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genmin 16th March 2009 08:27 PM

Speaker Dope
Hello to all, will put trust in the responses I get, send me down the right path. I have two 1940's Stephens P-52L's 15" drivers. Both are excellent one with no issues whatsoever. One although has a break at the frame edge on the cone paper. It is a hairline about 7/8" long and you can not see through it. On the opposite side there is some rubbing wear or a scuff from an installation from years past. I would like to keep these as original as long as possible and not re-cone until needed. I need a product name for repairing this type of crack and patch. Where available it may be and how much overlap of the product into the cone paper beyond the area of concern. All will be appreciated, Thanks genmin

blumenco 17th March 2009 06:04 AM

Parts Express has "speaker repair glue."

should get you along.


Piek 17th March 2009 07:40 AM

White wood glue with some water (the one that gets transparent when dried) if its just paper and maybe a piece of pocket tissue at the back, depending on stability.


badman 17th March 2009 07:50 AM

Micha is absolutely correct.

genmin 17th March 2009 03:42 PM

So what you are saying is that a semi brittle white glue is better than a resilient rubber solvent base like is used around the perimeter of the cone?

badman 17th March 2009 04:58 PM

You can use rubber cement, but the woodglue tends to soak into paper cones very well. It's not as brittle as you think, when it's thin. It's also easy to thin and apply, and since it's water solvent, it doesn't outgas it's solvents potentially deteriorating already old adhesives in the assembly.

I actually use this stuff extremely liberally inside sealed cabinets. Gloop it in, rotate, let it cure (keep rotating so it gets into all the gaps.

Does a great job of preventing airleaks and strengthening the cab.

HK26147 17th March 2009 05:11 PM

One off the first speaker repair kits I ever bought included a Material Data Sheet that listed the contents of the included glue.
It was the exact same makeup as white flexible fabric glue.
In fact another kit included a bottle of Aleene's Super Tacky.
Roscoe Flexbond is the same stuff.

I have used thin black wrapping paper as a backer; doped with that glue. It can be thinned with water and the smallest amount of a surfactant to improve absorption.
It drys quickly, especially with a hair dryer set to low.


Siggma 30th November 2012 09:10 PM

Just to poke my nose in here I have a story about speaker doping that seems on topic, even if it's an old topic.

Once a long time ago I bought a little bit of speaker dope as an experiment to see how it worked on dust caps. It turned out the recipe was very very simple consisting of MEK as in "Methyl Ethyl Ketone" and vinyl as in pool toy vinyl. Obtain about a pint of MEK and an old swimming pool toy, the bright green one's that are sticky and have a very closed tight surface are perfect. Cut up or shred the vinyl pieces in a jar along with some MEK and let it dissolve. You'll need to shake it often, it takes a while for it to dissolve. Get a small brush for application and go for it. You'll probably only need a 1/2 cup of MEK and a 6" square of vinyl. There is no magic to the recipe because the MEK evaporates leaving the vinyl wherever it is. Since the MEK is a liquid solvent it easily soaks into paper cones and other things so when it evaporates it leaves the vinyl where it sits. The more you apply the more gets deposited. The vinyl, while not really acting as a glue, can help bond layers of cloth, paper, wool, bamboo, wood fiber etc. It can also add "body" and stiffness while reducing surface vibrations by adding weight to the individual fibers or clumping the fibers together.

What does this do for the sound?

On simple paper cone speakers it can reduce distortion and help smooth out response, depending on how much you apply and where you apply it. It was sold to me as a way to seal the dust cap of a paper cone woofer that was making unmusical noises due to dust cap leakage. It was also touted as being able to smooth out the FR of inexpensive basic paper cone speakers. It also makes the speaker easy to clean, protects it from sunlight to some degree and leaves it looking very shiny and water resistant. As far as sound goes, it made a huge difference on all the speakers I used it on. One was a SEAS 4" woofer that had a little bit of nasty around 3K and it sounded better. It can also be used to increase the weight of the cone slightly but I'd be careful. Adding too much could significantly reduce efficiency which could literally destroy a good working speaker system due to fundamental changes in the function and parameters of the underlying driver rendering the currently functioning crossover dead wrong for the speaker so BE CAREFUL. On the other hand, if you're in the design phase you can apply as many coats as you want. Each coat dries quickly and the effects are immediate. I'd begin by benching the driver first and calculating T/S parameters watching for apparent changes in Fs, BL and MMS. I never noted any significant changes in T/S parameters but then I only applied 2 or 3 coats, just enough to make the look shiny and feel sticky.

While I don't expect it will make a huge difference in the FR of the average speaker nor will it turn a $4 4" full range into a single speaker symphony, it will destroy the speaker if you aren't careful. MEK is a solvent for more than just vinyl. If applied in too much quantity it might begin to dissolve the glues or epoxies used to bond the surround or spider so use it sparingly and test small areas first. Be especially careful with foam surrounds. Some of them might literally turn to jelly when they come in contact with MEK. I haven't ever applied this kind of dope to a foam surround so I don't know what it will do. Finally, MEK is a probable health hazard and is highly flammable. Be careful and read the MSDS sheet before using it.

turk 182 2nd December 2012 11:37 PM

bostic 4035 adhesive (surrounds & spiders)
3m scotchgrip 1300-L (dust caps)
both have a short shelf life and are hard to find in small quantities as they're generally only sold in bulk to industrial users

bear 3rd December 2012 01:42 AM

For a cone like the Stephens, I'd use a bit of gauze bandage (cotton), a single layer, for the backer (sort of like the fiberglass tape used for fixing walls), and then depending on what exactly needed repair - a JPEG here would be very useful, a reasonable coating material can be suggested.

As far as vinyl in MEK, that's maybe a suitable material for treating paper cones. It's not what is used for cloth surrounds, fwiw, and afaik. Keep in mind that some plastics don't hold up well over time due to oxidation and UV, so this can be a problem down the road. How far down the road is a big question. The commercial preparations have been used for a long time and checked for bad effects over time...


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