jdsalinger
Super Member
This is going to be a bit wordy, but it's for the benefit of future owners. I had to feel my way around in the dark because info on these is so scarce.
I picked these up locally caused I loved the looks, knew vintage Pioneers are something special and I needed a 100dB+ speaker for my 6B4G amp. The seller was very generous and gave me a very very god deal on them because there were a couple of cracks in the paper surround.
I tried to fix the cracks but I just didn't feel comfortable that they would hold up. If they are already brittle, then how much life is left in them? And how would that brittle paper surround affect the bass quality?
So, I researched ways to seal the surrounds and rejuvenate them. Got a lot of mixed opinions, but went to the hardware store to pick up some contact cement that had been recommended. Then, at the store, I started second-guessing & surfing again for more advice to get some clarity.
Found a post from a seemingly knowledgeable and experienced speaker repair tech who insisted that only a home-made solution from butyl rubber dissolved in solvent would work properly & stay flexible.
An associate at the hardware store and I started looking for butyl rubber products that I could dissolve, but came up empty. He then suggested, "what about flex seal?" (don't laugh).
I thought, "Well, it DOES say that it is liquid rubber, so why make my own flex seal, when I can just buy it?". Bad idea. Flex seal dries pretty plasticky and not rubbery. I should have tested it first.
So, yeah, in my haste, I ruined a pair of nice, vintage drivers.
I felt certain that this stiffness would impact the sound, so I just threw in the towel and cut out the mess I had made and started to research what the best surround would be.
I realize that the prevailing wisdom is that foam surrounds will give the best bass and that cloth accordion style can sometimes suffer from peaks. But I really wanted to keep these vintage looking and similar to the original single rib paper surround and felt I could live with some mid bass peaks. Additionally, I was a bit concerned that the gold tweeter bracket would interfere with the foam "bubble".
The accordion ribs are much lower profile, so that's what I finally went with. I found that the only ones that seem to be pre-treated and the proper number of ribs and dimensions were from China.
Well, they got here much sooner than I expected. I bought some with a slight downward angle to the inner diameter.
Well, the re"foam" went great except I had some glue on my finger when I pressed the cone to test interference. Ugh!! What HAD been perfect cones now one had a grey-ish glue spot. I'm very OCD, so it made me want to just give up. I couldn't sleep knowing I had mucked up the cosmetics.
I tried rubbing charcoal dust to cover it up. That didn't work. Then tried pencil lead and that was also shiny.
I was SICK to my stomach. All that work down the toilet.
Well, after rubbing in the charcoal and trying to smooth it out, I noticed the glue spot started to lift, so thankfully, I was able to get a razor under it and peel it off the cone, just taking a little paper micro-layer with it. So, now the spot is nearly invisible.
Next crisis was that I neglected to use a 30Hz tone to center the VC. I learned that with alnico speakers, the VC gap is even tighter than others. One of the two ended up having some VC rub. CURSES!! Now I have to start all over again!
More research looking for any way to fix VC rub turned up a post by @spkrdtr where he suggested a hack that you can use to center a VC without having to refoam. Basically, you need to cut out the dust cap, shim and wet the spider with acetone. I didn't really want to cut out the VC which looked perfect, so I came up with an idea to use fishing line and a screw-type tensioner to put tension on the VC just enough to eliminate the rub. I set up a fixture and it worked really well. After two attempts, I now have a smooth speaker! Thanks @spkrdtr.
Next step is to get them installed in cabinets.
I picked these up locally caused I loved the looks, knew vintage Pioneers are something special and I needed a 100dB+ speaker for my 6B4G amp. The seller was very generous and gave me a very very god deal on them because there were a couple of cracks in the paper surround.
I tried to fix the cracks but I just didn't feel comfortable that they would hold up. If they are already brittle, then how much life is left in them? And how would that brittle paper surround affect the bass quality?
So, I researched ways to seal the surrounds and rejuvenate them. Got a lot of mixed opinions, but went to the hardware store to pick up some contact cement that had been recommended. Then, at the store, I started second-guessing & surfing again for more advice to get some clarity.
Found a post from a seemingly knowledgeable and experienced speaker repair tech who insisted that only a home-made solution from butyl rubber dissolved in solvent would work properly & stay flexible.
An associate at the hardware store and I started looking for butyl rubber products that I could dissolve, but came up empty. He then suggested, "what about flex seal?" (don't laugh).
I thought, "Well, it DOES say that it is liquid rubber, so why make my own flex seal, when I can just buy it?". Bad idea. Flex seal dries pretty plasticky and not rubbery. I should have tested it first.
So, yeah, in my haste, I ruined a pair of nice, vintage drivers.
I felt certain that this stiffness would impact the sound, so I just threw in the towel and cut out the mess I had made and started to research what the best surround would be. I realize that the prevailing wisdom is that foam surrounds will give the best bass and that cloth accordion style can sometimes suffer from peaks. But I really wanted to keep these vintage looking and similar to the original single rib paper surround and felt I could live with some mid bass peaks. Additionally, I was a bit concerned that the gold tweeter bracket would interfere with the foam "bubble".
The accordion ribs are much lower profile, so that's what I finally went with. I found that the only ones that seem to be pre-treated and the proper number of ribs and dimensions were from China.
Well, they got here much sooner than I expected. I bought some with a slight downward angle to the inner diameter.
Well, the re"foam" went great except I had some glue on my finger when I pressed the cone to test interference. Ugh!! What HAD been perfect cones now one had a grey-ish glue spot. I'm very OCD, so it made me want to just give up. I couldn't sleep knowing I had mucked up the cosmetics.
I tried rubbing charcoal dust to cover it up. That didn't work. Then tried pencil lead and that was also shiny.
I was SICK to my stomach. All that work down the toilet.
Well, after rubbing in the charcoal and trying to smooth it out, I noticed the glue spot started to lift, so thankfully, I was able to get a razor under it and peel it off the cone, just taking a little paper micro-layer with it. So, now the spot is nearly invisible.
Next crisis was that I neglected to use a 30Hz tone to center the VC. I learned that with alnico speakers, the VC gap is even tighter than others. One of the two ended up having some VC rub. CURSES!! Now I have to start all over again!
More research looking for any way to fix VC rub turned up a post by @spkrdtr where he suggested a hack that you can use to center a VC without having to refoam. Basically, you need to cut out the dust cap, shim and wet the spider with acetone. I didn't really want to cut out the VC which looked perfect, so I came up with an idea to use fishing line and a screw-type tensioner to put tension on the VC just enough to eliminate the rub. I set up a fixture and it worked really well. After two attempts, I now have a smooth speaker! Thanks @spkrdtr.
Next step is to get them installed in cabinets.
