Loudspeaker Tutorial Includes:
What is a loudspeaker: basics Moving coil loudspeaker Loudspeaker enclosures Loudspeaker repairs Speaker wire / cable
Additional speaker repair topics: Replacing speaker unit in speaker system Repairing speaker cone Repairing / replacing speaker coil
One area of failures and faults with loudspeakers occurs with the coil. Everything from the coil becoming open circuit to the coil becoming off centre and gringing agaisnt the magnet.
Speaker coil faults and problems can often be fixed, sometimes very easily.
Speaker coil repair
There is a variety of issues that can occur with speaker voice coils, and sometimes it is possible to repair them. Typically the larger more expensive loudspeakers can be repaired more easily - smaller ones tend not to be repairable unless you are lucky:
- Speaker coil off centre (1): Even though modern loudspeakers are very good and seldom go off centre, sometimes this can occur. Moisture or dampness on part of the cone may cause this. This manifests itself by a grating noise as the speaker is used, or the rubbing can be heard if the cone is manually moved in and out. Occasionally on smaller speakers with no adjustments it can be possible to repair them by easing them back into the centre. Gently hold the cone - remember it is made of paper and can damage easily. Ease the cone so that it moves back to the centre. It may be necessary to repeat the action after a while, but this method can occasionally work.
- Speaker coil off centre (2) : On larger units where the speaker coil goes off- centre it is possible to repair them. It is possible that there are fixings that enable the magnet to be moved very slightly. The operation needs care and patience, but often it is possible to move the magnet so that no gating / rubbing can be felt on the speaker cone.
- Spider adjustment: Some speakers, especially older ones have a spider that holds the cone and coil in place. There can be a centre fixing screw that can be slacked off . With this done, the speaker coil can be centred so that the coil does not rub on the magnet. Re-tighten the screw being careful not to misalign the spider and check for the correct operation.
- Speaker cone detaches from voice coil: Another issue that has been seen is that the voice coil becomes detached from the cone. Heat and age can cause the glue to deteriorate and wit the constant vibration this can cause the two to detach. It is sometimes possible to gain sufficient access to re-glue the voice coil. Use a slow drying or curing glue and ensure that this is placed between the coil and the cone. Apply evenly all round so that as it dries or cures it pulls evenly on the cone and keeps the coil in place in the centre.
- Replacement of the coil: In some instances it is possible to replace the coil. An exact spare must be obtained - some companies offer replacement speaker coils for units requiring repair. Specific instructions for that speaker may come with the replacement coil. In any case careful disassembly of the magnet and coil area of the speaker is required. The operation may require the glue fixing the coil to the cone to be carefully dissolved or removed, the speaker coil replaced and the assembling re-assembled. Correct alignment is essential and care must be taken to ensure this otherwise the coli will rub and vibrate on the magnet causing distortion.
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