Totem Storm Subwoofer

I've had a Totem Storm for about a year now, only recently have I plugged it into the SW out on my Marantz AV8200 Receiver, previously I was using it to run my front monitors in "large" speaker mode directly from the amplifier.

I have noticed more and more than it "rattles" on the inside, hard to explain the sound, but is this the sound sub makes when it can't meet the frequencies coming from a song or movie? Ie: watching a sci fi movie with a very low hum engine noise as a spaceship flies by merely results in a tinny rattling sound, and not a full, bass sound.

Any way to know if I'm just reaching the lower limit of the subs ability, or if it is damaged?
Maybe needs a wire strapped back down...
If so,try the tack-able putty at the hardware store..great stuff.
This problem with the sub has picked back up again, but now particularly from voices on tv.

Think it is a bad idea to take off the back panel and check to see if anything is loose?
I am thinking it is distortion. This takes place when you set the xover around 40Hz and turn the volume a bit too high.

Try and reset the xover frequency at 80Hz or higher. The Storm is a wonderful sub but do not expect it to hit cleanly to the low 20Hz which is physically impossible.