curved walls/ceilings

gravikords · Post by **gravikords** » Sun Aug 08, 2004 12:52 pm

I haven't seen any questions reguarding the use of curved walls or ceilings in studio construction, any thoughts? I know they are a pain to construct, but was just wondering about thier acoustic properties . Also what is a good way to connect floated walls? It seems that if I were to build two seperate walls, I wouldn't want to attach the inside wall to the outside one if the outside wall was attached to the ceiling and floor joists! I plan on using r.c. on the ceiling.
One last question, since I didn't float my raised floor , could I somehow float my wood flooring (3/4") maybe on 2x4's laid flat??

cadesignr · Post by **cadesignr** » Sun Aug 08, 2004 2:21 pm

I believe concave surfaces will focus reflections, convex will diffuse them to an extent. Hence cylindrical diffuser use in studios. Size of the radius is probably relevant to the diffusive qualitys. From my understanding the size of reflective surfaces have a relationship to
wavelengths too. You are absolutely right though. Difficult to fabricate curved walls, but not impossible, however, I don't think anyone would recommend them for thier acoustical qualitys as they are probably unpredictable, and perhaps a waste of time and money, but I'm not an acoustician. Rectangular rooms are highly predictable in respect to modal behavior and treatment, and I've seen a few that have curved clouds suspended from the ceiling.

fitZ

Innovations · Post by **Innovations** » Sun Aug 08, 2004 2:45 pm

Correct...concave focuses, convex diffuses.

Rather than trying to handle the hassle of a curved ceiling you might be better to go with some curved lexan clouds to prevent the ceiling and floor from being parallel

Aaberg · Post by **Aaberg** » Tue Aug 10, 2004 4:40 am

I'm building a studio that uses a round grain bin, 18 feet in diameter and 22 feet high as part of the building. Grain bins are readily available here.
The room has angled flat surfaces on 3 sides, going up 10 feet, then the round shape takes over. Once I covered the bin with urethane and cellulose foam, the sound is quite good, largely because I mainly record piano in there, but our main problem right now is building a wall within the wall, since the upper 10 feet of the room is cylindrical, and the ceiling is a cone.
Any suggestions appreciated! I'll be happy to let you know what the results are when we finish...pretty soon.

dymaxian · Post by **dymaxian** » Tue Aug 10, 2004 6:08 am

Another interesting thought I had is that if you can build the wall so that you're actually bending the drywall a little bit as you mount it, it'll make it much more rigid- theoretically helping the low freq TL. Any thoughts from Knightfly?

Aaberg · Post by **Aaberg** » Wed Aug 11, 2004 3:13 am

Found several things about building in the round. You can actually bend drywall by wetting it a bit so that the paper doesn't break when you apply it. I assume this doesn't hurt the integrity of the gypsum but I don't know. But that'd probably mean you'd have to space the studs a little closer than normal to get a truly round wall.
I found a builder in Kansas who put up a 45 foot grain bin for a farmer who made it into an office and scale house. It wasn't built to the sound specs we're all trying to get, but he's been helpful.
My problem now is this: I've insulated the inside surface of the bin with urethane foam covered with 2 inches of celluse foam (sprayed). I did that first because I was hoping it would do the trick. The manufacturer claims that gets up to 60 STC, but I was in there listening during a rain storm and it's definitely not near that. So, I'm not defeated, since I figured I MIGHT have to do wall/space/wall to get anything good, but I didn't think very far ahead. It's going to be tough to get the studs aligned over the foam, although acoustically, it'd be ideal, I think. The idea, then, is to get at least an 8" airspace by bolting studs through the foam to the bin, then apply drywall. I was thinking of mounting 703 on each piece of drywall before screwing it in, but that makes it tough to seal. Then I thought of putting blocks on the inside of the studs and mounting the 703 between the studs before putting on the drywall. Then sealling the 703 with Silicone II. This is pretty dang labor intensive, but it really looks great, and my hope is that it'll sound much like the space my piano's already in (the tabernacle of a former church, which unfortunately, doesn't belong to me). Any ideas?
Thanks.

Innovations · Post by **Innovations** » Wed Aug 11, 2004 5:30 am

if you want more than a very wide radius you may have to shop a little for it, but you can find thinner sheets of wallboard...1/4 inch and 3/8 inch...specifically for the purpose of using 2 layers instead of one making curved walls, and yes, you do damp them down.

cadesignr · Post by **cadesignr** » Wed Aug 11, 2004 8:13 am

Bending wet 1/4" gyp bd is a real pain. I've done it. the problem comes from lining up the edges on incorrectly laid out stud or joists. You don't know how it lines up untill you tack to each successive stud. A little too dry makes bending difficult for tight radii, and a little to wet lets screws pull right through. Large radii may be easier, but what I worked on was a nightmare. Never again. And THEN you have taping on a curved surface

. Of course, I'm not a sheetrocker, and was only helping. Still, for experienced rock
guys, I bet they charge double.
fitZ

Aaberg · Post by **Aaberg** » Wed Aug 11, 2004 9:01 am

Aha...thanks for that. We're considering installing the sheetrock at different angles to make irregular straight walls (this is along a curved wall) . Sort of a dodecatetragrammhedron I realize there is no science to my thinking on this and that the shape is unpredictable. Are some angles better than others? We're not going to bolt the studs to the walls as I mentioned before, but figured that we'd float the sill and basically have an almost free-standing wall. We'll fill the airspace with regular fiberglass insulation. Any ideas? Will send drawing.

cadesignr · Post by **cadesignr** » Wed Aug 11, 2004 9:34 am

Consider this. The more you distort the shape of a room, the less predictable its modal response becomes. Round rooms are probably the only worse case than a square room as the reflections are focused to one point, but I'm no expert, so take that with a grain of salt.

It seems like common sense to me, but acoustics never did pay attention to my way of thinking. Ha!

fitZ

Aaberg · Post by **Aaberg** » Wed Aug 11, 2004 9:45 am

That said, perhaps we should try and make the walls inside the cylinder as regular as we can on one side, then follow the 6 degree solution?

Bulls Hit · Post by **Bulls Hit** » Wed Aug 11, 2004 6:17 pm

Aaberg wrote:Found several things about building in the round. You can actually bend drywall by wetting it a bit so that the paper doesn't break when you apply it. I assume this doesn't hurt the integrity of the gypsum but I don't know.

Wetting gib, in my experience, can seriously weaken it.

I have a similar situation with my ceiling which will be curved.
My builder told me the easiest way to bend gib is not to wet or score it, but to leave sheets on blocks overnight so they slowly sag. The amount of sag can be controlled by how high you build the blocks off the ground. Can't overdo it obviously or they'll split.
In the morning you should have some nicely bent gib.

knightfly · Post by **knightfly** » Thu Aug 12, 2004 8:05 am

Posted some comments re this in aaberg's other thread - hadn't seen this one yet. One reason why I like it better when people don't start multiple threads on the same project...

Fitz is right about spacing of studs, it would be a real SOB - theoretically, you could figure this out on CAD as points on a circle, then do a "multi-hedron" by connecting line segments between studs and measuring those segments. Realistically, the only way I can think of to make this work would be to space the studs a bit tight, then trim the ends of each sheet to center on a stud. PITA for sure...

On top of which, Fitz is also right (Damn, twice in one post - Musta been all that repartee with the G.D. Englishman on that "other" board

) about the round room being worse than square - picture a room with two parallel, infinetly long, walls - now, feed all that modal energy into a convex reflector - now DUCK before it KILLS you... You didn't mention a diameter that I saw, but if this room is (say) 16 feet in diameter, you'd have modes at all multiples of around 35 hZ - kick drums have a shell mode of around 300 hZ, which is why you need to pull out a bunch of that freq to keep them from sounding muddy - with that 16' diameter room, add a sub near the wall for some REALLY crazy vibes.

Most I can say for this project is "better you than me"...

not that I'm giving up, it's all fun... Steve

guitarguy · Post by **guitarguy** » Sat Aug 14, 2004 5:44 pm

If you were working with a curved room would it make sense to do
something like this for the wall layout....

And for a ceiling I would think that a flat ceiling with deflective panels would work best for structure stability.

knightfly · Post by **knightfly** » Sat Aug 14, 2004 6:24 pm

I tried to design a 5.1 surround room like that last year, ended up in a "rubber room" long before I got the reflection paths to work...

Steve

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