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Old 23rd September 2008, 12:48 AM   #1
coldcut is offline coldcut  Sweden
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Default Help to assemble a broken louspeaker..

Hello!

Recently dug up my old pair of Beyma 12"G-250/R from the basement, but on one the cone was stiff, and couldnt be moved. After some research and a closer look, the glue, holding the basket centered on the magnet has vanished. (air humidity, I guess) The result is a offset in the coil gap, jamming the voice coil. (see att. pict.)

Picture of Beyma disassembled

To fix this problem, I need to glue the basket back on the magnet, not very easily done, since the magnet is huge. To attain a correct coil gap, does the basket have to be "dead" center? What kind of glue is recommended? Later, when I recone it, what kind of glue should I use? Any other advice regarding this subject is appreciated..

Reg. John
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Old 23rd September 2008, 12:57 AM   #2
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Hi John,

That looks like a dead speaker. Is that the coil former in the picture? If so you not only need to reattach the magnet to the basket, you will have to recone also. That means you'll have to do both so they sound the same. Might be asking a bit much to reattach the magnet as any glue on there will have to be removed so the two pieces aren't separated by the thickness of the existing glue.

The coil is centered using shims between the pole piece and former. The recone kit should come with the right adhesives for the spider, dust cap and surround. If not, ask for them when you purchase. If you've not done a recone, best to leave it to those who have, it's a little tricky.
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Old 23rd September 2008, 01:26 PM   #3
coldcut is offline coldcut  Sweden
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Here is a picture on the jammed voicecoil when the dustcap was removed from the cone..

voicecoil

As you can see, the centerpiece is displaced, leaving no room för the vc to move.

The damage done to the vc in the 1st pict., is a result of the "force" needed during the disassembling.
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Old 23rd September 2008, 01:41 PM   #4
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Maybe Beyma themselves can recommend some type of glue. And yes, the centering has to be done very precisely. Thats the reason why speaker magnets are usually magnetised after assembling the driver.

Maybe you could make yourself some shim to do this.

Regards

Charles
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