Repairing cone surround and voice coil of a valuable Tannoy Dual Concentric

[David Pinnegar]

Hi!

A friend sent me a link about reconing a speaker, which contains generally good instructions -
http://www.ehow.com/how_5907213_recone-electro-voice-speaker.html

This reminded me that there might be people interested in repairing Tannoys. I bought a pair of 12 inch units and crossovers cheaply on Ebay recently. Both had the cloth surrounds to the cones shattered, but the pieces slotted together. I use Isoflex special roof sealer primer as an ultra flexible rubber membrane repair glue - and it's brilliant. So one was repaired easily.

The other unit had been damaged beyond this, having in addition, the final turns of the voice coil mangled as they had crashed back onto the pole piece. Normally one would have reconed but a new Tannoy cone seemed to be beyond my pocket money . . . I started to unpick the turns of the coil very gently, straightened out the wires, inserted some micro solder joints, rewound them into the cylinder and stuck with superglue and shellac  . . .

I had encompassed the possibility of cutting off the voice coil and attaching a new voice coil - and new voice coils are available on Ebay from China. I bought a 2 inch but this was too small, fitting snugly over the pole piece. To my surprise however, the Tannoy voice coil fitted snugly over the CHinese voice coil . . . so I used the unwound section of the Chinese voice coil as the shim in order to position the spider and stabilise entirely the cone assembly for stitching the shattered cloth cone surround with some drops of superglue before homogenising the surround together with the Isoflex.

Perhaps this might encourage anyone else in repairing speakers but if anyone would like something like this done, then I've done it before . . . I have also just finished refurbishing one of a Lowther PM7A pair for someone - the cone was distorted out of shape, the spider and surround rotted away, and the voice coil scraping on the corroded pole pieces . . . now working as good as new . . . . The voice coil gap of these is only 1mm, so with the thickness of voice coil there's only 1/8th to 1/4 mm to play with in recentring the coil in the gap and the secret to this is the jig necessary to re-form exact circularity of the voice coil . . .

Best wishes

David P