How to diagnose and hopefully repair a PA speaker? no sound

S

smili

New member
Hi all, this is pretty basic, but I've had trouble finding a how to on the web. Hoping somebody here had a pointer.

I've got a PA speaker (Sunn Model 2) in a 16ohm cabinet and one of the two 8 ohm speakers has died - killing the whole thing. Condition is fine - no visible damage. I'm hoping someone here can point me to somewhere that can help me troubleshoot what I need to check. (My mom was using it for square dancing classes and I wasn't there when it stopped working - don't know what happened).

When I put the multimeter on the terminals of one speaker it's fine - it comes in at 0.10 - so I'm guessing it's registering that one at 8ohm like it should be. When I put the multimeter probes on the terminals of the other speaker (the bad one I assume) I get nothing. It's like I haven't touched anything - infinite resistance essentially. I'm assuming this means wiring in the speaker is broken and signal can't get from one terminal to the other.

Is there a place I can go to learn what the "usual" suspects are to look for - especially if it's something I can try to fix myself before I just get another speaker? This is a very old cabinet - from at least the 80s, maybe earlier.

Appreciate suggestions. If "get a new speaker" is the best answer that's fine, but I figure there's probably some common things I can check first.
smili is online now Edit/Delete Message
 
Since you get no reading with the meter the voice coil is most likely shot which is a common failure with a speaker that old. That means that you must either have the speaker reconed or purchace a new speaker.
 
ocnor said:
Since you get no reading with the meter the voice coil is most likely shot which is a common failure with a speaker that old. That means that you must either have the speaker reconed or purchace a new speaker.
Click to expand...

thanks for the quick reply. Is reconing something I might give a shot at myself - or should I have done? I'm guessing I might could buy a new speaker for not much more than the repair cost? thanks again for the reply

edit: after your post I looked up reconing.... Doesn't look so straightforward for a DIY. hmmm.
http://www.eighteensound.com/index.aspx?mainMenu=service
 
Just check that the wring between the cone and the terminals has not fractured, these wires are subject to a lot of vibration, also check that there is not a bad solder joint where the wire fixes to the terminal (i have had this). It's a long shot but worth checking.

I would get a price on re-coning, if you get it done with a factory kit (original) it will be as good as a new speaker, so even if you saved 20% of the new price you are still in front, further more the recone people may be able to fix the coil without putting in a new kit, I have had this done in the past for a fraction of a new speaker. I should say that the cost saved will directly relate to how much the speaker is worth in the first place as the labour and materials will still be about the same for a low price speaker and a high price speaker.

Alan.
 
witzendoz said:
Just check that the wring between the cone and the terminals has not fractured, these wires are subject to a lot of vibration, also check that there is not a bad solder joint where the wire fixes to the terminal (i have had this). It's a long shot but worth checking.
Click to expand...

will do. thanks for the suggestion. This is an old small speaker - a Sunn Transducer 1016G from a Sunn Model 2 cabinet. 40W rms at 8ohm. I'm even having trouble finding a replacement it's so small if it is a PA woofer. I've posted on the Sunn board too - I'm thinking it may actually be designed as a guitar speaker - not a PA woofer. (the "G" 1016G in the model name makes me think it might be a guitar speaker. On the web I saw mention of one used in Fender Princeton Blackface amp - but info is very limited on what I can find)/ There's lots of guitar speakers with similar spec though.
 
I actually was just about to give up on the speaker and was poking around on it, checking the terminals, the wires underneath the terminals, etc - and then I put the probes on it and pushed down with pretty good force - and I got a little bit of beep on the multimeter and a change in resistance. I think I can even hear the speaker crackling just a little bit as I watched the resistance jump up and down. Maybe there is a short in the wires like you mention.

It's odd, because I touch the wires underneath the terminals and can't get anything except infinite resistance, but if I push down on the terminals I get a little bit less. Still maybe 30-50 ohms at best - but it never settles in - so it could be intermittent and is on the way down to @8ohm if the connection is better. I'm not real sure how to get up between and under the speaker cage and speaker cone, but going to see what might be going on... thanks for the rec. I've got some fiddling to do now.
 
chopped off dust cap - I think I've found the right wire where signal isn't getting through from the terminal. Going to see what I can do - try to maybe ooze some solder where the wire goes through the speaker cone... will see what happens.
 
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