Any way to shield a non-magnetically shielded speaker?

Discussion in 'Archived Threads 2001-2004' started by Brett_H, Oct 31, 2001.

  1. Brett_H

    Brett_H Second Unit

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    Hi,
    I recently got a free pair of Boston Acoustic bookshelf speakers from a friend, and I'm using them for my center channel. I've since learned (by the weird color patterns they impose on my TV) that they are not magnetically shielded. Thankfully, my TV de-gausses itself when it's powered on!
    Is there any non-destructive way to shield them? I'm not sure if he's going to want them back in the future, so I'd prefer not to crack them open.
    Ideas?
    Thanks,
    -Brett.
     
  2. Dave Poehlman

    Dave Poehlman Producer

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    Well, I can't think of any way to shield them externally. Short of moving them away from the TV.
    You could "try" some bucking magnets on the outside of the enclosure... I don't know if that would have any effect.
    Otherwise, ideally, if you can get the drivers out with minimal damage, your best bet is to apply bucking mags to the rear of the driver.
    You can find them at Parts Express. Part number 249-325
    The magnet will change the t/s parameters for the driver slightly, so, the resulting sound may not be exactly the same as when you started.
    Good luck.
     
  3. Dan M~

    Dan M~ Second Unit

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    Do a net search using "magetic shielding" and see what the commercial places do. They offer metal boxes to put your computer monitor in so maybe a metal box around your TV will work. This can be made out of low carbon steel and if your TV is in an entertainment center, it might be out of sight. Take a look at the commercial stuff for ideas.
    Good luck
    -Dan
    here's a start:
    http://www.advancemag.com/monitor.htm
    [Edited last by Dan M~ on October 31, 2001 at 01:56 PM]
     
  4. Brett_H

    Brett_H Second Unit

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    Guys,
    Thanks for the replies. To be honest, I never knew exactly how speakers were "shielded". I pictures the enclosures lined with metal or something! If it's really as simple as adding another magnet to the back of the existing driver, I think I could swing that.
    One more question: Would I need to do this to both the mid-bass (woofer isn't quite the word for a 5.25" driver...) and the tweeter, or just the mid-bass?
    Thanks!
    -Brett.
     
  5. Dave Poehlman

    Dave Poehlman Producer

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    Technically, you should sheild both drivers. You could try just the mid/bass and see how it works and add a magnet to the tweeter if you need to.
    A word of caution, the bucking magnet has to be mounted in reverse polarity to the voice coil magnet (and depending on the size of your original magnet, you may need more than one bucking magnet stacked on top of one another). It's going to put up a fight when you try to affix it. Plus, you will need to use some good adhesive to keep it in place once you get it there. If you could find a piece of tubing to slide the magnet down and keep it centered while you position it, that might help.
    Again.. good luck.
    The speakers are free anyway, so, if it doesn't work, you'll wind up with some heavy duty refrigerator magnets. [​IMG]
     
  6. Greg Monfort

    Greg Monfort Supporting Actor

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    I've gotten good results from laying a 10ga cold rolled steel (CRS) plate on top the TV, or laid up against the sides of a computer monitor. Ideally, it needs to be a little larger than the picture tube, but if the drivers are several inches up in the cab you can often get by with just a strip ~the width of the tube and a little bit wider than the depth of the speaker. You can get some sheared to whatever dimensions at any decent sheet metal fabrication shop.
    GM
    ------------------
    Loud is beautiful, if it's clean
     

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