Found this in the owner’s manual for JLAB earbuds:
Your new ear buds require a burn-in period to operate at their full potential. Simply plug them into your favorite sound device and let it play for 24 to 48 hours or more at normal to loud volume. This allows the driver to warm up and gain flexibility in order to reproduce a more accurate frequency range. The longer you listen to them, the better they will sound.
Interesting… NEVER heard of a driver needing to “warm up”.
Not saying it isn’t true, just… yeah. I’ll keep an eye on ’em.
PS: Even w/out the burn-in period these sound VERY nice.