Hi!

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 imagine:


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.

Heat

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 ?



cheers
Martin


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:
  

Hello,
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
  

-----

GeorgeKer~

http://tinyurl.com/georgeker

-----



On 14 October 2010 23:19, - <fallen_devil@gmx.de> wrote:

    Hi,

    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
    

clipping.
  

    Greetings
    -

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