Surround Goop Rejuvenation Success!

While working on my 756B project, I experimented with bringing dead goop back to life using acetone. It worked well according to measurements.

Speaker 1 had very little goop left. Most of it evaporated or slipped through the wormhole into another dimension.

Speaker 2 had a thick layer of shiny goop. However it was hard and not sticky to the touch like it should be.

When I ran TS measurements with a woofer tester, I found that the fs of Speaker 2 was ~20hz higher than Speaker 1, on the order of 55hz vs 78hz. Impedance peak at fs was much lower on Speaker 2.

I suspected the hardened goop was the culprit so I tried to re-soften it by applying acetone with a paintbrush. I hit it numerous times at 10 minute intervals, then measured a noticeable drop in fs.

Noting that there is another layer of goop on the underside of the surround, I brushed that side a few times with acetone as well. After letting the acetone evaporate, I measured the speaker again and fs was even lower--66hz!!

I think I can go a bit farther with this technique but I thought it wise to hook up the speakers and let them play and loosen up for a while. I'll remeasure and, if necessary, do another round of acetone when I take the drivers out of the boxes to paint them.

Here are the TS measurements. Dramatic changes.

1--756B with little goop remaining
2- Pre-acetone sweep of stiff goop 756B
3- Post treatment of stiff goop 756B

Just what's that goop really made of?petroleum, tree sap, latex, bees wax? Sounds like a marvel mystery compound. I would think that eventually the acetone will evaporate and leave the goop dryer than how you found it. Kind of like racers tire softener that works great for awhile, but leaves the rubber dried out, cracked and rotten in the long run.

Argggghhhhh. Don't tell me that. I treated the roller on my Rek-o-Kut TT with it. So far, so good.
I'm surprised at the acetone treatment, too. Let's see if it holds. You'd think that if it were to dry out the goop, it would have done by now.

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Kind of like racers tire softener that works great for awhile, but leaves the rubber dried out, cracked and rotten in the long run.

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Any resident chemists here?

What do we add to the Acetone to act as an emollient to the dope? That is the question.

But, first i suppose we need to know the composition of the dope, and i am under good advisement that there were several different types used by Altec/WE depending both on vintage and application.

For rubber rollers, what you want to use is the classic mix of solvent (toluene) and wintergreen oil, sold as "Rubber Renue" these days.

The solvent helps the mix to penetrate then it evaporates, leaving the oil embedded in the rubber. Works great.

This concoction might work on Altec goop too...but I'll let somebody else risk their 756Bs to find out!!

I think the acetone dissolves the hard outer layer and softens the rest of the goop. Eventually, it will probably dry out again.

What's the alternative?

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This concoction might work on Altec goop too...but I'll let somebody else risk their 756Bs to find out!!

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A 600B might be a suitable test bed. I have a fairly ratty one around, but it may be too ratty at this point. I'll see if i can dig it up.

Oil of wintergreen makes a great rust remover too, and just plain smells great.

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Oil of wintergreen makes a great rust remover too, and just plain smells great.

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That delicious medicinal aroma plus the brain cell depleting solvent huff buzz and you're there, buddy!

Now I'm wondering what happens to the solids content when the solvent evaporates? I have a pair of 414s that had a major goop accumulation at one side of the surround when I boxed them up and put them away and 7 years later, the goop is GONE. if I put acetone on these, will the goop magically reappear?

Vaselene is a petroleum product not sure if the goop is or not.

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Originally Posted by bowtie427ss

A 600B might be a suitable test bed. I have a fairly ratty one around, but it may be too ratty at this point. I'll see if i can dig it up.

Oil of wintergreen makes a great rust remover too, and just plain smells great.

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We have a product at work called ink out, works awesome on ink and it smells heavily of wintergreen. :)