Please help, damaged speaker

[JPeitzman]

To start, I will be out of town for the weekend starting Thursday afternoon, so if I don't reply that is why

I think something very bad happened that I am wondering if I can fix at all. I have a pair of Zenith Allegro 1000's that I picked up off the curb a little while back. I had one speaker hooked up to an LM3875 to see if there was a reason for me to pull them out of the junk pile, these are backup speakers normally driven by an Original JLH... nice retro class-A feel Anyways all was fine, then came a pop/thump, and no more bass. I know what happened from experience and the wonderful smell. My question, is there any hope form my speaker or is it done? Can the driver be repaired, or do they have to be sidelined while I keep and eye out for an original to replace it? I am keeping my fingers and toes crossed that it was just the woofer, the tweeter sounds OK, if it damaged my Foster tweeter I will be really hot! Any ideas, or just put them on the shelf and say hey look, I have a pair of Allegro's....no you can't listen to them


James

[J.R.Freeman]

Good morning James,

Forgive my comprehension abilities this morning, as I haven't had my coffee yet! From what you've described there is a chance the woofer has bottomed out, and its voice coil destroyed.

However, for the time it takes, you might as well remove the woofer from the enclosure, and check it. Either apply a signal to it (keep the level low, as free-air excursion can get out of control) or measure the DC resistance across the terminals. There is a smaller chance that something in the crossover burned out, and in that case your woofer might still be ok.

Best of luck,

Jim

edit: to be safe, if you have a multimeter, start by checking the woofer's resistance FIRST. There is a small chance that when a voice coil fails, it can effectively cause a short circuit. That could damage your amplifier. But more than likely it will fail and measure as an open circuit ( R = ∞ )

[JPeitzman]

Thank you very much, I will check it when I get the chance. Unfortunately I think it was the woofer, the crossover isn't much more than a capacitor on the tweeter. Of course it was my fault, I should have used one of my crappy test speakers first, even though I knew this was a working amp. I triple checked everything and I am not 100% sure what went wrong, but something did go wrong. I guess live and learn.

If it is the woofer, is there any hope to fix it? I don't know much about speaker repair, but is it possible to re-wind or repair, or not worth the cost and trouble?

Thanks

James

[J.R.Freeman]

Hi James,

Unfortunately if it is the woofer, it is very tricky to replace a voice coil and nothing else. There are kits available for some woofers called 're-cone' kits, that replace every moving part. The cone, surround, spider, voice coil, flying leads (or tinsel leads). You'd have to search around to see if they are available for your application, but replacing those parts can be tricky if you have never done it. Doable though, and there are instructional videos available (probably some on youtube).

What model of speaker is it?

edit: sorry, you mentioned the models. I'll check it out tonight but I doubt Zenith has re-cone kits available. You might be able to find replacement drivers on ebay, however.