# New build



## Jack N (Oct 7, 2006)

I’m in the process of building a home theater in my basement (mostly a dedicated theater but will be used occasionally for other functions) and I’m quite concerned about how I’m going to control the acoustics because of the overall shape and having all the wrong things in all the wrong places like windows on one side, a hallway on the other, and speakers in the corners. I can’t eliminate the hallway or change the layout because of support walls, and I don’t want to eliminate the windows (windows will have heavy curtains that open and shut when needed). I’d like to use a layer of plywood (for strength purposes to hold some heavy items that I’ll be hanging on the walls) followed by green glue and a layer of sheetrock. I plan on hanging sound traps on some of the walls however I doubt that’s going to be enough. I’m looking for suggestions. I've attached a rough sketch of the layout. The blue lines represent windows.


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## ajinfla (May 10, 2009)

What audible problems are your ears perceiving now?
Are the speakers literally "in the corner"?
Where are the subs?

cheers


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## bpape (Sep 14, 2006)

He's in the process of building. 

Are you looking for interior sound quality of isolation or both? You mentioned some asymmetric issues but then went into plywood, green glue, etc.

Understand that if you're doing isolation, you'll need to do basically the entire basement including hall, use all solid core doors, etc. If you were to use a solid door and decouple the walls of the area, you could just to the theater/concession area and get good isolation at a much reduced cost/labor.

The screen end of the room isn't bad at all once you close in the doorway. 

How big are the windows? Are they just typical small, higher up basement type windows or more full height ones like you'd have in a walk-out?


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## Jack N (Oct 7, 2006)

You are correct Bryan, this theater is in the process of being built. When I started there was absolutely nothing down there except for support walls and at present all the walls are studded and I’m just about ready to start with the wiring.

I am concerned only with the sound quality within the theater – primarily reflections and an even response throughout. As far as sounds outside the theater go, I don’t care about what sounds leave but I am concerned about sounds entering, mainly from the mechanical room. I have a gas forced air furnace and a gas water heater that is literally 3 times noisier than the furnace. I’ve never heard one that loud before.

I would like to sheetrock the mechanical room to help with sound but that’s going to be very difficult at best. It’s really hard to reach around the furnace, hot water heater, water softner, etc. because everything is jammed in there so close together and then if you manage to do that you still have to contend with all the pipes and ductwork. It’s about as close to an impossible task as you can get without literally ripping everything out so I rather doubt that’s going to happen.

Yes, I am planning on using solid 6-panel doors. There will not be a door that leads from the theater to the hallway, just a walk thru.

I gave some thought to having decoupled walls but I’m afraid that the theater will get to be too narrow. I’d really like to have 5 seats across but I think I’m going to have trouble getting 4 in the way it is.

All of the windows are 44” tall. The two windows closest to the screen end are 56” long each and the window on the far end is 84” long.


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## Jack N (Oct 7, 2006)

Anyone? Am I out of options?


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## bpape (Sep 14, 2006)

So the mechanicals are up against what? Foundation? Load bearing wall? Got a sketch/plan?


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## Jack N (Oct 7, 2006)

Sketch is in the original post. The furnace etc. is near the stairway.


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## bpape (Sep 14, 2006)

Sorry. Duh. :duh:

Just insulate the walls the best you can and cover with netting. That will do mids and highs. Then double drywall the outer wall and make sure to use a solid door.

Yet another reason to have a door where the open archway is.... :innocent::whistling:


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## Jack N (Oct 7, 2006)

Ok, thanks.

Is the netting you're talking about something special or do you mean just to use something to help hold the insulation in place?

The sound system will be somewhat stronger than most in that it will have multiple subs and the speakers will be powered by multiple amps. What would you recommend for the theater itself? Would sound panels be enough? Would you recommend bass traps? If so what placement would you recommend?


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## bpape (Sep 14, 2006)

Just something to hold the insulation in place but without having to use faced insulation.

http://www.homedepot.com/p/Tenax-4-ft-x-330-ft-Black-Insulation-Netting-411093/100384035

For the theater itself - again, we were talking about isolation, now we're talking about panels which will do nothing for isolation. They're purely for internal sound quality. What you need in the room has little to do with the power of the system. Bass control will be needed to bring decay time into expected and desired parameters. Reflection control on side walls and front wall too. Then more a matter of addressing any specific issues.


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## Jack N (Oct 7, 2006)

Back again. Haven’t had much of a chance to work on the theater lately. But since the last post I’ve found a product called Roxul Safe & Sound which has much better sound absorbing qualities than regular fiberglass insulation. Apparently its’ only function is to control sound as it’s not thermally rated at all. I plan on using it in the walls of the mechanical room. Combine that with double layers of sheetrock, solid doors, and weather stripping around the door, and that will be as good as I’ll be able to do to isolate the noise from the mechanical room. So hopefully this will be the end of the isolation concerns.

Now for the sound within the theater. Although I hate to get rid of windows, I think it will help a little bit with the acoustics (and a lot with the lighting). So I’ve contracted a carpenter to take out the two windows closest to the screen and wall in the openings. Weather permitting, that should happen within the next week. I’ve also decided to put in a proscenium and an acoustically transparent screen to hide the speakers. I’m deathly afraid of how the theater will sound because of the two drastically different surfaces on the left and right sides. I’m thinking the left side will be considerably more dead than the right because of the opening to the hallway (I know I should put in a door there but really don’t want to unless there’s just no other way around it) and because of the equipment rack. The equipment rack will have speaker cloth doors on the front and nothing on the back of the shelves (so it’s easy to get at the connections) so I’m thinking the sound will go thru the rack and into what will essentially be a small room where the sound waves will dissipate. So basically, there won’t be any first reflection point on the left side, only the right. By using sound traps on the right wall, will I be able to totally eliminate the first reflection point? Will I be forced to install a door for the hallway? Any other ideas?


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## bpape (Sep 14, 2006)

Actually the hall and the small room behind the rack do 3 things that aren't great.

1. It increases the volume that the subs have to try to pressurize.
2. Each of those other areas has it's own set of modes and then combinations that mix with your main room.
3. Re #2, those resonances will be heard but in a delayed fashion in the main space.


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## Jack N (Oct 7, 2006)

So it sounds like even if I put a door on the hallway, I’m still going to have a serious problem with the access way behind the equipment rack. Correct? If so, would solid doors on the back of the equipment rack help, or would it make for a source of multiple delays? Do I need to consider a redesign?


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## bpape (Sep 14, 2006)

A door to the hall and a door on the back of the cabinet will eliminate the issues, make the room easier to pressurize, and provide better isolation.


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## Jack N (Oct 7, 2006)

Thank-you for the advice Bryan. It’s not quite what I wanted to hear but it makes sense. At least now I’ll have more confidence in how the system will sound.


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