On 22/08/2012 7:29 a.m., Dave Plowman (News) wrote:
Rather stupidly, I left the rear speaker in place when the old Rover was
having a new rear wing fitted. Which is welded on so removing the old one
would have produced some steel swarf or whatever when drilling out the
spot welds - and a lot of it has ended up in the speaker. It's a fairly
pricey aftermarket 6x9 with a pair of tweeters mounted on a post in the
middle, and the swarf has got down between that and the voice coil former.
Any ideas on how to remove it? The post itself isn't the magnet pole piece
- it appears to be plastic. No idea how it's held in place - there are no
wires to the tweeters showing.


Coincidentally (and tangentially) I attended a very interesting talk
yesterday, presented by a young man who has just completed his PhD at
MIT. His topic was the design of small powerful linear motors using
permanent magnets - effectively, they use sophisticated voice coils.
the magnets are stacked with four different orientations in a way that
traps the magnetic field, and the current in the coils is controlled to
preserve the right phase relation with the magnetic field. The big
issue is getting rid of the heat generated in the voice coil, and to
facilitate this his little motors have close tolerances - he aims for 10
microns at operating temperature. You wouldn't want any swarf in there.