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Best way repairing tear in butyl rubber surround?

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  • Best way repairing tear in butyl rubber surround?

    Morning,

    To my despair, I've just spotted a little knick in the woofer surround of one of my JBL LSR308 studio monitors.

    I think it's made out of butyl rubber surround, based on a google, but I can't be 100% sure. However, assuming it is, and save for replacing the driver, what would be the best way of trying to repair the hole myself?

    Nail polish, shoe goo, rubber cement, contact cement, flexible epoxy, latex, rubber glue, GOOP, super glue, Elmers glue, hot glue, soft fabric glue, silicon glue or calk...? I've seen many recommendations but there seem to be little consensus on the optimal fix. Some of the suggestions floating around seem also to have originated in a student dorm back in the 60's, i.e. cheap but perhaps not entirely up-to-date given chemical advancements.

    This is a midrange, SQ takes precedent to durability. So I'm not sure whether the compound used should dry hard and stiff (piston-like) or have some flex to it. Also for SQ reasons, and the fact that the hole is relatively small, I'd prefer a method not involving a patch of some kind (nylon stocking, paper tissue, vinyl rubber, cloth, bicycle tyre, silk screen, cigarette paper etc), which also seem more likely to affect the cone's Fs, Mmd etc.
    Attached Files

  • #2
    First thing I'd try would be
    soft fabric glue
    in the form of Aileen's.
    Slightly thinned and applied with a fine brush; build up with several applications.
    "Not a Speaker Designer - Not even on the Internet"
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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    • #3
      I did a bunch of searching on what to use and actually purchased this and used it on both a rubber and foam surround. I applied it with a toothpick on the split edges and a 1/32 inch thick 1/4 inch area over the spilt on the out side. Very good adhesion and flexibility.

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      • #4
        Go to wherever you would buy a bicycle tube, buy the smallest patch kit for butyl tubes, go to the dollar store and buy the teensiest paint brush you can find. Gently apply the smallest amount of the glue you can. Wait 5 minutes, apply again. This will not stiifen over time, unlike acetate or urethane glues. Butyl glue for butyl. It's actually mostly solvent, with a few percent butyl rubber(no carbon black, so it's clear, usually). KLH used to use a butyl/toluene mixture to seal cloth surrounds, where added stiffness would be a problem(they used a lot, but toluene evaporates slowly from solution and they were sealing porous cloth).

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        • #5
          Also- no oily solvent to clean the brush. Stick to acetone(straight) or xylene/xylol & make sure brush is dry. No solvent? That's why I said cheap(disposable).I get a pack of a dozen brightly coloured little brushes for a buck.

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          • #6
            Originally posted by Sydney View Post
            First thing I'd try would be in the form of Aileen's.
            Slightly thinned and applied with a fine brush; build up with several applications.
            ​Thank you, Sydney. I actually think it was you I had seen mention this type of glue before. Specifically which product do you mean though because Aleene's have several that could fit the bill name-wise but not necessarily application-wise, e.g. this one: http://www.aleenes.com/aleenes-super-fabric-adhesive-2

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            • #7
              Originally posted by fdieck View Post
              I did a bunch of searching on what to use and actually purchased this and used it on both a rubber and foam surround. I applied it with a toothpick on the split edges and a 1/32 inch thick 1/4 inch area over the spilt on the out side. Very good adhesion and flexibility.
              ​Thanks for that, looks interesting since stays flexible. Is urethane compatible with butyl rubber though, as in doesn't dissolve it or anything...?

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              • #8
                Originally posted by davidB View Post
                Go to wherever you would buy a bicycle tube, buy the smallest patch kit for butyl tubes, go to the dollar store and buy the teensiest paint brush you can find. Gently apply the smallest amount of the glue you can. Wait 5 minutes, apply again. This will not stiifen over time, unlike acetate or urethane glues. Butyl glue for butyl. It's actually mostly solvent, with a few percent butyl rubber(no carbon black, so it's clear, usually). KLH used to use a butyl/toluene mixture to seal cloth surrounds, where added stiffness would be a problem(they used a lot, but toluene evaporates slowly from solution and they were sealing porous cloth).
                ​Thanks, David. The only problem with the vulcanizing glues is the damn smell! Is this what you mean by 'butyl glue'? Also, you're saying that the urethane glues stiffen over time whereas it says it doesn't on the packaging to the glue fdieck recommended above. Does your experience say otherwise?

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                • #9
                  Three replies and three different suggestions -- this is what I mean by no clear consensus on the optimal solution, which is confusing (I'll only get one shot!). They can't all be....or can they?

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                  • #10
                    That's the one. It is water soluble 100% Latex, and benign.
                    I have used Silicone RTV as well, without problems.


                    "Not a Speaker Designer - Not even on the Internet"
                    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                    • #11
                      I second the bicycle inner tube repair cement - "Butyl glue", which will basically desolve the edges of your tear so that they "melt" and then dry back together.

                      Clean the tear on both sides, then take a toothpick to push some glue into the tear, all along the tear - perhaps rub at it a little bit until you're confident the edges of the tear are softened by the solvent, then let it dry.

                      Ask the bicycle repair shop for a piece of an old inner tube to experiment with, if you would like to see how it works first? Make a cut that resembles the one on your speaker surround and perform a "test repair" on that.

                      In the meantime, you may stick a little piece of tape over the tear, if you wish to listen to the speakers.
                      "...this is not a subwoofer" - Jeff Bagby ;)

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                      • #12
                        Looking over my speakers(and remembering their stories), I can say that I have, over the last fourty or so years, used urethanes, acetates, silicons, latexes, and butyl based materials on foam, paper, cloth, butyl rubber, and silicone rubber- in all kinds of conditions(Vt,Pa,Az) and combinations. It gets very confusing when companies like Aileen's sell both acetate and latex products(both good when appropriate).
                        When I say something hardens over time, I have seen it. Labels are for reading, but only the ingredients list is merely misleading(the rest is selling). "vulcanising cement" is actually de-vulcanising cement(vulcanising hardens normally sticky rubber) much as "a convection oven" is actually an anti-convection oven(the fan forces the air,whereas convection is the "hot air rises" principle in regular ovens-just a little Franco-American confusion there).

                        Sometimes it doesn't matter much. You'd have some leeway on a speaker like the Tarkus' midrange, with a bass-capable surround not moving much as a midrange, but if that sucker's pumping bass you should try to keep compliance similar. Or if you're ordering surrounds & just need a few weeks, just be stingy with whatever you have(and keep it off the cone).
                        Last edited by davidB; 05-22-2017, 03:34 PM. Reason: sp

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