The Torus story - more Background hindsight from behind the lines. - AVS Forum
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post #1 of 51 Old 12-25-2000, 10:07 PM - Thread Starter
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THIS is a post from 6 1999. It was addressed at A Gouger. It is re-posted now aspart of a grassroots concerted effort to Make The Torus a Household word.

It shall become a hosehold word because it is a screen that belongs in many a household...

My apologies for any flaming of present industry luminaires, not you Don, the peolple that rejected the TORUS FOR 2 reasons that were just variations of the concept. Excessive brightness, and acoustical hot spots. Both minor imperfections which you and I put to sleep.

Am glad to meet someone that is open minded about screens. In 1992 NAB's I saw my first Torus screen at KODAK's demo. The gain must have been 3. But the surface seemed solid + porous like that of an egg. Like the inside of a giant eggshell 11 foot wide 1.85 . Trying to figure out how they got the thing in the room I got the name SIGMA DESIGN. Since I could't afford one, the next best thing was try installing some. The SONY HD facility at Columbia Pictures then became available for my demos. They had twin stacked 55k SONY PDIH1200HD (1125 optimised 9" driven very low with servo lenses and Liquid "Optical Coupling", electromagnetic focusing and the 1270 remote) the Screen was 16 x 9 feet greish- white. The First Gen HD transfer image was compared to 35mm in this room.

The projector was 55K back then thru the SONY 1125 HD group .

Sigma worked with Showscan and Major Simulation Platforms. A $7K design fee got you a Rod Steiguer's separated at birth, Gerald Nash (a Sigma Principal) to interface in the data collection of the audience for ray tracing the parabole custom to the seating area.

Then screen costs installed about 14,000( both costs are down in the 21 century by about 20%) which is separate with Stewart. I was expecting a corian structure with stainless screws and a plexiglass lit porthole, to demonstrate the Screen proximity sensor in action (nominal negative pressure forms the precise reverse spinnaker), but nawh.

The substructure's raw materials came out of Don's garage. 3 cans of flat Black on $300 worth of plywood with the proper curvature cutouts, with $75 in pool drainage round extrusions to protect the screen surface cornered round with clay, and a bushel of sheet rock screws. A proximity PVC toungue sensor and an astronaut ventilator on reverse complete the Bargain.

4 crewmembers of the "Dead", joint trailer owners in Barstow, show up on a truck, some Harleys, and tons of tattoos.

They put it all together. 1st 180" 1.66 screen delivered w 3.0 Silver. Superbright, but looked like an oversize Sony 100 aluminum curved screen. With bad timing, a month before Stereophile 94' "Producer" Joel Silver stops by. About to kick off ISF at Stereophile.


"Color Shifting this and that." Not having seen Kodak's and Columbia's Torus.

Thus this demonstration prompted an "auspicious occasion", a blacklist for the NTSC ENFORCERS. Don worked out with Sigma the minimum gain surface possible... 2.8 off pearlwhite for the next job.

I prepared press releases inviting the press to see both Torus installations. After the ISF (Pro Runco) monopolising the press for the Show... Gary Reber went from potentially touring, to giving general coverage, to then minimal coverage, then no acknowledgment. "Such Elitism ($35K projectors etc.) on 3 to 4 meter wide screens would never trickle to the masses. Not relevant!

Why did Gary attend the demo twice with Joel Silver then? Why was Joel Silver walking people in to pick at the Barco's non calibrated colorimetry and show people what EM blooming looked like. Since Runco's 7 " ES calibrated where too soft and blue.

Bottom line J. Gordon Holt called it the home theater sensation of the show. We whipped butt, but had Gary Reber been less offended by my "Ricky Ricardo oneupsmanship promotion of the Torus superiority" ... the Torus would have come down in price to synergistically complement most existing 9 inch tube installations. A pitty. TO WHICH I A HAVE RENEWED energies to resolve.

I later tried designing a "Rotating Trilon" of 3 aspect ratio Toruses with common chamber. Never happened, but you can scroll thru 3 different aspect ratio CCS's if you really want to.

That's the Torus story.

But im' not going down that easily until you have seen the TORUS by yourselves, whether you have DILA, DLP, or CRT the TORUS is king.

Please E mail your Torus manufacturer and inquire about THE ULTIMATE SCREEN.


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[This message has been edited by CINERAMAX (edited 12-26-2000).]
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post #2 of 51 Old 12-26-2000, 06:22 AM
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I just want to corroborate part of what Cineramax has been reporting, particularly with respect to the brightness of the torus screens.

I recently made some subjective comparisons using a DIY toroid shaped screen covered with M2500 material (10' wide 16:9). First, I partially unrolled the M2500 in front of a toroid matte white screen. The top half was then flat M2500 and the bottom half of the screen was matte white curved. From the sweet spot, the M2500 was only slightly brighter. Viewing the corners, or when viewing a little off axis, the matte white curved surface was actually brighter than the M2500.

The M2500 material attached to the toroid survace is brighter yet. If the flat M2500 is 2.2 times brighter than flat matte white, I would estimate the curved M2500 brightness to be in the 3-3.5 range.

Hotspotting is minimal. There is a little loss of brightness in the corners but no worse than with a flat screen and almost unnoticeable color shifting. Colors appear more vivid.

Total cost for this screen was less than 600.00. IMO, its a viable method to use CRT for a 10' wide screen (or possibly larger) without having to double stack or upgrade to a brighter digital projector.

Mike


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post #3 of 51 Old 12-26-2000, 04:17 PM - Thread Starter
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KGB:

When you say :"

It would very much look like a direct view CRT". You have no idea how correct you are.


To make cookie cutter injectiion molded 1.85 2.35 Torusses does not cost more than 20 grand for tooling. Perhaps a fourth of what it took Don to come up with microperfc perfection.

The problem is that the TORUS is 20 times better than a microperf. It is a matter of time before Don bytes the bullet and empowers the videophiles.



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post #4 of 51 Old 12-26-2000, 04:22 PM - Thread Starter
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Mike sorry I missed your post.

Yes the torus is the solution for 11 foot wide crt and anamorphic digital images.

If it is a 2.35 aspect, the whole thing can dissapear into a credensa. One in every billion homes by 2010. By hook or crook experience it.
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post #5 of 51 Old 12-26-2000, 07:24 PM
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Quote:
Originally posted by Mike2:
I just want to corroborate part of what Cineramax has been reporting, particularly with respect to the brightness of the torus screens.

I recently made some subjective comparisons using a DIY toroid shaped screen covered with M2500 material (10' wide 16:9).
Total cost for this screen was less than 600.00. IMO, its a viable method to use CRT for a 10' wide screen (or possibly larger) without having to double stack or upgrade to a brighter digital projector.

Mike


Mike
Not sure I understand you. Are you saying you already had a curved screen of this size, and you simply recovered it, or are you saying you did a DIY project from scratch for $600?
How would one build a DYI toroid screen? Is the amount of curvature
in the screen critical for optimum performance?
Are these expensive to buy?

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post #6 of 51 Old 12-26-2000, 09:15 PM
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The inherent ambient light rejection of a curved screen makes it worth the price of admission. When coupled with a high gain surface, the curved screen gives a contrast range that is unrivalled at any price. It would very much look like a direct view CRT. Delination of detail down at 'near black' would render a stunning image.

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post #7 of 51 Old 12-27-2000, 02:58 AM
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TEW


I made mine from scratch. I started with a "negative" mold. An array of curved plywood splines, covered with 1.5 inch wide 1/4 in. ply strips, coated with thin plaster, sanded smooth. Then the final "casting" via sprayed gel-coat and 3 layers of laid up fiberglass/polyester resin. Inexpensive but laborious. I will try another method next time. The fiberglass is light enough to be carried by one person. (BTW, gloss white gelcoat wet-sanded with 300 grit yields a nice matte white surface)

The amount of curvature is important. A little deeper curve seems to yield a lot brighter picture. I set this one up for almost the maximum curvature my projector geometry adjustments would allow, with a steeper curve in the vertical dimension and more shallow horizontally. The ray traced "focus" of this setup is a line roughly eye level along an 8 ft sofa for center seating.

Interestingly, even though this is curved to focus on a small viewing area, there is very little drop off from side to side. Much less than with M2500 flat or Dalite Hipower flat. Also not much change when viewing from high or low. I think the overall depth of curve can make a big difference, but trying to dial in any one "precise" radius is not so important. Cineramaxs suggestion of marketing a few preset shapes sounds feasible.

I dont know what commercial prices would be for something like this.

Also, I would try something other than M2500 if I do it again. The toroid shape would seem to allow an even higher gain surface. The M2500 has the "vertical streaks". And the M2500 is very transparent - irregularities in color of the backing or adhesive are visible through the screen when brightly lit.

Cineramax.
In your experience, what would be the best higher gain material for this? You mentioned some 3.1 gain material previously I think.

Thanks,
Mike

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post #8 of 51 Old 12-27-2000, 07:54 AM
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Mike,
That was quite a project!

I read Alan Grouger's DYI instructions but I don't understand all of it.

Would a curve in the vertical - but not in the horizontal - yield
as good or similar results?

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post #9 of 51 Old 12-27-2000, 04:32 PM
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It definitely would yeild great benifits. Half a curve is better than none.

The vaccumm assist screen works best, as the negative pressure suffers from no weighting problems and provides as geometrically accurate a curve as is humanly possible -nature will not allow otherwise.

The best bet is to provide for the horizontal curve.

If you wish to experiment along these lines, then try getting a 4'x 8' piece of plastic coated foam core, one that is flexable..... and try screwing it to the wall, on a board, in the vertical, in the middle. With a hinge of some sort on the bottom. put some string on the bottom, and top, and pull the sides together. You should get good geometry on the curve. It would give you an ideal of what to expect,and it shouldn't cost more than $30 as an experiment. Oh yes. tilt the top. That's why the bottom hinge. The foam core is lightly anchored to the vertically oriented board,that is hinged on the wall.

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post #10 of 51 Old 12-27-2000, 05:00 PM
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Mike,

Wow you've done in real life what I was going to suggest to Peter, you won't need 20k for tooling if you use epoxy or polyester on fiberglass, all that's required is a simple wood form. The advantage is that fiber-reinforced polyester will have much greater strength and stiffness than anything done with regular plastic (which I believe was considered before, from forming the plastic with a metal-impregnated bag to forming large sheets and laser-cutting perforations in them!).

Some questions and comments:

Mike, how did you support/mount your screen? I thought about possibly putting wood supports on the back of the screen and covering them with fiberglass and polyester to bond them to the screen. This would allow you to drill holes, etc. without affecting the screen surface .

Of course your hand lay-up process is pretty time-consuming, if Peter wished to take it into higher volume production he could always spray chopped fiber onto the form...

Finishing is an issue, as you said you had to sand the gelcoat down; however, if a regular screen fabric was attached to it there would be no need to sand the surface because it would be covered.

This is could be very economical, all you would need is the $600 for the fiberglass, polyester, and mold and whatever the screen costs without a frame and you could have yourself a DIY TORUS. Of course the hard part is optimizing the curvature of the screen...

For a small toriodal screen fibre-reinforced polyester is a much better solution than the vacuum used in very large screens, especially if you are going to produce a fair number of them. The screen would be light and wall mountable with no moving parts, if done right there would be less labour involved as well.

Regards,

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post #11 of 51 Old 12-28-2000, 03:03 AM
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Hello KFung

I included a 4-6" lip of fiberglass around the perimeter. Its stiff enough to maintain its shape without any additional framing. It seems the toroid shape itself is inherently stable. It can be set on a shelf, hung from above, or a wooden "shadowbox" frame can be screwed directly to the lip.

You are right about using a chop gun. It would have been easier and faster.

What do you think of this for a fabrication plan?

1. Start with a smooth "torus" screen in a temporary vacuum box setup as KBK recommends.

2. Flip this screen over so the viewing surface is facing upward.

3. Carefully spray gelcoat then fiberglass/resin onto the screen surface. This yields a perfectly shaped toroid negative mold.

4.Remove this mold, flip it over, then stretch the new high gain screen material over it and temporarily secure the edges. The high gain surface is facing down onto the mold. The back of the screen material is facing upward and is exposed.

5. Spray gelcoat then fiberglass/resin directly onto the back of the final screen material. This is assuming the gelcoat will bond to the screen without damaging it. If not, there may need to be an intermediate layer of something here.

You could incorporate a shadowbox type lip in the final casting so no extra support or mounting hardware is needed. Home size screens might be strong and light enough to ship using only an inexpensive cardboard container. Total material costs after moldmaking around 6-8.00/sf. Less in quantity.

Mike


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post #12 of 51 Old 12-28-2000, 04:42 AM
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Tha's why peter wants the paint. It's perfect for this application....He can have it, all he has to do is ask for some.

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post #13 of 51 Old 12-28-2000, 05:12 AM
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KBK,

A spray-on surface would simplify this tremendously. You could skip the moldmaking step and start spraying directly onto a negative shape in a forced air system instead of vacuum.

Can you really replicate the benefits of e.g. M2500 or a high gain pearlescent screen with paint?

Is there any way I can buy a sample?

Thanks,
Mike
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post #14 of 51 Old 12-28-2000, 11:58 AM
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Quote:
Originally posted by Mike2:
Hello KFung

I included a 4-6" lip of fiberglass around the perimeter. Its stiff enough to maintain its shape without any additional framing. It seems the toroid shape itself is inherently stable. It can be set on a shelf, hung from above, or a wooden "shadowbox" frame can be screwed directly to the lip.

You are right about using a chop gun. It would have been easier and faster.


Of course, not all of us have chop guns http://www.avsforum.com/ubb/smile.gif
Quote:

What do you think of this for a fabrication plan?

1. Start with a smooth "torus" screen in a temporary vacuum box setup as KBK recommends.

2. Flip this screen over so the viewing surface is facing upward.

3. Carefully spray gelcoat then fiberglass/resin onto the screen surface. This yields a perfectly shaped toroid negative mold.
The only concern would be that the screen would have to support the weight of the mold without deforming, I don't know how much tension there is in the current vacuum box setup...
Quote:

4.Remove this mold, flip it over, then stretch the new high gain screen material over it and temporarily secure the edges. The high gain surface is facing down onto the mold. The back of the screen material is facing upward and is exposed.
Have to finish the mold very carefully so you don't damage the viewing side of the screen...
Quote:

5. Spray gelcoat then fiberglass/resin directly onto the back of the final screen material. This is assuming the gelcoat will bond to the screen without damaging it. If not, there may need to be an intermediate layer of something here.
Yeah...that could be tough. Only way to know is to experiment...I hope the gelcoat won't eat the vinyl of the screen.
Quote:

You could incorporate a shadowbox type lip in the final casting so no extra support or mounting hardware is needed. Home size screens might be strong and light enough to ship using only an inexpensive cardboard container. Total material costs after moldmaking around 6-8.00/sf. Less in quantity.

Mike
Yeah, the idea of spraying onto the vacuum box is much better than trying to make your own mold out of wood...

Regards,

Kam Fung
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post #15 of 51 Old 12-28-2000, 12:26 PM
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Quote:
Originally posted by CINERAMAX:


.... That some kind of collaboration between the geniousses of the forum and SIGMA ( including Gerald Nash, and Don Stewart) will yield a comprehensive range of screens to fit 99% of home theater applications.

I know that Gerald Nash is game for Mass produced TORUS, is just getting D S to feel more adventurous, something possible , I hope.


The key is to mass produce the screens economically, so economically that people would want to buy it instead of buying a brighter projector. After all, the greatest concrete benefit (as oppossed to perceptual benefits) that the TORUS provides is to let you use a higher gain screen material without the normal problem of hotspotting. This would let you move to a larger screen or higher brightness.
Quote:

So Kung Fu/ No injection mold? Just spray on fiberglass like mike2 says?
Fiberglass is probably the best solution, but you have to make sure that the viewing surface is smoooooooth if you're going to spray paint right onto it. Of course I've never worked directly with fiberglass/polyester so I don't know what the surface will feel like or how smooth it needs to be before paint is sprayed onto it.
Quote:

Really KGB's paint surface makes more sense than a laminate.Because of the imperfections.

I am amased that mike2 was able to come up with the fiberglass technique.
I'm not so much amazed that he came up with it (I was thinking along the same lines myself), I'm amazed he actually DID it! http://www.avsforum.com/ubb/smile.gif
Quote:

Had he had a precise ray trace it would have perfect luminosity to the corners.

And of course the fiberglass toroidal screen could be jet sprayed , FOR ACOUSTICALLY TRANSPARENCY EXPERIMENTS.
Always with the acoustical transparency. http://www.avsforum.com/ubb/smile.gif I think the fiberglass would be too thick to transmit sound acceptably... Like all TORUS screens this one would probably not be able to take speakers behind it. http://www.avsforum.com/ubb/frown.gif
Quote:

I Honestly believe that this is something that is needed badly.

I ask the members of this forum to ask from SIGMA demonstration at CEDIA 2001. You will be blown away. And Home theater will never be the same.
I think this is definitely something that could have a larger place in the market, it's well suited for people who want a REALLY large screen (although a regular vacuum box is probably better here), or people who want large-ish screens with a low-brightness source like a CRT. Also, anyone who need high ambient light rejection and/or high brightness. After all, if the option is double stacking that Vidikron Vision One or buying a $2-3k (I'm just making that price up...) toroidal screen, guess what I'm going to buy?

The biggest challenge would be creating a curvature that would work for a large proportion of installations, lots of research and experimentation. A lower gain than an optimized installation would probably be necessary...

Also, there is the problem of excessively curving the screen to make a very high gain surface hotspot free. Not only do you run into problems with projector focus, but also perceptual problems when the curvature of the screen falls out of that "cool, it's curved!" range into the "ugh, why is it curved so much?" range.

Regards,

Kam Fung
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post #16 of 51 Old 12-28-2000, 12:47 PM - Thread Starter
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Kung Fu:

"Also, there is the problem of excessively curving the screen to make a very high gain surface hotspot free. Not only do you run into problems with projector focus, but also perceptual problems when the curvature of the screen falls out of that "cool, it's curved!" range into the "ugh, why is it curved so much?" range."

Leave that to Sigma. The fact that it was Gerald Nash that specified categorically, that three different designs for single lens are required at 15 feet, 20 feet, and 25 feet TD, gave me a good "picture" of how these screens can be made to work well...

On CRT with the Barco 1200 hd's I was always able to focus electronically and optically with the gt-17 lenses.

Apparently the experiences learned at the AMC theatre Torusses, using the ISCO/Schneider cinamascope lensing,these anamorphic lensings range of focus are best matched by a TORUS than by flat screens.




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post #17 of 51 Old 12-28-2000, 04:39 PM
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I still don't get it. I would think that you would have more problems with hot-spotting in off-axis viewing with this kind of screen. For instance, if you're sitting off to one side of the theater: the side of the screen farthest from you would be curved toward you (which sounds good) but the side of the screen closest to you would be curved even farther away from you (in other words, your angle of view would be even more extreme then a flat screen which would seem to increase your hot spotting).

I can easily see where the screen would be great from a central viewing position, but it seems like it would be much worse in off-axis viewing. Am I confused? If the benefits of this screen type include an improvement in off-axis viewing, then that would be truly impressive.

Would Peter, or anyone who has actually seen this screen type, comment on what happens to the picture when you walk from side to side, walk out of the "sweet spot", move up or down, etc.

The only Torus screens I have seen in the past were the silver kind and looked awful, with terrible brightness irregularities. It was the same effect you get on current rear projection TVs, except much worse.

NOW...assuming that it is better all-around, it seems like we at the forum could get together and come up with some sort of process to make our own.

I am sure that the ray tracing, although important, must have some gross generalizations that would apply to most home theaters. Is the tracing done from the projector or from the seating area? I always assumed it was done from the projector. How can it be done from the seating area when the seating area has no central point? Couldn't we come up with a general tracing based on a screen size and average viewing area that would suit many of our theaters?

This would be an inexpensive, but bulky idea, but how about a giant "sandbox" as your mold. You would obviously have to do it in a semi clean environment, but it wouldn't have to be sterile. I would think that a garage would do, at least until you get to the point where you apply your finish (such as KBK's paint). Entire swimming pools are made in extremely complex shapes using a procedure of vinyl over top of sculpted sand (in our application I would assume we use sprayed on fiberglass etc.). It would be easy to adjust your shape initially, and once you get your first layer down you could build up your thickness to whatever you require. By the time you got to your final surface, the entire fiberglass or plastic shell would be self-supporting enough to be moved, sanded, etc. as needed.

Even if you use a vacuum box, what does the screen material form to in order to achieve its proper curve? Unless the screen material itself is stretch free and properly shaped, all the vacuum can do is hold it up against something that already has the proper shape. What exactly is that "something"?

I wouldn't think this wouldn't be quite as complicated as trying to plan for a commercial theater. Couldn't we come up with specifications for screens 9 ft., 10 ft., etc. in width?

The idea of this project intrigues me. For the moment, I'm just going to focus on the screen and leave out micro-perforations.

Let the brainstorming begin!

------------------
Jeff
Currently - Zenith 7" CRT, 80x60 1.3 gain screen

Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT

Thanks,

Jeff

Finally went digital: RS20, ISCO IIIs, DIY 10.5' wide torus screen, Stewart StudioTek 1.3 G3 with 4 way masking and adjustable image size
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post #18 of 51 Old 12-28-2000, 09:23 PM - Thread Starter
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Mike2 said:
I would try something other than M2500 if I do it again. The toroid shape would seem to allow an even higher gain surface. ABSOLUTELY! This one was specially made by D S, some kind of pearlescent special mix that was like 3.1 gain.

He also says:"
"I included a 4-6" lip of fiberglass around the perimeter" The extra lip going straight back unto the wall , or rounded like the torus makes much sense and can add to the aesthetics.

My Parameter was : Give me the maximum gain but keep the screen white.

The silver screen (3d) of the first torus was way to silvery.

I like my whites white.

I really think that such a project should be done with the collaboration of Sigma. They have the ray tracing down pat. With the screen properly done there is even illumination all the way to the cornerers.

Hopefully I'll be installing another SIGMA/TORUS soon.

I was hoping that this can spark renewed interest at SIGMA and with support from the members of the forum.... YOU HAVE TO WANT YOUR MTV!!!

.... That some kind of collaboration between the geniousses of the forum and SIGMA ( including Gerald Nash, and Don Stewart) will yield a comprehensive range of screens to fit 99% of home theater applications.

I know that Gerald Nash is game for Mass produced TORUS, is just getting D S to feel more adventurous, something possible , I hope.

So Kung Fu/ No injection mold? Just spray on fiberglass like mike2 says?

Really KGB's paint surface makes more sense than a laminate.Because of the imperfections.

I am amased that mike2 was able to come up with the fiberglass technique.

Had he had a precise ray trace it would have perfect luminosity to the corners.

And of course the fiberglass toroidal screen could be jet sprayed , FOR ACOUSTICALLY TRANSPARENCY EXPERIMENTS.

I Honestly believe that this is something that is needed badly.

I ask the members of this forum to ask from SIGMA demonstration at CEDIA 2001. You will be blown away. And Home theater will never be the same.

Thanks





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post #19 of 51 Old 12-29-2000, 03:04 AM
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Quote:
Originally posted by Jeff Smith:

Let the brainstorming begin!
Hi Jeff
I"ve been thinking about this a little myself. But all of these ideas
to build a curved screen seem way to elaborate to me. I used to build fiberglass kit cars, and I have no desire to start messing with that stuff
again.Seems to be a much simple way to do this would be to use a laminate or some of that 1/4 inch white paneling they sell at Home Depot/Lowes, which is generally used in bathrooms. Either is flexible enough to be curved in at the ends. That would provide an even surface for attaching screen material, or, the white paneling I'm talking about might even be good enough to be used by itself.
the problem I have with this method is all of this material comes in 4 x 8 sheets, and I want a screen bigger than that. I'm sure two pieces could be combined in a frame of some sort however. If enough attention is paid to the seam with fillers, a screen material covering it would hide the seams.
What do you think?

[This message has been edited by TEW (edited 12-29-2000).]

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post #20 of 51 Old 12-29-2000, 05:58 AM
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Jeff

Those are all relevant questions. Unfortunately, there is little or no quantitative data published that I know of to address these concerns. I just made several shapes and sizes to experiment for myself.

Yes, the ideal viewing area is reduced compared to a flat matte white screen. But even with a deeply curved screen, I find the sweet spot is quite large. With a 10ft screen width, sitting 5 ft or so off center is still good. Much better than a flat M2500 or Dalite Hipower. When sitting within this area the screen, when lit, appears flat even though I know it is curved.

Your sandbox idea would probably work too. You might also suspend the screen material in a frame - face upward. Apply a layer of clean sand and smooth it around until the weight of the sand has deformed the screen into the desired curved shape. Then, from underneath, apply gelcoat followed by fiberglass/resin in thin layers.

Mike

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post #21 of 51 Old 12-29-2000, 04:34 PM
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Quote:
Originally posted by TEW:
Hi Jeff
all of this material comes in 4 x 8 sheets, and I want a screen bigger than that. I'm sure two pieces could be combined in a frame of some sort however. If enough attention is paid to the seam with fillers, a screen material covering it would hide the seams.
What do you think?

[This message has been edited by TEW (edited 12-29-2000).]
Custom sizes are easily availible, but a bit more pricey.

Remember the huge drywall pieces availible when you are doing walls in higher prices houses.... 16 footers...12 footers, etc.

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post #22 of 51 Old 12-29-2000, 05:02 PM - Thread Starter
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Guys:

I too have thought about the single curve, specially for perforated situations.

I still say that the only way to float the "Magic Image" is with the TORUS.

You will not see a TORUS at CES this year, thanks to this screen's previous STEREOPHILE 1994 dismissal by Joel Silver (for being too bright- true only on the Siver material), Joe Kane (for it's acoustical hotspot, easily eliminated with absorbency),besides JOE Kane an acoustician?
And also Gary Reber which refused to see it based on it's high price, and the fact that he did not like the fact that I had declared Miami the home Theater capital of the world.

I have now the renewed interest from a previous TORUS owner that has seen it all, and called me on xmas eve to thank me, and to say that he wants a bigger one in his new house. That has given me renewed interest in exposing the Torus to all the HIGH END projector manufacturers, and hopefully to convince Sigma to develop a comprehensive range of SOLID FORMED screens to cover:

In maybe 8, 9, 10, 11, 12, and 13 feet wide.

CRT projection , and anamorphic single lens projectionat 3 to 4 range sizes.

I am very attracted to the idea of fiberglass. Such a screen hanging on a wall would look like a work of modern art.

Although the idea is primarily PERFORMANCE DRIVEN, (to me flat screens don't cut it, only tro & optical RP), I don't see the reason to mass produce these animals where there are afordable for the MID-HI end. Say 7k to 12K.

Not to do this at this age in time is copping the easy and mediocre way out, please those of you that are in a possition to make this happen, think about your social obligations to THE HIGH ROAD to Videophile Nirvana.

At minimum some HIGH END MANUFACTURER of PROJECTORs, say John Herron of Madrigal could ask Gina Harman (I wonder if she still married?) to buy him a screen to try. I would bet to anyone "my contingent repropriation rights to the farm lost to the revolution Cuba", yes, i would bet the farm...


That if that scenario with harman happened, the TORUS SCREEN would appear as the MARK LEVINSON SUPER-ECRAN in an upcoming CEDIA or CES.

So... while my pocket sympathizes with the idea of keeping the cost down,
getting it right , and exposing fairly to the previously subserved Videophile PRESS and Early adopter community, is what 's needed, S.O.S.
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post #23 of 51 Old 12-29-2000, 06:33 PM
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Ah Peter,

Think not that it is a cause for sadness but a cause for rejoicing that those of us with limited means may take-up this holy quest!

Into garages and workshops across the land the task shall be taken, for it is said, "Oh, seeker of video perfection thy name is nerd".

In other words...most of these great video projects start out in small shops belonging to people with weird names like Faroudja.

I don't expect perfection, but if we can come up with something that ignites (or rekindles as the case may be) the interest of the accepted industry names, while at the same time helping to achieve a little piece of personal video Nirvana, then haven't we accomplished the same goal?

So out with your ideas, all of you!

For instance, does anybody have any ray tracing figures or facts?

Does anyone have access to a proper toroid screen, regardless of size or material?

Where, in fact, do you draw your central tracing from?

Does anyone have any schematics, Web sites, old high school yearbook pictures, or clandestine spy photos for us to start with?

Finally, and most importantly, in the zero gravity of the "space station, in orbit" which way do you lay your wine bottles for proper storage?

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Currently - Zenith 7" CRT, 80x60 1.3 gain screen

Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT

[This message has been edited by Jeff Smith (edited 12-30-2000).]

Thanks,

Jeff

Finally went digital: RS20, ISCO IIIs, DIY 10.5' wide torus screen, Stewart StudioTek 1.3 G3 with 4 way masking and adjustable image size
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post #24 of 51 Old 12-29-2000, 09:35 PM
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Tim,

Most likely the compound curve would be too difficult to do, and I will end up doing a simple horizontal curve (if I do it at all). It would seem simple enough to have the radius of the curve calculated out, and have two pieces of one inch square aluminum stock bent by a machine shop. These would serve as the top and bottom supports for the screen. The side supports would not have to be curved. This could be made in any size you wish, using actual screen material by whichever company you wish (perhaps even using your existing screen). The material would be applied to the backside of the frame, allowing an even curve. The frame itself could be sprayed in a flat black or similar treatment to form the border. Is quite easy to bend material such as this, it would just have to be carefully done by someone who could get it fairly even. We would then apply our own snaps, Velcro, or fasteners of choice to the frame and screen material as needed.

As a variation on this theme, how about simply using something like PVC pipe or wood for a temporary and very inexpensive trial frame. Maybe we could set something up where we could adjust the curve by increasing or decreasing the bow in the material (perhaps using wire with adjustable cable stays attached to each end of the long pieces). We would tighten or loosen the wire it would alter the curve. Obviously this would not be a finished product, but it would seem something could be set up with the screen stretched tightly enough to focus the projector and get a good idea what the finished product would look like. The trial frame doesn't have to be the exact size, just the exact curve.

I'm still up in the air as to the screen material itself. If I stick with CRT, and the curve improves the perceived brightness, I would probably just curve a 1.3 gain screen. With a digital projector, I would consider curving a gray screen (perhaps Don Stewart's new product).

I'm still waiting to hear what everybody sees at CES before making decisions. Now that the hectic holiday season is over, perhaps this winter we could rig something up and try it. I am still planning on looking at the Seleco 250 whenever and wherever I can. The other front runners I envision or the proxima DX3 and In Focus 350 (although after a number of great initial reports, it seems there are some questions about that last model).

Happy new year

------------------
Jeff
Currently - Zenith 7" CRT, 80x60 1.3 gain screen

Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT

[This message has been edited by Jeff Smith (edited 12-29-2000).]

Thanks,

Jeff

Finally went digital: RS20, ISCO IIIs, DIY 10.5' wide torus screen, Stewart StudioTek 1.3 G3 with 4 way masking and adjustable image size
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post #25 of 51 Old 12-30-2000, 03:26 PM
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Quote:
Originally posted by Jeff Smith:
I still don't get it. I would think that you would have more problems with hot-spotting in off-axis viewing with this kind of screen. For instance, if you're sitting off to one side of the theater: the side of the screen farthest from you would be curved toward you (which sounds good) but the side of the screen closest to you would be curved even farther away from you (in other words, your angle of view would be even more extreme then a flat screen which would seem to increase your hot spotting).

I can easily see where the screen would be great from a central viewing position, but it seems like it would be much worse in off-axis viewing. Am I confused? If the benefits of this screen type include an improvement in off-axis viewing, then that would be truly impressive.
Close, but not quite! The goal of the TORUS (especially in movie theaters) has always been to eliminate hotspotting for ALL seats. The case studies in the the information they sent me showed brightness readings from different seats in a TORUS-equipped theatre and the worst seat in the house still has no hotspotting.

Remember, the light source projecting on the screen is a point source of light (or 3 closely spaced ones in the case of CRTs). When you project onto a flat screen with a high gain material, the spot in the corner is the dimmest no matter where you sit! The light from the projector hits the screen at the greatest angle at the corners and the light is reflected into the side walls where in the center of the screen the light is reflected back at the projector. The curvature of a toroidal screen actually IMPROVES the image for people in the far corner because it reflects light back to them rather than into the walls on the side. It's much easier to visualize if you just draw a top down view and draw in some light rays originating from a projector and boucing off a screen (no caculations or anything, just a rough drawing should give you the idea).
Quote:
<snip>

I am sure that the ray tracing, although important, must have some gross generalizations that would apply to most home theaters. Is the tracing done from the projector or from the seating area? I always assumed it was done from the projector. How can it be done from the seating area when the seating area has no central point? Couldn't we come up with a general tracing based on a screen size and average viewing area that would suit many of our theaters?
<snip>
If I had to guess, I would say that Sigma Design raytraces from the projector to EVERY seat in the house, optimizing gain and screen curvature for each and every seat. If it was just optimizing for the center seat or for the seats in the corner, I could do the calculations myself with some paper and a calculator (it's just some trig and calculus, if a bit time consuming). They don't charge thousands of dollars for their design fee for fun! I would guess that their software tries many different curvatures, calculating the brightness across the screen for each seat, closing in on the optimum each time until it hits the ideal curvature and gain.

I am sure a set of curvatures could be calculated for a typical home theater, but the question is: what's a typical home theater? It could be done, but it requires research. Right now every TORUS screen is a custom job with a custom set of curvatures.

Quote:
Originally posted by TEW:
Hi Jeff
I"ve been thinking about this a little myself. But all of these ideas
to build a curved screen seem way to elaborate to me. I used to build fiberglass kit cars, and I have no desire to start messing with that stuff
again.Seems to be a much simple way to do this would be to use a laminate or some of that 1/4 inch white paneling they sell at Home Depot/Lowes, which is generally used in bathrooms. Either is flexible enough to be curved in at the ends. That would provide an even surface for attaching screen material, or, the white paneling I'm talking about might even be good enough to be used by itself.
the problem I have with this method is all of this material comes in 4 x 8 sheets, and I want a screen bigger than that. I'm sure two pieces could be combined in a frame of some sort however. If enough attention is paid to the seam with fillers, a screen material covering it would hide the seams.
What do you think?
This method is definitely possible, in fact I think Mike used a similar method for his mold. This would be fine for a DIY project (and probably easier). However, when you want to make a lot of these it is pretty time consuming to make each screen and carefully fill in the seams with filler. The sprayed fiberglass method is an easier way to produce many of these screens. Consider:

- you only need one (or a few) molds
- when you spray on the fiberglass/polyester mix you don't have to be real exact because you have a mold
- when you bend your wood in place you have to be exact, even with a jig of some sort.
- harder jobs = more highly skilled labour = higher wages
- it also takes more people-hours

Of course, when you're only planning to make one your method is probably easier to carry out than just making the MOLD!

Regards,

Kam Fung
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post #26 of 51 Old 12-31-2000, 03:39 PM
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Absolutely.

I wanted to make a post stating that I DON"T NEED NO $5000 to tell me how to curve a screen, several genralizations will be more than adequate.

I just figured it would be a bit rude to say so, and it probably still is. But.. I said it anyway.

I figure, that if you can do any level of approximation of the ray tracing, and then slid the the emphasis across the least amount of numbers required (at least a few points along the line, to say you have it right enough) then, for these experimental purposes, it would be entirly adequate.


AND, Peter, if when you saw the units being assembled, and after they where assembled, then, well, where there any strange contours to the frame corners? If there were not, and the system is vaccumm assisted, then nature will not allow anything but an NATURAL curve.... which obviates any need for curve tracing. The ray tracing would be fully 'naturalized' by the time the curve was fully established at the center of the screen (meaning fully established by the forces of nature alone, which means, in effect, that a generalization IS taking place).

The errors, due to the lenses on CRT's in today's market REQUIRE a geralization to take place, as the outer focus rings only allow for a total of approximately three points on the line ANYWAY.........


I forgot to add, that since the lenses are ROUND, then there is only one curve, that is -identical- in all four quadrants.
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[This message has been edited by KBK (edited 12-31-2000).]

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post #27 of 51 Old 12-31-2000, 09:40 PM
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Thanks Kam,

I think I am finally beginning to get it (regarding off axis seating), but I still think the ray tracing must use several generalizations.

It is mathematically impossible to come up with the same angle of light reflection to each seat individually. If you only have one seat to focus on, it could be done. Therefore you must live with relative increases in reflective brightness to various all the seats around the theater.

It is this fact that makes me think we can use some of these generalizations in our own designs without having to go through all the elaborate calculus.

The vertical curve should be fairly fixed with most screens, since even with multiple seating levels the focal points should remain in a fairly close area. Because of this, I have wondered how much extra brightness is achieved by including the vertical curve. Obviously a single curve is much easier to achieve then the torus shape, but many seem to think it is worth the extra effort.

As far as the horizontal curve goes, I still say there are some guidelines that if closely followed should be able to produce the vast majority of the benefits to be gained. Perhaps we could not come as close as Sigma Designs, but I think we can get close enough that the cost/benefit phenomenon comes into effect (i.e. more and more cost for smaller and smaller benefit is the rule as you near state-of-the-art).

I am not saying this would be terribly easy to do, but I do think with proper planning,we could achieve 80-90 percent of state-of-the-art at our level for far less cost.

------------------
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Currently - Zenith 7" CRT, 80x60 1.3 gain screen

Soon to be - 107x60 1.3 gain...with ?Seleco 250 with Panamorph or "cheap" 9" CRT

Thanks,

Jeff

Finally went digital: RS20, ISCO IIIs, DIY 10.5' wide torus screen, Stewart StudioTek 1.3 G3 with 4 way masking and adjustable image size
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post #28 of 51 Old 01-01-2001, 03:57 PM
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Quote:
<font face="Verdana, Arial" size="2">Originally posted by Jeff Smith:
Thanks Kam,

I think I am finally beginning to get it (regarding off axis seating), but I still think the ray tracing must use several generalizations.

It is mathematically impossible to come up with the same angle of light reflection to each seat individually. If you only have one seat to focus on, it could be done. Therefore you must live with relative increases in reflective brightness to various all the seats around the theater.

</font>
That's right (if I'm interpreting you correctly). You can only maximize brightness for one seat or focal point. However, there are also immense gains for the other seats. What you CAN optimize for each seat is the uniformity of the image on the screen, you don't have to have dim corners in any of the seats. So, while each seat may not have the maximum possible brightness they can ALL have a perfectly uniform image. In the end that is a more perceptible difference than just a little more brightness.

You can see the difficulty in optimizing uniformity for all seats!
Quote:
<font face="Verdana, Arial" size="2">

It is this fact that makes me think we can use some of these generalizations in our own designs without having to go through all the elaborate calculus.

</font>
Well I think the calculus would be benificial, you just wouldn't need as much. http://www.avsforum.com/ubb/smilies/smile.gif For example, just optimizing the uniformity for the corner seats would get you very close to the optimum.
Quote:
<font face="Verdana, Arial" size="2">

The vertical curve should be fairly fixed with most screens, since even with multiple seating levels the focal points should remain in a fairly close area. Because of this, I have wondered how much extra brightness is achieved by including the vertical curve. Obviously a single curve is much easier to achieve then the torus shape, but many seem to think it is worth the extra effort.

</font>
We are enthusiasts after all, perfection is the goal! You are correct, the focal points, as you put it, are closely spaced in the vertical direction and the screen dimensions are also smaller in the vertical dimensions. This is really more important in commercial theaters with "stadium seating". However, those of us at home can still derive some benefits from curving in the vertical dimension. Of course, just horizontal curvature will get you pretty close and is much easier to implement than a toroidal screen.
Quote:
<font face="Verdana, Arial" size="2">

As far as the horizontal curve goes, I still say there are some guidelines that if closely followed should be able to produce the vast majority of the benefits to be gained. Perhaps we could not come as close as Sigma Designs, but I think we can get close enough that the cost/benefit phenomenon comes into effect (i.e. more and more cost for smaller and smaller benefit is the rule as you near state-of-the-art).

I am not saying this would be terribly easy to do, but I do think with proper planning,we could achieve 80-90 percent of state-of-the-art at our level for far less cost.

</font>
Agreed! A design optimized for a general home theater would give perfect results in a wide variety of installations, but a sacrifice in the gain of the screen would probably be necessary. There's no reason we couldn't have ALL of the benefits of the TORUS except with a slightly lower level of brightness.

If you want more information, go the the Sigma Design Group's website http://www.sigmadesigngroup.com/ and ask for an information package. It had case studies and lots of useful info.

Regards,

Kam Fung
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post #29 of 51 Old 01-01-2001, 04:06 PM
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Quote:
<font face="Verdana, Arial" size="2">Originally posted by KBK:
Absolutely.

I wanted to make a post stating that I DON"T NEED NO $5000 to tell me how to curve a screen, several genralizations will be more than adequate.

I just figured it would be a bit rude to say so, and it probably still is. But.. I said it anyway.

</font>
Let it be said that the $5000 will get you the rest of the way toward the optimum!
Quote:
<font face="Verdana, Arial" size="2">

&lt;snip&gt;
AND, Peter, if when you saw the units being assembled, and after they where assembled, then, well, where there any strange contours to the frame corners? If there were not, and the system is vaccumm assisted, then nature will not allow anything but an NATURAL curve.... which obviates any need for curve tracing. The ray tracing would be fully 'naturalized' by the time the curve was fully established at the center of the screen (meaning fully established by the forces of nature alone, which means, in effect, that a generalization IS taking place).

</font>
Ah I think you misunderstood the result of raytracing the curvature of the screen. Raytracing only determines how curved the screen should be, which is determined by the shape of the frame (what's in between should be a smoothly curved as possible). The natural curvature generated by air-pressure is the desired outcome because that shape is the mathematical optimum. Sigma describes their screen as a mathematical "section" of a torus (hence the name). You can think of it like cutting a piece out of a hollow donut, what the raytracing determines is where to cut, how large the donut is, and how large the hole in the middle is.

Regards,

Kam Fung
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post #30 of 51 Old 01-01-2001, 05:02 PM
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Raytracing only determines how curved the screen should be, which is determined by the shape of the frame (what's in between should be a smoothly curved as possible). The natural curvature generated by air-pressure is the desired outcome because that shape is the mathematical optimum. Sigma describes their screen as a mathematical "section" of a torus (hence the name). You can think of it like cutting a piece out of a hollow donut, what the raytracing determines is where to cut, how large the donut is, and how large the hole in the middle is.

Regards,

Kam Fung[/b][/quote]

Right again Kam...What do you do for a living?

Regards,
Don


<FONT COLOR="#ffff00" SIZE="1" FACE="Verdana, Arial">This message has been edited by Don Stewart on 01-01-2001 at 09:08 PM</font>
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