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Thread: 3143 metal box interfere with coils

  1. #1
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    3143 metal box interfere with coils

    Hi everyone!
    I'm about to make an upgrade to a pair of 4343 crossovers with Mundorf parts, removed the original parts and started with the new ones placement until.... I realise that metal case interferes with the new coils!!!! No matter what kind of core (air, Iron, etc) except for the E cores, they donīt changes a damn bit!!!!!! (like the jbl originals)
    Do you know why is that?
    Can I just take off som turns of the new coils to reach the desired value "inside the box"?
    Will this degrade the audio?
    Thanks in advance

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  2. #2
    Senior Member grumpy's Avatar
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    Place the coil further away from the box surface... the change should be minimized.
    If it were on a printed circuit board, it could be inches away from the box.

    Having an open magnetic circuit next to a ferrous object/surface will change the
    behavior (inductance in this case). I would be reluctant to change the coil value
    to accommodate the box.

  3. #3
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    Quote Originally Posted by grumpy View Post
    Place the coil further away from the box surface... the change should be minimized.
    If it were on a printed circuit board, it could be inches away from the box.

    Having an open magnetic circuit next to a ferrous object/surface will change the
    behavior (inductance in this case). I would be reluctant to change the coil value
    to accommodate the box.
    Is true that this phenomenon decreases with distance but the problem is that I have to place 5 coils inside the box so not only the box is the problem!
    I will do my best to avoid interaction between the coils and box...not a simple task!
    What keeps me wondering is why the E cores don't change with proximity, not only with the box but neither with other coils!

  4. #4
    Administrator Mr. Widget's Avatar
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    The best solution is to not use the steel box. Aluminum or plastic would not be a problem, or simply mount your board inside the speaker or even externally.


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  5. #5
    Senior Member grumpy's Avatar
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    Sure... but I can see wanting to maintain the original form factor/layout... at least somewhat

    With an E-I core, the magnetic flux travels almost entirely within the core with much less potential for external coupling
    vs other inductor types.

  6. #6
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    Mr. Grumpy nailed it!!!
    Is my wish to preserve the box.
    Later I will post some images of my experience....if there is some
    Thank you

  7. #7
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by u-47 View Post
    Mr. Grumpy nailed it!!!
    He's pretty good at that.

    Actually I pretty much assumed that was the case… However if you're going to go over the audiophile grade parts, I'd suggest going all the way.

    Keep us posted.


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