CURVED AT screen build with 2.35:1 (158" wide) - AVS Forum
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post #1 of 14 Old 06-27-2014, 04:25 AM - Thread Starter
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Cool CURVED AT screen build with 2.35:1 (158" wide)

Sceen Build
For my new home theater I built a curved and acoustical transparent screen (Center Stage XD). I want to present my solution which worked very well.

The problem with a curved screen is the tensioning. When tensioned horizontally the fabric comes out of the frame which gives a ugly bulge. So I searched for a solution which tensions only vertically with an equally distributed force.
I stumbled over piping profiles used for the stands at exhibitions. Furtenately I live in Hannover which is home of the CeBIT so there are many companies around which produce such piping profiles.

I ordered two 4 m long profiles which were bended with a radius of 7 m. Then I let another company stew a strap on the long sides of the fabric. Inside this strap a flexible plastic pipe was inserted. So the whole straps could be inserted into the piping profiles. Which gives a equally distributed force for the vertical tension.



The profiles are connected directly to floor and ceiling. I used tightener to adjust the tension.





I was concerned that vertical waves still remain inside the fabric, because of the lack of horizontal tensioning. But this was not the case. I don't see any irregularities from my seat.


Focus
At the moment there is only a cheap DLP projector. But a good one with 4k will follow.

The depth of focus is great enough for the corners. The loss of focus is negligible. And usually the eye looks in the middle of the screen. Even with a windows dektop I hardly notice it. The mighty Sony G90 was worse in its corners than that ( I owned one).

Middle:


Corner:



Geometry correction

The biggest problem with digital projectors and curved screens is the geometry distortion. This must be corrected otherwise it looks horrible. CRT's were much more flexible in this regard.
Anyway, I use a Geobox G-202 to correct geometry. It is a small warping box which supports passive 3D, too.

Without geometry correction:


With geometry correction:


Of course there are scaling artifacts visible in test patterns, but absolutely not in the movie picture. And I don't see any loss of sharpness although my seat is only 3.7 m away from the screen. It works very well!


Conclusion

Just wow!
A curved screen with that size and absolutely no visible speakers, subwoofers etc. around is an absolutely stunning experience. It feels like real theater and not like home theater.



PS: the baffle wall build can found here...
Attached Images
File Type: jpg screen 1.jpg (93.1 KB, 221 views)
File Type: jpg screen 2.jpg (69.9 KB, 209 views)
File Type: jpg screen 3.jpg (101.9 KB, 211 views)
File Type: jpg screen 4.jpg (271.3 KB, 208 views)
File Type: jpg screen 5.jpg (276.8 KB, 209 views)
File Type: jpg screen 6.jpg (286.3 KB, 207 views)
File Type: jpg screen 7.jpg (257.8 KB, 206 views)
File Type: jpg screen 8.jpg (256.4 KB, 216 views)
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post #2 of 14 Old 06-27-2014, 06:45 AM
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A ridiculously well done Project, one that just might encourage a few of our more ambitions DIY'er to follow suit.

Of course they will want every little detail of the build and have lots of questions, so "steel yur wool".

But that should not be an issue for you. Your Baffle Wall thread is one of the more epic designs that AVS has had the pleasure of hosting.

Thanks for sharing such resplendent results!

To quote James T. Kirk;
"I'm laughing at the superior intellect"
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post #3 of 14 Old 07-10-2014, 09:57 AM
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Hi,
Stunning. Just got my Epson 5030UB. Planning to build a 135" 16:9 curved screen. My questions are as follows,
1.Did you use Aussie Bob or any other excel calculator for the curvature,
2.Does the pic automatically focus evenly on curved screen just as it would on a flat screen or did you have to do any calibration on the projector to make it evenly focused.
Any answer would be of help. Much appreciated
Thanks
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post #4 of 14 Old 07-10-2014, 01:21 PM - Thread Starter
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Quote:
Originally Posted by MississippiMan View Post
A ridiculously well done Project, one that just might encourage a few of our more ambitions DIY'er to follow suit.
Thanks!

Quote:
Originally Posted by Sundarraj Venkataraman View Post
1.Did you use Aussie Bob or any other excel calculator for the curvature,
I calculated the curvature with this calculator (only in german). I wanted a curvature of 7%. This means the sides come out with 7% of the screen width. 7% of 4 m is 0,28 m. This is a in the calculator. The width (4 m) is s. This gives a radius of about 7 m.

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2.Does the pic automatically focus evenly on curved screen just as it would on a flat screen or did you have to do any calibration on the projector to make it evenly focused.
There was no trick necessary. I focused the projector in the middle of the screen. The screenshots above show how much focus is left in the corners. There is so few focus loss that I wouldn't worry to even apply a smaller radius. But this depends on the depth of field of your projector. You can test it with a sheet of paper. Just move it away from the screen and watch how much focus is left and when it becomes unacceptable.
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post #5 of 14 Old 07-14-2014, 02:37 PM
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I am sure you have already figured out how much to the penny you have invested in the room, but what's a good range? With and without the amazing speaker wall please.

What sound modifying material is on the ceiling?

Superb job, it looks beautiful!

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post #6 of 14 Old 07-14-2014, 11:56 PM - Thread Starter
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I am sure you have already figured out how much to the penny you have invested in the room, but what's a good range? With and without the amazing speaker wall please.
I always try to reduce costs with intelligent constructions. Here is a list of the largest costs I had:

Screen: 600 €
Subwoofers + amplifier: 3500 €
Large bass absorber: 300 €
Main speakers (including amplifiers): 3000 €
Skyline diffusers: 1200 €
Riser with spring isolators: 350 €
Electronics (Projector, AV pre amp, Equalizer, Warping Box): 3500 €
HTPC: ??? (too many hard disk upgrades over the years... )

Much of the hardware I did already use in my old theater. E.g. when I built the main speakers a few years ago I already knew that they will be placed in a baffle wall some day. Now this decision saved me a lot of money. I think other people spent much more for less.

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What sound modifying material is on the ceiling?
These are the Vicoustic Multi Fuser DC2. Half of them where grey and I had to paint them black (what a pain!). The other half was black already.

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Superb job, it looks beautiful!
Thank you very much!
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post #7 of 14 Old 07-15-2014, 12:33 AM - Thread Starter
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Beside the great experience a curved AT screen will deliver I don't want to suppress the drawbacks.

Fabrics like the Center Stage XD offer a gain < 1. This means that the light is reflected equally in all directions. When the screen is curved it will also reflect on itself! This lowers the ANSI contrast. A curved screen with a higher gain factor doesn't suffer from this problem. Perfect would be a fabric with gain > 1 combined with the good acoustical properties of a meshed fabric.

Though the problem is not that bad as it sounds. Rember the old CRT days: ANSI contrast was very low (about 50:1), but picture quality was astonishing because of the high on/off contrast.
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post #8 of 14 Old 07-17-2014, 11:07 AM
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Thanks for all the info I appreciate it!

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You don't happen to have any pictures of the profile you used do you?
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post #10 of 14 Old Yesterday, 01:35 PM
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So you do not use a anamorphic lens, What is a warping box' and what does that cost. Will keystone controls work on helping the geometry fix, Thanks
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post #11 of 14 Old Yesterday, 01:35 PM - Thread Starter
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Quote:
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You don't happen to have any pictures of the profile you used do you?
Here are a few pictures how it looks like and how the fabric is inserted. The profile itself is this:

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post #12 of 14 Old Yesterday, 01:44 PM - Thread Starter
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Quote:
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So you do not use a anamorphic lens, What is a warping box' and what does that cost. Will keystone controls work on helping the geometry fix, Thanks
No, I don't have an anamorphig lens.

Warping means geometry correction. This term is widely used in the broadcast area. Keystone correction alone is not sufficient (and barely needed at all). You need independant pincushion correction for the upper and the lower half of the picture. The reason for the zone based pincushion correction is the optical axis of the projector which has a certain angle to the screen. That means that the lower half must be corrected stronger than the upper half.
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post #13 of 14 Old Today, 12:01 AM - Thread Starter
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I forgot to mention that low cost warping boxes are available from VNS (here are catalogs). They have several processors for warping, edge blending and passive 3D. I own the GeoBox 202 which can warp or edge blend a single channel. It cost me about $350. I ordered it directly at VNS in Taiwan. After 2 days it arrived in Germany. Very fast for such a long way!

The larger GeoBoxes can process 2 channels (for 3D) and cost around $800. Warping boxes from other companies are much more expensive (several thousand dollars). Btw, the larger GeoBoxes are available with 19" mounts.
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post #14 of 14 Old Today, 04:21 AM
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Thanks Nils. Your screen is very nice. So many have said curve screen only works with a anamorphic lens but you have proven them wrong.
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