More detail: It's because different speaker construction techniques make for different frequency response curves - i.e. there's sounds a cheap speaker can't pro

More detail: It's because different speaker construction techniques make for different frequency response curves - i.e. there's sounds a cheap speaker can't produce well, so music mastered for listening on commodity hardware of a bygone era sounds "compressed", because they squeeze all of the sound into a narrower band, so you could hear all of it.