A Tale of Two Screens...SF 2.5 4.0 and Spandex, White over Black - AVS Forum
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post #1 of 15 Old 12-11-2014, 08:42 AM - Thread Starter
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A Tale of Two Screens...SF 2.5 4.0 and Spandex, White over Black

Came a time where in a smallish area someone decided that they could not have a very large screen, yet being enamored of the Panasonic 8000 and having a 2.39:1 C.I.H. setup, determined to go with a 2.39:1 format at a 104" diagonal (40" x 96") size Painted Sintra board screen.





Then came the time to actually set up the system and waddya think'ed happened? The unanimous decision was that the screen was just too damnable small.

Issues arrose however as the Sintra was glued to the Drywall, and taking it down was going to be a PITA, and besides all that, there are 4 Audio Transducers applied to the Drywall directly behind the Sintra, and no one wanted to risk tearing undue amount of Paper off the wall concerned.

What to do? I know! Let's make up a acoustically transparent Spandex screen 51" x 122" (132 " diag.) and simply hang it over the existing screen.

This has to be done quickly....no time to wait for Spandex World to get Silver Milliskin in stock, so I decided now was the time to try a White over Black Milliskin variety.

Ordered up 4 Yards of both, had it shipped on two rolls (nix on the folded method) and today I will build the Frame.

This does present a unique opportunity to show the difference between the two applications. Naturally the small SF will blaze compared to the much larger Spandex screen. But it is image clarity that is most important here andthis experience will help quantify the performance of Spandex vs Painted.

The latter not really being in question here, but also one must realize that there is little else available that will allow the continued use of the Center Channel Transducers as well as avoid any necessary wall refinishing.

So onward.......pictures of the build process will be forthcoming, and screenies perhaps by early this weekend.
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post #2 of 15 Old 12-12-2014, 03:49 AM
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Looking forward to this direct comparison. Especially interested in the difference in contrast and black levels between the two.

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post #3 of 15 Old 12-12-2014, 08:59 AM - Thread Starter
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Santa came early......the Spandex has arrived.



Two separate Rolls, neatly and securely packaged.

About to go PU the wood, and then start ripping and assembling the frame.
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post #4 of 15 Old 12-12-2014, 11:46 AM
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Ok MM, get to work. We want to see the results.
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post #5 of 15 Old 12-13-2014, 09:04 AM - Thread Starter
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Well........................,

Santa gave me a lump of Coal.

Got to work on building the Screen Frame, using my trusty Kreg Pocket Screw Jig (...of which I cannot recommend too highly....)



No Braces or such needed to construct a really sturdy frame.....



I got the Frame assembled and hung over the existing Screen to confirm placement criteria......Mo' Bedder size fur shur !!!



Now came the time to open the very well wrapped rolls of Black and white Spandex. I was all a'tingle.



Then...upon close inspection of the Masking taped ends, what do I find? A very disappointing notation on the Tape stating that each Roll contained "3 YARDS", not the 4 Yards ea. I ordered.

Screeeech......everything slams to a stop, because no way 108" of Spandex is gonna stretch out to cover a 122" (width) sized Frame.

In truth, I am not sure who is to blame in this, a mis-ordered amount by me, (...doesn't make any sense at all...) or a miscue by them in fulfilling my order. (...what I hope is the case...) Whatever, it means early Monday AM I must place another order for 4 yards, shipped Rolled via 2 Day Express, and get this thing over and done with before next Friday, as I absolutely DO NOT intend to be working on anyone's projects after Monday the 22nd.

BTW....since I do not do many Spandex Screens, if anyone is interested in the 108" x 60" Black & White Spandex, it's available at cost....but I'll pay shipping.
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post #6 of 15 Old 12-13-2014, 10:03 AM - Thread Starter
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Actually, I just effected another order online, then called (Spandex world is open on Saturday! Who'd a thunk it? )

Found out that I was to blame since the order was placed online. leastwise that's their take, and sadly I must be inclined to agree.

In any case, I will hang the Panny based on the Screen's Frame location, take some screenies of that picayune, little SF screen, and be loaded for bear when the Spandex re-order arrives on Wednesday.

Now I must slink off to a corner of the Barn and get small.

To quote James T. Kirk;
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post #7 of 15 Old 12-13-2014, 12:23 PM
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Quote:
Originally Posted by MississippiMan View Post
Well........................,

Screeeech......everything slams to a stop, because no way 108" of Spandex is gonna stretch out to cover a 122" (width) sized Frame.

BTW....since I do not do many Spandex Screens, if anyone is interested in the 108" x 60" Black & White Spandex, it's available at cost....but I'll pay shipping.

I'm guessing if you're not comfortable with it stretching to cover 122" width frame that 3 yards won't be enough for my upcoming 135" 16:9 (66x118) screen?
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post #8 of 15 Old 12-13-2014, 12:34 PM
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3yds/9ft would only need about 1ft of stretch to get around a 135" 16:9, so I'd expect that to be perfect.
..just re-read the width on MM's screen-build..
Wouldn't 9ft of spandex be fine for a 10ft screen-width?

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Easy $25-40 DIY black/dark-grey ambient-light rejecting screen, grab two things from a local store..mix..roll..done.
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post #9 of 15 Old 12-13-2014, 06:35 PM
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Quote:
Originally Posted by Ftoast View Post
3yds/9ft would only need about 1ft of stretch to get around a 135" 16:9, so I'd expect that to be perfect.
..just re-read the width on MM's screen-build..
Wouldn't 9ft of spandex be fine for a 10ft screen-width?
At 20% stretch, it should more than stretch to cover a 122" frame width. I'm guessing MM must have a reason he wants minimal stretch from the spandex -- just enough to keep it unwrinkled but not enough to make it thin and reduce gain, maybe ?

I'll be interested in his reasoning, because I was thinking of using just 3yrds for a 128"x60" image area.
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post #10 of 15 Old 12-13-2014, 08:05 PM - Thread Starter
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If one had ever stretched Spandex to a really tight pull, they would see how the weave of the Fabric will distort as it opens up. This creates larger spaces in the weave that can be / are visible during projection, and even create a degree of Morie patterning in areas.

My experience has allowed me to use lengths that are just under the length of the frame, and then stretch about 6-8" on each side (end)before stapling. That does amount to being 12"-16" stretch.

However in this particular case, we are talking about a 14" difference between the actual length of the cloth and the Frame. Add another 12" to that and the total amount of stretch is 26".

Is that too much? Only a visual observence can speak for that, and I'll tell ya sumpthin'...the time to find out that your stretching it too much is not after you have effected about 30-40% of the job. Also, stretching the fabric evenly is far more difficult under the amount of pull we are talking about being necessary. I know.....having been there, done that.

Now when one is attempting such on their own, and wants to save cash, the end results can be (ie: might be) accepted as a risk worth taking. Not so in this case. I would rather myself to observe the degree of pull needed to effect a taunt surface.....but no more, and sacrifice the overage amount in trimming, than try to force a too small piece to cover a too large frame, and have both a visible fabric pattern distortion be created, and also risk having the material pull out from, tear off the staples.

I don't want to talk overly about profit & loss here, but hey, by the very nature of such I'm not into spending any more than necessary any more than any other DIY'er, and after all, everything I do, both Visual and Aurally is all DIY. In this instance I'm taking a $89.00 hit*** on behalf of my customer, and my own time possibly wasted on a poor result. *** 1st order cost $54.90 for 2-Day delivery

...and having my Guy make note how I did not hesitate one instant to make it right? Priceless.


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Originally Posted by dreamer View Post

I'll be interested in his reasoning, because I was thinking of using just 3yrds for a 128"x60" image area.
Awww....don't even. What's another $9.00 compared to the risk?
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post #11 of 15 Old 12-17-2014, 08:19 PM - Thread Starter
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The replacement Spandex arrived today. I have scheduled up a trip to stretch out the material onto the frame for tomorrow after 12 pm.

It is my intent to not vacate the premises until I have an image up onto the screen.

To quote James T. Kirk;
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post #12 of 15 Old Yesterday, 02:15 AM
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Quote:
Originally Posted by MississippiMan View Post
The replacement Spandex arrived today. I have scheduled up a trip to stretch out the material onto the frame for tomorrow after 12 pm.

It is my intent to not vacate the premises until I have an image up onto the screen.
Could you please take a piece of plain white paper with you and place against both screens during picture taking ? Possibly also a piece of scrap Flexi-white if you have it ? It would be interesting to see all four materials' gains in direct comparison.
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post #13 of 15 Old Yesterday, 05:58 AM - Thread Starter
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I just don't think it's possible, as because of the Spandex snafu I'm far behind on this project, ....the Owner is taking off a half day to be there, and they still have me having to wait to come in until after Lunch.

Also, I have no Flexi on hand.

Besides, this screen will have a gain of 0.7, being White over Black Spandex, and the capabilities of such a low gain screen, as well as it's limitations are already well known and documented. Unless you plan on using either of the requested test materials, the only end result is going to show the gain difference between them and a Spandex app....and as I stated, that is already well known.

The screen is 120" x 50" (130" diag.)
I will set the PJ at 14' -7" to achieve 13-14 fl ...which should be sufficient in the well light protected Nook the screen will reside in.

It has been my experience that although the Spandex looks on paper to have a low gain, using an appropriate PJ overcomes that limitation. But only if one does use such. From the Get-Go we / I have never suggested using any Pj of less than 2400 lumen for any Spandex application over 130" diagonal.

Now I might be able to revisit this location after the press is off, but my order today is to make the Screen, hang the PJ according to it's location (screen), assemble a A/V Rack, install equipment, and get this Puppy up and running before the weekend.

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post #14 of 15 Old Yesterday, 08:29 PM
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I didn't realize you had so much left to do. I thought with the last minute addition of the spandex screen over the SF, and the delay in getting the spandex, that everything else would have gotten done over the last week. I'd hoped you would have plenty of time for screenies today after assembling and hanging the spandex.

I've seen the 0.7 number for white over black and the 0.8 for white over silver and the 0.9 for white over white, but I didn't realize they were more than estimates and I don't recall seeing any direct comparisons with the flexiwhite or even white copier paper set on a screen. I'll look again.

My problem is that I haven't used anything but my mis-labeled VuTec for 13 years. I recall it being slightly brighter than my previous BOC (Joannes) screen and I recently noticed it is NOT as bright as plain white copy paper. So I don't know what I am coming from in trying to decide between spandex and flexiwhite. My new screen will be the same size as the VuTec 60x106=122" when in 16:9 mode but masked to 54x128=138" when in 2.40:1 mode with a simple dual prism HE lens. I'd like more contrast for my W1070, but not sure how much gain I can sacrifice compared to what I now suspect is my VuTec's ~1.0 true gain.

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post #15 of 15 Old Today, 12:43 AM
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This might tide you over until MM gets some pictures of the real deal.

Left/center/right: white-over-white spandex, white-over-black spandex, flat/matte-white painted screen.
Top/center/bottom: high-APL, middle-APL, low-APL.

A fairly big difference here is that this spandex isn't stretched, so I'd imagine stretched spandex will drop the gain farther.

For a little reference, this same copy-paper is a dead-on match for the grey 1.3gain Stewart hanging in many BestBuy magnolia's.

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