Yes. In this case it's maybe a little face palmy how fill in the blanks are... but heh. It cites a Bang & Olufsen patent (https://patents.google.com/patent/US2

Yes. In this case it's maybe a little face palmy how fill in the blanks are... but heh. It cites a Bang & Olufsen patent (https://patents.google.com/patent/US20090257599A1/en https://patents.google.com/patent/US20090257599A1/en) which implements voice-coil protection via measuring the resistance/impedance of the speaker while it's being driven. It also cites another patent (https://patents.google.com/patent/US20120020488A1/en https://patents.google.com/patent/US20120020488A1/en) which implements control of a speaker via combination of impedance measurements of the speaker while it's being driven + a baseline ("binding") measurement of impedance + ambient temperature that is taken at device power up - ie generating a per device calibration curve. From quickly staring at these, the Apple patents threads the needle by: * Implementing speaker control using the output of a temperature model (which is fed by the resistance measurement), instead of "directly" operating on speaker resistance. * Not implementing per-speaker calibration. (Note! There are other cited patents that I didn't look at, this wasn't meant to be exhaustive, just illustrative... and just to generally satisfy an itch)