Iron filings in a speaker

[Dave Plowman (News)]

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.

[The Natural Philosopher]

plasticene has worked for me once or twice. also vaseline on a card followed by alcohol to get the grease out

its possble that compressed gas/air might blow it out as well.

I assume the spider is still intact?

[Harry Bloomfield]

A neomibium (sp?) (rare earth) magnet on a stick might be of some use to get out the more accessible bits.

[Tim Lamb]

In message , "Dave Plowman (News)" writes

If you have access, try a conventional sewing needle. The metal particles may prefer the induced magnetism at the needle point.

Never tried it with a speaker magnet but it used to work with moving coil instruments when I was an apprentice:-)

regards

>

[Andy Champ]

Neodymium?

[Harry Bloomfield]

Something like that!

[The Natural Philosopher]

in a nut shell. IF its stronger than the speaker magnet ..

[Gib Bogle]

If it's a good speaker with a very powerful magnet it might be time for a new speaker.

[Graham.]

OO0oo I wouldn't put them in a nut shell, someone might swallow them. One wouldn't be so bad, but two might cause a nasty obstruction.

[John Rumm]

I have visions of a rare earth magnet getting ripped through the cone on its way to sticking forcefully to the speaker magnet ;-)

[Gib Bogle]

Or squashing a finger.

[Frank Erskine]

Agreed, and just put it down to experience, unless you're prepared to muck around with a pair of sharp tweezers for a fortnight or so...

Fortunately modern speakers seem to have a sort of protection of the voice coil at the front by way of a sort of mini dome.

[Gib Bogle]

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.

[Harry Bloomfield]

An aspirin sized one is strong, but not that strong.

[Brian Gaff]

You cannot, its buggered I'm afraid. The mereest sniff will rub it away, and damage it. it cannot be recentred once this has occured. Brian

[The Natural Philosopher]

rubbish

[Muddymike]

Rather stupidly, I left the rear speaker in place when the old Rover was

Was the work done by a pro body shop? If so take it back and make it their problem.

Mike

[Dave Plowman (News)]

Not possible with this construction - common on car speakers - where the tweeters are mounted on a central post.

[Dave Plowman (News)]

I would normally agree - but the quote involved me removing and replacing any necessary trim. For some reason I forgot the speaker even although it was exposed by my removal of the other trim and very easy to remove at that point.

[Andrew Gabriel]

The EU will solve that according to the other thread, by requiring you to remove your unapproved aftermarket speaker anyway. Was the new wing approved by Rover? What about the paint?

;-)