[ElvisIncognito]

I tried using the Parkland plastic material, and have now experienced the hazards of a non-flat screen (and the impact it has on alignment, convergence and especiallyfocus.) I'm sure I could get it flat given enough/the right backing/reinforcement, but weight is an issue, since I'll be dropping this assembly down from the attic via a concealed slot in the ceiling. The center channel speaker (which, at 22 pounds is pretty hefty all by itself) will definitely be a part of this assembly, in one form or another, so you can see why I hope to keep the overall weight of the screen assembly down as much as possible.


With that in mind, a tensioned cloth screen seems like the best way to go, but I'm curious as to how other DIYers have ensured that their frame is/remains flat/true. Heat, humidity and the relative moisture content of the wood available from sources such as Home Depot, etc. all speak to the likelihood of twist/warp in the future, especially given the free-standing (suspended) nature of my screen. (Even "kiln-dried" lumber from a reputable lumberyard will not insure against this, and) I don't have weeks/months to wait while some nice, stable mahogany dries/acclimates in the middle of my living room. Nor do I (currently) have the equipment (let alone the inclination) to turn this into a fine woodworking project with jointed and planed wood.


MDF is nice and stable, but way too heavy for my application. I'm considering L-shaped aluminum bars and/or U-shaped channel (with a protective layer of felt between the aluminum and the back of the screen cloth.) I eagerly await your opinions/recommendations on frame material and construction methods.


Also, given my overall plan (and the space limitations of my attic), it's almost crucial for me to be able to place the center channel speaker behind the screen. If I can accomplish this, it might solve everything, as it would allow me to construct a box (slightly deeper than my center channel's depth dimension), open at the back for reduced weight, but semi-closed on the sides for stability, then stretch the screen cloth over the front frame. The box would be inherently much more stable than a simple frame, but this whole concept is dependent on acoustically transparent screen cloth. If anyone has significant experience with (and a DIY source for) such cloth, PLEASE let me know.)

 

[anticowboyism]

well, acoustic cloth operates on the basis of being an open weave cloth. This makes it a bad choice for a screen material. You would effectively be losing half your image through the fabric. I guess you can experiment with small samples of different cloths from your fabric store. Try the Thermo Suede at Joann's. Get a 1/4 yard of it or a remnant and tack it around the front of a speaker. See if you're happy with the sound. People have been saying good things about this fabric (projectionwise), even left untreated.


But I think your best option for good sound and good picture would be to figure a way for the speaker to be in front. Then the acoustic properties of the fabric wouldn't be an issue. And you could paint it to improve the picture more.


Aluminum would work fine for a frame, however you need to figure out how to attach fabric to it, since you obviously can't use staples. Also the joints between sides will be seen through the fabric, since you can't miter, and will need to use some sort of bolts. If you know someone who has an arc welder and the skills and patients to weld aluminum, you can weld the sides together from the back using a third joining piece, thus preserving the flatness of the front.


All this into consideration, it would be much easier, and probably very stable to just make a wood frame with proper bracing across the long side and possibly across the diagonal or on corners.

 

[anticowboyism]

ok, here's how you do it easy with aluminum. Use aluminum pipe. Attach the sides with the 90° elbows. Weld if possible, if not liquid nails or similar should work fine because the screen will hold it together. Now you need to put grommets in the edge of the screen every few inches. Depending on your screen size, about 5 inches. Now wrap the screen around the frame and attach one side's grommet to it's match on the other side with wire. The best way to do this would be to use 2 lengths of wire, one for each half. In the center they would be joined with a turnbuckle so you can tighten it to the proper tension. I'm not sure if this would end up being lighter than wood, but it would definitely withstand the test of humidity/heat and warping.

 

[ElvisIncognito]

Actually, I was thinking aluminum u-channel would be the way to go... I could saw a 90 degree "V" through 2/3 of the channel (in three spots) and bend it into a 45, then mitre the final corner with a hacksaw.


A wooden subframe of the proper dimensions would then be (snugly) inserted into the channel, holding the thing together at the final corner. The inserted wood also gives me something to attach the screen to. Screws from the back side of the "U" and into the wood will help to tension the fabric.

 

[mcfoo]

It would be very difficult to make a true rectangle by cutting vees. Much better to make a 1x2 or 1x3 wood frame and then screw aluminum angle to it. No need to miter the wood if you have or can borrow a biscuit cutter.

 

[WatchThis]

1x2 furring strips are cheap, light, easy to work with, and plenty strong enuf for a tensioned canvas frame, if u use a design that distributes the forces properly.

i wouldnt worry too much about warping once u get it assembled. u could always use a primer/sealer on it, but i doubt that would be necessary.


this frame goes from home depot's lumber rack to fully assembled in about an hour...

 

[WatchThis]

here's a close-up of how the middle section fits within the outer frame. this makes it stronger, and u dont have to worry about show-thru, since the frame is back ~1/4 inch from the canvas surface... and it makes it easier to keep the thing square, b/c u wont get very good "dimensioned" lumber from 1x2's unless u have a good planer and jointer in your shop. i dont have those either, so i kinda designed-out those problems by turning the inside 90 degrees

to figure out the lengths of each piece of wood where W is screen width and H is screen height:


small pieces (u need 6 of them): length = (W - 6) / 4


vertical pieces (u need 5 of them): length = (H - 1.5)


main long pieces (u need 2 of them): length = W


go thru the racks and get the straightest pieces u can, and it will lay flat.


to machine those joint pocket holes, u need: this


this frame is very easy to build... no clamping, or mitre cuts, or anything like that. u dont even need to use glue if u dont really want to.

 

[ElvisIncognito]

Quote:

Originally posted by WatchThis 1x2 furring strips are cheap, light, easy to work with, and plenty strong enuf for a tensioned canvas frame, if u use a design that distributes the forces properly. i wouldnt worry too much about warping once u get it assembled. u could always use a primer/sealer on it, but i doubt that would be necessary. this frame goes from home depot's lumber rack to fully assembled in about an hour...

Nice frame & excellent KISS construction techniques. I'm sure this would be great if affixed to a wall after assembly is complete - rigidity of the wall would certainly prevent twist/warp, but my screen will be freestanding (hanging), and with the moisture content in HD furring strips, I just can't imagine that this frame would not twist/bow/warp as the wood dries... I can't even imagine kiln-dried 1x2's being impervious to this - especially once tension is applied.

 

[ElvisIncognito]

Quote:

Originally posted by mcfoo It would be very difficult to make a true rectangle by cutting vees. Much better to make a 1x2 or 1x3 wood frame and then screw aluminum angle to it. No need to miter the wood if you have or can borrow a biscuit cutter.

I don't see why... if you make the vees slightly larger than 90 degrees, then you need only bend the channel until you have a right angle. This would, I think, be much more rigid than attaching angle iron to a wooden frame.

 

[mcfoo]

I'm just saying that bending a piece of channel is not an exact science...it doesn't always bend exactly where you want it to, and your screen has to be a perfect rectangle. Besides, for my screen (96" diag) it would take a piece of channel about 23 feet long to do what you want. I considered attaching angle to my wood frame but decided not to. Mine is hinged and spends half the time flat against the ceiling...no warping in over a year of use.

 

[ElvisIncognito]

Quote:

Originally posted by mcfoo it would take a piece of channel about 23 feet long to do what you want.

*ROFL* I never even thought about the length of the channel I'd need! Man, what an oversight! That's what's great about this forum - plenty of people to point it out to you when you're overlooking something!
Quote:

Originally posted by mcfoo Mine is hinged and spends half the time flat against the ceiling...no warping in over a year of use.

Interesting! How heavy is it (roughly)? Can you post your construction details? Thanks!


WatchThis - looks like you were right... and I'll be making a Home Depot run real soon! (Been wanting a Kreg jig anyway! ) Thanks for the detailed construction tips!

 

[BrickTop]

Mcfoo,


I'm about to build my own 80" flip up screen. I am planning on using curtain rod mounts and a rod, threaded through some mounts on the top of the screen, just above a large window in the living room(I'm an apartment dweller so no dedicated HT for me). How do you keep your screen against the ceiling? I was just going to use a spring loaded catch, but any other ideas are welcome. Have you any pictures of your screen? Did you cover the back so the wood is hidden? I was going to use canvas or a white sheet to cover the back. Any info from someone who has allready done that would be great.


Thanks,

BrickTop


I thought I would be the only one with a big DIY projector screen strapped to his ceiling.

 

[J. L.]

Elvis...


I think you have a real challenge ahead of you.


I currently have a pine frame screen covered with "blackout cloth" in my theater. This originally was constructed with straight, dry pine and when constructed was flat and had 90 degree corners.


In less than 6 months of hanging from the top frame member only (similar to what you are describing as your eventual installation) the frame had twisted and warped. The primary cause of this was the tension exerted on the frame by the screen material itself. I think you will find that it is not as easy as you might think to get the screen material attached to the frame with even tension.

This link shows how I solved the problem with the frame warping


I still have the screen supported from the top, but I have made it easy to individually adjust each corner to get the screen square and true to the projector. Unfortunately, the turnbuckle solution I use won't work on a screen you lower from the ceiling.


I am planning on replacing this screen (constructed by the prior owner of the projector) with something more substantial. I can be pretty sure I will need diagonal bracing in addition to a much more substantial frame to keep the screen dimensionally stable.


I'll be curious how you solve the problem of getting the screen to be light, strong, and stay flat and true so you can focus for best image.


Please keep us informed on your DIY effort.


J. L.

 

[mcfoo]

I think the secret to stretching the blackout cloth is not to pull too much. Staple the cloth with a small amount of tension in the middle of each side and then pull and staple a small length on each side of the original staple, stapling opposite sides alternatively. My screen suspension is articulated so that it can be folded up without hitting my ceiling lights. It weighs around 20 pounds (just a guess...it's the weight of three eight foot 1x3's). here's a link to my site:

http://home.columbus.rr.com/handbell...s/Theater1.htm


Details of construction are on page 2.

 

[StuartL]

What about using a sheet of 1/8" Masonite screwed to a 2 by 2 outer frame on the back side. Glue the fabric to the masonite with spray adhesive. This would be slightly heavier than an aluminum frame, but would also assure a straight plane for projection focus.

 

[ElvisIncognito]

I have considered a sheet of masonite over a 1x2 frame... I could cut large holes at strategic places in the masonite to reduce weight - the trick will be to maintain enough of it so that the rigidity remains intact. Something like this, maybe (brown = masonite, white = cutout):

 

[ElvisIncognito]

Bricktop-


At one point (before I realized I had adequate clearance in my attic,) I was considering a hinged, flip-up screen. My thought at that time was to insert rare-earth magnets into holes in the bottom of the screen, then make what amounts to "a big sock" to slide on over the frame. Some well-placed screws in the ceiling (could even paint the exposed screwheads white) would "complete the circuit" and the thing would basically stay up there as if by magic...

 

[anticowboyism]

masonite is a perfect idea. It will always stay true no matter what. Then adding some simple framing to the back to keep it flat. How about just some aluminum corner braces and maybe a few strips across diagonally?


I don't think your cutout design will be very strong though. Try just drilling random holes with your largest drill bit 1~2".

 

[Robert Cobler]

If you use tempered Masonite as opposed to usual stuff, you don't need any frame at all. It is very stiff and hangs flat when supported at the top in 3 places. I would recommend sanding the smooth surface with a fine grit sandpaper before the 1st coat of paint--to help the paint adhere better.


I am delighted with my screen using 2 coats of Liqitex white gesso. I too have compared the result with high-end screens and I prefer my DIY model. Note that I have a DLP with excellent blacks, so white is fine. Should also be fine with CRT PJ's. I also found a 6" black velvet border all around helps set off the sharp white sides of the screen and also prevents any overscan being visible. Keep it simple.

 

[ElvisIncognito]

Thanks for the info, Robert, it may prove very helpful to others, but a masonite screen leaves me with a problem (as stated in my original post): "Also, given my overall plan (and the space limitations of my attic), it's almost crucial for me to be able to place the center channel speaker behind the screen."