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Old 24th June 2003, 09:06 PM   #1
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Default magnetic shielding

I'm trying to hook up a center speaker. However, I can't place it far enough away to prevent electron deflection. Does anyone know how magnetic shielding works, and if it is feasable to implement?
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Old 24th June 2003, 11:13 PM   #2
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aluminum foil duct tape on the interior wall of the box
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Old 24th June 2003, 11:21 PM   #3
Keld is offline Keld  Sweden
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Hi
I dont think that aluminum foil will make any difference. This subject have been discussed several times before on this forum try doing a search.

DVC Keld
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Old 24th June 2003, 11:34 PM   #4
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Default Mu Metal

Two companies come to mind:

Magnetic Shield Corp:
http://www.magnetic-shield.com/products/alloys.html

and

FMS

http://www.fms-corp.com/emf-basics.shtml

Both sell alloy products with I think contain a ferric and non-ferric (like nickel) component. As magnet flux crosses this alloy interaction between the molecules cancels much of the field density.

Both sites have some good tutorials. It would also be worth googling for surplus Mu-metal (I think that its someone else’s brand name). Ideally you will find some that is self adhesive and can be applied like the aluminum tape that JD referred to.

One more, duh:

Mu Shield
http://www.mushield.com/raw_materials.html
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Old 24th June 2003, 11:55 PM   #5
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You can also attach cancellation magnets to the back of your drivers; I'm not sure how one finds the correct magnet to properly cancel the field of a given driver, but Parts Express sells a range of the magnets and I imagine there is information to be found on the web somewhere.
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Old 25th June 2003, 12:30 AM   #6
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Quote:
Originally posted by HeatMiser
You can also attach cancellation magnets to the back of your drivers; I'm not sure how one finds the correct magnet to properly cancel the field of a given driver
I know that putting a pr of speakers in a magnet-to-magnet push-push works really well to magnetically shield a centre channel.

MuMetal will work to a somewhat lesser extent as will a big plate of some magnetic material (ie iron). Aluminum should have no effect.

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Old 25th June 2003, 12:36 AM   #7
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How are computer speakers shielded? don't they put a cap filled with rubber over the magnet? something like that might work.
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Old 25th June 2003, 01:06 AM   #8
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Quote:
Originally posted by bobcat190
How are computer speakers shielded? don't they put a cap filled with rubber over the magnet? something like that might work.
Typical shielded speakers have a bucking magnet added (essentially what i'm doing with the push-push above) with a can over the whole thing to improve its effectiveness slightly.

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Old 25th June 2003, 01:47 AM   #9
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You don't need expensive mu-metal, 12ga cold rolled steel (CRS) will do just fine for lining a cab and is cheap enough that sheetmetal fabricators will normally either give you scraps or just charge a nominal fee to shear it to size.

For that matter, you don't even need to line the cab with it. I used to have a 25" console with a sheet of it sitting on top, hanging off the back far enough to 'mask' the gun. This was sufficient to shield it from a 1.4T ceramic prosound 15" sitting on top.

GM
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Old 25th June 2003, 04:13 AM   #10
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Depending on how complex your center speaker is, I'd probably opt to just line the cabinet, as using bucking magnets can alter the properties of the drivers.
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