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Speaker Repair

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[Document Version: 1.00] [Last Updated: 3/26/96]

1. Big Speakers

Make certain that the voice coil didn't "just" jump out and jam on the face of the magnet's center pole! If this is the case, a bit of

Big speakers are actually not too bad to redo. Remember that you're only other option is to toss it out, so you have nothing to loose by trying to repair it. Having good manual dexterity and a knack for detail work is an asset (ie: a model builder skills). So, once you have determined that the problem is internal (voice coil) and you want

  1. Paint an alignment line from the cone edge over the suspension and onto the basket so that you can line everything upon reassembly.
  2. Do the same to the spider
  3. Unsolder the voice coil leads from the tab on the basket
  4. Using a razor blade or an Exacto knife cut all around the suspension as close to the basket as possible to free up the wide end of the cone
  5. Do the same where the spider meets the basket
  6. Lift the cone and voice coil assemble out (be careful here, if the coil has come apart you may snag things and damage the voice coil form).
  7. Examine it, you may be able to fix a short or bridge an open and reassemble at this point.
  8. Get a dowel rod that just fits inside the voice coil (light friction fit) and insert it. Handle the voice coil/cone assembly by this "handle" if at all possible. It will also keep the voice coil form from collapsing when you rewind it.
  9. Carefully unwind the voice coil and write down how long it is, how many layers, and how many turns and direction of winding (ie: clockwise from front)
  10. Obtain some replacement wire of the same OUTSIDE diameter (note that depending on the particular enamel insulation, the same wire gauge may have differing insulation thickness)
  11. Rewind the coil one layer at a time (remember to solder it to the braided lead-outs !), use Q-dope to hold it to the voice coil form, and to also hold it together. Do not over do it on the Q-Dope on the outside layer. If you make it too thick it will not fit back in!
  12. Reassemble, using the alignment marks as guides
  13. With the speaker sitting cone up, everything should be sitting pretty much lined up with where you cut it free
  14. Use contact cement and a fine artist brush to glue the suspension back Together (I have assumed a foam suspension)
  15. Use silicon RTV to put a fillet around the spider where it contacts the basket, again a small artists brush is used.
  16. Solder the leads back to the tab
  17. Let the glues dry
  18. Test it

2. Common Failures (why)

While working my way through college, I managed a pro-sound company in the SF Bay area. We would get a customer into our repair dept. with your complaint at least twice a week. The typical failure modes for abused musical instrument amps are either shorted or open voice coils in the speaker, followed by the destruction of the final amplifier stages. It starts out as a buzz from the cone. The reason for all this is that the voice coil/spider assembly overheats and then distorts. The clearance between the voice coil and the magnet pole pieces are fairly small and a little deformation of the cylindrical voice coil will make it bind and buzz. After that happens, it heats up alot faster and either fuses open or wears through the voicecoil wire insulation and shorts to the pole piece.

The repair is usually to replace the speaker. The real expensive pro-audio drivers like the EVs, JBLs, etc could be reconed cheaper than replacement but low end drivers like those in Crates aren't cost effective to have repaired (nobody will touch them - [but see section above]). On the rare occasion that one can find someone to recone them, they usually have substitued parts and really screw it up so you have to buy a new speaker anyway. The moral is take care of your equipment, especially if you depend

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