Shielding

mbond24
mbond24 Posts: 17
edited December 2010 in Basic Hookup/Wiring Questions
need help. I have some RC85i speakers mounted in the wall next to my TV as Right/Left channels. The problem is that one speaker is very close to electrical wire running down the wall. Should I find a way to shield the speaker and wire? If so, where can I find some shielding?

Thanks in advance for your help.
Post edited by mbond24 on
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  • nguyendot
    nguyendot Posts: 3,594
    edited December 2010
    Paint that wall with lead. :)
    Main Surround -
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  • cristo
    cristo Posts: 231
    edited December 2010
    Lead doesn't work very well unless there's something radioactive behind the wall.
    Plate the wall with Mu-metal shielding instead.









    from Wikipedia:

    Mu-metal is a nickel-iron alloy (approximately 75% nickel, 15% iron, plus copper and molybdenum) that has very high magnetic permeability. The high permeability makes mu-metal very effective at screening static or low-frequency magnetic fields, which cannot be attenuated by other methods. The name came from the Greek letter mu (μ) which represents permeability. A number of different proprietary formulations of the alloy are sold under trade names such as Mumetal, MuMetal, and MuShield; this article will cover their common features.

    Mu-metal can have relative permeabilities of 80,000–100,000 compared to several thousand for ordinary steel. In addition it has low coercivity and magnetostriction resulting in low hysteresis loss. Other high permeability alloys such as permalloy have similar magnetic properties; mu-metal's advantage is that it is more ductile and workable.[1]

    Mu-metal objects require heat treatment after they are in final form — annealing in a magnetic field in hydrogen atmosphere, which reportedly increases the magnetic permeability about 40 times. The annealing alters the material's crystal structure, aligning the grains and removing some impurities, especially carbon, which obstruct the free motion of the magnetic domain boundaries. Bending or mechanical shock after annealing may disrupt the material's grain alignment, leading to a drop in the permeability of the affected areas, which can be restored by repeating the hydrogen annealing step.
    cristo

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  • Tour2ma
    Tour2ma Posts: 10,177
    edited December 2010
    mbond24 wrote: »
    Should I find a way to shield the speaker and wire?
    AC does generate a magnetic field (emf), but in straight wire 110/220V runs it's so-o-o-o-o weak that it's not going to be a problem.

    If you are hearing a buzz, it's far more likely to be a ground loop issue.

    Do you hear a problem?
    More later,
    Tour...
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