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Repairing a carbon fiber cone separated from the rubber surround

Discussion in 'Amps [BG]' started by mack_kenamond, Oct 26, 2013.


  1. mack_kenamond

    mack_kenamond

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    I have a sub that an underinformed tech blew by bridging my stereo amp and not compensating with the gains. Anyway, the cone is carbon fiber epoxy and the surround is "mystery-rubber". I think the speaker is fine except for the separated surround...went from "good" to "slap/farty" immediately, and after we pulled the sub from the cab, I saw the surround/cone separation. $350 for a replacement is not in my immediate future. I've read a bunch of sites about fixing surrounds, but most of them talk about paper or fiber cones, not fiber/epoxy. Is there anything special about fiber/epoxy cone and rubber surround repair or do I treat it the same as a paper cone?

    BTW, I own a 5-string Fender P-Bass, but I'm a guitarist...though I do favor the E and A string! My neighbor owns a Veillette (Woodstock, NY) baritone nylon string piezo-electric guitar that he refuses to sell to me...half way between bass and guitar is where I think my soul resides. Maybe I should up my offer to him...$2000 for it. Hell, I can't afford $350 for a speaker. :(
     
  2. 1958Bassman

    1958Bassman

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    If the "tech" has a real business, he should fire up for at least part of the repair cost. Call the manufacturer for advice about repairing it. What brand of driver is it?
     
  3. mack_kenamond

    mack_kenamond

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    There was mass confusion about what was wrong, several cooks in the kitchen, etc. and I honestly don't blame the guy for the snafoo. One guy bridged the amp to check for a bad stereo chennel and the other was checking left vs right channels...like 10 minutes apart. It's an old setup (15 years old), and though I had something that worked before and have a busted 10" speaker at the moment (and a functional serial setup with the remaining 10" speaker), I really just want to know how to or if I can fix it. I'm pretty convinced that the bulk of the bad 10" speaker is okay, and the only issue is with re-bonding the surround to the carbon-fiber cone. I've been Googling and have found numerous sites describing the process, but they all speak in terms of fiber or paper cones. I'm willing to let bygones be bygones (and not go to that particular business again) if I can glue the cone/surround on my own.

    So is there anything special about bonding carbon fiber cones to rubber surrounds that is somehow different than bonding paper or fiber cones to rubber or foam surrounds? Worst case is that I run my stereo rig mono off of one 10" speaker which is working just fine now.

    Thanks for the response!
     
  4. Roscoe East

    Roscoe East

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    That's $350 to replace the entire driver, right? Find out what a professional reconing would cost from a reputible speaker tech. Should be closer to $100.
     
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  6. 1958Bassman

    1958Bassman

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    If someone is going to attempt a repair, they should A) know what they're doing, B) make sure anyone else knows what tests are being done and C) do it without additional interference from others unless they ask for it and even then, the next person should check for wiring configuration. This is basic stuff- blindly connecting cables to an amp or ignoring what has been done is irresponsible, at best and the fact that it's 15 years old is irrelevant.

    If this came apart between the surround and cone and failed only at the bond between its edge and the cone, meaning that it simply came off of the cone, it may be repairable. If the surround failed where the curve transitions to the area that bonds to the cone or the frame, it's not- that's where all of the stress occurs and you have seen what happens when its capacity for stress is exceeded. However, you may be able to find a replacement part for teh surround, although you will need to measure the diameter of the cone and frame, provide the brand (with part number) and hope the size is available. Many of these parts are available, but many of the dimensions aren't metric unless it was made outside of the US. Simply Speakers sells parts/cone assemblies and the contact cement they provide is really tacky, so it holds well. However, it's hard to get the cement to stick to some cones, like the original polypropylene used by Infinity.
     
  7. BassmanPaul

    BassmanPaul Gold Supporting Member

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    Mack, if you filled out your profile properly we would know in what part of the world you live. One of us could recommend a company who could repair your driver that is near you.
     
  8. mack_kenamond

    mack_kenamond

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    First, thanks for the speedy feedback!

    Done. Thanks for the recommendation.

    First of all, I agree that someone screwed up, but it's water under the bridge and a note in my head not to go there again.

    As for the damage, the surround seems to have cleanly separated from the cone. There were no tears to the surround, no apparent damage to the cone. The two parts separated for maybe 120 degrees (1/3) around the cone. I suspect that the bridged amp x-max'ed the speaker and pulled the cone off the surround. There could be other damage in the voice coil, but with the detached surround, it's impossible to tell (rattles/buzzes like crazy). I've found several sites that imply that this is a common do-it-yourself fix, but they're always talking about a paper cone, not a carbon-fiber-epoxy cone. Because certain bonding agents work better/worse/not-at-all depending on the materials being bonded, I'm concerned that a paper-rubber adhesive may not work for a rubber/carbon-fiber-epoxy situation. My guess is that the cone's epoxy is what matters; the carbon fiber weave is embedded in an epoxy matrix, so the adhesive would have to bond rubber to epoxy, not rubber to carbon fiber. So I probably need something that bonds rubber to epoxy and will handle the temperature changes and high frequency vibration/fatigue loading. They bonded it together when they made it after all, so there's something out there that should work, but I don't know what it is.

    After I find an appropriate adhesive and attempt the repair, I'll be able to see if there is additional damage in the spider or voice coil. If so, I may have to punt...the speaker has a dust cap that is also carbon fiber and is glued to the cone, so I'm not sure how I'd get in to look at the inner guts.
     
  9. wighat

    wighat

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    Loctite 401 Prism Instant Adhesive?
     
  10. mack_kenamond

    mack_kenamond

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    Thanks for the input, but I'd feel better if your reply ended in a period or exclamation point rather than a question mark. ;)
     
  11. wighat

    wighat

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    Just because I haven't used this product to glue butyl and resin together. It is however spec'd for those materials, IIRC. You could test it on a piece of pond liner and a piece of fiberglass. It might help to contact the manufacturer and ask what was used originally and what type of resin is used in the cone. This endeavor is somewhat complicated by the fact that you may actually be gluing the original adhesive to itself or to one of the surfaces. Other issues are you can't really clamp and you don't want to add weight by using a significant amount if adhesive.
     
  12. seamonkey

    seamonkey

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    Search for foam surround repair
    There's all kinds of kits and videos
    I don't know of many professional drivers that use foam surrounds. Not really road worthy.
     
  13. wighat

    wighat

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    Not foam, butyl.
     
  14. mack_kenamond

    mack_kenamond

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    I can appreciate your conservatism. I may just try it and see what happens. I'm one of those obsessive folks who'll likely spend two weeks becoming an "expert" on speaker repair technique (err...book-smart "expert") before I attempt anything. Good point on applying pressure. The surround "stays put" so if I can force the cone out uniformly and then use my fingers to squeeze the two together (to get a more uniform glue thickness in the bond) maybe that will be good enough, though the basket doesn't offer as much finger space as I'd like. More reading in my future. Also, good point on adding weight via glue and having to bond glue to glue. I'm hoping that the glue weight won't be an issue, because the mass of the cone, dust cover, spider, coil and surround should be MUCH greater than the glue weight, though uneven distribution around the surround might torque the coil and cause issues. Not sure about glue-glue adhesion.

    Thanks for the input!
     
  15. will33

    will33

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    I've been following your thread, just don't have enough knowledge/experience to be helpful, other than to say, I might stray away from speaker specific type stuff and just look at the materials and adhesives involved to find the right product.

    In other words, look for a type of adhesive that has the right properties to use with those 2 materials while maintaining a similar level of rigidity or flexibility.

    The answer might be something developed for use in rockets, or women's shoes....who knows?
     

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