CURVED AT screen build with 2.35:1 (158" wide) - AVS Forum
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post #1 of 24 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...
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post #2 of 24 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!

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post #3 of 24 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 24 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 24 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 24 Old 07-14-2014, 11:56 PM - Thread Starter
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Originally Posted by Morlince View Post
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 24 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 24 Old 07-17-2014, 11:07 AM
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Thanks for all the info I appreciate it!

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post #9 of 24 Old 07-22-2014, 12:55 PM
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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 24 Old 07-22-2014, 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 24 Old 07-22-2014, 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 24 Old 07-22-2014, 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 24 Old 07-23-2014, 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 24 Old 07-23-2014, 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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post #15 of 24 Old 07-23-2014, 08:56 AM - Thread Starter
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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.
Thanks! It was not me, but the industry!

Warping for curved or irregular surfaces is not a new thing at all. But I have never seen it in a home theater environment. Most people even don't know that warping exists. It is a professional thing only. And the "pixel perfect" paradigm is so deep inside the community that no one really tried digital geometry correction. Of course 1-pixel-test-patterns look awful and show strong moire, but they don't represent the real world. Movies just don't contain such high spatial frequencies. And depth of field is high enough for acceptable focus in the corners.

Btw. VNS is working on 4k support for their GeoBoxes. Currently the bigger boxes support it via dual link DVI.

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post #16 of 24 Old 07-23-2014, 10:36 AM
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Lots of this go over my head. And I have no use for 4k any time soon. Blue ray for me is all I need on a large screen. I just need to figure out if I want to go curve or flat. Thanks for all your info.
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post #17 of 24 Old 07-24-2014, 04:47 AM
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May I ask Nils. I check the VNS web site. It says the Geo 202 box and while it says it works with Blueray it says it only has DVI inputs and outputs. So it does not have HMDI . How could it work then with a blueray player. Thanks for any help on this.
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post #18 of 24 Old 07-24-2014, 04:52 AM - Thread Starter
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Quote:
Originally Posted by hotpepper007 View Post
May I ask Nils. I check the VNS web site. It says the Geo 202 box and while it says it works with Blueray it says it only has DVI inputs and outputs. So it does not have HMDI . How could it work then with a blueray player. Thanks for any help on this.
DVI and HDMI are compatible. You need an adapter. But I don't know if all GeoBoxes support HDCP. It was never an issue for me since I use a HTPC.

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post #19 of 24 Old 08-12-2014, 10:05 AM
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So does this box do the vertical stretch and remove the black bars?

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post #20 of 24 Old 08-12-2014, 10:10 PM - Thread Starter
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So does this box do the vertical stretch and remove the black bars?
Are you refering to the use of an anamorphot? I don't use one and I don't know if the stretching can be done by the GeoBox. I think the geometry correction are for warping (non-flat surfaces) only.

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post #21 of 24 Old 08-13-2014, 04:20 AM
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The Geobox does not strech. It will bend the pic for those using a curve screen to make it fit perfectly.
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post #22 of 24 Old 08-13-2014, 06:20 AM
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Quote:
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Are you refering to the use of an anamorphot? I don't use one and I don't know if the stretching can be done by the GeoBox. I think the geometry correction are for warping (non-flat surfaces) only.
I was just curious how you're filling the 2.35:1 screen.

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The Geobox does not strech. It will bend the pic for those using a curve screen to make it fit perfectly.
Got it.

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post #23 of 24 Old 08-13-2014, 07:07 AM - Thread Starter
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Quote:
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I was just curious how you're filling the 2.35:1 screen.
I use a HTPC with an AMD card. I just reduce the visible desktop to 1920x816. The graphics card still outputs the full 1920x1080 with black bars. This is good (compatible) for GeoBox/projector and the Windows desktop perfectly fits into my cinemascope screen without blanking anything. Very easy to set up.

The disadvantage is that I have to scale down 16:9 movies. With an anamorphot I could avoid this.

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post #24 of 24 Old 08-13-2014, 08:53 AM
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Even so, the use of the GeoBox does allow those who have a CIH set up using a Panasonic AE 8000u the opportunity to consider a Curved Screen format.

All my 2.39:1 builds so far have been on "the Flat", primarily because they exist as Painted Drywall Screens. But it would be easy to construct a Curved screen using Sintra Board and Blocking at each end.

I am doing to look into this so this might just be something upcoming, so...........thank you FoLLgoTT

BTW, can you relate to specifically which product your using?

oops....I just went back and read your using a GeoBox 202.

We do need to find out if the 202 supports HDCP because if not that will be a huge Deal Breaker. Most current products that still use DVI do support HDCP so I have my fingers crossed. Toes too. I'd say chances are excellent it does support HDCP because anything that can play a BluRay must support such.

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