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Discussion Starter · #1 ·
I have an NEC XG-110LC and am going to be using it in my new theater in the back room of my house. I am building the soffit and the hushbox right now and was planning on running a 58.5"x104" wide (16:9) screen. I have read numerous places that this size a screen is too big for an 8" CRT. I am looking at the math and scratching my head.


The NEC puts out 1100 lumens. Figuring that a 104"x58.5" screen equal 6084 sq. in or 42.25 sq. ft, than:


FtL=Lumens*Gain/Sq.Ft


FtL=1100*1.5/42.25


FtL=39


With a 50% reduction in brightness as the bulbs age, I should be getting nearly 20 Foot Lamberts.


Using ANSI Lumens, rated at 240, I get:


FtL=240*1.5/42/25


FtL=8.5


I was under the impression that you want it between 8 and 12 FtL. My options are to get a second projector for a double stack (expensive and more maintainance), a higher gain screen (hotspotting), run the projector at a higher output (shorten the bulb life) or have a smaller screen (AAAGH!)


I thought I had found another XG-110LC at a decent price, but it turned out to be a standard XG-110, so I am currently stuck at one projector for the time being. Should I:


A.) Run a single with a 1.5 gain screen?


B.) Go with the High Power (my projector/s will be ceiling mounted - 8' high ceilings, seats raised 8" in the back row) and just live with color shift/hotspotting?


C.) Redesign the soffit and hushbox to bring the projector out about a foot further into the room?


I am just wanting to make sure that I do it right the first time, as I don't want to tear the room up or have to replace the screen at a not so later date.


I will have 100% light control in this room and it will have a black ceiling with dark walls to minimize the light reflection back onto the screen.


Thanks,

Mike
 

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That wasn't the 110LC on ebay last weeK? That was not an LC, but it was in pristine condition.

Still, to use such a large screen you will tend to push the tubes to get a good contrast picture. It will do it, though. I have seen old sony's set for 200" diagonal. Dim, but there it was..... I guess it depends on personal taste. Personally I'll stop at 92" wide.


Marc
 

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I agree. I had a 92" wide and dropped back to an 80". Byo am I glad I did. Huge difference in the punchiness of the picture. I just moved my seat about 18: closer to it. Watching it now, I can't imagine having it any larger than it is!
 

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Just try it on the floor at various distances and make up your own mind, as no one can tell you what you will like. I run an 8000 at 104" wide 16:9, and love it.
 

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I helped Bob Wood go from a 80" width screen up to 92", with his 3600 8" Ampro, which I believe is brighter than our XG110LCs...it was a big mistake. We tried for two days to get the same punch and black levels, and just couldn't do it. Bob went back to his 80" screen, and we were both shown first hand why a single 8" shouldn't go much over 80" width.

Having said that, I just setup a Barco 1209 with a 102" screen that I built using ScreenGoo. The customer wanted his picture to look like mine...I let the customer know that I felt anything over a 96" width would cause a severe degradation.

I have to say, it looks alot better than I thought it would.

However, I'm keeping him away from my system, I'm afraid if he starts comparing them, I'll be pulling his pj off the ceiling, moving it forward a foot, and making a new, smaller screen.

I would NEVER drive a 104" width screen with a single 8" pj. I've never seen a double stack, but knowing my need for perfect convergence (it's a must for fine detail) I don't think I'd go that route either.

If I had to have a larger screen, I'd go with a G90, 9500, or 1209s, and limit the screen to 96" width.
 

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Anyone seen an NEC 6PG running on a 92" 16:9 1.4 gain mini perf screen?

(I'm considering Harkness Hall Perlux 140MP material)


You guys have now got me worried !!!


The other option I was considering was a 96" 2.35:1 1.4 gain mini perf screen with masking for 16:9.


Any thoughts??

OR should I stick with 16:9?
 

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So if you go with an 80" screen what gain would you use for the NEC XG? 1.0 1.3 1.5?

Just wondering.. I'm in the same boat as the poster... I have a homemade 107" diag. screen but I'm looking into getting a new screen...

I also agree with the thinking of keep it on the floor and move it back and forth to see what you like, but I would like to get a prof. oppinion.


Thanks

Dave

Quote:
Originally posted by KennyG
I helped Bob Wood go from a 80" width screen up to 92", with his 3600 8" Ampro, which I believe is brighter than our XG110LCs...it was a big mistake. We tried for two days to get the same punch and black levels, and just couldn't do it. Bob went back to his 80" screen, and we were both shown first hand why a single 8" shouldn't go much over 80" width.

Having said that, I just setup a Barco 1209 with a 102" screen that I built using ScreenGoo. The customer wanted his picture to look like mine...I let the customer know that I felt anything over a 96" width would cause a severe degradation.

I have to say, it looks alot better than I thought it would.

However, I'm keeping him away from my system, I'm afraid if he starts comparing them, I'll be pulling his pj off the ceiling, moving it forward a foot, and making a new, smaller screen.

I would NEVER drive a 104" width screen with a single 8" pj. I've never seen a double stack, but knowing my need for perfect convergence (it's a must for fine detail) I don't think I'd go that route either.

If I had to have a larger screen, I'd go with a G90, 9500, or 1209s, and limit the screen to 96" width.
 

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Quote:
Originally posted by Mr.Poindexter
I have an NEC XG-110LC and am going to be using it in my new theater in the back room of my house. I am building the soffit and the hushbox right now and was planning on running a 58.5"x104" wide (16:9) screen. I have read numerous places that this size a screen is too big for an 8" CRT. I am looking at the math and scratching my head.


I will have 100% light control in this room and it will have a black ceiling with dark walls to minimize the light reflection back onto the screen.


Thanks,

Mike
Your proposed screen is almost exactly the same dimensions as mine.

While I agree that a little smaller would probably be better, I still think that you'll have to judge for yourself. Like you, I have 100% light control and a black ceiling. In my opinion, my display is plenty bright. My contrast setting is moderate at 65%.


Everyone who has been in my theater comments about how amazing the image looks.


Here's an older photo of my screen http://www.armorform.com/hollowman.jpg


Good luck.
 

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Discussion Starter · #9 ·
Mark, what gain of screen do you use? I read your site, but it just states you have a DIY screen painted with Behr Ultra White or something like that. Any idea what kind of gain it is?


Mike
 

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Quote:
Originally posted by Mr.Poindexter
Mark, what gain of screen do you use? I read your site, but it just states you have a DIY screen painted with Behr Ultra White or something like that. Any idea what kind of gain it is?


Mike
I have compared it to sample cards from a screen supplier and it appears to be about 1.3 gain.


You mention "a 50% reduction in brightness as the bulbs age." What kind of age? I have about 1,300 hrs. on my projector. I would hope the CRTs are just as bright as when new (or close to it). BTW, please don't say, "bulbs".


Lastly, I recomend satying away from high gain screens. You'll be much happier with the colors, contrast, etc. with a 1.0 to 1.5 screen.
 

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I'd like to add a few things that may or may not be of use. The number of hours I've heard thrown around when CRTs have lost most of their initial light output is around 2000 hours. This is where mine are now.The remaining reduction is not linear but levels significantly for the remaining life of the CRTs.


I have a stacked pair that work well together but the age of the CRTs themselves seem to be one factor in stability, that is they should all be close in hours.


I'm not sure which PJ Runco used as their 991 ultra ( an LC NEC XG) , but I've also been told that that this is the ultimate CRT for stacking ( great convergence range, stable and point convergence for extremely fine adjustment potential ). This is the PJ stack used in the Home Theater magazine " "installation of the millennium" issue.


Art
 

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Discussion Starter · #12 ·
My guess is that they would have used the XG-135LC. My current CRT projector has approximately 5 hours on the tubes and about 10,000 hours on the chassis. My current plan is going to go forward then with a 58.5"x104" 1.5 gain screen and I will look for a second projector for a double stack.


It is my understanding that the projector will put out the same number of lumens on a 16:9 screen as a 4:3 screen and so should also do the same with a 2.35:1 screen, correct? That would bump me up to a nicer 11.26 Ft. Lamberts for 2.35:1 movies. Perhaps it will be fine as long as I stick to 2.35:1 films until I get a second projector...
 

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Quote:
Originally posted by Mr.Poindexter
My guess is that they would have used the XG-135LC. My current CRT projector has approximately 5 hours on the tubes and about 10,000 hours on the chassis. My current plan is going to go forward then with a 58.5"x104" 1.5 gain screen and I will look for a second projector for a double stack.


It is my understanding that the projector will put out the same number of lumens on a 16:9 screen as a 4:3 screen and so should also do the same with a 2.35:1 screen, correct?
Only if you've found a source of CRT sized anamorphic lenses.


Otherwise, at the same throw distance your ft-l numbers will be the same as they are on a 4:3 screen. This is because you'll be using just (9/16)/(3/4) = 75% of the phospher on a 16:9 screen and getting just 75% of the Lumens. For a 2.35:1 screen, the percentage will (1/2.35)/(3/4) = 56%. The screen shrinks by the same ratio, so the brightness per unit area remains the same.


Of course, with a wider screen you'll be using a narrower chunk out of the middle trapezoid of phospher used for a 4:3 image. This will be narrower so you'll be able to reduce the throw distance, increase the phospher utilization, and increase light output proportionally to the inverse square of the throw distance change.


That said, I wouldn't try to justify it purely using mathematics. Tastes _really_ vary - with a 225 ANSI lumen CRT I think a 1.3 gain screen in the 7' wide range works best, while Vern Dias is running a scope screen 10'? wide off a single projector.


Maybe see where light output becomes unacceptable on a white surface with 1.0 gain (perhaps a Parkland Plastic home brew screen), and then either stop there or think about increasing size by the square root of whatever gain screen you can live with?
 

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Vern uses a 12' wide screen with scope aspect ratio. I guess you have to use his example since he must represent the far end of the spectrum when quoting acceptable foot Lambert numbers:confused:. I wouldn't go much larger ( if at all ) than I have now with my stack since I'm only doing about 11fL. This is precisely why I've been looking to other PJs for the next screen size I want to use ( about 11' wide ).


Art
 

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Clearly this screen width / brightness issue is subject to personal opinion.


However I run my XG135LC on the same size screen being proposed (104" wide - 119" diag 16:9). The screen I use is a Da-Lite Cinema Vision (1.3 gain).


With good light control in the room, I have my brightness turned down to 55 from the default 60 setting, as the image is otherwise too bright for my liking.


One significant factor however, that contributes to light output, is what you are using to drive the projector. eg: On these projectors if you are using a line doubler, your light output will be a lot less than if you are line quadrupling (960p).

Or to put it another way, with the optimum setup where your scan lines are just touching (versus visible scan line spacing), you will be getting optimum phosphor coverage and therefore higher light output.


Personally I would avoid a stacked setup (but that's because I am very picky when it comes to mechanical alignment and bang on convergence, so I couldn't imagine trying to get a stacked setup tweaked to my satisfaction - and have it stay there!).


The bottom line is that putting the math aside, you really need to just try it for yourself with your PJ, and see what is good for you.


Greg
 

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Quote:
Originally posted by Mr.Poindexter
Mark, what gain of screen do you use? I read your site, but it just states you have a DIY screen painted with Behr Ultra White or something like that. Any idea what kind of gain it is?
Hi Mike! FYI - I have a 54x96 screen painted with Behr Ultrawhite eggshell finish and using samples from Draper & Stewart, was able to determine that my gain comes in at 1.4. (Brighter then the 1.3 samples, not as bright as the 1.5 samples).


Kal
 

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In reference to Behr Ultrawhite:

Quote:
Originally posted by kal
(Brighter then the 1.3 samples, not as bright as the 1.5 samples).Kal
I agree and in my opinion its the perfect gain.
 
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