Film-Tech Forum ARCHIVE: Speaker trouble

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Posted by Paul Looker (Member # 5420) on 05-13-2010, 05:04 PM:

Hi all, was just hoping for a little insight. We've been having some speaker trouble. First a really loud frequent pop and crackle. I was told that it was most likely the crossover in the setup we were using. Was losing a cabinet in another house to age so instead of pulling them one at a time for repair we decided to replace the popping speaker. Put the new one in yesterday. Brand new JBL and while we are no longer getting the popping noise there is a bit of a hiss that has me worried that it will eventually get worse and start the whole process over again.

I'm not getting it over non-sync. It doesn't get any better or worse no matter how I adjust the gain or volume to try and tune it out. It's a QSC 1400 amp. JB ultra stereo processor. Any thoughts?

Posted by Mike Blakesley (Member # 26) on 05-13-2010, 11:21 PM:

Well....no idea what could have caused the popping, but the hiss almost definitely is coming from a signal somewhere, not caused by the speaker itself.

It's easy to blame the speakers because that's where the sound is coming from, but the electronics are probably to blame. Sounds like a tech visit is in order.

Posted by Sean McKinnon (Member # 612) on 05-14-2010, 08:56 AM:

is the hiss in all the stage channels? If so it could be a signal to noise ratio issue. Second question is the replacement speaker the exact same model as it's predecessor? Is it operating at the proper resistance to match the rest of the channel? It could be that it is operating at a different resistance which is causing the speaker to be louder then the rest making the "normal" operating hiss louder then normal. You should check the wiring, crossover, speaker, and amp to confirm that everything for that speaker system is operating at the proper resistance. Someone who is compotent in calibrating cinema sound systems should come in and check the eq of the speaker and re set the Sound Pressure Level.

Posted by Joe Elliott (Member # 4006) on 05-14-2010, 09:09 AM:

Usually when we have a popping issue, it's the amp. As for the hiss, I don't know.

Posted by Michael Voiland (Member # 5386) on 05-15-2010, 01:39 AM:

Hiss would be noise. popping would be something coming loose. Check your amp rack for a wiring coming lose or a bad xlr. Slightly move each cable well someone is listening if it pops well you move a curtain cable then you got a bad connection try all signal connections. It sounds like it could be an amplifier issue also.

Posted by Monte L Fullmer (Member # 2797) on 05-15-2010, 03:37 AM:

it's that dang STANDBY Power Button on the power supply of the JB processor!

This button are the very weak link in these power supplies (it's a weak button and burns up quite easily), for what's happening is that this button is going out and it causes the current from the power supply to go slightly intermittent into the processor.

With your system on an turned down the sound real low, touch that flippin' button and I bet your system goes terribly insane.

I've had to take apart the power supply, remove that switch and put jumpers in it's place on many of them units.

See what happens ... - Monte