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From: frank@ulticorp.UUCP (Frank Cannavale III/1024000)
Newsgroups: sci.electronics,rec.boats
Subject: Re: non-magnetic speakers
Message-ID: <410@ulticorp.UUCP>
Date: 17 Oct 90 23:11:15 GMT
References: <1990Oct16.140417.15202@phri.nyu.edu>
Reply-To: frank@ulticorp.UUCP (Frank Cannavale III/1024000)
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In article <1990Oct16.140417.15202@phri.nyu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes:

>       I want to put a pair of speakers on my boat, for a stereo.
>Unfortunately, the place where the speakers should go is within a couple of
>feet of the compass, so anything magnetic is bad.  Are there speakers which
>do not generate any magnetic fields?  They should be weatherproof too.

So sorry, but no.  Most speakers are basically electric motors.
Linear motors rather than rotational motors you are familiar with.
Usually there's a permanent magnet fixed by a frame. A coil of wire
is attached to the speaker cone. As alternating current (from the
stereo) is feed to the coil, it produces a varying magnetic field that
is alternatively attracted or repulsed from the PM. That's about it.

There are some rather exotic alternatives.  The first that comes to
mind is electo-static.  Usually a charged membrane with a grid placed
near it.  The amplifier feeds a transformer that steps the voltage up.
The voltage potential causes the charged membrane to be attracted and
repulsed from the grid.  Very expensive for full range speakers.  Also
very large.  The Accoustats <sp?> I saw were 2x8 feet each!  (and a
few grand too) The 1x8 model did not generate much bass and required a
sub-woofer.  This speaker type is not useful on a boat.  (Makes a
good tweeter only though.) The second alternative (I'm really fuzzy on
this one) used a hot wire to drive a cloud of electrons off.  The
electrons were moved by using a high voltage charge.  That explanation
does not make much sense to me either, I just don't remember the
technique very well.

Basically, pick another location.

Sony and Babs make ok marine type speakers. I have the Sony's  and
an Alpine car stereo on my boat. They are ok, but not as good as, say
ADS or Boston Acoustics car stereo speakers.

--
Frank Cannavale III   !uunet!ulticorp!frank   The Ultimate Corp, E. Hanover, NJ
"Yes, you can afford the Trojan 12 Meter that is fiscally irresponsible for
you to buy. And I'm not talking about loans here. Banks suck, forget about
banks." ... "Technically, if the bank owns the boat, then it owns the bilge, and
who wants to wipe his banker's bilge?" - Berkeley "Bonefish" Breathed