I'm currious to know what amp you are driving your Utopias with ?
It appears to me that this is another case, in my experience with HT systems, where THE POWERED SUB SHOULD BE HANDLING THE BASS!
PASSIVE speaker systems, LARGELY should not be handling demanding bass from dd/dts soundtracks! I know far too many people play there "full range" speakers as "large" for movies in a "passive speaker system". And it's never going to have enough control over the bass drivers in a PASSIVE speaker to handle bass properly! I can CLEARLY overdrive the bass woofers on a pair of large Dunlavy SCIV's (4 X 12" woofers)when playing full range on some of the movie mixes out there. And I can do the same on other large speakers. I don't seem to have this kind of challenge driving active woofer designs, like Def Tech BP2000's or Infinity Prelude MTS's!!!
I've said it time and time again...."Unless you're using full range speakers WITH ACTIVE POWERED WOOFERS, you should be configuring your speakers as "small" on your pre/pro, and letting the ACTIVE POWERED sub handle the bass!!
The damping factor and control that's possible through PASSIVE CROSSOVER NETWORKS, isn't sufficient for dynamic transparancy in the bass reigion at the very least. In a powered subwoofer, the AMPLIFIER is RIGHT ON TOP of the bass driver, utilizing "TIGHTFISTED" control over the driver.
There's a reason THX has specified a 80hz setting for it's processing between bass woofer and main speakers...because it works!!!!
I bet what happened here was a case of Amplifier clipping, which cause the woofers to overheat and melt the voice coils! What Did JM Labs Say?
Anyway, my theory...