Woofer damage from new Star Wars THX DVD?


Both woofers in my JM Lab Utopias blew with the THX intro (exploding sphere) on the new Star Wars DVD. Happened at normal listening level through my Theta Casablanca II/VTL 7.5 preamp/Halcro dm58 amps. I've not blown a driver in over 30 years of being an audiophile. I've heard that the base was boosted as much as 36db on some of these DVDs. Even though the speakers are under warranty, I'm out $1,200 for a new Focal woofer (JM Lab only covers 1 driver for this kind of damage). Anybody with information or suggestions? Needless to say, I'm not happy about eating this expense if the fault really lies with an overmodulated DVD with no warning about increased bass levels. At the verey least, I'm curious to see if this happened to anyone else. The sound level was high enough that the concern for hearing loss came to mind (I'm a physician and I don't think I'm this concern is frivolous). Thanks for any thoughts or other input.
Ag insider logo xs@2xavimar
Tsrart, your theories are largely incorrect for your reference. It really doesn't work that way. What happens is largely that drivers(usually the tweeters first) get blown from being UNDERPOWERED when asked to handle more demanding levels! The amp cannot supply the current to properly control the driver(s), and therefore "clips", causing the drivers to distort, to simplify.!
It's a common misconception amoung new audio enthusiests, to think that too much power is the cause of breaking speaker components. It's not the case largely.
Also, a speaker will only respond to the signal and current that it's being fed. If you have more expensive/higher out-put potential gear, the gear isn't going to "try harder" or drive harder per se, simply because they have more potential.
It's not like a race car engine that's "more tightly wound" or anything. We're just talking about passive components that are sometimes overpushed from what they can comfortable handle. Or they are underdriven from the volume they're being asked to handle. Talking about speakers of course.
Thanks for your comments, Sean; always helpful.

I went back and played the DVD again last night on my Mezzo Utopias (powered by a Belles 350A) and on my Paradigm 100s (Parasound 1500A) with and without VMPS sub (Crown K2). I played them both hellishly loud (paintings on the walls went crooked and stuff in the china cabinet rattled and danced around) and none of the woofers even bottomed, let alone blew.

Something pathological has to be going on with Avimar's system.

will
I did the same thing Will. I could not understand how that could damage ANY system, even at massive volume. I turned my pre / pro up seven notches higher than normal ( and i like it LOUD ) and nothing even flinched. There just isn't that much bass during the opening THX "electrified exploding sphere" sequence. Something is really wrong somewhere. To blow up a driver ( let alone two ) with that big of a motor structure would really take a lot of brute force over an extended period of time. Either the drivers themselves should have never been shipped out the door ( defective ) or the amp has got BIG, BIG problems. Sean
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Sean... is it possible for the drivers to blow
if they are sent a signal that is simply below their
achievable level? So this could be a problem caused
by a PRE/PRO capable of sending a signal below 20hz
and the speakers not being capable. I know in some
of the newer PRE/PROS you have an option of declaring
a sub as either THX or non-THX. And if you do declare
your SUB or MAINS as being THX a lower signal will be
passed. I remember reading about this problem somewhere
a while back...

I also played THX intro on mine and think unless he had
the volume UP WAY TO HIGH this shoulent have happened.
Spluta: As i mentioned above, feeding a high level signal that is below the point of resonance to a vented speaker system will cause the woofer to throw wildly i.e. make excursions that can be dangerous to the woofer itself. I doubt that this is the situation with this specific case though as there really isn't a great amount of deep bass in the THX intro to that movie. Sean
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