Small particles could collect and be forced into the gap by dropping
where they will stack up an cause a rub issue. The magnetic assembly
shifting is usually when they are transported vertically. It's really
hard to shift the magnet face down. What I have seen, with high
compliance loose suspension, big voice coil drivers is the coil fall
out of the gap, then foul the voice coil former.

Remove the dust cap and have a look. It's all you can do at this
point. Sometimes Xylene or Acetone or Toulene can soften the glue to
permit removal, or you can use a razor blade.

Pull the cone toward you and see what is actually rubbing.

Debris can be fished out with masking tape, compressed air, shims,
etc.

If the gap is not symeterical and concentric, the speaker is toast. It
has to be reglued and remagnetized. Unless it is a holy grail speaker,
buy a new one.

If the former is deformed, maybe you can finesse it back with shims
but a new voice coil is usually required.

Good luck




On Jul 21, 7:51 am, "N Cook" wrote:
Anyone come across the situation where presumably some crud that was
otherwise safe in the bottom of the voice coil slot is now shifted and
causing distortion.
Owner in the habit of transporting face down - to avoid anything falling
onto the front face.
Any opinions on transporting face-down or cures. ?
Try operating for a while horizontally perhaps but face up or face down.?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/