I am not sure how they do it, possibly aluminum or some exotic metal.
Remember when speakers first came out for PCs and if you placed them close
to a monitor, the CRT was distorted? Then specialty "shielded" PC speakers
came out that can be placed on either side of the CRT. I have eliminated
sailboat tiller pilot problems by replacing high quality stereo speakers
mounted in the transom with marine grade ones.
Doug K7ABX
"Maynard G. Krebbs" wrote in message
...
On 15 Dec 2003 11:14:07 -0800, (boatalec) wrote:

Maynard G. Krebbs wrote in message
. ..
On Tue, 09 Dec 2003 19:00:29 GMT, "Doug"
wrote:

I know you can shield RF and other electronic interferance but how can
you shield magnetic interferiance?
Mark E. Williams

Most marine speakers are manufactured with rigid plastic baskets (the
part that the cone and magnet are glued to) and shields that keep salt
water out of the voice coil assembly (because most magnets have a high
component of ferrous, or iron that rusts).

If you buy a regular pair of high end car speakers, they will sound
great for a season, then rust out.

Alec


Thanks
Mark E. Williams