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Old 3rd September 2014, 08:00 PM   #1
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Default Help me with my PA speakers

Hi, I was given two carlsbro PA speakers because they were not working and I said I reckoned I could fix them ;-)

Anyway, turns out I can't. I get them home and I connect then to my amp and nothing. Hmm.. They are broken so I then Open them up and they look absolutely fine.... All connections look good etc etc. I decide to remove the 8" woofer and connect the + and - cables from the amp directly to the corresponding connections on the back of the speaker itself (expecting to get some sound). And absolutely nothing. I had obviously double checked the amp/cable on a known good speaker and was all fine.

When connecting directly to a speaker like that I would expect to hear audio, wouldn't you? I have done this on another speaker and I do. What would cause you to get no sound out of the driver like this (not even a crackle) and if these are faulty would you expect to hear some sound from the tweeter???

Your help appreciated

Last edited by Nobby001; 3rd September 2014 at 08:14 PM.
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Old 3rd September 2014, 08:46 PM   #2
wg_ski is offline wg_ski  United States
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If the woofer (and/or tweeter) measure open circuit on an ohm meter or produce absolutely no sound when hooked directly to an amp they are indeed fried. Do they smell funny? If so that ought to be a clue. If both the woofer and tweeter are out I'd expect to smell something.

I have seen rare cases on woofers where the wire going to the voice coil has come loose or fractured. Those won't necessarily smell burnt. If it's a tinsel lead that came loose from the coil wire under the dust cap it's fixable, if it broke off where it enters the coil it's not. That happens and you recone or replace - same as if you turned the VC to carbon.

On tweeters the lead wires getting fractured happens quite often - this can result from having too low a crossover frequency even if you don't 'toast' it. Most PA tweeter diaphragms are replaceable so it's not as big a deal.
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Old 3rd September 2014, 08:56 PM   #3
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There are two bare cables that go from the connectors to attach to the cone seem to look fine; They are in tact. Is this what you mean? I didn't notice a strange smell. This is both speakers in the pair that are at fault so it's all very odd.

Thanks for your help

Last edited by Nobby001; 3rd September 2014 at 09:13 PM.
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Old 3rd September 2014, 10:07 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

Get an ohm meter. Measure the drivers. If open they are fried.

FWIW with an idiot who fries drivers, the tweeters go long
before the bassmids, and when they go they are very dead.

rgds, sreten.
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Old 3rd September 2014, 10:19 PM   #5
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Easy method:
If you have a AA battery you can check. One speaker terminal on either end of the battery, you will hear a pop and the cone will move. If not, the circuit is open and you have to hope wg_ski is right about a tinsel lead or similar. Also, the smell is a good thing to check.
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Old 4th September 2014, 05:21 PM   #6
JMFahey is offline JMFahey  Argentina
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Frying home HiFi speakers is not very usual, because neighbours/police often stop you before long, but PA systems are used full power and beyond in large spaces full of people who demand that, so .... there its quite common.

If your speakers are dead, reconing is an option, but browsing through some speaker shop will be much faster and probably cheaper.

This will give an idea on good 8" PA woofers.

As of tweeters, you supply no data but something here should match what you have:

High frequency compression 1" and 2" drivers by Eminence, JBL, Peavey, RCF, Beyma and P Audio.

EMINENCE HIGH POWER SUPER TWEETERS

Reasonably close generic speakers are fine.
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