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Old 2 weeks ago
  #17
Lives for gear
 

Yes, any speaker will have to move air It appears you've missed my point, though.

The 12" woofer in a good PA speaker might have a linear range of 5mm each way from rest, where what goes in is pretty much what comes out.
A guitar speaker typically uses a short coil with minimal overhang, so the linear excursion available might only be 1mm.

If we hit each speaker with a "chug", the guitar speaker will mechanically soft-clip that, while the PA speaker will move considerably further because it has a larger linear region.


There are similar things happening in other areas, too. A high-quality PA speaker will feature demodulating rings, which help to keep the permanent magnetic field nice and linear, directly lowering midband distortion.
I haven't heard of a guitar speaker which employs such a device, so now you've got to simulate flux modulation, too. How much there is will depend on a lot of factors.

The suspension/surround of a good PA speaker will also be much more linear than that of a guitar speaker, which might have lots of non-linearity engineered in! For instance, it'd be trivially easy to make a driver where the suspension shows lower compliance in the "out" direction vs "in". In that case, your driver will show higher 2nd order harmonic distortion, and that's a simple case! Suspension linearity is typically a curve (rather than the linear example I gave), and guitarists typically like to operate right at the edge of that curve.

These will all show up in harmonic distortion graphs, but the difficult part is this: music is dynamic.

As you hit a note, there'll be the initial transient which the speaker will soft-clip (we're assuming fairly high power levels here), and then the note itself, which the driver will add it's own harmonic distortion signature to.
As the note decays, the power levels begin to recede and the harmonic distortion contribution from the speaker will also reduce.

So, we must continually adjust the distortion of the speaker according to the instantaneous signal level, and that becomes a very difficult piece of software to produce!

Chris