The Magnetic Force

[saurabh]

What would be called a safe distance between TV and speaker(non-shielded). I know that most center and front spks are magnetically shielded but the SUB isnt. So lets say for a CRT TV on a stand and if you need to keep the SUB on the floor near the TV, what would be a safe distance to place it ????.

Ah! another question that comes to my mind is, how can the Magnetic force of the speakers damage a TV or can it also damage the other devices like the AMP or the DVD or interference in cables ????, can it damage the Picture tube or the circuits also.

 

[sjdgpt]

What would be called a safe distance between TV and speaker(non-shielded). I know that most center and front spks are magnetically shielded but the SUB isnt. So lets say for a CRT TV on a stand and if you need to keep the SUB on the floor near the TV, what would be a safe distance to place it ????.

I don't believe we can quote you an absolute number of feet to keep between the sub and TV. The size of magnet on the sub, combined with the thickness and type of construction for the sub cabinet, would make a hard and fast rule next to impossible to calculate, unless specific models of components were known.

In the past, when tower speakers where not magnetically shielded, it was common for the manufacturer to specify 1' or 2' distance from the TV. Remember, distance is your best friend.

I have a small 8" sub that front of the woofer is in the same plane as the front of the big CRT (in other words both facing me). The top external corner of the sub is diagonally situated 27 inches below the outer corner of the TV case. Since the TV has external speakers to sides, the nearest portion of the screen would be about 31.5 inches from the outer corner of the sub's cabinent. Add a little distance for the woofer to be mounted in the sub cabinet, and suddently I have a sub that is nearly 3 feet from the edge of the TV screen.

No problems.

I did notice problem with my old (unshielded) towers if the distance between the outside of the tower and the outside of the TV case was less than 12".

If your sub is on the floor, you are already have at least 1' of space, and most likely about 2' of space separating the TV and sub. Watch the corner of the picture closest to the sub, you can notice the problem... best described as a distortion in the color display of the TV... for me, I was able to observe a green halo effect when the towers got too close to the TV.

can the Magnetic force of the speakers also damage the other devices like the AMP or the DVD or interference in cables

Yes, in theory, but you are not going to typically find such problems with home equipment.

Even the guys that use their sub as the base unit for their entire HT system seldom have any problems. The shielding on the cables and the metal case for the equipment is usually all that is needed to prevent problems with equipment stacked on the sub.

 

[tbewick]

I would be surprised if the sub damaged the your television, seeing as it's on the floor. The subwoofer manual should say how near it can be placed near a television.

Most applicances will say if they cannot be placed near magnets.

The reason why TV's are affected is because they use magnets to defect the electron beam that draws the picture. If these magnets have their magnetism altered by another magnet, they will deflect the beam incorrectly, resulting in coloured patches on the screen. The materials used in speaker cable (copper, silver, plastic, etc.) are not magnetic, ie. they are non-ferromagnetic, hence they are totally unaffected by magnets.

 

[Dumar]

how can the Magnetic force of the speakers damage a TV or can it also damage the other devices like the AMP or the DVD or interference in cables ????, can it damage the Picture tube or the circuits also.

When you say "damage" it sounds like you are worried about the magnetic fields permanently damaging your equipment. This is unlikely due to the relatively weak fields we are talking about. However, when CRT's are exposed to high magnetic fields the picture can remain distorted after the field is removed. It then becomes necessary to degauss the display to correct the problem. Also, magnetic tape can become damaged if stored or placed near magnetic fields, so don't leave cassettes on top of the sub.

The materials used in speaker cable (copper, silver, plastic, etc.) are not magnetic, ie. they are non-ferromagnetic, hence they are totally unaffected by magnets.

Unfortunately, when speaker cables and other interconnects are exposed to magnetic fields in motion, like those produced around power cables, current is induced into the wire (EMI) and can cause hum and other problems. Try and keep your interconnects separated from power sources.