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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
spluta
58 posts
 
Avimar..

Sorry about your wolfers that really sucks.
I would raise hell with company over that...
Please do and let us know.. Maybe we all can
help you in some way?

I just tried that DVD (my sons favorite) I
measured with my SPL meter. I set my system
to a pretty high level and tested with an agressive
DVD-A first and was coming in at 100db max.
Then i left volume at same point and ran the
THX intro. I didnt see a jump in DB's but i
can tell you my Velodyne is pretty taxed on that
part. Im guessing its not the DB's that got you
but the fact that that intro hits some pretty
low freq's. Im crossed over at 90 for movies...
works well with my setup.

Its not a party till something gets broke!
slartibartfast
100 posts
 
Spluta- You probably don't have your system set to video reference levels. When properly calibrated, you will see transients (as per the spec of dolby digital ex) well above 100 db. I believe 115 db is the transient max for Dolby Digital EX but I have measured some movies in excess of 120 db. With the Star Wars Attack of the Clones turned down a good 10 dB from reference, I am really taxing my MBL subwoofers. At reference level in a decent sized room, I can see how someone could blow a driver out on some of the explosions in the movie.

To properly set the reference level of your HT to movie theater standard, you need to calibrate each of your speakers to 85 dB with Avia when your processor is set to reference volume. Most processors set reference to 75 dB but this is innacurate.
sidssp
1,077 posts
 
I don't watch too much movies so I don't really know what reference level is correct but I think if you listen at over 100db level, you might be risking yourself to permanent hearing damages.
spluta
58 posts
 
Slartibartfast..

Thanks for input.. I am somewhat new to PROPER
system setup and appreciate any and all advice.

Isnt the test pattern different for each PRE/PRO
.. louder/quiter?

When i use the test pattern on my pre and turn up
volume to where my speakers are before being stressed
im right at 75db's for all. This equates to about 100db's
consistent when im in two channel for a busy redbook. 105db's for DVD-A and upwards toward 110 for movie peaks.

Is this because my speakers are small and room is fairly
large or is it a setup problem. Should i be using something
besides Pre test pattern?
sidssp
1,077 posts
 
Spluta,

You said 75db do you mean the display on your preamp shows 75db? If so, that is not how the setup works. You can not go by the number on the display because different power amps and speakers have different sensivitives. You need to run a test signal and measure with a SPL meter at the listening position. Someone said it should be 85db, some said 75. I don't know what is right but I will go by the lower number just to be safe.

On the other hand, if you did measure with a SPL and your speaker begain being stressed than I think your room maybe too large for your speakers. A speaker should not show stress at 75db at the listening position.

My comments were based on what I understand from your message. I could be totally wrong here because I don't quite understand what you meant by 100db for busy redbook and 105db for DVD-A.
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