The walpurgis fix for buzzing and rubbing speakers!
Sometimes, a driver voicecoil may become misaligned in the magnet gap and rub against either the pole piece or outer face of the gap. If your bass driver is buzzing or has a binding coil, this may help. I've offered this advice several times and provided a remedy to a few people. I've used this trick myself successfully on occasion. Lets face it, if you have a dodgy bass driver, you have nothing to lose by trying it.
One bass driver. I this case, an 8" KLH.
http://i66.tinypic.com/15hirrq.jpg
This is the important bit. The area where the back of the cone meets the rear suspension spider (the corrugated part).
http://i64.tinypic.com/29qmc0i.jpg
Using a finger poked through the chassis opening, work the cone back and forth on its suspension whilst pressing it forward (across) just in front of the join with the rear spider. Do this all the way round the cone. If the coil is fouling, you will feel it rubbing. Do this as many times as it takes you to identify the point at which it rubs most.
http://i63.tinypic.com/21b4288.jpg
Once you are sure where it is rubbing most, mark this point with a felt tip pen.
http://i66.tinypic.com/j980ac.jpg
Next. Feed reasonably strong elastic bands through the speaker chassis openings and around the back of the cone so that they pull in the opposite direction to the felt tip pen mark you made on the chassis, ensuring the bands pull firmly, but not so hard as to risk causing damage and secure the bands in place using sticky tape or tying them or as I did using a paper clip.
http://i68.tinypic.com/2pod251.jpg
http://i64.tinypic.com/zkpc3d.jpg
Then, use a hairdryer set to hot through the chassis openings and onto the rear spider all the way round. This relaxes the spider and allows the coil to move over slightly.
http://i68.tinypic.com/fdd4aw.jpg
Set the dryer to cold and go round the spider again. This 'sets' the new coil position.
Remove the elastic bands and hopefully you will have a cured drive unit. Occasionally you may need to try this technique a couple of times before you get it spot on!
Note: This will not work if the coil has been overheated and is binding due to swelled lacquer nor will it work if the coil is distorted and no longer circular.
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