magnetic shielding

daniel_paul_
daniel_paul_ Posts: 189
edited November 2007 in Speakers
How would you magnetically shield a home made speaker enclosure?
Post edited by daniel_paul_ on
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  • ben62670
    ben62670 Posts: 15,969
    edited November 2007
    Partexpress.com
    look under clearance, and you will find cheap magnets that you can epoxy to the magnets of you speakers.

    http://www.partsexpress.com/clearance.cfm
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • Yashu
    Yashu Posts: 772
    edited November 2007
    Ok you have to give more info than that... hehe...

    Daniel, you need to first measure the magnets on your woofers that you want to shield, then you need to buy magnets that come close to that... you don't want larger, you want roughly the same size as the metal part in the back, the woofer's magnet usually overhangs, and then there is a metal backing, that metal backing is the size you want to get your magnet's OD (outside diameter) for. Find one as close to that as you can and epoxy it to the back of the speaker... you want to "buck" the field, so you may need to look more into this, because I am not an expert, it has been a while since I looked into this, but I think you want to oppose the poles.
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  • daniel_paul_
    daniel_paul_ Posts: 189
    edited November 2007
    For $1 a piece I'll have to experiment.
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  • F1nut
    F1nut Posts: 50,779
    edited November 2007
    you want to "buck" the field, so you may need to look more into this, because I am not an expert, it has been a while since I looked into this, but I think you want to oppose the poles.

    That would be correct.

    I should also add that using the bucking magnets will not totally kill the magnetic field, but will make a large difference. There may also be a slight change in the Q of the drivers you attach the bucking magnets to, although I've never heard a difference.
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  • Yashu
    Yashu Posts: 772
    edited November 2007
    I have heard it can be about a 1 DB difference... like nothing basically. Yeah, it doesn't totally contain it... but it is enough for monitors with a degaussing feature. Once you place the speakers, hit degauss, and things will return to normal. There are some monitors, computer monitors, that are "smart" enough to project a good picture with a certain amount of magnetic field, and sometimes you don't even need shielded speakers, you just put them in the final resting place and hit degauss.

    There are only a few reasons you would need to shield, you must have speakers you want to place next to a computer CRT, or really close to a CRT TV, like a center channel on top of the unit. I have a large CRT monitor for my computer... pro monitor, calibrated colors, that sort of thing... LCDs weren't as good then, for graphics. Anyway, I had to experiment with this. My old CRT could "map" around the fields, but not this one... this one, I had to look into new speakers. Good excuse for me to look for new speakers! :)
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