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# Re: [femm] Modelling loudspeaker magnets..

- To: <femm@yahoogroups.com>
- Subject: Re: [femm] Modelling loudspeaker magnets..
- From: "C F Cheuk" <c_f_cheuk@yahoo.com>
- Date: Sat, 2 Mar 2002 10:05:56 -0000
- Disposition-notification-to: "C F Cheuk" <c_f_cheuk@yahoo.com>
- References: <a5o2fh+pv0q@eGroups.com>

    Hi Mike,

    I was in the same boat before so I can't stand seeing you suffer. I have modelled the magnet, pole piece and yoke of a loudspeaker coil configuration,but I have not studied the effect of the coil current on the magnetic field nor indeed the combined effects of the 2 magnetic fields on the coil current (assuming constant Vrms drive). The attached file depicts half of the magnet assembly which is assumed axis symmetry in Polar coordinate. The configuration and the value of B in the coil gap have been verified experimentally. The model is belivable, ask me for the zone of uncertainty if you needto. I cannot remember without looking it up in my data files.

    I would dearly like to know the conculsion of your study if it is OK with you.

    Cheuk
    ----- Original Message -----
    From: emacoustics
    To: femm@yahoogroups.com
    Sent: Friday, March 01, 2002 2:16 PM
    Subject: [femm] Modelling loudspeaker magnets..

    Hello folks,

    I'm kind of new to using FEMM, and am trying to model a loudspeaker
    coil/magnet assembly for my final year university project. I'm
    modelling to observe the effect the flux generated by the coil has on
    the permanent magnetic field. The model is really simple - one block
    of steel, one block of Neodinium, and one (and sometimes two) coils
    (which are represented by square blocks at present, though may get
    changed to circles) in the gap between them. My problem is in not
    understanding how to input data for magnets - I modelled the system
    with no current in the coil (and with no coil at all) expecting to
    see field lines between the neodinium and the steel, and saw
    nothing. When looking at material properties, there are lots of
    values for constants I don't understand, nor did I really understand
    the manual either. Can anybody point me in the right direction? 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.

    Many many thanks, I'm getting desperate!

    Best Wishes,

    Mike Wheeler
    Final Year Undergraduate, BEng Mechanical Engineering
    Imperial College, London

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    <DIV><FONT face=Arial size=2>Hi Mike,</FONT></DIV>
    <DIV>&nbsp;</DIV>
    <DIV><FONT face=Arial size=2>I was in the same boat before so I can't stand
    seeing you suffer. I have modelled the magnet, pole piece and yoke of a
    loudspeaker coil configuration, but I have not studied the effect of the coil
    current on the magnetic field nor indeed the combined effects of the 2 magnetic
    fields on the coil current (assuming constant Vrms drive). The attached file
    depicts half of the magnet assembly which is assumed axis symmetry in Polar
    coordinate. The configuration and the value of B in the coil gap have been
    verified experimentally. The model is belivable, ask me for the zone of
    uncertainty if you need to. I cannot remember without looking it up in my
    data&nbsp; files.</FONT></DIV>
    <DIV>&nbsp;</DIV>
    <DIV><FONT face=Arial size=2>I would dearly like to know the conculsionof your
    study if it is OK with you.</FONT></DIV>
    <DIV>&nbsp;</DIV>
    <DIV>&nbsp;</DIV>
    <DIV>&nbsp;</DIV>
    <DIV>&nbsp;</DIV>
    <DIV><FONT face=Arial size=2>Cheuk</FONT></DIV>
    <BLOCKQUOTE
    style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
    <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
    <DIV
    style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
    <A href="mailto:michael.wheeler@ic.ac.uk";
    title=michael.wheeler@ic.ac.uk>emacoustics</A> </DIV>
    <DIV style="FONT: 10pt arial"><B>To:</B> <A href="mailto:femm@yahoogroups.com";
    title=femm@yahoogroups.com>femm@yahoogroups.com</A> </DIV>
    <DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, March 01, 2002 2:16
    PM</DIV>
    <DIV style="FONT: 10pt arial"><B>Subject:</B> [femm] Modelling loudspeaker
    magnets..</DIV>
    <DIV><BR></DIV><TT>Hello folks,<BR><BR>I'm kind of new to using FEMM, andam
    trying to model a loudspeaker <BR>coil/magnet assembly for my final year
    university project.&nbsp; I'm <BR>modelling to observe the effect the flux
    generated by the coil has on <BR>the permanent magnetic field.&nbsp; The model
    is really simple - one block <BR>of steel, one block of Neodinium, and one
    (and sometimes two) coils <BR>(which are represented by square blocks at
    present, though may get <BR>changed to circles) in the gap between them.&nbsp;
    My problem is in not <BR>understanding how to input data for magnets - I
    modelled the system <BR>with no current in the coil (and with no coil at all)
    expecting to <BR>see field lines between the neodinium and the steel, andsaw
    <BR>nothing.&nbsp; When looking at material properties, there are lots of
    <BR>values for constants I don't understand, nor did I really understand
    <BR>the manual either.&nbsp; Can anybody point me in the right
    direction?&nbsp; The <BR>model is just to show that the coil affects the
    permanent field when <BR>a current runs through it, and by adding a seconc
    coil in antiphase <BR>this can reduce this problem.<BR><BR>Many many thanks,
    I'm getting desperate!<BR><BR>Best Wishes,<BR><BR>Mike Wheeler<BR>Final Year
    Undergraduate, BEng Mechanical Engineering<BR>Imperial College,
    London<BR><BR><BR><BR></TT><BR><BR><TT>Your
    use of Yahoo! Groups is subject to the <A
    href="http://docs.yahoo.com/info/terms/";>Yahoo! Terms of Service</A>.</TT>
    <BR></BLOCKQUOTE></BODY></HTML>

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    - From: "emacoustics" <michael.wheeler@ic.ac.uk>

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