110" DIY Spandex AT Screen - Page 21 - AVS Forum
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post #601 of 617 Old 05-18-2014, 06:41 PM
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Quote:
Originally Posted by MississippiMan View Post

You can manually change both the Throw and Diagonal by clicking on their respective button on the Graph on the left side.
Simply adjust the Throw on the right side Graphic Bar, the go left, click on Diagonal, and slide the Bean to 130"

You will note that when you use the Left Slider for Throw, the Screen measurements remain the same.
Use the Left Slider in Diagonal Mode and the Screen measurements all change, but not the Throw distance on the Right side graphic Bar.

If you only just use the +/- buttons for Diagonal or Throw on the right, every value involved changes proportionately.

Here is the Calculator set correctly...




Don't beat yourself up....it's a commonly overlooked feature...by many if not most....just as many take the advised "mid-point" throw distance value as sacred and final.

Okay! It looks like the disconnect was that I was assuming 130" wide meant the horizontal width, while you took it to mean the diagonal length. Diagonal is likely the more accepted measurement so you're probably right. I was fixating on the horizontal width since, coincidently, my planned screen is going to be 130" wide (149" diagonal).
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post #602 of 617 Old 05-18-2014, 07:22 PM
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I too am looking at a 130" wide (horiz not diagonal) screen
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post #603 of 617 Old 05-18-2014, 08:30 PM
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I know that several of you have used staples. Can you describe the method you used? Also I thought I remembered seeing a link to stretching and stapling methods but looked through the thread and couldn't find it.
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post #604 of 617 Old 05-18-2014, 10:42 PM
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Quote:
Originally Posted by Claybe View Post

I know that several of you have used staples. Can you describe the method you used? Also I thought I remembered seeing a link to stretching and stapling methods but looked through the thread and couldn't find it.

This worked for me. Don't know what the "right" way to do it is.
A thousand words is worth a picture (or video) so here you go.
Cut the spandex roughly to size and lay it out on the frame (or under if you are wrapping it around to the back as I did.
Start on a long side. Line up the edge of the spandex along the edge of the frame.
Place one staple directly in the middle of the length of the side. Then pull the material along the length of the side and place a staple on each end.
If this is the first layer then pull it taught, if this is the reflective layer than just give it enough stretch to pull out wrinkles and prevent sagging.
Continue to work along the one side. Cut the distances on either side of the center staple in half again with other staples and keep going until you have a complete row of staples no more than an inch apart.
When the one long side is done, switch to the opposite side. Start with the center staple of the opposite side, then pull the fabric and staple near the ends of the second side. This is a bit tricky because now you have two directions in which to maintain an even stretch; left and right, and across the screen. Once the second side is done, start on the short ends in the same way.
When all sides have been stapled you will be left with just the corners. You will want to cut out some of the fabric on either side of the corner but leave enough to staple. I tuck the edges in then pull the tip of excess fabric right at the corner over top of them and staple several times.
The last step is to trim the excess spandex from the perimeter. The side you started on shouldn't require trimming if you stapled right along the edge. The other three sides will need to be trimmed. If you have done a good job of keeping the tension equal all the way around, the off cuts will be close to the same width all the way along a particular edge. In fact, when pulling the fabric for stapling I strive to have the overhangs straight, then I know the tension is even.

I have done it often enough that the technique comes easily, but I remember my first piece being a bit wacky. Thankfully the first layer isn't the visible layer so if you goof up just pop a few staples and try again.
Spandex is very stretchy, which makes it easy to wrap around a frame, but difficult to tension evenly.

This is probably a lot more confusing then it seems in my mind.

Good luck.

.
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post #605 of 617 Old 05-19-2014, 06:41 AM
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Quote:
Originally Posted by wraunch View Post

I too am looking at a 130" wide (horiz not diagonal) screen

So I was told the formula for calculating the screen brightness, given accurate (measured) lumens. The formula is:
Code:
(lumens * gain) / sq ft

A good place for measured lumens is projectorreviews.com and here's the BenQ W1070 info from that site: http://www.projectorreviews.com/benq/benq-w1070-projector-performance/

In "dynamic" mode (bright) the farthest zoom was 1629 lumens and the closest zoom was 1843 lumens. Impressive! Switching to "smart eco" mode dropped it by 35% consistently.

A 130" wide screen in 16:9 has dimensions 130" W x 73" H or a screen size of 66 sq ft.

Given a 130" wide picture, the closest you could get is 12'-5" and the farthest is 16'-3".

Assuming a spandex screen gain of 0.8, we can finally plug in our numbers:

12'-5" => (1843 * 0.8) / 66 = 22.3 fl
16'-3" => (1629 * 0.8) / 66 = 19.7 fl

That's impressive! Even lopping off 35% of the lumens in "Smart Eco" mode gives you 14.5 lumens and 12.8 lumens, respectively.
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post #606 of 617 Old 05-19-2014, 09:20 AM
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I just used Draper's fL calculator found here: http://www.draperinc.com/drapermobile/fl/

Based on it if I bump it down to 1600 lumens, with a .8 gain, my 130" wide screen would result in 19 fL. Something doesn't seem right. How can ProjectorCentral be so highly regarded yet be so off in their calculator?
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post #607 of 617 Old 05-19-2014, 06:00 PM
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What I've heard about PC is that they strictly use the published lumen numbers, which are absolutely meaningless most of the time -- but not all the time. They have to use some number, though, so it might as well be that.

Their original calculator doesn't show brightness as a value at all. That's arguably more accurate, as a result.
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post #608 of 617 Old 05-21-2014, 09:47 PM
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I've been looking for spandex in Canada and the local Fabricland had nothing. Spandexworld is out of stock on product # 795 matte white milliskin. This looks like a viable alternative and is available with reasonable shipping costs ($13 for 4 yards) in Canada. I'm waiting for one more local supplier to get back to me and if they don't have anything I will be the guinea pig for this material.

http://www.spandexbyyard.com/index.cgi?category=Nylon_Spandex_Solids&back=0&cart_id=1400722366.9624&pid=121
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post #609 of 617 Old 05-22-2014, 01:29 AM
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Quote:
Originally Posted by ShaunM View Post

I've been looking for spandex in Canada and the local Fabricland had nothing. Spandexworld is out of stock on product # 795 matte white milliskin. This looks like a viable alternative and is available with reasonable shipping costs ($13 for 4 yards) in Canada. I'm waiting for one more local supplier to get back to me and if they don't have anything I will be the guinea pig for this material.

http://www.spandexbyyard.com/index.cgi?category=Nylon_Spandex_Solids&back=0&cart_id=1400722366.9624&pid=121

They are probably wondering why the heck they are going through so much white spandex. They would be even more curious if they knew a bunch of guys were buying it.
I'm surprised your Fabricland doesn't carry Spandex because ours has had a wide range of colors every time I go in. Good luck with your alternate supplier.

.
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post #610 of 617 Old 05-22-2014, 04:33 AM
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Quote:
Originally Posted by DavidK442 View Post

They are probably wondering why the heck they are going through so much white spandex. They would be even more curious if they knew a bunch of guys were buying it.
I'm surprised your Fabricland doesn't carry Spandex because ours has had a wide range of colors every time I go in. Good luck with your alternate supplier.

When I called SpandexWorld to place my order, I told them I was building a projection screen. All I got was a very disinterested "oh, ok." And matt white #795 appears to have been replaced with #12479.

M.
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post #611 of 617 Old 05-22-2014, 07:59 AM
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Quote:
Originally Posted by mherington View Post

When I called SpandexWorld to place my order, I told them I was building a projection screen. All I got was a very disinterested "oh, ok." And matt white #795 appears to have been replaced with #12479.

M.

I saw that too although the weight is slightly different than 795. Then again, so is the potential product I found.
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post #612 of 617 Old 05-22-2014, 10:17 AM
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Does anyone know the gain of a white over white milliskin screen versus white over gray or white over black?
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post #613 of 617 Old 05-22-2014, 10:21 AM
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Just making sure I have the math right. If I want to do a 130" wide screen I need 4 yds? 130/36=3.6
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post #614 of 617 Old 05-22-2014, 11:30 AM
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Quote:
Originally Posted by wraunch View Post

Does anyone know the gain of a white over white milliskin screen versus white over gray or white over black?

Quote:
Originally Posted by wraunch View Post

Just making sure I have the math right. If I want to do a 130" wide screen I need 4 yds? 130/36=3.6

Based on the regularity of your posts it seems that you have been following this thread quite closely for a while.
If you go back a few pages to refresh yourself on some of the discussions you will see that these questions have already been addressed to some degree.

.
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post #615 of 617 Old 05-22-2014, 12:08 PM
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Sorry forgot. So 4 yds of each milliskin silver and milliskin white for my 130" wide 16x9 screen.
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post #616 of 617 Old 05-28-2014, 08:54 AM
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Quote:
Originally Posted by DavidK442 View Post

This worked for me. Don't know what the "right" way to do it is.
A thousand words is worth a picture (or video) so here you go.
Cut the spandex roughly to size and lay it out on the frame (or under if you are wrapping it around to the back as I did.
Start on a long side. Line up the edge of the spandex along the edge of the frame.
Place one staple directly in the middle of the length of the side. Then pull the material along the length of the side and place a staple on each end.
If this is the first layer then pull it taught, if this is the reflective layer than just give it enough stretch to pull out wrinkles and prevent sagging.
Continue to work along the one side. Cut the distances on either side of the center staple in half again with other staples and keep going until you have a complete row of staples no more than an inch apart.
When the one long side is done, switch to the opposite side. Start with the center staple of the opposite side, then pull the fabric and staple near the ends of the second side. This is a bit tricky because now you have two directions in which to maintain an even stretch; left and right, and across the screen. Once the second side is done, start on the short ends in the same way.
When all sides have been stapled you will be left with just the corners. You will want to cut out some of the fabric on either side of the corner but leave enough to staple. I tuck the edges in then pull the tip of excess fabric right at the corner over top of them and staple several times.
The last step is to trim the excess spandex from the perimeter. The side you started on shouldn't require trimming if you stapled right along the edge. The other three sides will need to be trimmed. If you have done a good job of keeping the tension equal all the way around, the off cuts will be close to the same width all the way along a particular edge. In fact, when pulling the fabric for stapling I strive to have the overhangs straight, then I know the tension is even.

I have done it often enough that the technique comes easily, but I remember my first piece being a bit wacky. Thankfully the first layer isn't the visible layer so if you goof up just pop a few staples and try again.
Spandex is very stretchy, which makes it easy to wrap around a frame, but difficult to tension evenly.

This is probably a lot more confusing then it seems in my mind.

Good luck.

This method worked great! I went with the white over silver combo. It seems dark to me without the PJ. I can't wait to see how it looks with the Panny 8000, but hope it is not too dark. How much gain is achieved with white over white? Does the white over white hide the wood frame?
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post #617 of 617 Old 05-28-2014, 01:32 PM
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Quote:
Originally Posted by Claybe View Post


This method worked great! I went with the white over silver combo. It seems dark to me without the PJ. I can't wait to see how it looks with the Panny 8000, but hope it is not too dark. How much gain is achieved with white over white? Does the white over white hide the wood frame?


From a previous post: (I should add that my screen frame itself is painted flat black.)

General advice is to only go with an Acoustically Transparent screen (ie Spandex) if you plan on putting your speakers in behind.
I am using the W1070 on a white over black spandex screen that is 114 inches wide (130 diagonal). Based on direct comparison to screen samples (which have been measured by others) I would say that the white over black combination gives a gain of a little over 0.8. White over silver is probably high 0.8's and white over white low 0.9's. It may not seem like there is much difference between these values but in direct comparison, and even separately, the differences are significant. Over the last couple years I have tried each of the three combinations and have settled on white over black. While I appreciate the brighter image with a lighter colored backing fabric, I watch a lot of dark movies (sci-fi & horror) and ultimately the mediocre black level of the W1070 was the deciding factor. If I had a higher end projector (JVC, Sony, Epson 5030) or watched a lot of 3-D, I would likely go white over silver. With white over white on very bright scenes the 1X4 center supports of my diy screen gave faint shadows from the light passing through the screen and bouncing off the flat black painted wall behind. (Yes, believe it or not!) This wasn't noticeable with the silver in behind.
Bare in mind that my room is a black velvet trimmed, flat black painted pit, so I'm not contending with much if any reflected light.

.
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