Do I have a bad speaker or what? The left woofer on my Cornwalls will flutter when a specific bass frequency is hit. I know it's the same frequency because the stanzas in a tune repeat for the bass guitar, and it will flutter on particular songs at the same note in repeating stanzas. It sounds a little bit like bending one of those spring door stops and letting it go. Doy-y-y-y-y-y-ing. The flutter lasts as long as the note... or less, so it's not like the system sounds bad all the time. Actually, it plays great on most everything.... Just that certain frequency.