I'm using an AX500 sub, which Ian has told me performs similarly to an EP175. I'm using M3s as the mains, and the Arcam AVR100 for a receiver. I have the sub's crossover turned up all the way, since the receiver's crossover is 100 Hz. The sub's volume level is between 1/3 and 1/2.

The only movie I've noticed this problem with is the Star Wars Episode 1, and I've never felt it with music. During the podrace scene, there are a few moments of intense bass that almost feels like somebody is giving me chest compressions.

What's causing this, is there any way to prevent it (apart from watching a better movie), and is there any risk to the sub from this phenomenon?

Thanks

I remember that movie. The podrace scene does have very intense bass, and your sub is simply reproducing it. You could lower the volume of your sub during this scene. As long as the volume is at 1/2 or less, I don't see how it could damage your sub.