This is somewhat hard/awkward to explain...so here I go:
I usually have my Monitor 70's set to Large (Full Band) on my Onkyo for 2-channel music. Well, I turned on a hip-hop song (Drake - Miss Me) and the song happens to have a constant bass line of <29Hz and the Monitor 70's themselves are supposed to cut off. Well, what's odd, is all 4 "woofers" on the Monitor 70's fluctuate to the song corresponding to that bass line even though they are not producing any sound. I don't know how to really describe this, and I might have to make a video, but I was curious if it HURTS the speaker?
Like...the woofers are not moving to the beat of the song. Instead they fluctuate (even at VERY low volumes!) -- the woofers just move in and out, at a very steady motion and all in complete synchronization - and at the same time, it produces all the other sounds (mids/lows) of the song perfectly.
Why I'm asking this, is it's the first song I've seen them do this on. And if I change my crossover on the receiver to 40Hz it goes away...and it almost seems as if, since the woofers are swaying in and out on the song, the other "bass-lines" and what not are putting pressure on top of the swaying...almost as if it could be doing this swaying motion, and if another bass-line were to hit at high volume, it'd put pressure on the voice-coil itself and bend it into the cone..I don't know if that's even possible. But it's what it "appears" to possibly be able to do if I were to "let them loose" on the song.
If this happens to hurt the speakers, I guess I'm going to have to keep them at 40-60Hz at all times (even during 2-channel audio). I'd hate to have a random playlist going and have a song like this start blaring out.
I hope I didn't butcher my explanation too much.