Question for the scientifically minded amongst you. How does burn-in actually change the sound of a speaker? I always thought that the concept of audio gear burn-in was more audiophile mumbo jumbo but a recent experience with new speakers has changed my mind. They’ve gone from overly bright ear drum scrapers to sounding great after burning in.
Ok, so answering OP’s question, what is actually changing during burn-in in a speaker?
Yes, the effect is measurable, but I read the question as being “what’s changed in my speaker?”
From your final para, it sounds like it’s not the driver because putting a new one made no difference.