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Subwoofer affecting LCD TV?

post #1 of 8
3/11/10 at 4:51pm
Thread Starter 
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.
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post #2 of 8
3/11/10 at 7:35pm
Magnets in unshielded speakers can affect CRT monitors (computer or TV)  They do this because they can deflect the stream of electrons that is fired from the gun(s) at the back of the tube to the inside of the glass screen, which is covered in phosphor dots which glow when excited by the electron beam.

There is no analogous process in an LCD panel.  It isn't that magnets don't affect LCDs it is that they can't.  (I don't know enough about the inner workings of plasma sets to know about them one way or another.)  You could hold a bar magnet up to the screen of an LCD panel and it would not affect the picture at all.  I know because I've done this with computer monitors to illustrate this very point. 

Also the description you're giving of the distortion doesn't resemble the kind of distortion that a magnet will produce on a CRT monitor at all.  If you hold a magnet up to a CRT screen the image will literally bend around it.  Move it and the colors will smear.  A double image and lines of static are not what you would see.  

If the sub is the source of the problem, it is more likely a power issue that is screwing up the Samsung.  You may have a grounding problem, there could be too much of a load on a shared circuit or the sub's power supply may be out of spec and causing RF interference which in turn is affect other components by induction.  But a magnet problem this aint.  Try plugging the sub into another wall outlet on another circuit.  Is you gear plugged directly into the wall, or do you have surge protectors and/or battery back-ups? 

Is the audio system still under warranty?  Try having the sub tested or see if you can swap it out for another, at least for an overnight test.  

Hope this helps.

Joe
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post #3 of 8
3/11/10 at 8:13pm
Thread Starter 
That was acutally very helpful. You're right about the magnets, I didn't think it could affect it either and I know how CRTs react to magnets. It's just the only thing that could cross my mind, but your explanation makes more sense since I've also been having trouble with my Logitech RF remote and delays in getting signals to the Receiver. I'm going to try and plug the sub into a different outlet. Currently, the sub is plugged into the reciever and the receiver is plugged into a surge protecter. Together they are probably drawing a lot of power from one outlet.
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post #4 of 8
3/12/10 at 5:34am
Make sure the new outlet you choose for your sub is on a different circuit.  If both outlets are on the same circuit then the same thing may still happen if it is a power issue.
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post #5 of 8
3/13/10 at 4:39pm
Thread Starter 
Well the same thing is still happening. What do you mean on a different circuit? Like a different outlet? Or do you mean like on a completely different section of the house? My circuit box has just one switch for the entire living room. If you're talking about a different circuit switch the sub would have to go in the kitchen or something. Is there another way of doing this without moving the sub so far away? Could i get one of those Monster Power Conditioners? Would that work?
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post #6 of 8
3/13/10 at 8:37pm
If your living room has one breaker switch then the entire living room is on the same circuit.  That means it doesn't matter which plug you choose in that room, they are all essentially the same plug.  For example, all of my 15amp outlets in my theater are on a single circuit.  I also have three 20amp outlets each its own circuit.  All four circuits are on the same leg (right side) of my breaker box.  Power is easily overlooked but it all makes a difference.

If you have a heavy duty extension cord, power the sub from another room just to see if power is the issue.  A conditional may work but there are ones cheaper than Monster.
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post #7 of 8
3/13/10 at 9:55pm
I agree with Robert:  The test with an extension cord is a very good quick & dirty way to establish if it is a power issue.  And stay away from anything with "Monster" in its name, unless you just like to piss away money on a brand name.  You can buy an equivalent of every product Monster makes that will be as good or better, and cost much less, from other companies.  Like Bose in the world of all-in-one HT audio systems, Monster represents the triumph of marketing over reality.  

BTW, if you do find everything works just fine with the sub drawing power from another room, you may want to invest in an electrical tester and check your wiring - or hire a professional to do it.  The distortion on your LCD panel could be just a symptom of a much more serious issue, the kind that can result in shocks or over-heated wiring and electrical fire.  Your TV could be acting as your canary in the coal mine.  

Regards,

Joe
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post #8 of 8
3/15/10 at 2:44pm
Thread Starter 
Well, I don't pay retail cost for Monster stuff since I have friends who work at Best Buy. I bought an $85 Monster power conditioner for $16. Well, the power conditioner all my electrical components did not solve the issue. I'll get an extension cord and try that test. Thanks for the input.
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