sound on sound's synth secrets backs me up when I say resonant filters amplify bands of frequencies ;)
shttp://www.soundonsound.com/sos/oct99/articles/synthsecrets.htm not alone after all 2015-01-13 13:48 GMT-02:00 Alexandre Torres Porres <por...@gmail.com>: > This bit of the wikipedia article on resonance about "Q" ( > http://en.wikipedia.org/wiki/Resonance#Q_factor ) mentions a lot of what > we read about "Ringing Filter", and how a higher Q will make it "ring" > longer... this is what you get from that bandpass in the EQ Cookbook that > says it has "constant skirt gain, peak gain = Q" - or what I'm assuming > to be a "resonant filter by excellence" or whatever... > > cheers > > > > 2015-01-13 13:38 GMT-02:00 Alexandre Torres Porres <por...@gmail.com>: > > "*Ultimately I think "resonant" is a general descriptive term for >> filters, that shouldn't be interpreted as a detail of implementation.*" >> >> I guess you have a point there, and I was also driving to this conclusion. >> >> "*It sounds like the Resonz UGen in supercollider is exactly what Julius >> Smith is talking about in that description of the two-pole filter.*" >> >> Actually, the Resonz UGen is a Two Pole / Two Zero filter, which is very >> more closely related to [cyclone/reson~]. >> >> A Two-Pole only filter (no zeros) like the one Julius is describing is >> actually what the [bp~] object is! >> >> "*But then there's the other supercollider filter UGens with "resonant" >> in the name, which seem more like what Martin was describing - RLPF >> (resonant low-pass filter) for example is a low-pass filter where you can >> adjust the resonance near the cutoff.* " >> >> Yep, and this is also much like the [cyclone/lores~] object in Pd. Check >> that patch I sent for more detailed info on these filters. >> >> I've always assumed that a filter, in order to be called a "resonant >> filter" or a "resonator" - being it a low pass, a high pass or a band pass >> -, needed to boost/add gain to a particular cutoff frequency (in the case >> of lowpass and highpas - which is the case for [lores~] or RLPF) or add >> gain to some center frequency (in the case of a bandpass) - which is also >> called "resonant frequency". >> >> The quote from Julius in that link - where he says "*A resonator is a >> recursive filter that boosts signal amplitude at a particular frequency*" >> - is in line with my assumption. >> >> But the concept of resonance in physics, in its utmost purity according >> to wikipedia, is that it "is the tendency of a system to oscillate with >> greater amplitude at some frequencies than at others". Meaning that it >> doesn't really have to add gain to something, but only favor a frequency >> amongst others... In this context, a bandpass - in general - is a >> "resonator"... >> >> But it'd be cool if I could find a definitive word about this in the >> filter literature! >> >> Cheers >> >> 2015-01-13 13:16 GMT-02:00 Brian Fay <ovaltinevor...@gmail.com>: >> >> It sounds like the Resonz UGen in supercollider is exactly what Julius >>> Smith is talking about in that description of the two-pole filter. >>> >>> But then there's the other supercollider filter UGens with "resonant" in >>> the name, which seem more like what Martin was describing - RLPF (resonant >>> low-pass filter) for example is a low-pass filter where you can adjust the >>> resonance near the cutoff. I haven't played with this too much myself, but >>> I'm guessing with the right Q value you could drive this to >>> self-oscillation? >>> >>> Ultimately I think "resonant" is a general descriptive term for filters, >>> that shouldn't be interpreted as a detail of implementation. >>> >>> On Tue, Jan 13, 2015 at 9:28 AM, Alexandre Torres Porres < >>> por...@gmail.com> wrote: >>> >>>> I'm pending to say that there is no real distinction between "Resonant >>>> filter" and a "resonator", and a "bandpass" can be implicitly thought of as >>>> a resonator. Here's what I also found in Julius' website >>>> >>>> >>>> https://ccrma.stanford.edu/~jos/filters/First_Order_Complex_Resonators.html >>>> >>>> Pass the mouse cursor over the "Resonator" over the title "First-Order >>>> Complex Resonators >>>> <https://ccrma.stanford.edu/~jos/filters/Two_Pole.html>" to see the >>>> popup (also attached). >>>> >>>> cheers >>>> >>>> 2015-01-13 1:20 GMT-02:00 Martin Peach <chakekat...@gmail.com>: >>>> >>>> I was looking at circuit diagrams for analog synthesizers recently and >>>>> noticed that the "resonance" control is nothing more than feeding some >>>>> fraction of the output back to the input. With more feedback oscillation >>>>> occurs at the cutoff frequency for any type of filter, highpass, bandpass >>>>> or lowpass. >>>>> >>>>> Martin >>>>> >>>>> >>>>> On Mon, Jan 12, 2015 at 9:09 PM, Alexandre Torres Porres < >>>>> por...@gmail.com> wrote: >>>>> >>>>>> Nice I give an impression to be an expert, but filters is just >>>>>> something I've actually recently started studying :) >>>>>> >>>>>> > I'm wondering if by "resonant" filter you mean the >>>>>> > same thing as "resonator" filter? >>>>>> >>>>>> Now you got me... good question, and I'm not sure, haha. The link >>>>>> looks nice btw, will definitely check it. Thanks. >>>>>> >>>>>> So now I'm even more confused. Is "resonant filter" and "resonator" >>>>>> two different concepts? Maybe I'm having trouble with the english >>>>>> nomenclature and everything. >>>>>> >>>>>> To be honest and more detailed about the issues I'm encountering, I >>>>>> ask this based on another topic I was discussing with Julius Smith in the >>>>>> Supercollider list, but it went dead and I got no replies. In it I was >>>>>> asking if the object "Resonz" should really be called a "Resonant >>>>>> filter", >>>>>> because it was just a bandpass filter in my opinion. Then Julius was >>>>>> mentioning how "*A resonator is a special case of a passband filter >>>>>> having a nearly zero-width passband.*" >>>>>> >>>>>> I see he used the term "resonator" and not "Resonant Filter" (as >>>>>> Resonz is described). So yeah, now I'm more confused... is resonator the >>>>>> same as resonant or what? >>>>>> >>>>>> But anyway, we can bring the discussion into the Pd world, and talk >>>>>> about the [reson~] object, as I will do later on. >>>>>> >>>>>> I was googling and saw how the term resonant filter could be used to >>>>>> describe a regular bandpass filter. And how the bandpass' center >>>>>> frequency >>>>>> could also be called "resonant frequency". So they might be used in the >>>>>> same way... (accurately or not). >>>>>> >>>>>> Now here is my opinion. Just like a resonant low pass filter (the >>>>>> [lores~] object in Pd), the concept of resonance in a filter relates to >>>>>> how >>>>>> it adds gain around the resonant frequency. >>>>>> >>>>>> In the Audio-EQ-Cookbook (link: >>>>>> http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt ) that presents >>>>>> formulas for biquad coeficients you have two different bandpass filters, >>>>>> lets call them BPF1 and BPF2. So, BPF2 has "constant 0 dB peak >>>>>> gain", meaning it doesn't affect anything arounf the center frequency. >>>>>> Now >>>>>> BPF1 says it has "constant skirt gain, peak gain = Q", meaning that >>>>>> the Q or bandwidth controls the gain of the filter. I consider BPF2 >>>>>> to be a regular bandpass filter, whereas BPF1, which adds gain for >>>>>> narrower >>>>>> bandwidths, seems to be a "resonant" one... (which makes me think Resonz >>>>>> shouldn't be described as resonant filter, as it's just a bandpass, or >>>>>> "BPF2"). >>>>>> >>>>>> Oh, there's another term around, the "ringing" filter, which seems to >>>>>> be another term for resonant filter. In SuperCollider they have Ringz, >>>>>> which was supposed to be the same as Resonz object (or a resonant filter >>>>>> for that matter), but they are different like the two different kinds of >>>>>> bandpass in the EQ Cookbook (Ringz = BPF1 / Resonz = BPF2). >>>>>> >>>>>> Coming into the Pd world we can talk about the [reson~] object. As >>>>>> the name implies, it is a resonant filter. But the helpfile says it is a >>>>>> "Bandpass >>>>>> filter" (damn). Funny enough, in Max, the [reson~] object is said to be >>>>>> indded a *Resonant Bandpass Filter*. So maybe we should update [reson~]'s >>>>>> help file in Pd... But the deal is: [reson~] is actually a bandpass like >>>>>> BFP2 or Resonz, but it has a separate parameter for the gain. Meaning it >>>>>> works basically as a bandpass filter, where changing the Q doesn't affect >>>>>> the gain. But you can also give it a boost or a cut with the gain >>>>>> parameter. By giving it a boost it would behave in a way that I'm >>>>>> considering to be an actual "resonant" filter. >>>>>> >>>>>> Now let me go ahead and share a patch that I'm writing for my >>>>>> computer music classes. It's about several filters that can be obtained >>>>>> with biquad. So I present Pd's vanilla filters such as [lop~], [hip~] and >>>>>> [bp~]. I also present externals like [lores~] and [reson~] and I do >>>>>> present >>>>>> all the filters from the Audio Eq Cookbook as well. It's in portuguese, >>>>>> and >>>>>> part of a big series of examples, but what the hell... >>>>>> >>>>>> By the way, I was also able to implement Resonz and Ringz as >>>>>> [biquad~] in Pd, but I don't have it on this example (but to hell with >>>>>> supercollider already, hehe). >>>>>> >>>>>> So there you can check the behaviour and differences that I've >>>>>> pointed. For [reson~], I have two separate parameters, one is for "Q", >>>>>> and >>>>>> the other one, which is originally "gain", I'm calling the "resonance" >>>>>> parameter. Much like the resonance parameter in [lores~]... >>>>>> >>>>>> As for the Cookbook filters, BPF2 is what I'm calling a regular >>>>>> "bandpass", and it has a parameter of "Q". As for BPF1, I'm calling it a >>>>>> "resonant filter", and it has a parameter of "resonance" instead of "Q" >>>>>> (but the idea is that more Q gives more gain/resonance). >>>>>> >>>>>> I hope I'm clear in the midst of so much detail and information. It's >>>>>> just a stupid doubt on the nomenclature of filters, but this kind of >>>>>> issue >>>>>> can be quite a pain in the ass, and the subject of many confusions. >>>>>> >>>>>> So, in short, I still keep my original question: Are bandpass and >>>>>> resonant filters the same? Or is there a difference between calling one a >>>>>> resonant and not a bandpass? Moreover, what about a resonator? Is my >>>>>> assumption on how to call one a bandpass and a resonant correct or it >>>>>> doesn't have anything to do with the official literature? And how about >>>>>> what Julius Smith had to say? >>>>>> >>>>>> Cheers >>>>>> >>>>>> 2015-01-12 20:03 GMT-02:00 Brian Fay <ovaltinevor...@gmail.com>: >>>>>> >>>>>> Based on your posts in this group, you definitely know more about >>>>>>> filters than I do, so I don't really have an answer to this question - >>>>>>> but >>>>>>> I'm wondering if by "resonant" filter you mean the same thing as >>>>>>> "resonator" filter? >>>>>>> >>>>>>> I saw something interesting earlier today about using resonator >>>>>>> filters as control sources for FM synthesis: >>>>>>> http://tai-studio.org/index.php/projects/sound-programming/complexres/ >>>>>>> >>>>>>> The paper that is linked in the article has some details on the >>>>>>> mathematical implementation of the filter, but that's mostly >>>>>>> mumbo-jumbo to >>>>>>> me. >>>>>>> >>>>>>> On Mon, Jan 12, 2015 at 4:24 PM, Alexandre Torres Porres < >>>>>>> por...@gmail.com> wrote: >>>>>>> >>>>>>>> Hi, are bandpass and resonant filters the same? Or is there a >>>>>>>> difference between calling one a resonant and not a bandpass? >>>>>>>> >>>>>>>> thanks >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> Pd-list@lists.iem.at mailing list >>>>>>>> UNSUBSCRIBE and account-management -> >>>>>>>> http://lists.puredata.info/listinfo/pd-list >>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> Pd-list@lists.iem.at mailing list >>>>>> UNSUBSCRIBE and account-management -> >>>>>> http://lists.puredata.info/listinfo/pd-list >>>>>> >>>>>> >>>>> >>>> >>> >> >
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