[PD] overdriven speaker
fallen_devil at gmx.de
Thu Mar 10 13:21:06 CET 2011
the papers on http://www.klippel.de/pubs/papers.asp where quiet
interesting. But the page went down.
It looks like it went to:
Am 16.10.2010 06:46, schrieb Martin Schied:
> I'm no speaker modeling expert at all, but I can try to describe what
> produces sounds in an overloaded speaker. There are various sources of
> distortion, symmetrical (mechanic suspension) and asymmetrical
> (magnetic field) and also time variant (temperature) and modulation
> (doppler effect / amplitude modulation) effects. I don't know which
> effects have a stronger or weaker influence, but I describe what I
> High peak amplitude, positive wave:
> speaker moves to the front, parts of the coil will not be in the
> magnetic field anymore. The field isn't zero outside the magnet gap,
> but I guess it decreases rapidly and is almost zero (so for example if
> half the coil is inside the magnet, the parts outside will not produce
> a force. So the force is only half as strong as it should. For
> simplicity you could say the field outside the magnet's gap is zero,
> so you have a linear function of excitation / current. Also If the
> coil moves out of the field its impedance will decrease which has
> influence on frequency response for higher frequencies a bit.
> If the impedance is reduced as described above, a higher current will
> flow and heat the coil more than usual. The resistance of the coil
> will increase when it gets warmed and thus the efficiency of the
> speaker decreases (up to -7 dB I read somewhere, but this wasn't meant
> for almost dead speakers but heavy load). The heat needs some time to
> dissipate, so some kind of slow pumping compression effect occurs.
> High amplitude, negative wave:
> The speaker's coil might crash into the magnet and create different
> mechanical noises. Also the speakers diaphragm will be deformed by
> this crash and create various kinds of noise. Additionally it carries
> the noises the coil created - depending on the material and shape this
> sound different (paper, Kevlar, aluminum, etc sound different). If
> this crash doesn't occur (professional speakers don't have this issue
> usually) the negative wave will not be distorted too much and maybe
> distortion can be ignored.
> In both directions the spider (basically a spring) starts to become
> nonlinear. Different manufacturers have different curves, but for
> small amplitudes they all pretend to be linear - so some experiments
> with sin~ or tanh~ might do it here.
> Then generally there are happening doppler-effects on all speakers
> with big excursion. You could model them through a variable delay,
> modulated by a differentiated, low pass filtered signal (don't bite if
> I'm wrong, it's already very late... ). Amplitude modulation can be
> applied the same way (lowpass and apply it to higher frequencies).
> so to sum it up:
> apply symmetric distortion for the spider, split the path into
> positive and negative parts, for positive samples: tanh~, polynomials
> or other wave shapers, for negative parts let the signal untouched or
> add noises of a crashing coil (don't know how to achieve this), then
> sum both signals up, apply doppler effect, amplitude modulation and
> pumping compression. perhaps that sounds like your speakers then :)
> I'm not sure if this works at all, but it definitely will sound very
> distorted in the end.
> did you already discover http://www.klippel.de/pubs/papers.asp ?
> On 15.10.2010 21:10, - wrote:
>> Thank you for your answer,
>> but as I wrote I don't want the sound of simple clipping like clip~,
>> tanh~ or overdrive~. I want the sound of a speaker crying for mercy
>> because you put just too much through it.
>> But I don't know where to start. I know there are complex distortion
>> effects, which are able to simulate different speaker cabinets after
>> variable amps recorded by different microphones. But they all cost big
>> money. Also I don't need the physical simulation. I just want the sound.
>> If you want I can try to record the sound I'm talking about.
>> I tried to search for information how to do this but couldn't find
>> anything usable. Not even an analysis what happens inside the speaker
>> when you torture it like this.
>> I already know the forum but don't want to doublepost. I really liked
>> the post about the oto biscuit. Neat distortion possibility's.
>> Am 15.10.2010 17:12, schrieb George Ker:
>>> I can't really understand, so , you mean something different from
>> [clip~] ?
>>> I' m sure you can find really good patches in the puredata.hurleur.com
>> forum searching about distortion , overdrive clip etc
>>> On 14 October 2010 23:19, - <fallen_devil at gmx.de> <mailto:fallen_devil at gmx.de> wrote:
>>> does anyone know how to simulate the sound of an overdriven
>> speaker? You
>>> know the crunchy sound when you torture it with a strong bass. It's
>>> nowhere near the sound of an normal overdrive with some kind of
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