One for the speaker repair experts

Discussion in 'The Workbench' started by shakti, Oct 19, 2020.

  1. shakti

    shakti Active Member

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    I have been working on a pair of early 70s Cerwin Vega ER123 speakers, and I am soooo close to having them fixed, but need some support and suggestions to keep my spirits up...hang on...

    Some of you will have heard of these rather short-lived speakers made by the Hollywood company more known for high-powered hi-fi and car stereo speakers. But in the early 70s they made this full-range 12 inch speaker which found favour with Duane Allman. It was sort of under the radar until the early 2000s when it was revealed that it was one of his favourite speakers and that he used them at least on occasion toward the end of his short career. The details are sketchy, we don’t know when he started using them or if it was a deliberate change, if they were swapped into his Marshall cabs or if they were in a different cab to the side of his main rig. We do know he used JBL D120Fs at least in early 1970. However, once you try these speakers it’s one of those «Eureka!» moments and those Fillmore East lines almost play themselves.

    The ER123 was only in production for a few years AFAIK, but found their way into cabs from Sunn and Traynor and a few other companies. There was also a Fender labeled version with red baskets called the PS-12. It was superceded by the ER124 which had a cloth suspension and sounds different. These days they are very hard to find.

    I bought a pair of these on Ebay UK in 2006. Unfortunately they fell victim to a particularly shpddy packaging job, and arrived with cones trashed and ripped beyond repair. I was devastated, and it took me 3 years or so to find another pair. I have been using them along with a pair of Celestion T1281s as it was rumoured that it was a combination that Allman preferred, and it sounded really good. I have a video on Youtube demonstrating the sound.

    The original, damaged pair have been sitting in boxes for 14 years since I almost never throw anything out, and I thought that perhaps one day I could get around to reconing them. But finding suitable parts was really hard. They use a 2 inch voice coil with vented aluminium former, a 6 ridge cup spider and a 6 rib all paper cone with double fold suspension. I couldn’t find anything currently made that matched these well enough. So I decided to see if I could recycle some of the original parts. Long story short, I’ve had these on the bench several times the past few years and always decided that it was going to be impossible to do. The aluminium dustcap had to be removed and none of the old glue on these was easy to remove (old Celestions are a walk in the park compared to these!), the spiders were very thin and brittle, and the original cone looked like it was epoxied on. Nevertheless, I was magically able to patch up the spiders, remove the dustcap and original cone without too much damage, and then fit a new cone on the original voice coil, former and spider. I found one which was very close to the original, not exactly the same suspension but close, and 8 vs 6 ribs.

    The big problem is with the voice coil wires. These are too short to reach up to where you attach the flexible tinsel wire going to the terminals. So I have to splice and extend them. I did so using just a single strand from a standard stranded signal wire, and I managed to get them working. Enough to hear that they work as expected and sounding great along with (though not identical with) the original working pair I have. But after playing loud for a little while, there was intermittent buzzing and it was apparent that I am not making good enough contact with the voice coil. I have been making several attempts now and have on several occasions almost given up. I had epoxied the splices when I thought I had it made, only to discover I was getting problems again. I had to use a Dremel with the smallest bit I had to carefully remove the epoxy and expose the frail voice coil wires again, and I think I have only one attempt left before I have to give them up.

    See the photo I have posted below! On one the speakers, I have only about 2 mm left to work with, where I have to graft/splice an extension to the voice coil wire. The voice coil is intact, so it’s only a matter of making a sound connection from it and on to the tinsel wires and on to the terminals. Epoxy it, and the speakers should be functioning again. But I need some moral support as I have been so close to giving up. Does anyone have *any* tips on how best to do it? I am wondering if the extension I previously made, with just a single strand from a multi-strand wire, was too thin? It’s only going to be about an inch long, so I thought it wouldn’t matter, but do I need to find the correct gauge of copper wire to make the extension? And what about the technique for splicing it? Any clever suggestions?
     
  2. shakti

    shakti Active Member

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    image.jpeg I think in these photos the small piece of voice coil wire I have to work with is not even visible!
     
  3. shakti

    shakti Active Member

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  4. shakti

    shakti Active Member

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    578066C4-CEFD-442B-AC33-0EDAED2206F3.jpeg 0D6C6E18-1025-4997-9668-F427F41CF604.jpeg 9008DA05-33D0-4AAD-8605-22B85B0F5EB0.jpeg 578066C4-CEFD-442B-AC33-0EDAED2206F3.jpeg 0D6C6E18-1025-4997-9668-F427F41CF604.jpeg Here’s what the spider and voice coil looked like before I patched the spiders and attached new cones. You might be able to see how little voice coil wire there was sticking out, and now it’s even less...
     
  5. shakti

    shakti Active Member

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    Bump. Even though I’ve fixed many a speaker with a rub and other mechanical issues, I don’t have too much knowledge about the electromechanical principles. Any particular things to take into consideration when I have to extend the voice coil wires?
     
  6. Scumback Speakers

    Scumback Speakers Well-Known Member

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    You will want to be VERY CAREFUL with the solder to the new wire, and not overheat it. That's about all I have for you, sir!
     
  7. shakti

    shakti Active Member

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    Thanks! Another option is to just run the tinsel wire from the solder terminal, through the cone, and solder it to the little stump of voice coil wire. That way there will be less splices, but I am worried it will be harder to get a good contact that way. I won’t be able to wrap the voice coil wire around the tinsel wire or vice versa.
     
  8. Scumback Speakers

    Scumback Speakers Well-Known Member

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    When they are broken off that short, it's always a challenge.
     
  9. shakti

    shakti Active Member

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    OK, I am sooooo close now. I have managed to extend the voice coil wires nicely. There is continuity, the speakers are working....but as soon as there is sufficient volume, I am getting crackling and intermittent connection. I was about to toss them out, but I am almost certain it is actually coming from the connection between the voice coil wire (extension) and the tinsel wire to the terminals. The physical vibration from the cone is causing the noise. I don’t know if it’s my technique when soldering to the tinsel wire, if it’s using the wrong glue to secure the voice coil wire and joint (I used epoxy), or maybe I have the joint too far up on the cone, where there is more vibration.

    I am completely obsessed with getting these to work by now. Not ready to give up. Any more tips?
     

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