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Steve's Theater - some construction questions

post #1 of 7
Thread Starter 
I'm about to start building my 12x20 room within a room theater in my basement (I've made a couple of other posts over the last couple of weeks). I'm not doing anything fancy other than the sound isolation; no stages, curtains or anything like that. But I do have a few questions that I need to answer quickly...

1. How important is it to make the room non-square? Easiest would probably be to make the ceiling a couple of inches lower at the front. Would that suffice?

2. I'm planning on 2x3 seating, with the rear row on a riser. What riser height is recommended (keep in mind that the ceiling is less than 7'5", so I can't go too high)?

3. Due to the location of a steel beam that runs the length of the house, one double wall of my theater will be about 10" between drywall sheets. Should I fill it completely with insulation, or will R13 on each set of studs (with a 4" air gap in the middle) be sufficient?

4. I'm building the new ceiling joists between the existing ceiling joists. I will be putting in unfaced R11 fiberglass between the existing joists. Is there any advantage to covering the existing joists with fiberglass, in addition to filling the spaces?

5. There is a heating pipe near the ceiling that will be exposed in the completed project (it would be too much work and expense to move it). Where the pipe goes through the ceiling drywall, how should I seal it? Should I cover the pipe with fiberglass pipe insulation (which can be painted to match the ceiling)?

More questions as I think of them. You guys have been great so far.

Thanks,

Steve
post #2 of 7
Quote:
Originally Posted by swechsler View Post

I'm about to start building my 12x20 room within a room theater in my basement (I've made a couple of other posts over the last couple of weeks). I'm not doing anything fancy other than the sound isolation; no stages, curtains or anything like that. But I do have a few questions that I need to answer quickly...

1. How important is it to make the room non-square? Easiest would probably be to make the ceiling a couple of inches lower at the front. Would that suffice?

2. I'm planning on 2x3 seating, with the rear row on a riser. What riser height is recommended (keep in mind that the ceiling is less than 7'5", so I can't go too high)?

3. Due to the location of a steel beam that runs the length of the house, one double wall of my theater will be about 10" between drywall sheets. Should I fill it completely with insulation, or will R13 on each set of studs (with a 4" air gap in the middle) be sufficient?

4. I'm building the new ceiling joists between the existing ceiling joists. I will be putting in unfaced R11 fiberglass between the existing joists. Is there any advantage to covering the existing joists with fiberglass, in addition to filling the spaces?

5. There is a heating pipe near the ceiling that will be exposed in the completed project (it would be too much work and expense to move it). Where the pipe goes through the ceiling drywall, how should I seal it? Should I cover the pipe with fiberglass pipe insulation (which can be painted to match the ceiling)?

More questions as I think of them. You guys have been great so far.

Thanks,

Steve

1. I think the general recommendation would be to avoid it if at all possible, but your dimensions above are already non square. Re-reading your post I think you may mean not having all the walls parallel. That would be a great question to post in the accoustic thread, but I think in general most people just build it square and use room treatments.

2. There is a post for a riser height calculator in the forum. Just plug in your room dimensions and you should have your answer.

3. I think you should be good to go and the air gap will probably help you.

4. My guess on this one would be probably not, but I would differ to those who know more than myself.

5. Can you just build a soffit around it? Is it a pipe or duct? A picture might help others chime in on this one also.

Best of luck with your project.
post #3 of 7
Thread Starter 
Hi, thanks for your response. Some more comments:

1. Yes, I was talking non-square in a carpentry sense...since I haven't started framing yet it's easy enough to do it, and less expensive than adding room treatments later...

5. A soffit is a good idea, thanks...I will only lose a few inches of headroom, and only against two walls. Much nicer than a painted pipe.

Steve
post #4 of 7
Quote:
Originally Posted by swechsler View Post

I'm about to start building my 12x20 room within a room theater in my basement (I've made a couple of other posts over the last couple of weeks). I'm not doing anything fancy other than the sound isolation; no stages, curtains or anything like that. But I do have a few questions that I need to answer quickly...

1. How important is it to make the room non-square? Easiest would probably be to make the ceiling a couple of inches lower at the front. Would that suffice?

2. I'm planning on 2x3 seating, with the rear row on a riser. What riser height is recommended (keep in mind that the ceiling is less than 7'5", so I can't go too high)?

3. Due to the location of a steel beam that runs the length of the house, one double wall of my theater will be about 10" between drywall sheets. Should I fill it completely with insulation, or will R13 on each set of studs (with a 4" air gap in the middle) be sufficient?

4. I'm building the new ceiling joists between the existing ceiling joists. I will be putting in unfaced R11 fiberglass between the existing joists. Is there any advantage to covering the existing joists with fiberglass, in addition to filling the spaces?

5. There is a heating pipe near the ceiling that will be exposed in the completed project (it would be too much work and expense to move it). Where the pipe goes through the ceiling drywall, how should I seal it? Should I cover the pipe with fiberglass pipe insulation (which can be painted to match the ceiling)?

More questions as I think of them. You guys have been great so far.

Thanks,

Steve

Hi Steve I am no theater expert by any means but I am a union carpenter who does alot of basement finishing on the side. I dont know anything about movie roon sizes or requirements so I will just comment on your construction questions.
1: I dont know if non square is better but if you "splay" ceiling you might want to find your maximun height you can get of your back riser and measure the same distance of the ground from the front of the room so it actually follows the angle of the stairs. You might want to use an accoustical ceiling system as it will be alot easier to run any future wires. Fish em up the wall run em thru the ceiling to wherever and fish em back down the wall. Trust me if you sheetrock the ceiling and want do do something down the road you will wish you had done accoustical

2: I wousnt go anymore than a foot then cause you will only have a 6.5 ceiling height and thats pushing it!!

3: You dont need a double wall!! You will lose valuable space!!!!! Just line the wall up so it is flush with one side of the beam so the drywall will pass oby it and on the other side of the wall hopefully outside your room you can leave it exposed or just soffit it tight

4: R 11 is not gonna do to much sount attenuation!! your better of with a R-30. R-11 is only for 2x4 walls and you insulating floor joist which are prolly at least 2x8s if not 2x10s or 12s so you can put more insuation in the cavity giving you more R value and better sound control. If you already have the R-11 you can double it up.

5 if its a hot water pipe then I would insulate it as it should be already. otherwise do not!! Can you get away with lowering the new ceiling to cover it so you dont have to soffit it?? Is so thats what I would do if not just a simple board framed soffit


Good luck PM me with any construction questions. Not electronics questions as I am new to all that
post #5 of 7
Thread Starter 
Thanks for your response, Dhark, but it appears that you may be unfamiliar with sound isolation techniques. A double wall is one of the easiest ways to isolate your theater (I am doing double walls plus a double ceiling, thus a "room within a room". This has been well documented by several people here).

To respond to your points:

1. Since I still haven't framed out the interior walls or ceiling, I'm hoping if someone can tell me if I should do them "out of square" to reduce standing waves. It'd be better than having to deal with sound treatments later...if it works, that is...

2. I was thinking more like 6-9". A foot is definitely too much...

4. The idea of the R11 between the joists is to dampen any sound that escapes the inner wall. It's not really for isolation per se (correct me, any acoustics experts).

5. I'm going to soffit the pipe, it's going to require about a 6" drop, which is something I can't afford to lose from this already low ceiling...

Thanks again.

Steve
post #6 of 7
Room dimensions are important, but it is only one piece of the puzzle. Just because you have successfully achieved a proper room dimension and sound isolation techniques will not mean you will have good acoustics in the room. There are many other factors that contribute such as proper speaker placement, seating placement, RT60 issues, parametric equalization, dynamic range, proper sightlines, HVAC and electrical considerations NC ratings to achieve a smooth frequency response of the room.

In addition, the use of fiberglass insulation in walls alone will do a reasonably good job in absorbing higher frequencies, but will do nothing for the lower end below 250hz. In fact a standard residential room has a noise floor of 30db. Reference level for music and cinema ranges from 85db to 105db. Required transmission loss for proper sound isolation in this instance is 55db. A standard 2x4 wall with fiberglass insulation and half inch sheet rock nets a 30db transmission loss. You will be short 25db!
post #7 of 7
Thread Starter 
Hi Marc,

I know that making the walls off-square is not a panacea for perfect room response. What I was basically asking was if it was a reliable way to eliminate standing waves...

Steve
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