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Feb. 2018
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Harbeth HL MK2 For my Log Cabin, what glue can I use to re-seal cone to surrounding rubber?

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  • Harbeth HL MK2 For my Log Cabin, what glue can I use to re-seal cone to surrounding rubber?

    Hi guys, I recently purchased some older Harbeth HL MK2's for my Log Cabin (going alongside 4 Harbeth Xpressions with new cones) Just to add some temporary Bass to the situation.

    The only downside is on one of the older Harbeth HL MK2's, the cone seems to have become dis-attatched to the rubber around it (shown in image below) Just wondering if anyone could suggest what glue would be best to re attatch it to the surroundings?

    I do have some spare 'Rubber Cement' but not sure if this would be best fitted for the job? Just wondering what kind of glue would be best to use on the old MK2 polypropylene cones?? Any advice would be appreciated. Many thanks!
    Attached Files

  • #2
    Glue?

    Anyone have any ideas? Would like to make a start on fixing them tonight -
    Best regards

    Comment


    • #3
      Before gluing: lock the voice coil/cone height

      Sorry for the delay: I overlooked your post.

      The key point is that without a jig, there is a danger that you will glue the cone/surround such that the voice coil is slightly off-centre and will rub. The best way, as you have already removed the entire surround from the cone (inadvisable), although this may alarm you, is to peel off the dust cap (you will re-use it) and find a sheet of paper that can be slid down into the tiny gap between the inside of the voice coil and magnet pole piece. The idea is to lock the cone/coil with a suitable shim at the correct rest height before attempting to glue the surround onto the cone. If the coil is pushed too deep or stands too proud at rest, the surround will have to stretch to make contact with the cone, which will greatly reduce the excursion possibility of the drive unit.

      Do that first, then please report back. Rushing ahead now will negate your chances of a successful repair.
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

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      • #4
        Whatglue

        Thank you for the detailed response, I shall try this, also another part of my question is just, what kind of glue to use, Areldite or Rubber Cement? Kind regards

        Comment


        • #5
          Glue suggestions

          Neither.

          Rubber cement is for glueing rubber to rubber. It works by effectively melting the surface of rubber so the two pieces mix and fuse. It's for repairing things like the inner tubes of bicycle tyres and unlikely to glue anything to polypropylene.

          Araldite is extremely strong however it is unlikely to adhere well to rubber, and it does not function well in any kind of flexing situation because it sets absolutely rigid.

          I recommend impact adhesive - since you have a log cabin it's unlikely you are in the UK so this may have another name in your country, but it is very tough and flexible. It's the smelly stuff that people sometimes abuse because it is full of the solvent toluene, usually a dull yellow colour. There are many brands. You apply it to both sides, let it become tacky and then press them together and in general they don't come apart again.

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