|   Non-shielded speakers | _Luke_
Feb 22, 2002 5:47 AM | | If a set of speakers are not magnetically shielded, how close to the TV can I put them? I'm thinking floor standers next to a RPTV. Thanks.
Luke |
| Fear not, Luke - | woodman
Feb 22, 2002 8:51 AM | | when the TV set in question is an RPTV, you can put your speakers as close to the set as you want. RPTVs do not suffer from screen impurities from magnetic fields the way that direct-view sets do, because the CRTs in projection TV are not color tubes (with the necessary "shadow mask") but are monochrome tubes - one each for red, green, and blue. No shadow mask - no screen impurity.
What is the screen size and how close will you sit from it?
woodman |
| Fear not, Luke - | _Luke_
Feb 22, 2002 9:50 AM | | Excellent! That's good news. Thanks for making my speaker shopping alot easier.
I have a 55" and I'll be sitting at about 9' (when my furniture shows).
Thanks, Woodman. |
| Thanks for responding, Luke | woodman
Feb 24, 2002 9:39 AM | | The reason I asked about your viewing distance is, that when the viewing distance is much greater than the axis-to-axis distance of the speakers, the "soundstage" width is diminished. If you NEED to put speakers flush with the sides of the TV cabinet for space limitations - that's one thing. If you WANT to put them that close for aesthetic reasons, that's OK too - just be aware that you're somewhat compromising your sonics by doing so.
Don't be alarmed by some of the other replies you're getting on this thread. Although there ARE some speaker drivers with large enough magnet structures to affect an RPTV, they are in the distinct minority. Also, the magnetic field generated by a loudspeaker's magnet will be essentially a "figure 8" pattern that's perpendicular to it's greatest dimension. Therefore, the effect exerted on a CRT's electron beam will be determined to a great extent by it's orientation to it.
Speaker magnets definitely cannot affect screen purity however - but only cause possible geometric distortions of one CRT. Either the red tube or the the blue one, depending on which side of the set the offending magnet is. These distortions of geometry can be corrected by merely "re-converging" the distorted image of the affected tube. There will not be any sustained damage - longterm or otherwise to a CRT or any other internal parts, contrary to what any misinformed salespeople might try to tell you.
Hope this helps you
woodman |
| My experience was different... | Mike D
Feb 22, 2002 3:12 PM | | Hi woodman and All,
A few weeks ago I did some tests and found unshielded speakers definitely affect RPTVs. I owned a Paradigm Reference surround system with Studio 100s up front. These are great, but unshielded, speakers. I was thinking of upgrading to a big screen RPTV, which would require placing the speakers about 10 inches from the TV cabinet. I got conflicting info from sales types about how far the unshielded speakers had to be placed from an RPTV - some said no problem, but most said 18 to 24 inches away. I could not get the TV if the speakers had to be 18 to 24 inches away.
To resolve the issue, I took a 10 inch woofer with a heavy, unshielded magnet to a local big screen TV dealer. They let me hold the speaker close to several different RPTVs, both HD and standard. Brands tested included Mitsubishi, Sony, Toshiba and Samsung. In every case, the speaker affected the picture quite noticably when it got within 14-18 inches of the side of the TV cabinet. (I also took a tape measure). The sales guy at this shop also said I'd need to take into account the long term effect of the magnets being near the TV.
Discouraged, I contacted the tech department at Paradigm, who build their own speakers in house. They said there's no way to reduce this effect via aftermarket products or mods. They recommended I use a different speaker if the speaker had to be placed close to a TV.
I ultimately solved the problem by trading in the Studio 100s on a pair of Revel F30s, which are shielded.
Regards,
Mike |
| Interesting...... | Terrible Terrence
Feb 22, 2002 3:57 PM | | Mike,
My center speaker stands vertically 5" in front of my 55" RPTV. No color distortion whatsoever. It is unshielded. I guess this is one of those things that make you say hmmmmm...
Terrence |
| Agree re Hmmm.... | Mike D
Feb 22, 2002 4:48 PM | | Hi Terrance,
A few years ago, I had a 36 inch Mitsubishi "big tube" TV sitting directly on top of two unshielded downfiring subwoofers, each of which contained a 5 lb. magnet. The TV picture was unaffected. The only thing I could figure was that the fields from the two magnets somehow cancelled each other out. Perhaps if your center channel has more than one magnet, you're experiencing a similar effect(?)
I later tried an arrangement with the same TV on a stand, and one of the subs below it, and the bottom half of the picture was a massive rainbow effect.
I used one of those same woofers with the 5 lb. magnet, sans cabinet, in my tests on the RPTVs mentioned above.
As I said, I got different answers from different people at different stores. I assumed people's own experience must have differed, but I also assumed there were good grounds for concern about what would happen in my case. I put the big magnet near the TVs I was looking at, and each picture was distorted. RGB got out of alignment, and the picture distorted.
I'd love to see some controlled tests done on this.
Regards,
Mike |
| Interesting...... | kelsci
Feb 23, 2002 9:09 PM | | Perhaps degaussing took care of the non-shielded speaker. |
| Interesting...... | IsmaVA
Feb 24, 2002 3:17 PM | | An unshielded speaker place on top of an RPTV hardly ever causes any problems even if it sits directly on top of it. CRT are normally on the lower part of the RPTV cabinet, so an unshielded speaker on top of the cabinet is actually farther. much farther away from the CRT than one placed on the side of the cabinet. |
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