magnetic shielding

[slackerbob]

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?

 

[JOE DIRT®]

aluminum foil duct tape on the interior wall of the box

 

[Keld]

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

 

[Da5id4Vz]

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

 

[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, but Parts Express sells a range of the magnets and I imagine there is information to be found on the web somewhere.

 

[planet10]

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.

dave

 

[bobcat190]

How are computer speakers shielded? don't they put a cap filled with rubber over the magnet? something like that might work.

 

[planet10]

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.

dave

 

[GM]

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

 

[Super]

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.

 

[The Paulinator]

Does the aluminium foil with the adhesive backing work ok with smaller drivers like 6" and under? I have had a Vifa 6 1/2" and tweeter for a center channel I was going to make, but I forgot to order them in sheilded form. I have quite a bit of adhesive back foil tape about 1" wide and a little under a centimeter thick.

 

[JOE DIRT®]

I have my centre channel speaker sitting on top of my tv and I used alcan 2"aluminum tape and sprayed it with automotive undercoating and it works for me....but I`m not a expert in magnetics

DIRT®

 

[7V]

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.

I believe that the driver properties aren't altered very much. Certainly not significant if you're using for a 'centre speech speaker'.


Steve

 

[slackerbob]

I like stuff cheap

Thanks for all the feedback. I think I'll go with either the aluminum foil, or the CRS, as that seems to be the cheapest.

Thanks a bunch

 

[slackerbob]

I tried ordinary aluminum foil placed on top of the TV. It helped a bunch. More than 1 sheet is necessary though. And it looks terrible.

 

[Da5id4Vz]

I never met a potato that I didnt like.

 

[The Paulinator]

I like potatoes.

 

[GM]

I tried ordinary aluminum foil placed on top of the TV. It helped a bunch. More than 1 sheet is necessary though.

Interesting. I wonder what all 'aluminum' foil is comprised of since ~pure aluminum won't have any visible affect on reducing the magnetic effects on a nearby signal.

GM

 

[planet10]

Interesting. I wonder what all 'aluminum' foil is comprised of since ~pure aluminum won't have any visible affect on reducing the magnetic effects on a nearby signal.

A good test is to see if the foil sticks to a magnet.

dave

 

[swirv]

Ok now this it intresting. I have a pair of LX5's that I modified a while ago. I plugged the ports and stuffed the hell out of them and I also lined the inside with Dynamat Extreme. These speakers before the mods were not sheilded. In fact I though it was cool that if I placed a paperclip near the side it would stick to the outside of the box.

Well a few days ago I purchaced a new 6.1 Yamaha receiver. I was playing around and found that without a center speaker I was missing a lot. I grabbed one of the LX5's and brought it into the living room and was curious as to how close I could put the LX5 to the TV. Its sitting right on top of the damn thing right now with no distortion of color or shape on the tube.

I figure the Dynamat linning has helped not only kill the ringging of the aluminum cab but also made the unit 'sheilded'.

I say just put a layer or two of Dynamat Extreme (or equivalent as long as it is the sticky type with the metal backing) on the interior walls of your center speaker. It will help to 'sheild' it and help to kill box resonance.