Peculiar problem? Show me the light...

OK, I'm going to try and explain this as best as I can. I don't usually listen at mega volumes so this has not been noticed before. My Revel M20s can handle just about anything I put through them, and my subwoofer picks up the base inadequacies. There are some pieces of music that have tremendous base punch, and at very loud volumes I hear my Revels cracking up. Not my sub, but the M20s. Both speakers. If I turn down the volume gain from the neutral setting, on my subwoofer, the crackling goes away in the M20s. It's wierd. If I play the same piece of music with the sub off, I can play at prodigious volumes with no crackling at all. How can my self-powered sub, effect what's coming out of my speakers. I have it hooked up via the preout from my integrated. The sound, otherwise, is wonderful, but at the loudest levels with some powerful transient response type stuff, it'll crackle. I hope I'm explaining this properly. This is a very livable situation, for I just, in a blue moon, crank it up to satiate a sonic desire, sometimes. And it doesn't happen with most music. Anybody have any ideas? You might need more information, so hit me. Thanks in advance my audiophool friends. warren
Here's my system:
YBA Passion Integre
Micromega CDP
Sufire Architectural sub
Revel M20s
Audio Magic Stealth
Cardas GR Ics.
Sistrum Rack system
Sistrum Mini Monitor speaker stands
Sistrum Subwoofer stand