Isn’t it about time we started utilizing the LIGO interferometer to measure the transfer function of a speaker diaphragm? We could finally have an instrument clearly superior in fidelity to our ears come into play at the interface where audio science this day keeps failing and everything is cast to the doubt of the ears.
This LIGO approach could also be used for a servo system, but more importantly, measuring the very transfer function from watts to SPL from a diaphragm’s acceleration.
This is a bit of a joke, but still, microphones simply will not do in this task. They can do ok, but by nature come with too many kinetic handshakes sweating up any attempt at measuring absolute fidelity of diaphragm output - the precise transfer function.