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-   -   NO SOUND on PA mains please help (http://www.diyaudio.com/forums/pa-systems/185721-no-sound-pa-mains-please-help.html)

imetetsupos 24th March 2011 08:45 PM

NO SOUND on PA mains please help
 
Hello, I'm fairly new to speakers and brand new to this forum and I'm in need of some advice. I have a pair of Acoustic PA mains I bought used off a guy and after maybe 40 shows, sound went out on one and months later on the second.

I can't find any information on these speakers online or on the speaker box so I don't even know what wattage rating they have. Each PA speaker has a hefty metal horn and two 'black widow' 15" speakers. The speaker's don't look ripped at all, and the crossover fuses don't look blown either. I've double checked connections, wire quality, and my power amp and signals and all I am getting is no sound in one speaker, and in the other, there is a very very faint sound signal coming through the horn only.

Can anybody offer advice on how to figure out what's wrong and what to replace. Could the fuses be bad even though they look ok? Thank you

GoranB 24th March 2011 09:00 PM

It will be the best if you can use an digital multimeter to meassure the ressistance of fuses (no ressistance) and driver units.

chris661 24th March 2011 09:06 PM

Black Widow (Peavey?) are, from memory, well-known drivers. Recone kits are probably available, you could get a professional to do it for you.

Also seconded on the measuring the resistance of the drivers.

pinkmouse 24th March 2011 09:09 PM

These things are robust. Use a 9v battery with flying leads, briefly tap the terminals of the speakers, and if the driver pops, it's fine, if not, likely they've been overdriven and the voice coils inside the motor have burnt out.

firechief 24th March 2011 09:22 PM

Pinkmouse offers old and usefull trick. Disconnect from amp, use 9v batt and find out if speakers are blown.

Arty 24th March 2011 09:58 PM

i would not do that to tweeters, but woofers are just fine with that.
Are You sure Your amp is okay?

Andrew Eckhardt 24th March 2011 10:02 PM

One good thing about replaceable basket speakers from the used market is you can always unbolt them from the magnet and inspect the coil assembly.

pinkmouse 24th March 2011 10:35 PM

Quote:

Originally Posted by Arty (Post 2515188)
i would not do that to tweeters, but woofers are just fine with that.

Nah, any decent compression driver will be fine, though I only use 3V on domestic tweeters.

imix500 24th March 2011 10:46 PM

The woofers as several have already said, are totally re-basketable. You don't have to send them to anyone to get it done. Takes all of 5 min to replace one. If there are any power resistors in the crossover I would check those. They can open up or change resistance when driven really hard.

BobEllis 25th March 2011 03:05 PM

Forgive me if you've already done this, but have you verified that the electronics work with another set of speakers? It's not clear that you have from your troubleshooting description. You don't need anything with PA durability, just turn it down and hook up any set of speakers and verify that decent quality sound is being fed to the speakers. Hafler DH500's have a speaker fusing arrangement that allows a very thin sound through if blown...

I use Al's battery trick, albeit with a AA battery. Try it from cabinet input connector. I've seen bad jacks allow plugs to be blown out with slap bass. If the 1/4" jack turns out to be the problem you might consider modifying the cabinet with Speak-Ons.

If you can't get a sound from the input then move to the drivers as Al suggested. If the drivers are OK, then there's an issue between input and driver. Try the battery at the crossover input. If that works, it's most likely a bad jack. If not, your fuses may have gone slowly and just look OK.

You just need to step through the system methodically to find the bad part. Good luck.


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