TIL (today, I learned)

This thread is dedicated to knowledge "learned today"...

I'll go first.

Today, I learned my Audio Techinica ATH-R70x are not only headphones, but microphones in parallel with the output (line and HP amp are the same output in this case)... If I hit them like a drum, my subwoofer mimics it. This isn't an issue, as I don't leave them plugged in, just interesting... I knew headphones were also microphones, but I've never had any that made LF.