Audio Systems: Speaker shielding, coil area, stray fields

Question
Hi, I'm planning to make a center speaker for my home theater. I would like some info on how to shield the speaker since it will be close to the VCR and TV screen.
Thank you.

Answer
Best to purchase a speaker that is already rated for use in a/v systems.  These speakers have a magnetic circuit already employed that keeps the magnetic field focused around the speaker basket and the stray field is very low.

Too sheild one by yourself requires very heavy magnetic material places around the magnetic structure of the speaker to keep the stray field focused inward to the speaker voice coil area.  Soft iron or similar material must be used and it must be thick and heavy.  Making these shields requires heavy duty workshop tools that can provide for cutting into steel stock.

There is a section on this subject towards the end of this site:

http://www.repairfaq.org/REPAIR/F_audiofaq4.html

The design of a shield is either by cut and try or by finite element modeling to know the optimum design of the speaker motor assembly and the added shield to concentrate the field into the voice coil and keep the stray fields small.

It is not an easy matter for the hobbyist.

But, let me know if you need further assistance or advice.

C