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kexodusc
08-23-2004, 05:50 AM
Is there any rule of thumb as to how close you can place unshielded drivers to your tv set?

If it's a trial and error thing, what damage would happen to the tv if I get too close, and is it easily fixed? Anything I should look for as a symptom that my speakers are too close?

This Guy
08-23-2004, 06:55 AM
You will see the colors distort on the television. You can actually just move the speaker right next to the TV and see what it looks like...it won't hurt if you just do it for a second or two. Also, many TV's are different. Currently, I have my subwoofer a foot away from the TV and it has a 50oz. magnet and it doesn't affect it at all. On my other TV, it was affected from about 5 ft. from it (cheap GE 19"). It's usually pretty obvious when the magent is affecting it, so If you don't see anything now you should be fine.

kexodusc
08-23-2004, 07:25 AM
You will see the colors distort on the television. You can actually just move the speaker right next to the TV and see what it looks like...it won't hurt if you just do it for a second or two. Also, many TV's are different. Currently, I have my subwoofer a foot away from the TV and it has a 50oz. magnet and it doesn't affect it at all. On my other TV, it was affected from about 5 ft. from it (cheap GE 19"). It's usually pretty obvious when the magent is affecting it, so If you don't see anything now you should be fine.

Hmmm, my TV's actually got speakers on either side of the screen, maybe it's self shielded? Okay...if I do screw up the colors, is the damage permanent or will it heal itself?

Geez, I dont' know what I'm so worried about, I use to blast some big Cerwin Vega's back in college next to an old sony tv I had, this was before "magnetically shielded" was buzzword.

This Guy
08-23-2004, 07:47 AM
If you move the speaker right neext to it, the colors will be screwed up for a minute or two. Turn it off than on again and it will be gone. The only time it's permanent is if you leave it there for quite some time. I think you're fine.

kexodusc
08-23-2004, 07:56 AM
Don't actually have the speakers finished yet, but I'm anticipating building a few more...I'd like to stick with this design instead of moving to shielded drivers which might not be exactly the same...guess I'll just have to test. They'll be about 2-1/2 to 3 ft' away from the screen anyway...thanks This Guy!

Woochifer
08-23-2004, 09:43 AM
I guess that would really depend on the TV and the speakers. With my TV, I have my Studio 40s about 1' away, and they don't present any issues at all with the TV. But, if you put the speakers within about six inches, then the image does show color distortions.

kexodusc
08-23-2004, 09:56 AM
Yeah, Wooch, my Studio 40's are about 2-3 ft away, I've never had any issues, but aren't they shielded? Or just the Studio CC?

woodman
08-23-2004, 05:23 PM
Is there any rule of thumb as to how close you can place unshielded drivers to your tv set?

If it's a trial and error thing, what damage would happen to the tv if I get too close, and is it easily fixed? Anything I should look for as a symptom that my speakers are too close?

Ken:
What type of TV set are you talking about? That makes a world of difference, since RPTVs are [b]not[/b[ subject to the "magnetic problem" that affect direct-view CRT sets. If you ARE talking about a direct-view set, then it indeed is a "trial and error" deal ... no such thing as a "rule of thumb". The effect is a distortion of the color at various places on the screen. As to "damage" to the set: NO, there is not permanent damage of any sort. It can and will be corrected by the de-gaussing circuit that's built into virtually every set today.

But, I must correct a statement made by "ThisGuy" which implied that if you notice such a distortion - just turn the set off and back on again to correct it. This is misleading at best. The de-gauss circuit will only function when the set is turned on from a "cold start" - meaning that it has to have been in an off condition for at least 5 to 10 minutes to allow the de-gauss circuit (primarily the thermistor) to become cool. Then and only then will it do its job.

If the set (direct-view only) has been subjected to a humongous magnetic field, then it may need to be de-gaussed with a professional tool called a de-gaussing coil. But such a situation is rare.

If an RPTV is subjected to such a magnetic field, it could affect the "convergence" by pulling the output of one of the three CRTs away from it's intended path. But this too is quite rare in the real world.

Clear?

kexodusc
08-24-2004, 03:47 AM
That's great Woodman, my TV is just a crappy , 3 year old CRT type 36" JVC unit...150 bucks at a police auction, couldn't go wrong!!!

To tell you the truth, if I did fry the TV I might be able to pursuade the fiancee that we need a bigger, newer one...I'm moving to Canada though, until the house is sold money's tight :(

risabet
01-01-2005, 01:18 PM
Is there any rule of thumb as to how close you can place unshielded drivers to your tv set?

If it's a trial and error thing, what damage would happen to the tv if I get too close, and is it easily fixed? Anything I should look for as a symptom that my speakers are too close?

If you can't see any effect than they are far enough away, 1 foot is usually enough, magnetic fields dissiapate rapidly with distance, 2 to 3 feet is better.

SAPSEC
01-06-2005, 09:32 AM
This issue had bothered me more than 2 weeks before I decided to buy a pair of BW DM-303
before Christmas (non-shielded). When you see a green or purple circle appeared on tv
then it starts get distorted (ie : hair color changed to green ..) I tried it with my cheap Wega Sony
TV, as long as I can keep them 18 inches away from TV, I don't have any problems.

I later asked BW and JM Lab support and they said the minimum safe distance is to keep
non-shielded speakers 3 feet away (or 90 cm) from your TV screen and this guideline could be
applied to all kinds of speakers and TV screens. Hope this helps !

woodman
01-06-2005, 11:33 AM
I later asked BW and JM Lab support and they said the minimum safe distance is to keep
non-shielded speakers 3 feet away (or 90 cm) from your TV screen and this guideline could be applied to all kinds of speakers and TV screens. Hope this helps !

Ahh - the Peter Principle shows up yet again to prove people incompetent at the jobs they are supposed to be competent to perform. This "advice" you were given by people who should know their business (but quite obviously, don't) is wrong from start to finish! There simply is no "minimum safe distance", nor is there any distance at all that is "unsafe". When a speaker causes color distortion on a CRT, there will be NO permanent damage caused. Furthermore, as I already stated in my post above, whether or not a given loudspeaker will cause a "problem" with a TV set, depends on what type of display technology is involved. A speaker that will distort the color badly on a direct-view CRT set, will not affect an RPTV at all - no matter how close it's placed - whether that RPTV is one that is CRT-based, or LCD or DLP-based. Tsk, tsk ... those that dispensed this incorrect "advice" should consider either taking up a different line of work, or else they should actually learn about the business that they're involved with.

markw
01-06-2005, 11:42 AM
I've found that sometimes people won't go away unless they are given a simple, definitive answer to a question.

Ya gotta admit, three feet IS a pretty safe answer. ;)

Sir Terrence the Terrible
01-06-2005, 05:06 PM
A speaker that will distort the color badly on a direct-view CRT set, will not affect an RPTV at all - no matter how close it's placed - whether that RPTV is one that is CRT-based, or LCD or DLP-based.

Woodman, can you explain to me why when I moved a speaker that is identical to my left/right mains into the center position just in front of my RPTV it began to discolor and distort until I moved it away? I have read where you have said this before, and I was damn confused when I saw distortion on my RPTV.

woodman
01-07-2005, 08:37 AM
Woodman, can you explain to me why when I moved a speaker that is identical to my left/right mains into the center position just in front of my RPTV it began to discolor and distort until I moved it away? I have read where you have said this before, and I was damn confused when I saw distortion on my RPTV.

TT:
I'll give it a shot, but first - would you please elaborate and describe your phrase "it began to discolor and distort". Specifics please. Also, what size magnetic structures do these speakers of yours have?

Sir Terrence the Terrible
01-07-2005, 10:40 AM
TT:
I'll give it a shot, but first - would you please elaborate and describe your phrase "it began to discolor and distort". Specifics please. Also, what size magnetic structures do these speakers of yours have?

Thanks for your help on this. Well I moved the speaker to just in front of the RPTV, and when I did, the picture started to look like broadcast ghosting. Instead of getting a single S-video prompt from the onscreen display, it looked like three seperate S-video prompts superimposed over one another. It also looked like the convergence was totally off. Once I moved the speaker away, these effects disappear.

The woofer driver on the speaker is a 15", and it weighs about 30lbs. Its a hefty bugger!!

Thanks so much for your help on this, I would REALLY like to use this speaker as my center speaker, but if it is going to mess up the picture, I will keep the one I have, or figure out how to shield the speaker.

kexodusc
01-07-2005, 10:50 AM
LOL - Sweet Jebus, and I thought the Studio CC was big...Sir Terrence, your center channel is bigger than most people's subwoofers....A 15" woofer? I'd expect that to cause a bit of distortion to ANYTHING it's beside. :)
Don't tell me you've got a 6-1/2" tweeter in that thing too... :)

Sir Terrence the Terrible
01-07-2005, 11:19 AM
LOL - Sweet Jebus, and I thought the Studio CC was big...Sir Terrence, your center channel is bigger than most people's subwoofers....A 15" woofer? I'd expect that to cause a bit of distortion to ANYTHING it's beside. :)
Don't tell me you've got a 6-1/2" tweeter in that thing too... :)

<img src="http://drumcorpsplanet.org/forums//style_emoticons/default/lol.gif">
<img src="http://drumcorpsplanet.org/forums//style_emoticons/default/laugh.gif">
<img src="http://drumcorpsplanet.org/forums//style_emoticons/default/laughing.gif">

Yeah, my center makes the studio CC look like a bose cube. But I figure if a RPTV is not supposed to distorted when near a unshielded speaker, then using this size center shouldn't be a problem. Boy I was wrong. I really want this as my center speaker though, so I earnestly want to see if I can make it work. Dialog is so clean and clear, I can actually hear the different eq setting used, dialog loops, and unfortunately the disparity between the ADR booth were dialog is replaced, and the organic sounds that create the atmosphere of the room during a scene.(or better put, dry dialog in a reverberant room)

It has a 15" woofer with a 5 1/2 midbass coaxially mounted in center of the woofer, a horn loaded midrange and tweeter. Big, efficient, and VERY powerful sounding speaker

kexodusc
01-07-2005, 11:27 AM
Curious, can you tell me a bit more about this speaker? Design, enclosure, efficiency,how does it handle at low volumes? Dare I ask what the rest of your HT consists of?
I feel so small and inadequate now...this gives new meaning to the phrase "go big, or go home".

Sir Terrence the Terrible
01-07-2005, 12:55 PM
Curious, can you tell me a bit more about this speaker? Design, enclosure, efficiency,how does it handle at low volumes? Dare I ask what the rest of your HT consists of?
I feel so small and inadequate now...this gives new meaning to the phrase "go big, or go home".

LOLOLOLOL......can't you see I am tryin to eat lunch here!!!.....waaahahahehehehehe.....you are on quite a roll man.

The speakers are a custom jobber. The drivers on all of my speakers are made by TAD, and are designed to be exceptionally low in distortion at very high volumes.. The enclosure is 30x17x12.5, real wood veneer, no resonances when you knock on the wood(feels like rapping on cement) efficiency is 99db per watt at 1 meter, maxiumum power recommended is 700 watts, frequency response is listed at 20hz-45khz +/- 3db, between 20hz-20khz in room is measured at +/- 1db at 10ft away, and at least 4ft from any wall. The speakers are time and phase correct, and use constant directivity horn technology. It sound pretty good at low levels, but it really kicks azz at high levels because it's quite a mellow speaker for a horn hybrid. They don't sound like horn hybrids at all. It is very revealing, even to a fault as you hear things that you really shouldn't be hearing(like bad edits, looping, different eq's for dialog, ADR discrepancies with location atmosphere). Not a perfect speaker, but exceptionally good on so many levels.

Three of these speakers make up the L/C/R front setup. I am currently not using a sub because that would be a major overkill in my setup(my mains outperform most subs at 20hz). I am using two custom refitted horn hybrid bipolar speakers, that are voiced identically to the fronts from 80hz up. Their sensitivity is also 99db per watt, one meter distance. These also play VERY loud with low distortion. Frequency response is 50hz-45khz. they have a 6.5" woofer/mid, and a two horn loaded tweeter faced at 45 degree angles.

This whole speaker package belongs in a room three time the size of the room it is currently in. I like the sound of these speakers alot, and I better because I paid enough money for the custom refit.

kexodusc
01-07-2005, 02:21 PM
And I was getting all horny having built my own 2-ways, a few established designs and, looking forward to a 15" sub. There's always someone with cooler toys :rolleyes:
I bet you find it a bit drafty in your room when a movie's on, I can imagine 15" L/C/R's pushing quite a bit of air...
99 dB efficiency? That's a recipe for "disturbing the peace" charges.

Sir Terrence the Terrible
01-07-2005, 03:28 PM
And I was getting all horny having built my own 2-ways, a few established designs and, looking forward to a 15" sub. There's always someone with cooler toys :rolleyes:
I bet you find it a bit drafty in your room when a movie's on, I can imagine 15" L/C/R's pushing quite a bit of air...
99 dB efficiency? That's a recipe for "disturbing the peace" charges.

You are too funny man...hehehehe. Yeah, I have a pretty unique problem that just happens to be the polar opposite of everyone else. Everyone else has problems with soundtracks that overload their subs. My problem is that occassionally the bass coming from these speakers overloads the room. The air is shaking, the windows, the dishes, and my grandmothers front teeth. As good as their bass is, they are extremely well balanced from top to bottom, and that is what I like about them.

kexodusc
01-07-2005, 05:51 PM
You must have all kinds of ideas for room treatments for us then...I can't imagine the setup of those to be a piece of cake to get the kind of measurements you've accomplished...let me know the next time you're up my way...

woodman
01-08-2005, 02:11 PM
Thanks for your help on this. Well I moved the speaker to just in front of the RPTV, and when I did, the picture started to look like broadcast ghosting. Instead of getting a single S-video prompt from the onscreen display, it looked like three seperate S-video prompts superimposed over one another. It also looked like the convergence was totally off. Once I moved the speaker away, these effects disappear.

The woofer driver on the speaker is a 15", and it weighs about 30lbs. Its a hefty bugger!!

Thanks so much for your help on this, I would REALLY like to use this speaker as my center speaker, but if it is going to mess up the picture, I will keep the one I have, or figure out how to shield the speaker.

OK ... now I know just how to answer your question(s). Sorry I was slow getting back to you about it ... I've been tied up for the last 24 or so re-wiring my home (music-making) studio.

1. When I've stated (numerous times) on these boards that an unshielded speaker will not cause distortion to the pix on an RPTV no matter what type of technology it uses, I was referring to what could loosely be called normal loudspeakers. Your speakers do not qualify ... they are waaaaaaaay beyond being included in such a description. I was also referring to the left and right main speakers ... not to a center channel speaker placed below the screen, which evidently was where you placed yours.

2. As to why your (center channel) speaker causes a problem, it's because of the humongous magnetic structure of the 15" woofer AND to where it was placed. In CRT-based RPTVs, the tubes are positioned in a sort of semi-circle at the bottom of the cabinet with the screens facing the rear. The tube necks (where the electron gun assemblies are) are very close to the front of the cabinet ... right where you placed your CC speaker. The very, very, very, very, very, very strong magnetic field produced by that 30lb. magnet being in close proximity to the necks of the CRTs causes a slight deflection of the electron beam in one or more of the CRTs - resulting in a failure of the three images to superimpose on top of each other ... in other words, misconvergence.

3. Since you gave one of the dimensions of this center channel beast as 30", I assume that the other two (as "mains") stand upright at 30" tall, and you were placing the third one being used as a CC laying down on its side ... correct? So why can't you place it on top of the RPTV cabinet instead of laying it on the floor in front of the set? Is there some reason why you rejected this placement?

4. Lastly, if you still want to use this speaker for your CC (and placing it on top of the set is not an option), there's a way to do it if you're willing to spend the time (or the money to hire someone else to spend his time). Simply re-do the setup with the CC speaker in the position where you want it to be to make the pix look "right". Of course, if you need to move the speaker from its position for any reason, the pix will look "bad" again until the speaker is returned to where it was.

P.S. I will continue to assert that unshielded speakers will not affect RPTVs - perhaps with the caveat ... unless you have an abnormal speaker like Sir TT has and you want to place it on the floor in front of the set like he did. Then, all bets are off. Teehee!

kexodusc
01-08-2005, 04:37 PM
Wow, Woodman, my own doctor wasn't as thorough when he diagnosed me with cancer, and he charged waaaay more than you.

Sir Terrence, that behemoth is gonna look aweful funny on top of your tv, but don't feel bad, it would topple mine. Could there be some 15" bucking magnets out there that would remedy this situation?

gonefishin
05-19-2005, 09:23 PM
Hi Sir Terrence,


Have you ever figured out a solution to your problem? I'd certainly imagine exactly how a nice TAD based center would sound matched up with your main speakers. I know I used to have my mains sitting next to my television with no ill effect. Granted, The drivers were alnico, which is usually much friendlier with a television near by due to it's more spherical shaped, front to back, magnetic pattern. But this still isn't full proof with the sides entirely. Depending on the TAD model woofer, it also may be alnico. Which may not rid the problem...but offer some hope.

My suggestion, if you haven't already remedied the situation, place the driver (or speaker) in the exact position that it would be in above or beneath the television. Directly in front of will almost ensure that you'll get interference. But place so many inches away from the screen (due to the speaker enclosure) and using the angle that you intend to have on the driver. You may find that things may work out after all. If your using TAD drivers that are a material other than alnico. You may want to look into the effects that a similar alnico (TAD) driver will have. Although the TAD drivers are not priced to simply buy a couple and play around with the results.

Hope you found a resolution to your center speaker address ;)

Hopefully this may give you cause to at least pursue a fix to your problem with those much more qualified to give advice than myself. But I'd love to hear an update :)


dan