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Kef 105/3 B200 sp1256 driver repair

 
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mylar
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Joined: 27 Jul 2005
Posts: 1

PostPosted: Wed Jul 27, 2005 2:42 pm    Post subject: Kef 105/3 B200 sp1256 driver repair Reply with quote

Hi,
Does anyone know of a source of re-foaming kits for the B200 sp1256 drivers? They are from KEF 105.3 speakers. The inside/outside surrounds are completely rotted out and due to the unusual design (torque rod thru middle) I'm having difficulty finding a repair kit/replacement. KEF has not been much help. Any suggestions would be greatly appreatiated. Thanks-John
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ColinR
Über Contributor 1000+


Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Jul 27, 2005 6:45 pm    Post subject: Reply with quote

As with many "members" of SpeakerTalk you have failed to register your domicile, occupation and interests.
I suggest you look at my previous posts to find a competent professional speaker re-builder who can fabricate foam donuts.

If you want an alternative solution to an expensive knotty problem here is an "underground" solution.
Cavity coupling of drive units depends upon having a leak free system.
So, why not discard the force-cancelling rod and refoam the drive unit as normal making sure that the dustcap is up to the job.
The force-cancelling rod just provides some extra rigidity to the cabinet and three or four thinner long threaded rods, nuts, washers and bits of sheet steel recycled from "white goods" can be used to beef up the box if you're handy with a drill and a hacksaw.
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clem_o
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Joined: 30 May 2005
Posts: 44
Location: Manila, the Philippines

PostPosted: Wed Aug 10, 2005 3:59 am    Post subject: Reply with quote

I definitely considered that course of action some time ago, was fortunate enough to have KEF send me the proper kit. In the future however I will probably have to face the same problem again, so Collin - "...and three or four thinner long threaded rods, nuts, washers and bits of sheet steel recycled from "white goods" can be used to beef up the box if you're handy with a drill and a hacksaw" - what exactly did you have in mind - where would you put those rods and what about the sheet metal, where would it be used?

Many thanks!
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Aug 10, 2005 3:02 pm    Post subject: Reply with quote

Cool I was thinking laterally about the problem of replacing a central pole/strut.

Just like the medical frames that replace the spinal column when an injury has occurred to one of the neck bones.

You can go to your local boatyard or chandler and get some suitably sized rigging/bottle screws, dismantle one and insert a similarly threaded rod and cut small cups out of some scrap and tension against the existing speaker mounts.

OR

Drill oversized holes top and bottom to take a threaded rod, insert rod after constructing some suitably sized "washers" out of scrap and use nuts to tension against the panels.

In the latter case things don't have to be vertical.

In both cases the mid-treble baffle will have to be removed and additional woodwork molested depending upon the specific design to gain access to the cavities.

The resulting jobs could be made airtight with silicone mastic or whatever one thinks fit.

Enough clues now?
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clem_o
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Joined: 30 May 2005
Posts: 44
Location: Manila, the Philippines

PostPosted: Thu Aug 11, 2005 2:16 am    Post subject: Reply with quote

Ah, that's certainly clearer! Sigh - seems no quick solution to this eh?

I was considering inverting the bottom driver (of course also inverting the polarity of the connection), putting in a long-enough bolt and nut through the units before gluing on a dustcap. Unscrew 3 mounting screws for the bottom driver, turn them around and thread them in from the middle (reflex) chamber, but only up to the point where the screw ends are flush with the mounting baffle wood.

Then have an appropriate (shorter) rod fabricated, screw onto top driver first, then mount bottom driver through the bottom cover, rotating the driver so it screws onto the rod, align mounting holes, then turn mounting screws all the way in. Thread the screw nuts and torque as needed.

Caveats:

1. Since drivers are now "back to back", harmonics cancellation will probably be not as good...

2. Someone has to do a fairly exacting measurement of "how much shorter" the stiffening rod has to be with this config.

3. Volume of AS box for the lower driver will no longer be the same as before (but then consider: in the 104/2 the volumes for the top and bottom were equal anyway, seemingly disregarding driver cone volume; for the 105/3 the bottom AS is a bit larger than the top, but it is "just a little bit larger", maybe to compensate the space taken by the crossover?)

4. A small hole will have to be drilled (then filled) to allow the wires to go from the crossover to the bottom driver that now has its connectors in the BR chamber.

5. Aesthetically - to see the driver basket when looking through the rather massive port hole... hmmm

Opinions / comments?

Cheers!
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Thu Aug 11, 2005 12:08 pm    Post subject: Reply with quote

Quote:
2. Someone has to do a fairly exacting measurement of "how much shorter" the stiffening rod has to be with this config.


Not really, that's why I specifically metioned small boat rigging screws.
Although built for tension, the left and right handed screw threads are "specked" for fairly significant compression loads, as really they're just glorified stainless steel bolts.

Some examples

http://www.s3i.co.uk/turnbuckleclosed.php
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clem_o
Intermediate Contributor 25+


Joined: 30 May 2005
Posts: 44
Location: Manila, the Philippines

PostPosted: Thu Aug 11, 2005 12:31 pm    Post subject: Reply with quote

Nice - wonder if there are such things in Manila... !

Cheers!
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