GK 200MB speaker issue & solution

[Rhodesplyr]

A client brought a Gallien-Krueger 200MB bass amp to me, complaining that there seemed to be something wrong with the speaker. He'd already taken it to two other shops that had thrown up their hands. It has a replacement speaker supplied by GK a while back.

The nuts holding the speaker to the front of the enclosure were loose, so I tightened them, but the back panel was still rattling and vibrating severely. That's when I noticed a large cylindrical rubber bumper attached to the back panel. There was a small gap between it and the speaker magnet. Reasoning that it was probably there to create a positive pressure connection between the front and back panels via the speaker frame, I attached an adhesive felt pad to the rubber bumper to fill the gap between it and the speaker magnet.

Result: no more rattles whatsoever. It works fine.

A google search on this topic shows quite a few people complaining about strange rattles from this combo associated with replacement speakers. I've never worked on a speaker enclosure quite like this one (all metal), but it appears that there needs to be a tight fit between the speaker and the rubber bumper to avoid problems.

[52 Bill]

The original speaker frame was deeper and it did fit tight to the rubber bumper. I've seen the bumper come loose and fall into the cabinet. It amazes me that no one else could figure that out. I'd guess that nobody else opened up the cabinet.

All of the screws in these amps are constantly coming loose and or are stripped by over tightening. Trying to stop rattles on these can be a real adventure sometimes.

I'm sure that the original speaker needed to be re-foamed, and was replaced instead.