False wall questions

[ParadigmDawg]

I built a small bird house about 25 years ago, it looked ok but broke in half after about 1 week.

Let me know if you need my help...

 

[jostenmeat]

I built a small bird house about 25 years ago, it looked ok but broke in half after about 1 week.

Let me know if you need my help...

Thanks. I think you simply weren't given the proper motivation for building the birdhouse.

 

[basspig]

I will clarify that my 'wall' is not really a wall at all. It's a frame that supports sheer black fabric liner and velvet drapes. It has to be acoustically-transparent at lower frequencies, because it conceals a wall of woofers. So the framework has no panelling attached to it. It lets sound pass right through it, as does the CenterStageXD material itself.

I don't use metal studs in a situation like mine, because it is near-impossible to damp them completely. If you strike a stud with a fingernail, it still makes a metallic noise, like hitting an aluminum ladder rung with a tool.

I chose Doug Fir 2x4s because it provided the right combination of rigidity for the screen opening and supporting of drapes, while being stable and straight. After buying lumber, I paint it and let it stand for several days. All pieces remained ruler-straight. I then assembled my 'wall' and raised it into position.

The screen frame itself is of poplar, painted black to seal in the moisture so it doesn't dry out too much or shrink. It has remained dimensionally accurate throughout four seasons and is now starting its second year in service. This frame is held together by biscuits and metal L brackets and has two support struts at 1/3 intervals (4').

Even so, I have had minor rattling issues with the curtain hooks rattling on the metal tracks/rods, so I've added rubber channeling along the length of the rods to stop the rattling of the hooks at low frequencies. To stop the screen flapping noises against the struts, I added felt strips to the struts.

Overall, the whole screen wall is pretty quiet and doesn't add much distortion to the sound after much testing and troubleshooting to find specific rattles and sources of noise.

The rest of the room is still a problem, with floor joists making cracking noises and wall studs and window frames that rattle. Ceiling panels and light fixtures continue to be a source of distortion and dust precipitation at low frequencies.

 

[jostenmeat]

Thank you very much indeed, mr. basspig.

I am leaning towards imitating your setup in regards to the false wall, er, frame.

I would ideally like to have my TH up front, and with something like what you did, I can move the frame out to access it. I will foresee having to access it very, very rarely, but I still will need access eventually.

I think I will also do Douglas + Poplar. I'll eventually check out the recommended lumber store, and compare pricing, perhaps along with Maple, out of curiosity. I will research the relative weight and rigidity of these three woods, and any other recommended wood at some point. I hope I can eventually find the proper information.

 

[basspig]

Thank you very much indeed, mr. basspig.

I am leaning towards imitating your setup in regards to the false wall, er, frame.

I would ideally like to have my TH up front, and with something like what you did, I can move the frame out to access it. I will foresee having to access it very, very rarely, but I still will need access eventually.

I think I will also do Douglas + Poplar. I'll eventually check out the recommended lumber store, and compare pricing, perhaps along with Maple, out of curiosity. I will research the relative weight and rigidity of these three woods, and any other recommended wood at some point. I hope I can eventually find the proper information.

I think you will have no problems whether you go with maple or poplar for the sub frame. The important thing is to pre-select the wood carefully at purchase time, make sure there are no cracks and avoid knots, and look for dimensionally-straight pieces.

Couple things I forgot to answer from your previous post..

Blackout cloth.. I did indeed use it. I selected a polyester and spandex fabric that can easily be blown through, but blocks 85% of light transmission. That was stretched somewhat tawtly on the back side of the subframe before the CenterStageXD was applied. There are objects back there that would reflect light, like my tweeter arrays of brushed aluminum faces, so I wasn't about to take a chance with that.

On the rest of the 2x4 framework, I used felt where there are no speakers, at the top section over the screen, and filled some batts with rigid fiberglass for additional bass trapping. One of the benefits of the acoustic treatment I did before constructing this screen was that it improved my sound 90%. System went from sounding like a concert PA to more like some Wilson Sophias with all the frequency deviations from comb filtering just about banished.

Portions of the framework that have woofers behind it are covered with the thin spandex material, under the velvet drapes.

Frame is screwed together with 3" drywall screws, 3 on each joint where a stud meets another stud.

Finishing touches: I used small brass deadbolts and L brackets at the top of the screen frame and wall frame, to allow for easy unlocking of the screen for maintenance purposes. I put a small pull tab in the center top and friction holds it in place until I tug on the tab and pull it loose against the friction of felt sidewalls. In this manner, the 60 sq ft screen may be easily managed by one person.

I was going to link one of my Youtube theater in action videos, but I see Fox just blocked it (so much for Fair Use) because Avatar was the movie being shown.

Hope this helps..

 

[basspig]

Give this link a try.. it plays when I'm logged in to Youtube. See if it plays for you:

http://www.youtube.com/watch?v=jU93n1HrT5s&hd=1

 

[jostenmeat]

Thanks a lot for your tips and experiences. I am pretty certain it will now be maple for the screen.

I tell you what, after browsing a bunch of pics, the whole scope thing is bugging me again. May I ask which lens you landed, and from where, ebay perhaps? You fabricated your own sled, right?

Last night I looked at ebay, videogon, avs classifieds, etc, and did not see much at all.

The only brands I am even somewhat familiar with are Panamorph and ISCO. I'm pretty sure these can be very expensive.

I would fear skimping on glass, as I read differing stories about pincushioning or distotion etc; I have no idea about the bang for buck glass. Sometimes they say it's about 1" of pincushioning, and sometimes they say it's only really detectable with test patterns. I dunno.

It looks cool, but the main reason I think scope can be cool is that I can get more out of my lumens for the screen size. With 126" 16:9, I'm pretty sure I am right around the limit for my PJ, but with a scope + stretch . . . Hmmm.

I'll probably go 16:9 still, but I want to think about this before I begin in earnest. I am also now intending to paint a rather large black fade on the ceiling before construction of screen wall begins.

 

[basspig]

Although I built the screen to be somewhat future proof, being Cinemascope aspect, I could not afford a lens either, as it would cost more than my entire actual cash outlay for the theater upgrade.

I have looked at DiY projects using lucite wedges to make a cylindrical lens, but they are unweildy and prone to chromatic aberrations. So for now, until a deal comes along, it's 16:9 projection.

For the ceiling, why not build some 1x2 frames 48" square, fill them with rigid fiberglass and cover them with black cloth? That will serve both to kill secondary reflections of light and will improve sound imaging by eliminating most of the bounch and slap echo off the ceiling.

I built my own sled out of 1/4" plywood and drawer sliders. Could not see spending $600 for a sled that hangs down 8" from the ceiling. I have only 8' from the bottom of the carrying beam to the floor, so have to make the most of it. I made the panel and cutout for all the ventilation openings and mounted tracks on the beam and on the panel and bolted the PJ to the panel. Works a treat!

 

[jostenmeat]

OH, thanks for clearing up that misunderstanding. Using zoom method, there is no way my PJ could light up 2.35 AR with the size I was sorta predicting with a scope screen. 16:9 maybe, but not supersized 2.35.

Yeah, I've looked towards treating the ceiling, and even had pieces of tape up there for quite a while. Since I never went for it, I took the pieces of tape off. I have to admit, I was worried about how visually distracting they would be. I also did consider putting up ceiling traps after I did go ahead with the paint, and if I did it black, with black treatments, I'd have less to worry about in that regard. I've got quite a few traps, double digit, just none for the ceiling. I did have to remove a corner trap to fit in my sub at the back wall. Thanks again.

 

[basspig]

The traps on the ceiling are not distracting at all. Their blackness makes them seem to vanish into a void (at least they do in my configuration).

I definately prefer a proper lens to using the zoom method. And in the case of my projector, which needs a room 30-35' in length to produce large image sizes, zooming is not an option. Some innovation is needed to find an economical alternative to Cinemascope lenses.

 

[jostenmeat]

The traps on the ceiling are not distracting at all. Their blackness makes them seem to vanish into a void (at least they do in my configuration).

I definately prefer a proper lens to using the zoom method. And in the case of my projector, which needs a room 30-35' in length to produce large image sizes, zooming is not an option. Some innovation is needed to find an economical alternative to Cinemascope lenses.

At the risk of understanding nothing that you may explain to me here, therefore wasting your time, I still gotta ask:

What kind of innovations have you come up with to use your rig with a scope screen, without use of either zoom or lens?

You have some processor that has multiple memory settings? Each with their own discrete calibration settings? What in fact do you use for a CMS/processor, if you are even implementing one? Thanks.

edit: while I haven't heard your techniques, I think I did talk myself (yet again) out of the scope lens. Of course there's the cost, but I wonder how often the menu bar is "off screen", and even worse would be when subtitles are offscreen. Then there's that one movie called The Dark Knight, haha.

 

[jostenmeat]

Update:

I bought the entire remaining roll of speaker cloth at Joann's, for $71. About 9.5 yards x 54". I have no idea how well this will work, or if I could find something else that might be more light absorbent, or have less sheen, while performing just as well in regards to being AT.

My driver, xover, and feet for my PSB arrived at my dealer today. I hope to stop by this afternoon.

I checked out various woods with my friend for the screen frame. He is thinking overkill, and I'm going along with it. I think it will be the buffest screen frame ever. I think the border is going to be 5", and 5/4 thick. We have set aside Phillipine Mahogany that the store is holding for us to purchase later this week. We wanted maple, but we couldn't find the right lengths that were straight enough. The PM was said to be very inert and straight or something, according to an employee that my friend trusts. IIRC, the straightest board we got might be 17' long!

Next to-do items will be ordering screen fabric, black paint, and shopping for Douglas Fir at a different location (a cheaper place).

 

[GO-NAD!]

.....3. Is there a preferred method of mounting the screen to the false wall? I hope to place my monster Danley sub's mouth below the screen to reduce the chances of pushing the screen back and forth (and I remember basspig had to specially secure his own for his certifiably insane system). But, it is a very slight concern. OTOH, I don't want it so tightly fastened that any possible future warping of the false wall would twist my frame. Oh, I don't know, someone enlighten me.

Hey JM. Just wondering if you had come to any conclusions on these issues. I'm still in the middle of my room reno, but the end result is never very far in the back of my mind.

I plan to build a couple of subs, using Dayton RSS315HF drivers and setting them on top of a component stand, behind the screen. I figure that with the enclosure dimensions, the drivers/ports will be a maximum 6" behind my screen - probably a couple of inches closer. Do you (or anybody else) think I should be concerned about pulsations in the screen? If it's a definite possibility, I think I would just make the component stand narrower and set the subs on the floor on either side, so that the drivers are firing through the false wall, rather than the screen.

 

[jostenmeat]

Hey JM. Just wondering if you had come to any conclusions on these issues. I'm still in the middle of my room reno, but the end result is never very far in the back of my mind.

I plan to build a couple of subs, using Dayton RSS315HF drivers and setting them on top of a component stand, behind the screen. I figure that with the enclosure dimensions, the drivers/ports will be a maximum 6" behind my screen - probably a couple of inches closer. Do you (or anybody else) think I should be concerned about pulsations in the screen? If it's a definite possibility, I think I would just make the component stand narrower and set the subs on the floor on either side, so that the drivers are firing through the false wall, rather than the screen.

GO-NAD!, smart of you to wonder about as many things as possible. Well, I am now +90% sure I am not going to put my monster sub behind the wall after all. The sub is so large, that I now worry about any funky imbalance that comes with the diffraction (or lack thereof) effects of essentially having a "wall" (read sub) between only two of the speakers. (Yeah, it's that big.)

The sub is actually serving as a convenient (if weird looking) piece of furniture. It serves as sort of this long bar that various movie titles are strewn on top of at times, remote, sometimes other things (never drinks, and sometimes I have to remind guests lol).

Lastly, while I can just get away with having the large mouth be unobstructed by the framing, if I ever change to more conventional subs, this would no longer be the case. I'm sure the effects are probably minimal, but anyways . . .

It is generally known not to have your sub drivers firing into your screen. That said, I'm sure you have seen basspig's system, so . . . well, I think he had to do something about the violent slapping of the screen or something, but I've been wrong about his system before, so I would read his thread if I were you.

I used to have a screen that shook more than it does now, and that's because my PJ used to simply sit on a bookshelf. The sub would shake the bookshelf, which would shake the pic. This effect was not as horrible as one might expect, at least at times, because it kind of increased the overall effect that something "earth moving" was going on. However, having it both ways, I definitely prefer having the accurate (non-shaking) picture.

Oh, I've been on a learning curve with paint (among many learning curves). I used Behr Mouse Ears paint on the ceiling, and if I did it all over again, I would try either Moore or Rosco. The Behr even as flat/matte is more reflective than I hoped for. So, even if you won't go black, but a mid color so to speak, read up on it, and get as many samples however you can, paint em all side by side on a board, and check out the reflectivity under a light source. I went with the Behr because it is said to be easier to apply, easier to touch up, cheaper, and at least one person said it performed as well as some other aforementioned products. I no longer believe that opinion, though. However, I will leave all alone for now.

For my present situation, the PM wood is still wrapped at the store. I believe the screen material arrives at the end of this week. I have Ook framing hooks arriving any day for the mounting of some panels directly on the front wall. I will be camping yet again this weekend, and the weekend after is likely shot as well, so this may very well be a very drawn out project, although if the cards are all played right, it could be done in a single weekend perhaps.

 

[jostenmeat]

I'd like to add that access to the sub behind the wall would be a major pain, and to ever remove the sub, I'd have to remove the entire false wall to do so. Then, to be more specific in my response to your query, yes, I'd say narrower component stand to have subs at floor. You might be able to use the subs as the speaker stands themselves, depending, I forget what's all being included.

 

[basspig]

At the risk of understanding nothing that you may explain to me here, therefore wasting your time, I still gotta ask:

What kind of innovations have you come up with to use your rig with a scope screen, without use of either zoom or lens?

You have some processor that has multiple memory settings? Each with their own discrete calibration settings? What in fact do you use for a CMS/processor, if you are even implementing one? Thanks.

edit: while I haven't heard your techniques, I think I did talk myself (yet again) out of the scope lens. Of course there's the cost, but I wonder how often the menu bar is "off screen", and even worse would be when subtitles are offscreen. Then there's that one movie called The Dark Knight, haha.

I haven't dealt with the cinemascope issue for now. I'm waiting for a few years to tackle that. Maybe then, LED projectors will have 5000 lumens and have a variety of options for making the conversion in formats automatic. Maybe not. Who knows? A lens is indeed more costly than a lot of entry level projectors. For now, we just live with letterboxed playback. The area is large enough that it is not distracting when watching a movie. But the perfectionist in me would like to see it fill the entire screen. Oh well, one day in the future perhaps.

 

[GO-NAD!]

I'd like to add that access to the sub behind the wall would be a major pain, and to ever remove the sub, I'd have to remove the entire false wall to do so. Then, to be more specific in my response to your query, yes, I'd say narrower component stand to have subs at floor. You might be able to use the subs as the speaker stands themselves, depending, I forget what's all being included.

Yeah, the more I think about it, the more I feel that it would be prudent to put the subs on the floor, so that they aren't directly behind the screen. I was initially leaning towards the wide component stand, with subs on top, so that I could incorporate some drawers for DVD/BDs. Maximize space usage in other words.

If the stand is narrower (about 3'), I will still have room for some drawers, so it's not major crippler. Thanks for the input.

 

[dapack69]

1) If you want a smoother black fabric, go to JoAnn fabrics- they have a grill cloth that's a lot more refined looking than that rough stuff that was so prevalent in the '90s. Also, Parts Express sells some but it's expensive compared with the stuff at JoAnn. What you really want right next to the screen is velvet. That reflects a lot less light than just about any other fabric and is what all of the fixed screens have on the frame.
.

If you want a smoother black fabric, go to JoAnn fabrics- they have a grill cloth that's a lot more refined looking than that rough stuff that was so prevalent in the '90s. Also, Parts Express sells some but it's expensive compared with the stuff at JoAnn. What you really want right next to the screen is velvet. That reflects a lot less light than just about any other fabric and is what all of the fixed screens have on the frame.

Why you going around copying and pasting what other people wrote?

 

[jostenmeat]

We finally acquired all of the wood, and cut everything yesterday. I am pretty excited. We cut rabbits into the entire screen back outer edges, so that it will fit snugly into the framing (we're still going to fasten very well of course). Wood splines for the corners. No extruded metal for the screen spline, but just instead bought the thickest rubber spline they had at HD (too bad they didn't carry solid spline, but the hollow stuff still seemed to be extremely firm). It's all now in the garage, waiting for the day for my friend and I to be free on the same weekend. The false wall's vertical supports have rabbit cuts too, so that the longest horizontal boards will fit into them, and strengthen it all since the boards are running perpendicularly (sorry I can't explain better). Maybe I have energy to post a pic or two now. Anyways, I've never been on wood cutting tools for this long in my life, and particularly such nice ones. His table saw fence is worth $850? Well, most of my work was involved with the chop saw, rabbit cuts, planing. It was a lot of fun, and I learned a heckuva lot, and I am extremely appreciative of my friend. He did all of the spline cutting, for both corners and screen dados (he probably would have walked me through these too, and explained all the whys, if time permitted). We don't know which method we will use to pull on the crowns/bows of the inner vertical boards; we might use a cable pulling outwards, for minimal blockage of speaker (it will be very strategically placed). I'm wondering if my friend is just overkill, though I trust him, because at least a couple of the vertical boards that I picked out were pretty darn straight.

OK, a few after all. Trucking the 17ft long and shorter PM boards to the shop. (We picked up the Doug Fir later that day).

Rabbit cuts on the PM screen frame.

Angled corners with screen spline dados.

Waiting to be installed, wrapped and/or covered.

 

[GO-NAD!]

That's some nice looking wood. They look rather large for a screen frame. What size is your screen going to be?