I hadn't thought about whether this would still with modern speakers, but this was the common assumption for several older types of speakers and microphones. O

I hadn't thought about whether this would still with modern speakers, but this was the common assumption for several older types of speakers and microphones. One of the first "science experiments" my dad showed me was the other direction: Dismantling our telephone and demonstrating that the carbon microphone (yes, I'm old) in the handset would also work as a (really bad) speaker.