What happened to Toroidal screens? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 15 Old 03-08-2013, 10:34 PM - Thread Starter
Member
 
sj64's Avatar
 
Join Date: May 2006
Location: Melbourne, Australia
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Has anyone been DIYing their own toroidal screen recently?

I've just moved house and I'm looking to build myself a new screen. I have an NEC XG110.
I was doing research on paints for a flat screen (having never gone down that route before) and then i came across toroidal screens. I became intrigued by the idea. I spent a good few hours late into the night reading up everything I could find on them and decided it's what I want to do for my next screen.

The first thing I need to do is workout where I could source some Vutec Pearlbrite. All the toroidal DIY threads I came across dated mostly 2005-2006. There was a contact on these very AVS forums that provided the Pearlbrite. I'm guessing that's no longer an option. So I've been working my way backwards through the 'DIY Screen Section' and nothing. Aside from paint, it's all been about spandex the last year or two.

I'm guessing interest in the curved toroidal screens has died away much as crt projectors have. With the current crop of projectors, adequate lumens and screen brightness are no longer an issue.
I however still love and have no reason to replace my NEC and I'm excited to try out the punch in brightness that a toroidal screen covered with a 3.0 gain material gives.

That said, does anyone know where I can get some Vutec Pearlbrite, or comparable, material from? (p.s. I'm in Australia. Shipping is my best friend)
Also, maybe I've missed it, but in the six odd years since the hubbub of toroidal screens has an even better screen idea come along for crt owners?

'cheers
Sim.
sj64 is offline  
Sponsored Links
Advertisement
 
post #2 of 15 Old 03-11-2013, 06:22 AM - Thread Starter
Member
 
sj64's Avatar
 
Join Date: May 2006
Location: Melbourne, Australia
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Update:
Well, I've had no luck finding a source for the Vutec Pearlbrite. I've contacted Vutec and unless they get back to me with some positive news or someone replies here. I might have to give up on my short-lived dream of a torus screen.
Also, further reading on torus threads seemed to indicate quality issues with Pearlbrite were rather common. Something about stretch marks. If Pearlbrite did turn out to be problematic, this might be a reason for the DIY torus screens disappearing.

Whilst I'm still hopeful that someone might be able to chime in on Pearlbrite and its availability. I've gone back to looking at paints.

I'm tossing up between two very attractive looking solutions: S-I-L-V-E-R and RS-MaxxMudd-LL.
Attracted to the gain of the first and the better ambient light handling of the 2nd.

Overall gain would be most important, but ability to handle ambient light would be a nice bonus. (Always wanted to try the idea of having friends over to watch sports on the big screen, but stopped at the thought of having to do it in complete darkness.) Most of our projector viewing is done at night, but with our young daughter there's the occasional daytime movie. -There's a big sliding glass door down one side of the room towards the screen end. Even if I can get something heavier over it than the current blinds, there'll still be a good bit of diffuse sun coming through the gap at the top. In this situation could MaxxMudd really make much of a difference over S-I-L-V-E-R?

'cheers
Sim.
sj64 is offline  
post #3 of 15 Old 03-11-2013, 09:47 AM
AVS Club Gold
 
MississippiMan's Avatar
 
Join Date: Nov 2002
Location: Byhalia, Mississippi. Waaaay down in the Bottoms
Posts: 14,654
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 47 Post(s)
Liked: 206
Quote:
Originally Posted by sj64 View Post

Update:
Well, I've had no luck finding a source for the Vutec Pearlbrite. I've contacted Vutec and unless they get back to me with some positive news or someone replies here. I might have to give up on my short-lived dream of a torus screen.
Also, further reading on torus threads seemed to indicate quality issues with Pearlbrite were rather common. Something about stretch marks. If Pearlbrite did turn out to be problematic, this might be a reason for the DIY torus screens disappearing.

Whilst I'm still hopeful that someone might be able to chime in on Pearlbrite and its availability. I've gone back to looking at paints.

Welcome back. But be forewarned, your desire to have a Torus Screen ain't dead yet...............
Quote:
I'm tossing up between two very attractive looking solutions: S-I-L-V-E-R and RS-MaxxMudd-LL.
Attracted to the gain of the first and the better ambient light handling of the 2nd.

RS-MaxxMudd LL is no slouch in the gain dept. I can assure you it has the ability to put up an image you'll be pleased with.
Quote:
Overall gain would be most important, but ability to handle ambient light would be a nice bonus. (Always wanted to try the idea of having friends over to watch sports on the big screen, but stopped at the thought of having to do it in complete darkness.) Most of our projector viewing is done at night, but with our young daughter there's the occasional daytime movie. -There's a big sliding glass door down one side of the room towards the screen end. Even if I can get something heavier over it than the current blinds, there'll still be a good bit of diffuse sun coming through the gap at the top. In this situation could MaxxMudd really make much of a difference over S-I-L-V-E-R?

'cheers
Sim.

As far as the ability to maintain better contrast under ambient light conditions, RS-MaxxMudd LL will be a better choice than S-I-L-V-E-R .

So ok...this "Torus" business. Well no problemo there,Senior Aussie. 6 mm Sintra is an excellent material. It has just the right combination of rigidity and controlled flexibility to bend evenly across the gradual degree required for a Torus-oriented curve without the need for much support along the curve. That means you can anchor one end then bend the Sintra into a desired curve, then plot out the supportive structural members wherever you feel they are most needed. I am certain that you will be able to find a Plastic Sheeting Mfg who has a selection of Rigid Expanded PVC Foam Board. You want it in White if possible, but take it in any color you can get it...especially if it cost less.

Sintra also comes in 1/4" thick size, and that is even more rigid, yet still retains enough flexibility. Cost a bundle more than the 6mm though.

What will please you most is the fact that once bent into shape, Sintra doesn't try to fight it's way into some other shape, making it very easy to work with when designing a supportive Cradle.

But.......you will still want to paint it before you bend it into it's permanent position.The paint is more than flexible enough so no worries there. I'd be interested in helping you decide what type design would be best suited to use for your Cradle. It won't need to be complex or heavy at all...just secure the ends and the center, so as to allow the Sintra's own curvature stresses to maintain the overall radius curve you'll need. I am thinking Screws only, situated around the perimeter edges.

So what say you?

To quote James T. Kirk;
"I'm laughing at the superior intellect"
MississippiMan is offline  
post #4 of 15 Old 03-12-2013, 08:06 AM - Thread Starter
Member
 
sj64's Avatar
 
Join Date: May 2006
Location: Melbourne, Australia
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by MississippiMan View Post

Welcome back. But be forewarned, your desire to have a Torus Screen ain't dead yet...............
RS-MaxxMudd LL is no slouch in the gain dept. I can assure you it has the ability to put up an image you'll be pleased with.
As far as the ability to maintain better contrast under ambient light conditions, RS-MaxxMudd LL will be a better choice than S-I-L-V-E-R .

So ok...this "Torus" business. Well no problemo there,Senior Aussie. 6 mm Sintra is an excellent material. It has just the right combination of rigidity and controlled flexibility to bend evenly across the gradual degree required for a Torus-oriented curve without the need for much support along the curve. That means you can anchor one end then bend the Sintra into a desired curve, then plot out the supportive structural members wherever you feel they are most needed. I am certain that you will be able to find a Plastic Sheeting Mfg who has a selection of Rigid Expanded PVC Foam Board. You want it in White if possible, but take it in any color you can get it...especially if it cost less.

Sintra also comes in 1/4" thick size, and that is even more rigid, yet still retains enough flexibility. Cost a bundle more than the 6mm though.

What will please you most is the fact that once bent into shape, Sintra doesn't try to fight it's way into some other shape, making it very easy to work with when designing a supportive Cradle.

But.......you will still want to paint it before you bend it into it's permanent position.The paint is more than flexible enough so no worries there. I'd be interested in helping you decide what type design would be best suited to use for your Cradle. It won't need to be complex or heavy at all...just secure the ends and the center, so as to allow the Sintra's own curvature stresses to maintain the overall radius curve you'll need. I am thinking Screws only, situated around the perimeter edges.

So what say you?

Hey,
just as I was giving up on a torus screen. Thanks to you MississippiMan, I'm excited again.

Enough so I even did a super crude scale mock up of a torus screen just to satisfy myself that rigid plastic can comfortably take a two-axis bend. It appears it does.

Here's two pics, my model was done with milk container plastic.. -Even made it 16:9!
photo testCurve.jpg
photo tesCurve2.jpg

MississippiMan, I am interested on what ideas you have for the cradle. All I've thought of so far is a simple wooden frame. And if I understand you correctly, rather than going through all the effort of carefully drawing out curves and then using a jigsaw to cut them out of the wood. Instead put risers on each corner of the frame, attach the Sintra to each raised corner and also on the middle of each length and let it curve the way it wants to?

I did a quick 3d mockup of how I've understood the construction idea.
photo 3dmockUp_01_screen.jpeg
photo 3dmockUp_01_noScreen.jpeg

i used the torus calc spreadsheet provided by Pjackso here.
Based on a screen of 91"x51", with a viewing distance of about 9' and a couch about 6' wide. -The spreed sheet gives me pretty low numbers for the risers. giving depths of 2.25" horizontal and 0.8" down the vertical sides. Which is what I've used in the model.

However Vince_B here. had a 88"x48" screen, similar size to mine, who after using much bigger values reduced them and ended up with depths of 3.5" horizontal and 1.75" vertical. He reported being very happy with this and I'm thinking of going closer to what he used.

Rang up about Sintra (Forex here in Oz), and so far if I want a single sheet larger than 4'x8', the next size is 10'x5' and that only comes in 3mm or 5mm thicknesses.
That said, we move into our new rental this Friday and then I can properly measure the lounge room and get a firm idea of what size screen and seating position we'll be using.


phew!

'cheers
Sim.
sj64 is offline  
post #5 of 15 Old 03-12-2013, 08:24 AM
AVS Club Gold
 
MississippiMan's Avatar
 
Join Date: Nov 2002
Location: Byhalia, Mississippi. Waaaay down in the Bottoms
Posts: 14,654
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 47 Post(s)
Liked: 206
You do want at least the 5mm thickness in whatever size you want to zero in on.

Your "Block-mounted" application does what needs to be done if the sheet's rigidity is maintained. All in all an excellent method, and exactly along the lines of the minimalist bracing I was describing. However, if a thinner material is used, it will still take minimal bracing.

It will be a great boon to those who have still the need / interest in Torus-type Screens to see your effort progress into a finished application. I do like how you applied yourself to the equations so quickly...( of course your a day ahead... wink.gif )

I'm glad you posted your desire (...and brief lament...) and even gladder still I could bring some new hope to your efforts.

MMan

To quote James T. Kirk;
"I'm laughing at the superior intellect"
MississippiMan is offline  
post #6 of 15 Old 03-12-2013, 07:45 PM
AVS Special Member
 
fitbrit's Avatar
 
Join Date: May 2006
Posts: 2,059
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 24
Quote:
Originally Posted by MississippiMan View Post


Sintra also comes in 1/4" thick size, and that is even more rigid, yet still retains enough flexibility. Cost a bundle more than the 6mm though.

An inch is 25.4 mm, so 1/4" is 6.35 mm. 0.35 mm seems pretty insignificant for the extra cost and claimed changes in rigidity. Was there a typo or a conversion error, MM?
fitbrit is offline  
post #7 of 15 Old 03-13-2013, 01:40 AM
AVS Club Gold
 
MississippiMan's Avatar
 
Join Date: Nov 2002
Location: Byhalia, Mississippi. Waaaay down in the Bottoms
Posts: 14,654
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 47 Post(s)
Liked: 206
Quote:
Originally Posted by fitbrit View Post

An inch is 25.4 mm, so 1/4" is 6.35 mm. 0.35 mm seems pretty insignificant for the extra cost and claimed changes in rigidity. Was there a typo or a conversion error, MM?

Probably...leastwise as far as they are concerned. In the US it's 6mm....all the time, all the way.

But perhaps not. After all, they do things strangely down in OZ.

Crikey!

To quote James T. Kirk;
"I'm laughing at the superior intellect"
MississippiMan is offline  
post #8 of 15 Old 04-03-2013, 06:33 AM - Thread Starter
Member
 
sj64's Avatar
 
Join Date: May 2006
Location: Melbourne, Australia
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
So I'm back and gearing up to start my painting and construction.
I've had to put things off for a few days thanks to an exam I've got tomorrow morning. I've been thinking a lot about the paint.
I've got a question about adjusting the paint, and tomorrow after my exam when I'll have more time - I'll put in some diagrams of my assumptions and thoughts. But for now:
Is there a way to increase the gain of the paint mix aside from increasing the silver content? Don't want to go with anything darker because of my light challenged crt. However I'm wondering if I can take advantage of the torus screen where hot-spotting is not an issue. (Rather the screen becomes one giant hotspot == increased brightness.)
I'm guessing one of the considerations of any paint mix is to improve gain whilst avoiding hot spotting and maintaining a decent viewing angle. Whereas a torus screen might benefit from a paint mix that has a tighter viewing angle caused by higher gain. This might also help with a torus issue referred to by Iceman as light washout.

Basically is there something in the MaxxMudd recipe I can increase the concentration of, like the White Pearl, or use a satin rather than flat finish white paint - to increase gain without concerns about hot spotting?

I've figured better to post this here, rather than in the MaxxMudd thread, due to it being a Torus specific question. Also I might be confused about the relationship between hot-spotting/gain/veiwing angle.
Like I said, I'll put in some diagrams showing my understanding of it all tomorrow.

'cheers
Sim.
sj64 is offline  
post #9 of 15 Old 04-05-2013, 11:50 PM
Advanced Member
 
Gunnar's Avatar
 
Join Date: Oct 1999
Location: Lillehammer, Norway
Posts: 933
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi! I built a toroidal screen back in 2003 (built in the dining room before restoring in our 1920 house..), using it with a Barco 1209. Built like a box with curved sides, and with a pc-fan at the back to do the torus shape. I used Draper M2500 material. Did a decent job, but I wasn`t totally happy with the material. It had vertical streaks that showed during bright scenes.

You can`t use a rigid material to make a true torus shape, except using a torus mold..


Gunnar is offline  
post #10 of 15 Old 04-06-2013, 04:37 AM - Thread Starter
Member
 
sj64's Avatar
 
Join Date: May 2006
Location: Melbourne, Australia
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Gunnar View Post

You can`t use a rigid material to make a true torus shape, except using a torus mold..]

Ha! I hope your wrong about that. I'll find out for myself tomorrow morning. Fingers crossed.
(Besides define 'true torus shape'? There's a few versions of what that means. - Initial torus designs placed the center of curvature at the projector and that would give very strong curvatures on the screen. Then later the center of curvature was placed behind the viewer and with the viewing area fitting inside the pie slice of the curvature: the screen curvature became much gentler and I believe my rigid sheet will be able to achieve those curves. That said, the curves on your screen look rather gentle. )

I've built the frame. Painted the screen. And I would have mounted the screen tonight and found out if this whole venture was going to work. Except we got invited out to dinner at a friends house and I couldn't explain to explain to my wife and friends that I'd rather stay home on a Saturday night to finish building a projector screen. cool.gif

Gunnar were/are you happy with your torus screen, did you overcome the streaks issue? Also how did your house restoration go? That big curved window behind your screen suggests a rather elegant architecture. Nice.

Tomorrow I'll post up the results and some pictures of the construction.

'cheers
Sim.
sj64 is offline  
post #11 of 15 Old 04-07-2013, 11:06 AM
Advanced Member
 
Gunnar's Avatar
 
Join Date: Oct 1999
Location: Lillehammer, Norway
Posts: 933
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
If you take a piece of paper, you can easily demonstrate that you can`t have a horizontal and vertical curve at the same time, unless the material is flexible. And then you need something to maintain the shape, eg a fan, and curved sides as on my screen "box". Outside of a donut is an exampe of a toroidal shape.


We got the house in 2001, and have been restoring it more or less continuously since then.

This is the finished dining room. The table can be extended to about 4m, and there is room for about 18 people. The windows, trim (except the wall panels) and furniture is original from 1920. Me and my wife removed all trim, all glass from the frames, removed all paint, repaired as necessary, and reinstalled the original glass eek.gif


ACD Systems Digital Imaging
ACD Systems Digital Imaging
Gunnar is offline  
post #12 of 15 Old 04-07-2013, 12:55 PM
AVS Club Gold
 
MississippiMan's Avatar
 
Join Date: Nov 2002
Location: Byhalia, Mississippi. Waaaay down in the Bottoms
Posts: 14,654
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 47 Post(s)
Liked: 206
Quote:
Originally Posted by Gunnar View Post

If you take a piece of paper, you can easily demonstrate that you can`t have a horizontal and vertical curve at the same time, unless the material is flexible. And then you need something to maintain the shape, eg a fan, and curved sides as on my screen "box". Outside of a donut is an example of a toroidal shape.

It's a case of "been there, done that" using Sintra and properly positioned Blocks. Sintra fits all the above specifications, and has just the right rigidity to maintain the correct "center shape" while the outside corners and side are curved.

What is missed here is an explanation as to the degree of shaping. The severe amount (degrees) of curvature present in older generations of Toroidal Screens simply is not required. Also, Toroidal Screens were designed more for focusing gain than to correct barreling. If anything, without there being a need to "correct", they actually distorted the image at the sides.

sj64's example-to-be represents the above mind-think, as well as current needs and requirements. I don't envy the Members who had to go toroidal out of sheer necessity. I do however respect and appreciate the DIY efforts they underwent to create something few others would attempt.

To quote James T. Kirk;
"I'm laughing at the superior intellect"
MississippiMan is offline  
post #13 of 15 Old 04-09-2013, 06:12 AM
Advanced Member
 
Gunnar's Avatar
 
Join Date: Oct 1999
Location: Lillehammer, Norway
Posts: 933
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
My motivation for building the torus screen was to get some more light from my Barco BG1209 CRT-projector, and also the challenge ofcourse:D
The lenses on most CRT-projectors have separate corner focus adjustments, and I could get a sharp focus everywhere on the screen. The radius was modest, about 40' as I remember..
Gunnar is offline  
post #14 of 15 Old 04-09-2013, 06:58 AM
AVS Club Gold
 
MississippiMan's Avatar
 
Join Date: Nov 2002
Location: Byhalia, Mississippi. Waaaay down in the Bottoms
Posts: 14,654
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 47 Post(s)
Liked: 206
Noted. But with 2000+ lumen Digital PJs the need for such light conservation and redirection has virtually diminished....and at most, what with recent innovations in Lens memory and built-in masking, today there exists on a very few reasons to even need a curved screen...and almost no reason to need a true Torus design.

As the need to use Anamorphic Lenses to create a CIH environment subsides, then the need for even a simple curved screen will be eliminated.

Of course that all applies to the vast majority of FP owners. For those who cherish the older CRT format (rightly so), already spend their Children's College tuition on a Anamorphic Lens Setup, or those who simply want to have the marked and distinct appearance a curved wide screen, at least here they can find ideas and validation for their efforts.

To quote James T. Kirk;
"I'm laughing at the superior intellect"
MississippiMan is offline  
post #15 of 15 Old 06-05-2013, 07:57 AM - Thread Starter
Member
 
sj64's Avatar
 
Join Date: May 2006
Location: Melbourne, Australia
Posts: 63
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hey all,
I've finally done a write up of the construction of the torus screen I built. Whilst it is the result of the discussion here, I figured it should go into a new thread.

It's here.
sj64 is offline  
Reply DIY Screen Section

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off