Film-Tech Forum ARCHIVE: Sound Levels-Speakers in the red!

This is topic Sound Levels-Speakers in the red! in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Peter David Bruce (Member # 4447) on 02-24-2008, 08:55 AM:

Hello everyone. Got an important question here.

We are now showing rambo in our biggest screen and im concerned... the subs on the equaliser on the amps is in the orange/red during all the explosions etc. Is it safe to run speakers when they are at their limit like this? Also, can I rely on the amps to give me an accurate readout of how much stress the speakers are under?

Im not just talking about it occasionally hitting the top end of the EQ - this is pretty constant through this movie, and although it sounds amazing in-screen im worried that I may be shortening the life of the subs.

Cheers. Wish i could answer this myself but no film (not even cloverfield) has pushed our subs this much.

we are running cp650 and ashly amps. volume set at 4.5.

Posted by Mark Gulbrandsen (Member # 72) on 02-24-2008, 09:26 AM:

Its definately not good to clip the amp constantly like that. Thats the equivelent of sending direct current to the voice coil. This will cause them to heat up and the enamel on the voice coil wire will burn and the coil will self destruct. Also check the amps to be sure they are ok... Ashley uses dime store switches for the stuff on the back panel and they may need a cleaning. At the age your amps are at it is pretty commmon. I just did a local plex full of Ashley's a couple of weeks ago and had to clean every switch and pot in them.

Posted by Peter David Bruce (Member # 4447) on 02-24-2008, 09:43 AM:

I wish I knew all you were talking about. Im a picture guy, not so hot on the sound front. I will pass your advice onto my manager who (I think) will understand what you are talking about.

Thanks again Mark. Seem to always be able to rely on you for a reply.

Peter

Posted by Louis Bornwasser (Member # 3063) on 02-24-2008, 11:06 AM:

Good, you have Ashly's. Since they are MOSFET design, they will not clip in the normal way. They were designed to run well into the red without putting DC on your speaker. (like "ordinary" amplifiers do.)

Now as regards the metering: "RED" is Ok if you have an 8 or higher impedance load. If lower, red may well be impossible to reach since it is a voltage reading.

I connect 2 8 ohm subs together and bridge the amp; red is OK. If, however, your installer is driving the amps at 2 ohms, red may also be impossible.

Don't worry about the amp; worry about the speake cone which may or may not be in trouble due to overdriving.

Ashly's are hard to find right now; I'm saving mine for the theatres that must be absolutely right. Louis

Posted by Peter David Bruce (Member # 4447) on 02-25-2008, 04:13 AM:

ooh okay Louis. Thats really good to know. I shall keep an eye on the subs and run some dolby loops on it, see if anything comes out of it.

Quite cool to know our amps are some of the better ones out there.

[ 02-26-2008, 04:48 AM: Message edited by: Peter David Bruce ]

Posted by Marin Zorica (Member # 1716) on 02-25-2008, 08:34 AM:

Probably film is mixed so "hard" and you're amps aren't have enought hadroom to deal with it, so take fader little down. [Big Grin]