AVS Forum Special Member
Join Date: Apr 1999
Location: On a large overstuffed couch in Virginia Beach, Va
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First find out (experiment) how much focus you are willing to lose in the corners...and in how much of the corners/sides. This fact alone will set the tone for how deep your curve can be. The depth of the horizontal curve using Guy's method (which I did) is almost 10" max on a 9' wide screen.
Mike2, who has a torus with a G70 says the out of focus edges/corners are a non-issue. If you accept this, you can go actual depth of Guy's string and Iceman's "sphere". You then can go higher gain (3-4). Mike is happy with his brightness and unphased by the focus issues.
OTOH - Alan has a 2.5 gain Platinum Stewart screen with a 4' deep, 9' wide horizontal only curve. He says he sees hot spotting only on a solid white scene or test pattern...with a movie, it is not visible. He said 6" depth probably would have been perfect. He can focus to the edges.
I took all the above info along with comments from Mike Parker (who tweaked my 9500LC) and CINERAMAX who said that (based on installation experience) that 10" sounded too deep for my PJ and lenses (my lenses are HD10 GT26, which Peter refered to as "simulation lenses"). He said 6-7" sounded more proper for my 9' wide screen. He said the deeper torus screens use "C" or "curved" lenses to achieve focus at full depths ($1300 each!).
BTW, he tried to get me to go wider...and he's a purist. EVERYONE who either owns , builds, or installs them says the benefits far outweigh the disadvantages...I chose to believe them.
I put all the posts and phone calls together and settled on Peter's 6-7" depth. I'm using the same material as Alan. The material itself was chosen by Don Stewart taking into account my theater size and shape, my PJ, and my screen size and depth of curve. He just left a message on my answering machine...it shipped out today!
BUT I RAMBLE...the point of all this was that you have to "temper" the string's measurements fo focus completely. In effect, computer models do the same when calculating for a larger width seating area.
I strongly believe the making of a torus screen is as much art as science, and am listening carefully to those who've actually done them.
My screen should be finished by mid week!
I've been too busy building it to post much, but by the weekend, I'll try to post a thorough progress report, with photos, of everything but the Stewart material. This will follow next week.
I tried to post a LONG report once, but my wife accidently erased it putting in the pics (hey, at least she's letting me do it and taking the pictures).
With my screen size, and input from all of the above, the 2.5 should give me more light than Alan, with no hot spotting.
I'm off the next few days, call me or page me. I have many more answers than questions at this stage. I'm very confident in everything so far. Much of it is easier than you think once you visualize it.
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