Repairing Kef B139 SP1044 Woofers

[revinyl]

I've found that the glue between the spider and the middle cone has deteriorated and resulted in a total separation. The spider is still in great shape so I don't really want to replace it. However, there is still a fair amount of old glue left on it.

The way I see it, I have 3 options:

1. Re-glue the spider on top of the old glue and be done with it.
2. Try to remove the old glue and then re-glue. I'm reluctant to do this option because isopropyl alcohol has had virtually no effect on the glue.
3. Replace the spider.

I'm a newbie so I'm sure there's a lot I'm not taking into account. I'd appreciate any feedback as to what the best course of action might be. Thanks

 

[CopperWizard]

Have you tried a new razor blade to mechanically separate the spider from frame? Delicate surgery. Don't replace the spider, re gluing over old glue is better than replacement of spider from cone, just make sure voice coil is centering properly while drying using test tone.

 

[revinyl]

Thanks for the reply. I did not consider centering, so I'm glad I asked. What resource do you use for test tones?

I had to look up a diagram of a speaker; when I said "spider and the middle cone", I was referring to the spider and the "former". I just learned the name for it now haha.

Also, this might be a dumb question, does the former get glued to the pole piece in the magnet structure? Currently, the underside of the former has a sticky substance and I don't know if it's old glue. Or if I should just leave it.

 

[CopperWizard]

I read the post wrong and thought it was separating from the frame. Pictures of the separation would be very helpful for assessment. Separation from spider to voice coil former sounds odd, so does sticky substance on bottom of former which leads one to wonder if terms are getting crossed here. Former is not glued to pole piece, it must move freely in magnetic gap. PICS at this point.

 

[revinyl]

The first picture shows where the separation is occurring (pointing with screwdriver). The second picture kinda shows the inside of the voice coil former. You can see the back of the foam has a sticky yellowy substance.

 

[CopperWizard]

I will leave further advice to the experts on this one. There is an appropriate glue to use on that application I have not done a coil former to spider yet. If glue chips away it could get into the small gap which is not good.

 

[mech986]

You may want to post a similar thread in British Audio forum where there will be more folks familiar with KEF and the B139.

If the separation is at the spider- cone junction, I would think a thin bead of cyanoacrylic glue on the bottom outside diameter of the voice coil former and spider junction (visible in picture #1) and the inside diameter of the top of the former/flat cone base (made of polystyrene foam that is visible in picture #2) would be the start. Then you would have to invert the driver on its back with the magnet installed and see if you can the put a bead of CYA glue at the top of the outside diameter of the voice coil/spider/cone junction.

Be sure to spread the glue so that it contacts all the pertinent surfaces, then wait at least 1-2 full hours to cure or whatever it says on the glue package. I'd suggest working in a warm room for optimal results. IMO, I'd wait a full day for the glue to cure. The liquid glues may spread easier, but gel glues may be more available and a bit easier to reach in with a long tip applicator. Weight change will be negligible.

To center, you can use a simple frequency generator app on your phone and hook the phone up to an amp, then hooked directly up to the driver. Probably use 60-80 hz at low volume, but only needed if you separate surround or if voice coil is completely loose from spider.

 

[CopperWizard]

Cyanoacrylic glue is also known as super glue

 

[sreten]

Hi,

Superglue is utter crap. The stuff to use is two part epoxy.

rgds, sreten.

 

[mech986]

Hi,

Superglue is utter crap. The stuff to use is two part epoxy.

rgds, sreten.

Properly used, cya glue will work. Two part epoxy is also good but can be quite viscous and hard to place in the confined area of the joints discussed. Now if one can load a syringe with the mixed epoxy and deliver and smooth it into the joints, then yes, I'd agree. Will add more mass though compared to CYA.

 

[revinyl]

and the inside diameter of the top of the former/flat cone base (made of polystyrene foam that is visible in picture #2)

What is the purpose of this second location of glue? The connection between the inside of the former and foam cone base is still fine.

I currently have a tube of the glue from Simply Speakers (http://www.simplyspeakers.com/speaker-repair-adhesive-mi-3035.html) which lists spider repair in it's applications. I haven't opened it yet, so I'm not sure how easy it will be to apply; I'm thinking I'll use a toothpick to apply (with the point cut off so it's a dull edge - easier to spread glue).

Thanks for the instructions - I'm feeling confident about this project. I might still post in the British Speakers thread just in case.

 

[revinyl]

If the separation is at the spider- cone junction

This was the problem, and I followed your advice with success! I scraped away as much old glue as a could, then put a single layer of new glue on the underside, hooked them up to my frequency generator app and let them dry for a couple hours. Repeat on the other side. It worked! Thanks so much for the help.

 

[mech986]

Revinyl, congrats on your repair. Where will you be using the woofers?

 

[revinyl]

Revinyl, congrats on your repair. Where will you be using the woofers?

Thanks, there from some Kef Concerto 3s that were transplanted into a gorgeous custom cabinet by the previous owner. They're really nice speakers but don't suit my music taste so I might be looking to unload them soon.

 

[WFM333]

Mine has seperated here. Should i try and remove glue somehow for metal to metal contact or just reglue? Thanks guys

 

[WFM333]

The glue looks impossible to remove!