Newbie struggling with Screen Choice(AT or normal)

Take a look at urm's test results on AT screens. They are at the bottom of the document Pay attention to seating distance..
http://accucalhd.com/documents/accuc...een_report.pdf

Having the speakers positioned behind the screen, "ties" the sound to the image in a way that outboard speakers cannot do. Your brain doesn't have to work as hard to associate what you hear with what you see. I think you'll find on this forum that those that have gone with AT setups highly recommend them and would never go back to an outboard arrangement. And with your viewing distance, any possibility of a visible screen fabric weave is very remote, thus allowing you more freedom (flexibility) in your choice of screen and AT fabric. (View distances shorter than about 8 feet make selection of a screen fabric more critical.) If you go with a fabric (woven) screen (as opposed to a perf screen), the impact to audio is minimal (and correctable by adjustment to hi freq. equalization) to being a non-issue.
See also the various brand-specific "The Official screen thread" entries in this subforum for more info on AT screens.

I'm struggling with a similar question, but far from a newbie. I currently have a 16:9, 110" diagonal screen and sitt at a distance of 10 feet. There is no option to move back any further. I want to switch to a scope screen and had pretty much set on a 119" diagonal (110" wide). I'm beginning to reconsider a AT screen as the more I read, the more concerned I get about seeing a pattern or texture in the screen material. I plan on building a screen wall in such a way that I could swap out for an AT screen in the future.

The speakers I'm using a very narrow, tall column type that I plan on putting right next to the screen, in the same plane, and covering with acoustically transparent fabric. The fabric will go around the whole frame, so from visual standpoint, the front wall would look the same if I use an AT-screen approach or solid one. The only difference being the speaker location being about 18" inboard if I go AT.

I guess my biggest concern is sacrificing image quality for an AT approach.

BTW...Using a JVC HD350 and plan on adding the upcoming Prismasonic A-lens.

I'm in a similar situation, totally light controlled room, JVC HD350 or RS 15/25 projector most likely source. I'm going with 54" tall, curved CIH screen (10'-10" wide) and seating distances are 11' and 15'. I can place my L+R speakers behind the screen or off to the side (hidden by acoustically transparent masking, not my first choice). Regardless, I'm sold on having the center channel above ear level and at or slightly below center of screen (and L+R speakers raised so drivers of exact same model Center Channel speaker are all at the same level).

I to don't wish to sacrifice audio or picture quality, so I'd like to know the "best" AT material and perhaps an "acceptable" material that costs less but sacrifices only the last percentages of audio and video quality. Seems there is Seymore, SMX, and Stuart who make decent (?) AT screen materials??? SMX 2k and 4k seem interesting, but no info on their web site on the 4k.

Thought perf was the way to go, but SteveHorn thinks woven fabric degrades sound and picture the least. Which is what I'm looking for.

Like the other posters here, I'll be glad to have recommendations for superior AT screen material!!!

AT screens are not necessarily more expensive. If you are handy, you can build your own. My 126" prolly came to about $400, and that's without sparing expenses; nicest velvet I knew of and a ton of it, maximum usable excess for maximum tilt, some pretty nice and very straight wood from the finest lumber store near me . . .

It's too bad about the ambient light, that will just kill performance. For example, I sort of equate $25 in black paint to an increase of $1000 (or more) on the PJ budget, in terms of performance.


I would definitely consider the 4K materials, where you cannot discern the weave until you are very close. I know the Screen Excellence is ISF certified for 4k. You very well may be ok with the other stuff, but you would be advised in obtaining the largest samples offered to see for yourself.

My problem with any woven material is that it lets a ton of light through. Why pay for an expensive projector only to have a large percentage of the light go through the screen. To the point that you can see the image from both sides. Yes, they offer a black backing for the screen but from what I remember, that takes it's THX certification. I could be completely wrong about that, it's been a while. It's great for audio, not so much for video.

Benny

The Seymour Center Stage XD screens have a black backing that reduces the light pass through to a minimum with less than 1 dB attenuation to the audio.

If everything behind the screen is black and non-reflective, you don't need the black backing as far as I am aware.

Correct on the Seymour screen but it being THX certified can be a big thing for some, especially considering that the speakers will be behind the screen. From what I recall, the black backing will not allow for it to be THX certified. Again, I could be wrong on that. I'm getting old and all this AV stuff just gets blurry after a while

But yeah.....the 1db loss is nothing to fret about. I think Stewart and a few others also loose somewhere along those lines to where you can't even hear the difference. Now going through two layers such as a black backing or a masking panel....that's a whole different story.

If the back room is completely black that helps but helps more with light reflecting back through the screen and causing some major image problems. You are still loosing a ton of light that literally goes through the screen.

Benny

Well, what do you call a "ton" of light? For instance, Jeff Meier measured the Seymour to have a gain of 0.94, and the Carada Cinema White to have a gain of 0.97. Do you consider 0.03 to be a ton?

I did a pretty ok job of blacking out the front wall, but I still used a black backing. However, I didn't use Seymour's black backing, but instead some cheap and thin black speaker cloth. The reason for this BB is because my speakers have metal tweeters and metallized woofers. When I get around to building new speakers, the odds are pretty high that the drivers will be all or mostly black. At which point, I can take my BB down.

Whatever the SPL loss truly is, I wonder what the total net loss would be after I remove these PSB grilles with a lot of plastic?

Very good question Josten......to me personally, anything over 10% is too much light loss. It's weird but I called a few screen companies up to try to get that info just for fun and no could give me a number except for Stewart. Stewart expects roughly 7-9 percent of the light to transmit through the screen.....that number I already knew. The other manufacturers could not provide me with that number. Kinda strange.

The gain you mentioned doesn't really factor into light being transmitted through the screen. More of light transmitted off the screen and back at the audience.

Benny

Can you please educate me on the relevance of this light loss? If the perceived brightness by the viewer is identical, the lost light being controlled at the front wall or by way of BB, and that we are getting all 2,073,600 pixles or whatever, how does this affect perceived performance?

Is your concern related to the difference between the extreme fill ratios of 3LCD vs 3LCOS, for example? Thanks.

I am sure if you asked Chris directly, he might be able to help you.

I just recently read that George Lucas uses Seymour fabric. I was already sold on the value of my screen, but now my $220 XD expenditure is even looking better yet.

All AT screens lose some light as not all the projector's lumens are being reflected by the screen, some is lost as it goes through the screen. Which is not true if compared to the same material if available as a solid screen. It is sometimes and apple to orange comparison though as not all screen materials have an equivalent solid vs AT version.

Since Stewart puches holes in their fabrics to make their microperf material their light loss is 10.2%. Other companies perforations and Stewart's theater perf lose even more.

It is tough to gauge some of the weaves because there is no solid equivalent of the same fabric. But no matter which type of AT screen some of the projector's light is lost through the screen. This why you need black backings and/or everything behind the screen to be black so light doesn't reflect off objects behind the screen and deteriorate your image quality.

There are advantages and disadvantages to both perforated and woven screens.
Perforated Advantages:
Many different screen materials. ie higher gain, high contrast, 3D, etc

perforated disadvantages:
Best when speaker(s) can be places at least 8" (preferrably 12") behind the screen.

Woven Advantages:
Speakers can be placed closer to the screen. Many will work with in walls behind the screen. Although placing a few inches or more behind the screen still has acoustic advantages but when placed closed it is still quite acceptable and not as detrimental as perforated.

Woven disadvantages:
Basic white or gray screen with few material options if any. The woven screens typically don't have coatings that other screens use for their many characterisitcs.

AT screens in general:
Advantages:
Proper placement of speakers

Disadvantages:
Some Light loss
Slight high frequency loss which can be compensated with EQ.
Some pixel distortion, it is just not as good as a very smooth non-AT screen but the question is how noticeable it is at the seating location?

Even with the limitations of AT screens the benefits for audio far out weigh non-AT solutions and the video difference is minor and might not even be noticeable unless you sit real close. Choose the AT screen that is appropriate for your application.

So upon doing some more measuring and trade-offs, I can get to about 11' viewing distance. Will that now be far enough away to not see any weave pattern in an AT screen like the SMX?

Also, I really would like to go 120" wide so I could get the speakers in the right locations. If I go AT, I fear 120" wide at 132" viewing distance might be a bit much and cause the ole' 'tennis-match' affect. Am I wrong...I hope!? :-)

120" wide will be fine for viewing, you need greater than 60 degree field of view before it gets too big. Your lumens may be low as the bulb ages unless you use a gain screen, replace it more frequently or use a brighter projector mode.

The SMX screen has a gain of 1.16 (published). Hopefully with an anamorphic lens, that will help as I'll be able to harness the full panel resolution. I'd rather put the right screen in with the ability to upgrade projectors over time v. limiting myself with a screen to what the current projector can drive. I'm hoping this is the last screen I'll ever put in at this home. BTW, I currently use the 'normal' lamp mode to light up my 110" 16:9 and its plenty bright. If I have to go to high power and replace the bulb more often....I think that's a fair tradeoff to get the 'immersive' experience.

Follow-up: Just ran the viewing distance calculator and at 11 feet viewing distance and 120" wide, the viewing angle is 48.9 degrees. That's mid-way between what I have righ now, and what you state is too big (60 degrees). One other limiting factor might be throw ratio to avoid excessive pin-cushion with the lens. Might have to go down to 110" wide for that reason alone. Guess I could sit a bit closer then if I wanted. :-)

jkscherk,

What will your throw distance be?


...Glenn

Glenn,

If I build a new, recessed opening into my existing back wall, the max I can get is 13' 6". Without doing that (mounting on the back wall) I can only get about 12'. BTW...do you measure from the lens of the projector or the front of the anamorphic lens? These measurements assume the former.

Already answered by BobL, but in addition, one of the guys here said, when going to CIH setup (2.35), that his first row seating distance remained the same when going from 16:9 screen to same height (and thus only wider) 2.35 screen. I believe he said he was pretty near "max." of 36 degrees with 16:9 setup - BUT, that there was not so much "action" at the added 12" approx. on each side, and the extra width just added to the "immersion" experience as opposed to introducing "tennis match" swiveling of head.

I'm going with this philosophy, partly because it makes sense and partly because I'm constrained with depth because of a column (that might get relocated) so I cannot get two rows of seating in if I move front row seating past 10' or so.

You are going from 10' seating with 54" tall screen to similar distance with similar (2.35) screen height. Seems you should be fine, based on above reasoning and experience.

I'll be interested in what other posters say about your throw distance as I'm in a similar pickle. I can do 15' max with flat screen on wall, but only 13' with desired curved AT 54" tall screen built out to accommodate center channel speaker - and 13' seems to be at or past the limit of some projectors (JVC RS15/25 for instance). From what I read, a throw distance of 15' to 17' is better for balance between picture quality (better further back) and brightness (more lumans, obviously, the closer the projector is to the screen). This assuming a decent projector in the $4K to $8K range, but not one as bright as a $30K piece would be. Disadvantage of having projector so close to the screen so as to be at its zoom limit: I've read the picture quality is supposed to be a little better the more you use the center portion of the lens (so try to not utilize the extreme outer regions of the lens, if you can help it).
[So, rule #1, it seems there is never any free lunch with this hobby... !]

Measure from the Projector Lens!


...Glenn

FYI, 36 degrees would be THX minimum recommended field of view. They do allow the cheaper seat to be a little further at 26 degrees. They have a recommended (36) and allowable (26) parameter for certification. 70 degrees is recommended for maximum field of view. I tend to be a little more conervative and keep it under 60 degree field of view for maximum screen size as you are getting close to that tennis match effect. SMPTE is 30 degrees minimum field of view.

Another thing to keep in mind with screens is the screen gain. If it is a 1.16 gain screen on a white base it probably won't matter much. But depending on the screen sometimes it is better to move the projector further back so you get more in the sweet spot for the gain of the screen. With a ceiling mounted PJ with a short throw your maximum gain from the screen might might be if you lie on the floor and not sit in the seats. In fact you might be far enough out of the viewing cone to have a negtive gain at the seats, so placing the PJ closer to get the added brightness is not always the best solution depending on the screen and set up.

Another thing to consider with screens and gain is the half gain angle or viewing cone. You can't just look at the gain number and use it as a reference. I'll use Stewart for example since I'm familiar with many of their screens and they are honest with their specs. A Studiotech 130 has a 1.3 gain and a half gain (half brightness) of 80 degrees. That's a pretty wide viewing area. So a screen with a lesser gain should have an even wider viewing area. The Firehawk has a gain of 1.25 with a half gain of 30 degrees, which is a smaller viewing area.

The reason it has a smaller viewing area is because its base material is gray and if we take off the gain it is probably ~.6 gain screen with a ~2.0 x gain structure. Where the 130 without the gain is probably pretty close to neutral at a 1.0 with a 1.3 gain structure. So a single gain number doesn't tell you everything about a screen.

Also, curved screens tend to do better with longer throws but make sure whatever company you are dealing with calculates the right curve for the screen to match the lens and throw for your PJ.

Since I'm reconfiguring some things, I could make a major change and rotate my setup 90 degrees (room would now be 15'W x 17'L instead of the inverse), but here are the impacts:
* throw distance can go to about 15' and obtain a throw ratio of about 2.0 = GOOD
* no room for false wall for screen; center would now have to be an in-wall behind an AT screen or a conventional speaker above or below the screen = BAD
* also..no false wall means the L & R mains would go on either side of the screen behind grill cloth and built-in setup = GOOD/BAD ???
* seating distance increases to 11-12' = GOOD

Has anyone ever used 2 center channels (6 or so feet apart) behind an AT screen? Since my mains would be at least 12-13 feet apart, I'm concerned a single center behind a 10'-wide screen would be too localized. I'd imagine it something like:

L.............C........C..............R

Thoughts??

Rotating 90 deg for lengthwise orientation = good.

Speakers outside of screen = depends on the particular situation = just fine. I have my speakers outside the screen, and so does Chris Seymour.

Two center speakers side by side = comb filtering up the yin yang = super duper bad.

In fact, some speaker super experts will choose drivers with narrower dispersion for DIY center speaker builds so that it doesn't interfere with the dispersion patterns of the mains.

Play with toe in of main speakers. If for whatever reason you are forced to have them outside the screen, pay attention to how close you are to sidewalls. I admit that I fear how close they will be to front wall as well. Inwall speakers are designed differently than most decent speakers in that they don't need to have BSC accounted for (as inwall install means an "infinite baffle"; no bass loss). When you have a speaker with BSC close to the multiple boundaries of a corner, you will suffer bass/midbass bloat that will mask plenty of frequencies. Look into massive broadband absorption, superchunk traps, and pay particular attn to absorbing front wall, besides the sidewalls. Seymour advises at least a few feet from the sidewalls, but mine are closer than that. However, I have near double digit traps just for the front stage (behind false wall).

jostenmeat,

Very good info. Definitely do not want to degrade my audio, so a single center it is! I thought that might be the case.

With respect to the side placements, I'm going to be switching over to speakers that are made to be placed in cabinets or behind a screen. They have a boundary gain compensation switch on them that tailors the crossover appropriately. They will also be at least 2 feet from the sidewalls. The subs would be placed in each corner below the mains. Therefore only the center would actually be behind the screen.

I think this approach should work well.

A question:
If I use no backing material behind my (let's say) 4K AT screen, the light passes through - so obviously it does not reflect back to me, thereby causing a dimmer picture. (?)

If I do use a backing material, the light still passes through the screen and is absorbed by the black fabric? Still, the picture is dimmer? Is my picture dimmer by the same amount, it's just that the area behind my screen/false wall is not lit up? Or, do I somehow get a sharper picture or better contrast or something, with the backing material, even though I'm still loosing brightness (compensated for, simply, by purchasing a better or suitable projector)?

Someone can correct me for any misunderstanding I may have in this post, but I'll give it a shot. First of all, more light doesn't make the picture dimmer, it makes it brighter.

Yes. Yes (if you're comparing it to extra* uncontrolled light hitting the screen).

Yes(huh?), ideally not(?).

No extra sharpness, yes extra contrast with BB. Look at it this way, if I brought in some 1000W highway construction mega lamp, and fired it directly at the screen at the same time as the projector was, I could say "my screen is not dimmer, but in fact brighter, and by the same amount!". (You would have nearly nothing for contrast though!)

I believe it goes something like this. Say your deepest black you could produce was 1 lumen. The brightest white you could produce was 1000 lumens. We have 1000:1 contrast. But, now you add 10 additional lumens by way of uncontrolled light. Now blackest black is 11 lumens, and brightest white is 1010 lumens. Now your contrast has dropped all the way from 1000:1 to 92:1.

Controlling light is obviously a big concern, and that's why I have black rugs, black ceiling paint, black velvet border, even some black acoustic treatments. Nothing absorbs better than black velvet (even flat black paint is not comparable), so the ideal room in terms of performance-only would have every inch covered in black velvet, you would be wearing black velvet clothes, and you would give yourself plenty of time for your eyes to adjust before starting the movie.

What is AT Screen?

acoustically transparent-sound will be passed through the screen.

Hmmm. Let ME try again!

I understand uncontrolled light in the room is a contrast killer, my question concerns the picture quality loss with an AT screen as compared to a (similarly constructed) regular screen and why black backing behind the AT screen improves picture quality.

Assume I have an AT screen attached to a false wall, and no light can escape from behind the screen because I've enclosed the false wall on all four sides and covered/blacked out all the area behind the screen with velvet fabric. Although I'm now not introducing any unwanted/extra light into the room, I still have a less bright picture with the AT screen (compared to regular), as between 6% and 10% of the light from my projector went through the weave of my AT screen instead of being reflected back to my eyes in the form of the picture (of the movie I'm watching).

My question is, what function does the backing material peform - how does it improve the picture quality of my AT screen (assuming I have an enclosed and 100% blacked out area behind my screen, in the false wall area)? If the backing is only to keep light from escaping back into the room, I can do that with velvet treatments behind the screen and won't have to worry about even more loss of audio quality by installing black backing (assuming my speakers are 100% black).

I perceive AT screen picture quality would still be better with the backing material directly behind/attached to the screen (even though, in the scenario described above, no light can escape into the room from behind the screen regardless of whether I have backing material attached to the screen or not). I'm just wondering, assuming I'm correct, why?