Just to play, I plugged my Dual into my receiver. It doesn't have a strobe, so my tuning method is crude: I put on a record and the same CD and played them in sync, and switched between them to set the speed.

This was the first time in a while I plugged in this turntable into my system... the last time I had speaker grille over the speakers, so if this was happening, I didn't see it.

I noticed when I was switched to the turntable, the midrange cone started going nuts. NUTS. It looked like it was going to pop out of the cabinet. I'd switch back to the CD (which sounded much louder) and it returned to normal.

What the heck is happening????