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# Re: Modelling loudspeaker magnets..

- To: femm@yahoogroups.com
- Subject: Re: Modelling loudspeaker magnets..
- From: "davehyre" <davehyre@yahoo.com>
- Date: Fri, 01 Mar 2002 19:32:14 -0000
- In-reply-to: <a5o2fh+pv0q@eGroups.com>
- User-agent: eGroups-EW/0.82

    --- In femm@y..., "emacoustics" wrote:
    > The model is just to show that the coil affects
    > the permanent field when a current runs through it,
    > and by adding a seconc coil in antiphase this can
    > reduce this problem.

    Hi Mike,

    This is an interesting effect; I've looked at it some, too. The
    idea of the counter-coil goes back to the 1920's or earlier,
    described in Thomas' U.S. patent, granted ~1935. Hall & Velodyne, US
    #5,832,096 (~1996) is a recent take on the same idea. I don't know
    which of their subwoofer models employ this approach, if any. You
    can dig up US patents at www.uspto.gov ; the recent ones are fully
    available.

    I'd be curious to hear what you find!

    David

- References:
  - Modelling loudspeaker magnets..
    - From: "emacoustics" <michael.wheeler@ic.ac.uk>

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