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Old 2 weeks ago
Lives for gear

Some thoughts:

- Running a frequency sweep through a guitar speaker and recording the result with your Cab Mic Of Choice will give you a first-order approximation of how that speaker behaves. You'll have frequency and phase responses, which can be Fourier'd into an impulse response if you so wish. That's probably how they go about producing those files.

- The above does not tell you all the information about how a speaker behaves. It gets the broad strokes: the level and phase relationships between the outgoing notes, once you put a signal in.

- The additional information that's missing is stuff like harmonic distortion, and producing frequency curves at different volume levels. For instance, if you hit a guitar speaker with a low palm-muted chug, the speaker will visibly jump if the amp is cranked. Since they tend to have a very small mechanically-linear region, large cone excursions will produce something akin to soft-clipping. Running a sweep at a low-ish (linear) level won't ever capture those details!

- There are further confounding variables, too: when a microphone is subject to high SPLs, it too will probably add some distortion. There's also the matter of mic positioning - who is to say that the harmonic distortion components of a driven speaker will have the same dispersion pattern as the cone itself?

I suspect it's possible to put such things into code, and we could have a very good software representation of a guitar speaker. Measuring all the things in the first place would be a loud and time-consuming task, though, which is probably why nobody has really bothered.