SpeakerTalk

AndyS

I have just noticed that one of my B110s has a half inch split in the surround, on the outside of the roll adjacent to one of the fixing holes.

Has anyone got experience of repairing this sort of split or replacing the surround?

The coating on the cone covers the edge of the surround so may be an issue if trying to remove the surround.

Your thoughts please.
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Always trying to figure out what will work and what won't!

audiolabtower · VIP Contributor 500+ Joined: 06 Jan 2009 Posts: 686

The surround on the 1003 is neoprene a type of synthetic rubber. You could try a suitable rubber glue, carefully applied front and back and see if it lasts once fully cured.
If the B110 is in an infinite baffle the tear will upset the sealing and response, if repair is not on the cards try eprey or falcon acoustics now make new 1003s for LS3/5a clones.
http://www.falconacoustics.co.uk/falcon-kef-b110-sp1003-new-ls35a-ab1.html

AndyS · Posted: Fri Jul 24, 2015 4:54 pm Post subject:

Hi, thanks for the reponse, I wish I could afford a pair of the new B110s, fortunately I have a spare one to use. They are 1973 vintage so begining to show their age, physically, the old unpainted chasis type. Will try the rubber cement, may be a bit difficult to get tp the underside as the problrm is alongside a mounting hole.
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Always trying to figure out what will work and what won't!

bdgdpc · Posted: Mon Aug 24, 2015 4:40 pm Post subject:

I've got another unusual B110 (SP1014) question...
I have a pair from a recent MA1 purchase, where the dustcap and small amount of laquer material seem to be de-laminating from the cone underneath except where the lead-in wires pass through. The drivers seam to work fine and the cone as it goes into the fabric ring looks fine too. I've re-foamed drivers before, and the last step is gluing on a new dustcap. My question is: can I just cut round the dustcap, cutting through the laquer but not the cone (obviously), and glue them back down? Looks like that'll work, but perhaps somebody out there has met this before....

Ta,
David
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David (UK)

audiolabtower · VIP Contributor 500+ Joined: 06 Jan 2009 Posts: 686

SP1014 is a B200 but I don't see why you can't just glue the dustcap down again, after all the driver is made by gluing it on?

bdgdpc · Posted: Mon Aug 24, 2015 6:58 pm Post subject:

I wish I could have posted a picture! The dustcap is lifting up, but it's taking the top laquered surface of the cone with it (or perhaps the other way around). It can be gently pushed down, but then just creeps up again over a few seconds. The underside of the cone is still rigid and not part of this process.
I think old Goodmans Magnum drivers suffered from this too.
I've also asked Kef - they normally respond. I'll pass on any wisdom and the results of an attempted glue-up: I'll eventually give in and try it.
David
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David (UK)

speakerguru · Posted: Tue Aug 25, 2015 8:06 am Post subject:

It's not lacquer, it's Plastiflex, a type of PVA adhesive. It does peel away from the cone quite easily once it's started. Ideally you should peel it off completely, stick the dust cap and re-coat over the whole lot. I don't know a modern equivalent.
See sticky about coatings: http://www.hifiloudspeakers.info/speakertalk/viewtopic.php?t=1655

bdgdpc · Posted: Tue Aug 25, 2015 8:35 am Post subject:

Excellent, thanks. I'm still working this problem and will report back.
David
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David (UK)

bdgdpc · Posted: Wed Sep 09, 2015 3:25 pm Post subject:

COATING INFORMATION
Research on speaker doping materials and bookbinding adhesives allowed the elimination of solvent-based, organic or two-part compounds. It also revealed that PVA adhesives have undergone significant evolution since the 1980’s. The most promising in terms of similarity to the description above was any PVA that was pH neutral (i.e. for bookbinding), but these tend to reversibly dissolve when damp and traditional PVA’s have the adhesion properties noted above. A plasticiser additive, vinyl acetate ethylene (VAE), can be added to PVA to make it more flexible but the problems of using PVA remain. This is also the case with methyl cellulose additives to increase the mixing time and ‘soaking’ into porous media which obviously doesn’t apply to bextrene. Vinyl Acetate Ethylene (VAE) Copolymers (50% mix with Acetate) have excellent adhesion to most surfaces and were also investigated but these are powders for hot-melt application and would cause more problems than they solve.
Finally, an commercial mix of PVA, VAE & Acrylic as a water-based emulsion was found which seemed to fit all requirements. It has the trade name Hydracure3205, from the UK company ADCO. Based on the description, a sample was obtained and tested with good results.
Surprisingly, other adhesives also gave results that were just as good in terms of ease of application and adhesion. Adhesives tried were:
Hydracure3205; Hydrocure PVCF; speaker foam adhesive from SpeakerWorks USA; Evostick pH neutrual PVA. Small (1mm) blobs were placed near the throat of the KEF driver in question, where the original coating had delaminated, and left for 24hrs to set. I attempted to pick the dried blobs off, but they all stuck so hard that the cone was starting to deform. In conclusion, it seams reasonable to conclude that the adhesives tried here are much better than what was available to KEF in the ‘70’s. Hydracure3205 was used on the strength of it’s description. In fact, probably any of them would have been effective.

REPAIR INFORMATION
Based on the response from KEF’s Andy Gough and Simply Speakers’ Sean Ryan, the process was to cut round the dustcap, then cut away the delaminated material as close to the cone as possible, then re-coat. The portion of the dustcap between the lead-in wires was still well stuck down to the cone, so this was left intact.

MA1 INFORMATION
I have a crossover circuit diagram and pics if anybody wants them. Some capacitor values were well out of spec, so all were replaced.

REFERENCES
http://www.kef.com/uploads/files/en/kef_units/A%20History%20of%20Kef%20Drive%20Units%20issue%203.pdf
http://www.simplyspeakers.com/
http://www.ibookbinding.com/blog/bookbinding-gluing-tips-techniques-types-info/
http://store.bookbinding.co.uk/store/product/5130/Eva-con-R-Adhesive-500ml/
http://www.adhesivesmag.com/articles/87133-bookbinding-adhesives
http://www.celanese.com/emulsion-polymers/Emulsions-Chemistries/Vinyl-aceteethylene-VAE-emulsion-Overview.aspx
http://www.chemquest.com/store/vinyl-acetate-ethylene-copolymers-european-adhesives.html
http://www.powerbond.co.uk/categories/vinyl_acetate_ethylene_copolymer_emulsion_vae.php
http://adco.co.uk/products-and-services/adhesive-products/pva-adhesives/
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David (UK)

bdgdpc · Posted: Wed Sep 09, 2015 3:27 pm Post subject:

The Hydracure3205 technical description:
"HydraCure 3205 is a high performance aqueous emulsion based adhesive for laminating of porous materials including paper, board, foams and leather. HydraCure 3205 exhibits fast setting characteristics with good wet tack, The final cured bond exhibits exceptional flexibility. Specialist applications include the laminating of filter media, and for a coating 'dope' for loudspeaker cones"
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David (UK)

speakerguru · Posted: Thu Sep 10, 2015 8:39 am Post subject:

Very interesting. I'd like to know who did the research on potential replacement coatings for old KEF drivers. Where did the "Coating Information" come from?

bdgdpc · Posted: Thu Sep 10, 2015 8:51 am Post subject:

The link a few posts above by speakerguru was excellent, saved me loads of time and started me off on the right path in the first place - the rest I just put together from the links shown above as I tried to learn more about what I was dealing with.
You've got to give enormous credit to KEF - they had very little to work with when they were doing this. Maybe they never anticipated people refurbing their drive units nearly half a century later!
Anyway, according to what I've seen, any 'speaker repair glue' available nowadays will do the job.
David.
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David (UK)

bdgdpc · Posted: Thu Sep 10, 2015 5:22 pm Post subject:

Apologies, speakerguru - I was in a rush to get to work and didn't realise I had just referred to you in my answer to you - at least it was good!
David
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David (UK)

speakerguru · Posted: Fri Sep 11, 2015 8:45 am Post subject:

bdgdpc · Posted: Fri Sep 11, 2015 8:52 am Post subject:

The advice on the mechanical repair came from KEF: the info on adhesives came from the web, I condensed it down to what's above.
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David (UK)