feedback resistor and cap bypass to eliminate ice pick

[uneumann]

F/R doesn't need to be measured with single frequency input. An alternative would be noise analysis. Zollner uses both.

That's a good point. But, doesn't the equivalence of single freq and noise analysis assume a linear system? It's likely that lower power tests meet that criteria better than high power.

That said, a high power NL system noise test can be revealing and may be useful. It's just not to be confused with F/R.

[Helmholtz]

That said, a high power NL system noise test can be revealing and may be useful. It's just not to be confused with F/R.

From Zollner's results it seems that guitar speakers are not really that non-linear with reasonable/typical drive.
I trust him to choose an appropriate measuring method.

To me the speaker response question is settled.

[uneumann]

From Zollner's results it seems that guitar speakers are not really that non-linear with reasonable/typical drive.
I trust him to choose an appropriate measuring method.

To me the speaker response question is settled.

It may be settled for you - that's fine. You can believe what you wish.

A quote from Zollner's book may help others decide for themselves.
On page 11.3 he describes the options for voice coil length within the magnetic circuit. He explains that NL distortion is a factor due to the efficiency goal for guitar spkrs..



On page 11.53 he restates the view that NL effects are significant....

The non-linearity in the magnetic system clearly is the transducer coefficient (the force-factor): as system-variable Bl, it takes care of the proportionality between current and Lorentz force: F = Bl ⋅ I. However, this proportionality requires that the system variable Bl is independent of the signal – specifically independent of the displacement. That is not the case here: with increasing displacement, the coil moves out of the magnetic field and therefore Bl decreases.

In fact the whole chapter 11.6 is devoted to the various sources of NL behaviors of speakers.

[Helmholtz]

A quote from Zollner's book may help others decide for themselves.

Yes, guitar speakers may have like 10% distortion at rated power (players usually don't complain).

I just don't see a relation to the question if guitar speakers lose treble when pushed.

As said, as a player I don't experience such treble loss at stage level and Zollner's measurements show that f/r doesn't change with power.
(BTW, the OP uses a 100W speaker with an 18W amp.)