Expert: Antonio Delgado - 2/1/2007

Question
I am planning to use an unshielded full range speaker as a center channel.  My TV is located right above the speaker. Do I have to worry about magnetic shielding with a plasma or LCD TV?

Answer
If you have an LCD, plasma, or DLP based TV, you do not have to worry about magnetic shielding.

The permanent magnets used in the motor systems of moving coil drivers cause stray magnetic fields that can extend at significant strength beyond the walls of the cabinet. If the speaker is placed close to a normal TV set or computer monitor (not a plasma or LCD screen), these stray fields can distort the picture on the screen. To prevent this happening, the individual magnets of each driver must be shielded. In the most common type of structure, using a ring magnet, this involves glueing an extra magnet on the backplate of the main magnet, magnetised in the opposite polarity. A steel cup is placed over the whole magnet structure, the inside of the base being glued to the rear of the second magnet and the sides extending close to the top plate. Unfortunately there are currently no effective standards that govern how well shielded a speaker should be, or how immune a screen should be.