Film-Tech Forum ARCHIVE: Subwoofer Amp Heat

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Posted by Bhaskar Dhungana (Member # 1283) on 07-06-2006, 04:43 AM:

While doing a routine check of the speakers we found one of the sub amps running unusually hot. The woofer itself seems to be working fine. The movie was "Fast & the Furious:Tokyo Drift" with lots of action, so perhaps its only natural. Is there something that I should look out for? Are there tests we can do to make sure its running properly? Are there precautions that I can take before a proper test can be done?

[ 07-06-2006, 11:52 AM: Message edited by: Bhaskar Dhungana ]

Posted by Louis Bornwasser (Member # 3063) on 07-06-2006, 09:06 AM:

With the amp on and no input, measure DC voltage and make sure there is no (or almost no dc volts) on the amplifier output. Other than that, enjoy. Serious subs require serious power and that mean heat. Louis

Posted by Alexander Smith (Member # 1769) on 07-06-2006, 10:08 AM:

I think the only problem with Fast And Furious 3 is the sound
mix is way-too-loud as an overall, subjective, assessment. The
sound mix uses _alot_ of sub-bass and that's probably why your
amp is overheating. It's having to do a bit more work than it
would normally do.

Turn your fader down a click and it'll be fine. :-)

Alex.

Posted by Cody Martin (Member # 2523) on 07-06-2006, 11:00 AM:

Had a similar problem. We turned the volume down a little for this film. This film shipped with a note asking theatres to run it under 80dbl. Can someone confirm?

cody

Posted by Alexander Smith (Member # 1769) on 07-06-2006, 05:59 PM:

Sorry to report we (in the UK) did not receive any note about
the fader level.

It's daft to mix a film sound track loud, and then ask cinemas
to play it quietly. Everyone else* in the industry gets it
right, except one or two sound mixers who think they know
better than Dolby. :-)

Alex.

*Mostly.

Posted by Jarrad Salmon (Member # 3818) on 07-06-2006, 10:20 PM:

This problem happens alot in concert sound.

Ventilation is the key... what are your amp racks like? If they have sealed backs, I suggest opening them up for the show as it can become an oven inside the rack. Amplifying the problem [Razz]

. I have also seen people put fans in front of amps to keep them from overheating. Mainly in older style amps. Turning down the amp will help a bit, but the problem is more to do with the complex signal entering it.

quote: Alexander Smith
Sorry to report we (in the UK) did not receive any note about
the fader level.

It's daft to mix a film sound track loud, and then ask cinemas
to play it quietly. Everyone else* in the industry gets it
right, except one or two sound mixers who think they know
better than Dolby. :-)

Alex.

*Mostly.

I agree... However I find this print is marketed to the type of people who like the music that is basically all sub woofer domination. I have some tracks they use to test car audio in competitions, songs like "sub voice coil tester" and "amp tester" speak for themselves. We didn't get any notices in Australia about this film. Are you sure it is mixed louder, or is it just percieved to be louder?

Posted by Charles Greenlee (Member # 3856) on 07-06-2006, 10:39 PM:

We had a similar situation with the first Fast and the Furious(sounds like and adult film doesn't it) movie. People complained about the loud bass, so we turned the fader down a notch. It was much better, but now they complained they can't hear the quiet talking (like there was much of that). What I ended up doing was to mark where the subwoofer amp gain was set to, and drop it little by little. What I ended up with was that it still sounded good, sounded better actually (there is such thing as too much bass), and people could hear the convo. Normally I'd save amp gain adjustments for the technitians, since they know more about that sort of thing. But since we had people wanting their money back, and our tech was unavailable, I had to make the adjustment. And don't worry, remember, I marked the setting, so it went back to it's proper/normal setting after the movie was gone. I ever breifed the tech on it when we could get him, he double checked it and said it was fine. Said that's what he'd have done if we'd had gotten him anyways.

Posted by John Hawkinson (Member # 1135) on 07-07-2006, 12:26 AM:

It seems to me there is quite a bit difference between an amp "running unusually hot," as the original poster described, and overheating or being too loud to the audience, as many of the replies have described.

If it's just hotter because it's doing more work, there's no problem. If there are concerns that it might be too hot, then measure the temperature and compare to the manufacturers' specifications, and start to run checks like the ones Louis suggests.

--jhawk

Posted by Charles Greenlee (Member # 3856) on 07-07-2006, 12:53 AM:

Sorry, John. I was kinda replying to the other replies, and not really the initial question.

Posted by Kevin Raisler (Member # 1761) on 07-08-2006, 05:56 PM:

Does the cooling fan work? our ashleys are running that flick with no additional heat what-so-ever. I got a fax with that print asking us to run it at 80 db.. I figure thats a typo.. I turned mine up to 7.5 just to give the kiddies chills [beer]