Magnetic shielding of speakers - The Project...

[cirrus1]

I have some old but very good speakers that I wish to use close to my CRT monitor, when I go to LAN parties. Due to the limited amount of space on the desk, the speakers have to stand quite close to the monitor.
Although the speakers are small they have very powerful magnets and produce a magnetic field strong enough to affect the monitor in a distance of around 30 cm.
This isn't very favorable and I'm thinking of a way to shield the speakers.
As far as I can see there are 4 options:

- Shielding on the outside. This would involve covering the entire case with some kind of shielding. I don't know what material would be best here, but copper or lead (or any heavy metal with high density) would be the best in my opinion. I have access to a wide array of metals sheets including iron, steel, stainless steel, alu, seawater-resistant alu, copper, lead and many others.
This option would be the easiest ( and a side-effect would be that it would be very cool to have a speaker covered with blank copper or alu )
I have tried doing a little experiment by loosely covering the speakers with the various materials and then "measure" the effect with a cheapo compass that I was willling to sacrifice. The copper seemed to have the best effect.

-Shielding inside This would involve making some sort of shielding the internal parts of the speaker the magnet etc... This will be harder to achive since the inside only can be accessed trough the back panel where the terminals reside.

-Use ferrit-magnets on the speakers magnet I have heard that this reduces the emitted magnetic field caused by the speaker by concentrating the energy where it is needed, around the magnet itself.

-Remove the speakers magnet and live with poor sound

Thanks for all inputs and thoughts guys

 

[rahvin]

1. You can only shield magnetic fields with the 3 elements that are magnetic. Unless you have access to boron or the other rare element I would say your shielding needs to be Iron based.

2. Sheilding magnetic fields is easily done with a thin layer of Ferrous metal, this layer can even be a grid. All the metal has to do is cut the field lines for the magnetic field being created by the magnets. In summary you can probably cover your speaker in chicken wire and shield most of the field.

3.If you take the magnets out of your speakers you won't have speakers. The magnents are essential to the sound production, all speakers contain them, or make them during use.

4. Copper is an electrical conductor and would sheild the electric field, but wouln't block the magnetic portion of the EM field because it is not Ferrous.

 

[sharkeeper]

Buy a LCD and remember to keep credit cards and floppies away from the speakers!

Cheers!

 

[Migroo]

<< 3.If you take the magnets out of your speakers you won't have speakers. The magnents are essential to the sound production, all speakers contain them, or make them during use. >>



Further to what rahvin said:

The magnets are what move the speaker drivers. Somehow I think cirrus1 was kidding when he mentioned removing the magnets though...