay a
> signal and then feed it back with some gain to the input of the delay "in
> phase"
>
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Re: [music-dsp] What is resonance?

[rolfsassinger]

Hello all

 

Is "feedback with delay" really resonance? I recognize many people describe the effects of "room resonanes this way", but to my understanding these are no resonances in the basic meaning but reflections. A resonance is a self standing oscillating system like a guitar string or an air mass in a Helmholtz resonator.

 

 Rolf

 

Gesendet: Samstag, 21. Juli 2018 um 04:33 Uhr
Von: "Andrew Simper" 
An: "A discussion list for music-related DSP" 
Cc: audit...@lists.mcgill.ca, local-us...@ccrma.stanford.edu, surso...@music.vt.edu
Betreff: Re: [music-dsp] What is resonance?





Resonance is just delay with feedback. Resonance occurs when you delay a signal and then feed it back with some gain to the input of the delay "in phase"

 





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Re: [music-dsp] What is resonance?

[Andrew Simper]

Resonance is just delay with feedback. Resonance occurs when you delay a
signal and then feed it back with some gain to the input of the delay "in
phase" with the original input, which means the delayed signal adds
together and boosts the input level to the delay. If you use a normal
digital delay line you get what is called a linear phase delay, so each
frequency is delayed by the same amount. If you use an IIR filter to delay
the signal you get what is called a non-linear phase delay, so each
frequency is delayed by a different amount. The particular arrangement of
multiple stages of delays and how the feedback is arranged both around
individual stages and globally all determine the structure of the filter,
and the type of filtering achieved.

Most synth filters use IIR filters. The amount of non-linear phase delay is
typically referred to in terms of degrees, as this is usually more useful
for filter design. When the signal has been delayed 360 degrees at a
particular frequency, if you add this to the input signal you get a boost
in amplitude of that frequency since it is back in phase with the input,
which is called constructive interference. With enough feedback gain a
resonant peak will form as the constructive interference is in a feedback
loop with itself. Most resonant filter designs use the fact that taking the
negative of a signal actually changes the phase by 180 degrees at all
frequencies. So most filters delay the phase of the signal by 180 degrees
somehow, then subtract this from the input with some gain (negative
feedback) and so form a resonant peak.

Many people have spent a lot of time forming many types of low pass
resonant filter structures. In synths it is mostly the non-linear
properties that very between different filters, there are actually only 3
structures typically used to form low pass resonant filters: multiple IIR
one pole integrators with feedback (svf) or multiple IIR one pole low pass
filters with feedback (sallen key, cascade).

Andy


On Sat, 21 Jul 2018 at 01:29, Spencer Jackson  wrote:

> Resonance is the characteristic of some systems to store and release
> energy at particular frequencies. It's not limited to filters, mechanical
> systems like springs or pendulums have resonance (get on a swing at the
> park and try to change your frequency and you'll feel the effects of
> resonance).
>
> In an electrical system, a minimal passive resonant circuit would be one
> with 2 capacitors and 2 resistors. Selecting the values of the components
> determines the frequency, but what happens is that at a certain frequency
> the energy gets stored and passed back and forth between the capacitors,
> like the swing going back and forth. This storage and energy swapping
> emphasizes that frequency. Depending on the "Quality factor" or amount of
> resonance that frequency can become much more apparent than the other
> frequencies in the signal even if the input is wide-band.
>
> When you are talking about delay and feedback, you are creating a digital
> filter, but I think it is worthwhile to spend some time understanding the
> theoretical concept and think in terms of energy and frequency. Your
> feedback delay becomes the storage and certain frequencies will resonate
> with that system.
>
> > But it is having the resonance in parralel to a dry sound that bothers
> me; but may be that's the only way to do ?
>
> I'm not sure what you mean but I think you need some study in filter
> design, because a single feedback delay causes comb filtering but its not a
> classical lowpass. Is that what you are trying to achieve? Digital filters
> are almost universally combinations of short delays (typically 1 sample)
> placed in different patterns and fed back in different amounts (e.g.
> https://en.wikipedia.org/wiki/Digital_filter#Filter_realization).
>
> Here are some resources that may help you:
> http://www.dspguide.com/ch14.htm
>
> https://www.native-instruments.com/fileadmin/ni_media/downloads/pdf/VAFilterDesign_2.0.0a.pdf
>
> That first one is a book that can help you more with the fundamentals in
> the early chapters as well. I hope this is somewhat helpful, if not perhaps
> I need to understand better specifically what you are trying to achieve.
> _Spencer
>
>
> On Fri, Jul 20, 2018 at 10:13 AM, Mehdi Touzani 
> wrote:
>
>> Hi all,
>> I follow the llist for a while, but I am not a DSP programmer, I do DSP
>> audio apps for about 20 years now, for sonic core plateform "Scope" and
>> Xite".   I begin with other things like juce or flowstone, but so far,
>> scope is still far superior in terms of sound results. Too bad there is no
>> scripting tool for it (well there is but it is not available to me).
>>
>> My question is probably weird for you  - like super noob - , because i am
>> NOT looking for math or codes, but hints about a general
>> design/architecture.
>>
>> So... how do you do a resonance in a lowpass circuit?   :-)   not the
>> math, not the code, just the architecture.
>>
>> 

Re: [music-dsp] What is resonance?

[Spencer Jackson]

Resonance is the characteristic of some systems to store and release energy
at particular frequencies. It's not limited to filters, mechanical systems
like springs or pendulums have resonance (get on a swing at the park and
try to change your frequency and you'll feel the effects of resonance).

In an electrical system, a minimal passive resonant circuit would be one
with 2 capacitors and 2 resistors. Selecting the values of the components
determines the frequency, but what happens is that at a certain frequency
the energy gets stored and passed back and forth between the capacitors,
like the swing going back and forth. This storage and energy swapping
emphasizes that frequency. Depending on the "Quality factor" or amount of
resonance that frequency can become much more apparent than the other
frequencies in the signal even if the input is wide-band.

When you are talking about delay and feedback, you are creating a digital
filter, but I think it is worthwhile to spend some time understanding the
theoretical concept and think in terms of energy and frequency. Your
feedback delay becomes the storage and certain frequencies will resonate
with that system.

> But it is having the resonance in parralel to a dry sound that bothers
me; but may be that's the only way to do ?

I'm not sure what you mean but I think you need some study in filter
design, because a single feedback delay causes comb filtering but its not a
classical lowpass. Is that what you are trying to achieve? Digital filters
are almost universally combinations of short delays (typically 1 sample)
placed in different patterns and fed back in different amounts (e.g.
https://en.wikipedia.org/wiki/Digital_filter#Filter_realization).

Here are some resources that may help you:
http://www.dspguide.com/ch14.htm
https://www.native-instruments.com/fileadmin/ni_media/downloads/pdf/VAFilterDesign_2.0.0a.pdf

That first one is a book that can help you more with the fundamentals in
the early chapters as well. I hope this is somewhat helpful, if not perhaps
I need to understand better specifically what you are trying to achieve.
_Spencer


On Fri, Jul 20, 2018 at 10:13 AM, Mehdi Touzani 
wrote:

> Hi all,
> I follow the llist for a while, but I am not a DSP programmer, I do DSP
> audio apps for about 20 years now, for sonic core plateform "Scope" and
> Xite".   I begin with other things like juce or flowstone, but so far,
> scope is still far superior in terms of sound results. Too bad there is no
> scripting tool for it (well there is but it is not available to me).
>
> My question is probably weird for you  - like super noob - , because i am
> NOT looking for math or codes, but hints about a general
> design/architecture.
>
> So... how do you do a resonance in a lowpass circuit?   :-)   not the
> math, not the code, just the architecture.
>
> Personnally,  i came to the conslusion that  some kind of very short delay
> with feedback, mixed in parallel with the non resonance low pass sound,
> could do the trick. . The more feedback, the more resonance, and with
> feedback over -6dB, it would begin to self resonate.
>
> But it is having the resonance in parralel to a dry sound that bothers me;
> but may be that's the only way to do ?
>
> I have read about hardware filters and ok, there is math, but there is
> also the effect of the hardware components. Some articles even suggest that
> a bandpass in parralel could do the trick : or more exactly, a bandpass
> fonction is created after the resonance, to remove frequencies that would
> overlap with the cutoff.
>
>
> So, any hints that could help me improve the process etc would be very
> welcome.
>
> Thanks
>
> Mehdi
>
> ___
> dupswapdrop: music-dsp mailing list
> music-dsp@music.columbia.edu
> https://lists.columbia.edu/mailman/listinfo/music-dsp
>
___
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Re: [music-dsp] What is resonance?

[STEFFAN DIEDRICHSEN]

The resonance in low pass filter with an order greater than 2 is basically just 
a feedback from the output to the input. You need to switch the polarity of the 
signal, in other words, you subtract the output from the input, in order to 
place the feedback point to the point, where the phase shift of the low pass 
filter is 180 degrees. 

Hope this helps you to get started. 

Best,

Steffan

Von meinem iPad gesendet

> Am 20.07.2018 um 12:13 schrieb Mehdi Touzani :
> 
> Hi all,
> I follow the llist for a while, but I am not a DSP programmer, I do DSP audio 
> apps for about 20 years now, for sonic core plateform "Scope" and Xite".   I 
> begin with other things like juce or flowstone, but so far, scope is still 
> far superior in terms of sound results. Too bad there is no scripting tool 
> for it (well there is but it is not available to me). 
> 
> My question is probably weird for you  - like super noob - , because i am NOT 
> looking for math or codes, but hints about a general design/architecture.
> 
> So... how do you do a resonance in a lowpass circuit?   :-)   not the math, 
> not the code, just the architecture. 
> 
> Personnally,  i came to the conslusion that  some kind of very short delay 
> with feedback, mixed in parallel with the non resonance low pass sound, could 
> do the trick. . The more feedback, the more resonance, and with feedback over 
> -6dB, it would begin to self resonate. 
> 
> But it is having the resonance in parralel to a dry sound that bothers me; 
> but may be that's the only way to do ? 
> 
> I have read about hardware filters and ok, there is math, but there is also 
> the effect of the hardware components. Some articles even suggest that a 
> bandpass in parralel could do the trick : or more exactly, a bandpass 
> fonction is created after the resonance, to remove frequencies that would 
> overlap with the cutoff.
> 
>  
> So, any hints that could help me improve the process etc would be very 
> welcome. 
> 
> Thanks
> 
> Mehdi
> ___
> dupswapdrop: music-dsp mailing list
> music-dsp@music.columbia.edu
> https://lists.columbia.edu/mailman/listinfo/music-dsp
___
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music-dsp@music.columbia.edu
https://lists.columbia.edu/mailman/listinfo/music-dsp

Re: [music-dsp] What is resonance?

[Mehdi Touzani]

Hi all,
I follow the llist for a while, but I am not a DSP programmer, I do DSP
audio apps for about 20 years now, for sonic core plateform "Scope" and
Xite".   I begin with other things like juce or flowstone, but so far,
scope is still far superior in terms of sound results. Too bad there is no
scripting tool for it (well there is but it is not available to me).

My question is probably weird for you  - like super noob - , because i am
NOT looking for math or codes, but hints about a general
design/architecture.

So... how do you do a resonance in a lowpass circuit?   :-)   not the math,
not the code, just the architecture.

Personnally,  i came to the conslusion that  some kind of very short delay
with feedback, mixed in parallel with the non resonance low pass sound,
could do the trick. . The more feedback, the more resonance, and with
feedback over -6dB, it would begin to self resonate.

But it is having the resonance in parralel to a dry sound that bothers me;
but may be that's the only way to do ?

I have read about hardware filters and ok, there is math, but there is also
the effect of the hardware components. Some articles even suggest that a
bandpass in parralel could do the trick : or more exactly, a bandpass
fonction is created after the resonance, to remove frequencies that would
overlap with the cutoff.


So, any hints that could help me improve the process etc would be very
welcome.

Thanks

Mehdi
___
dupswapdrop: music-dsp mailing list
music-dsp@music.columbia.edu
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