[matthewpartrick]

I have some Martin Logan in-walls for my home theater.  When the volume is really jacked, the left channel makes a super loud sound, sounds exactly like the test sweep but crazy loud, almost like a whip cracking right next to my left ear.  What's up with that?

[WGH]

Switch speaker wires at the receiver so the left channel is driven by the right amp channel and see if the noise stays on the left, then the left speaker is blown. If the noise moves to the right side then the receiver has a problem.

You may want to disconnect the right speaker completely, that way in case the left amp channel is bad you don't end up with 2 blown speakers.