Subwoofer Affecting LCD TV?

[nsainfreek]

I've read around and most people say that LCD and Plasma TVs are not susceptible to magnet damage from speakers, which has me confused about my problem. My Samsung LCD Tv was working fine three months ago with no sound system installed. Since then I installed a Definitive Pro 600 5.1 surround sound system with subwoofer. The subwoofer was placed on the floor slightly to the left of the Tv. Everything was ok, until about a week later when the picture on the left side of my Tv became distorted when I turned it on. After a few minutes the distortion would go away, but it had me concerned. Once it went away, powering the tv off and on immediately yielded no distortion, but if you went away for a few hours, came back and turned the tv back on the distortion would be back. The problem got progressively worse with the distortion persistinglonger and longer, but still going away if I left the Tv on long enough. It's hard to describe the distortion, it's like it has an image on top of an image and it is stretched with static lines traveling up an down. Again this distortion was only to the left side.

I decided to do a test and turn on the Tv without the sound system. The distortion still occurred. So I just unhooked the subwoofer and moved it to the other side of the room, waited a few hours and turned the Tv on. No distortion. I tried the Tv again after a few days and still no distortion. This leads me to believe that it is the sub is the culprit, I'm just not sure what the sub is doing to the Tv. I believe it's the magnet but that's counter to what I'm reading online. Any ideas?

Also, if the sub's magnet is affecting my Tv is there any recommendations on what I can do to leave the sub in it's place but shield it's affects from the Tv? For wire management purposes I would like to keep the sub where it is.

[MrBoylan]

I've read around and most people say that LCD and Plasma TVs are not susceptible to magnet damage from speakers, which has me confused about my problem. My Samsung LCD Tv was working fine three months ago with no sound system installed. Since then I installed a Definitive Pro 600 5.1 surround sound system with subwoofer. The subwoofer was placed on the floor slightly to the left of the Tv. Everything was ok, until about a week later when the picture on the left side of my Tv became distorted when I turned it on. After a few minutes the distortion would go away, but it had me concerned. Once it went away, powering the tv off and on immediately yielded no distortion, but if you went away for a few hours, came back and turned the tv back on the distortion would be back. The problem got progressively worse with the distortion persistinglonger and longer, but still going away if I left the Tv on long enough. It's hard to describe the distortion, it's like it has an image on top of an image and it is stretched with static lines traveling up an down. Again this distortion was only to the left side.

I decided to do a test and turn on the Tv without the sound system. The distortion still occurred. So I just unhooked the subwoofer and moved it to the other side of the room, waited a few hours and turned the Tv on. No distortion. I tried the Tv again after a few days and still no distortion. This leads me to believe that it is the sub is the culprit, I'm just not sure what the sub is doing to the Tv. I believe it's the magnet but that's counter to what I'm reading online. Any ideas?

Also, if the sub's magnet is affecting my Tv is there any recommendations on what I can do to leave the sub in it's place but shield it's affects from the Tv? For wire management purposes I would like to keep the sub where it is.

Hmmm... interesting. I've never seen a magnet affect a non-CRT TV before, but it is possible with a subwoofer since these typically include massive heavy magnets with strong magnetic fields that can effect certain circuitry if not properly shielded. With a CRT TV, magnetic fields are used in order to focus the cathode ray, so the effects of an external magnet (even a small one) are obvious and can be permanent. But with other electronics, magnetic fields can affect the signal in other less obvious ways.

If you want to definitively test that it is the magnet itself, and not the electronics of the powered sub affecting the image, then unplug the power cable from the subwoofer completely (not just powered off but unplugged from the wall) and see if the distortion remains with the subwoofer placed near the TV. If it is the magnet in the driver, and not the electronics, then you could try buying a "bucking magnet" which is basically just a strong magnet out of polarity from the driver magnet which cancels its radiated magnetic field. This *can* effect sound quality so normally this or magnetic shielding like Mu metal is used inside the cabinet as part of the speaker design.

This isn't a wireless sub by any chance, is it? Even though you say you're using wires, if your sub has a wireless option then it has a radio module in it, though this should be a receiver, not a transmitter so this also wouldn't easily explain the issue.

Rather than going in trying to fix the problem with a potentially unsightly home grown shielding solution, I'd recommend trying a different powered sub and see if the problem goes away. I know these things are heavy and unwieldy but if you buy something locally from a dealer that accepts returns (in case it doesn't help) then you may save yourself some grief.

Let us know how it goes and please post the subwoofer brand and model number as well as the TV model number in case anyone else happens to have similar problems in the future with this combination of gear.

--CB