Home Theater Soundproofing

[Paul H]

I've got my new home under construction which will have space for a home theater in the 17'x24' range when it's completed. The room will be in the basement of a bungalow, in a corner (2 exterior concrete walls).

I'm looking for very good soundproofing - think reference level home theater playback creating a faint occasional murmur upstairs.

What have you used to soundproof your home theater (walls and ceilings), and how well did it work?

Thanks,

[---k---]

I haven't done anything, but a while ago I spent a lot of time in AVS's dedicated home theater construction forum. It seemed like the biggest bang for the buck came from double layer dray wall. It is all about mass to stop the sound. That and attention to all the potential sources for leaks.

How much effort are you looking to extend? There is always things like resilient channel, and the Green Glue between layers of dry wall is supposedly really good, but I have my doubts.

[joecarrow]

I think that Art Ludwig's page is mandatory reading for this sort of question. If you've seen it before, now is a good time to revisit it. I know I've gone through it on more than one occasion.

http://www.silcom.com/~aludwig/

The really key thing, as far as I have read from his and other sites, is to build box-within-a-box construction with staggered studs, then fill the void with fiberglass. Obviously ventilation requires special consideration.

[Chris D]

I wrote an entire series of magazine articles about how to do this. It definitely depends on how in-depth and how much work you want to put into it. The first question is whether you're willing to rip out your current theater sheetrock walls or not. If not, you're pretty much looking at slapping another layer of drywall, and that's it.

(Paul, I just re-read your post... since it's a new construction, you haven't built the room yet, though?)

[Paul H]

Thanks for the responses.

(Paul, I just re-read your post... since it's a new construction, you haven't built the room yet, though?)

The room currently gets really wet when it rains It is new construction. The foundations are in and we're just starting framing. I'll be doing the home theater as a separate fit-up after we move in. It will be a dedicated theater built to a fairly high standard, including double stud and double drywall walls & ceilings if that's what works.

[AJINFLA]

Several of these on (high mass) 4 leg stands an inch off the side walls and raised (with the speakers facing the floor) so that the rear is about 3' from the ceiling.
Cardioid subs

Or, dipole towers on side walls with force cancelling arrangement (Linkwitz W or compact W "ripole") close to ceiling but with enough gap to direct null upwards.

Vertical Dipoles for all channels.

cheers,

AJ

[Dennis H]

The really key thing, as far as I have read from his and other sites, is to build box-within-a-box construction with staggered studs, then fill the void with fiberglass.

Yup. Actually double 2x4 walls with a small space between them is better than the common practice of using 2x6 top and bottom plates with staggered 2x4 studs because a lot of sound can go through the plates. Same thing with the ceiling. Basically try to minimize any solid mechanical connection between the inside and outside layers.

[joecarrow]

I think you'll also be extremely satisfied with the result of noiseproofing the theater room when you notice the decreased noise floor. I have the opposite problem- a commuter train goes past my window, and as a result I sometimes hear that instead of the quiet parts of whatever I'm listening to.

If you hadn't already thought of it, now's the time to consider building a closet or other way to hide away all of the amplifiers, servers, etc that could make noise in your theater room. You'll really thank yourself when you're done. For the sake of ventilation, it might be best to build the closet outside of the soundproofed area and run the cables in through gaskets.

[Paul H]

Thanks again for the info. Note that I am currently interested most in soundproofing - sound quality on the interior of the room is a different matter which I will get to in the future.

I've got the closet for equipment already - it's a 5'x10' alcove at one side of the room that isn't otherwise accessible or good for anything else but will be a great walk-in closet for equipment and media storage. :T

So what does one do to mechanically isolate the ceiling - metal track supports, wire hangers ..?

[Gir]

Just curious, will there be room for an IB?

[Dennis H]

So what does one do to mechanically isolate the ceiling - metal track supports, wire hangers ..?

Best choice, if you have room, is separate ceiling joists that don't touch the floor joists above. They don't need to be all that big because they only hold up the ceiling materials, not the floor loads from above.

Edit: that's only considering isolation though and assuming you'll use drywall or some hard material on the ceiling. But you'll get better SQ in the HT if you use acoustic tile and stuff the space above with fiberglass, letting the whole thing act like a base trap. But, if you do that, sound will get through to the floor above and there's really no point in doing the double layer. Choices.....

[Paul H]

Just curious, will there be room for an IB?

We're aiming for a Thomas-approved theater here, so yes ..

I'm planning to build a couple of ~ 24"x24"x9' high boxes to mount subwoofers in flush to (behind) the front screen wall. These "boxes" will likely be built as a typical wooden stud wall with an extra layer or two of drywall, osb and some x-bracing.

A 36 cubic foot box will provide approximately 10X the Vas for two 18" drivers per side ...

[Scottg]

Thanks again for the info. Note that I am currently interested most in soundproofing - sound quality on the interior of the room is a different matter which I will get to in the future.

the 2 aren't necessarily exclusive..

The number one thing to do is:

seal the room.

Make sure all sheet rock is "taped & floated" well. That the floor is physically connected to the sheet rock via silicone caulk (..higher grade that is more compliant is better). Of course this means using extraordinary measures with doors to seal the room properly (..and don't forget in-wall speakers).

The next thing you concentrate on is:

keeping the room from acting as a loudspeaker.

Walls that vibrate are a "no-no". The best method is to use at least a double layer of sheet rock with a compliant layer between them. The non-commercial suggestion I recommend is to use the cheapest version of "soft" carpet padding available in your nearby home improvement store. Use spray adhesive, (wearing a mask while spraying), on the first layer of sheet rock that has been taped and floated and sealed. Then *carefully* apply the foam padding to the walls and ceiling. Make sure that the padding is at least 2 inches from contacting the floor and use that same silicone caulk - applied by finger lightly - to the bottom edge of the padding (i.e. you don't want potential moisture wicking up through the padding and creating mold). Next, spray more adhesive on the padding. Then glue the next layer of sheet rock to the padding. Finally, tape, float, and seal the sheet rock. This method works better than commercial "equivalents" largely because commercial products are concerned with the depth of the resulting wall and as a result use a VERY thin compliant layer that doesn't work as well, (..and also because you aren't nailing/screwing one board to the next).

Note than an "in-wall" loudspeaker (particularly an IB sub) compounds the sound transmission problem - EVEN if the speaker utilizes its own enclosure. Here you are once again concerned with transmission from the box walls, assuming you have them (an enclosure that is), to the wall cavity. A 1/4 inch + of that same "lossy" caulk covering that box enclosure, (completely), can work wonders (..especially if you have a higher weight covering connected to that caulk - like lead sheeting).

Anyway.. good luck! :T

[cobbpa]

Very cool thread, I was going to be posting similar quesitons soon as I'm hoping my parents start converting a basement room of ours into a theater. It also has 2 concrete walls and will have 2 sheetrock walls. A couple of things I had thought of before & I still wonder about while reading this thread:

When doubling up drywall, or for that sandwiched layer of carpet padding scott wrote about, would the bottom drywall layer or carpet padding be more effective if the (sort of) stiff fibergalss product was used? I believe it's OC 703 I'm talking about. Or is the mass of the drywall more effective?

This stems more by my inexperience with construction, but for ceilings, how much height would be lost in adding a 2nd set of joists to attach to? 3 inches? 6 inches?

What about doing a sheetrock ceiling on a 2nd set of joists and then gluing acoustic ceiling panels to that--best of both worlds, or more trouble than its worth? Maybe gluing instead of hanging the panels negates some of their upside though.

What about doors? Is it best to use a standard one and really try to deaden / seal it, or to try & sandwich several layers of drywall together and make it fit the doorway very tightly? I saw something like this in a wine cellar once, the guy had a really thick door to seal it off and it made me think of home theater applications.

Paul, sorry if you see this as a hijack, but it's so similar to the thread I was going to start that I thought I'd throw in some of my own questions! Hope you don't mind.

[Scottg]

Very cool thread, I was going to be posting similar quesitons soon as I'm hoping my parents start converting a basement room of ours into a theater. It also has 2 concrete walls and will have 2 sheetrock walls. A couple of things I had thought of before & I still wonder about while reading this thread:

When doubling up drywall, or for that sandwiched layer of carpet padding scott wrote about, would the bottom drywall layer or carpet padding be more effective if the (sort of) stiff fibergalss product was used? I believe it's OC 703 I'm talking about. Or is the mass of the drywall more effective?

This stems more by my inexperience with construction, but for ceilings, how much height would be lost in adding a 2nd set of joists to attach to? 3 inches? 6 inches?

What about doing a sheetrock ceiling on a 2nd set of joists and then gluing acoustic ceiling panels to that--best of both worlds, or more trouble than its worth? Maybe gluing instead of hanging the panels negates some of their upside though.

What about doors? Is it best to use a standard one and really try to deaden / seal it, or to try & sandwich several layers of drywall together and make it fit the doorway very tightly? I saw something like this in a wine cellar once, the guy had a really thick door to seal it off and it made me think of home theater applications.

Paul, sorry if you see this as a hijack, but it's so similar to the thread I was going to start that I thought I'd throw in some of my own questions! Hope you don't mind.

Good questions!

1. The drywall is more effective (even considering the higher density grades of the 700 series), and it costs less to.

2. A second set of ceiling joists depends entirely on what you want as long as a two joist system isn't required mechanically for support.

3. Ceiling panels - see number 1.

4. Really good question -

A. use an exterior grade door, door frame, and sill combination - that has a good seal for the door. Usually the door is steel with a foam core, (make sure it has a foam core), and the sill is aluminum. The sill must be dampened (filled with the same silicone caulk) if its the typical hollow aluminum versions. Use a thin poly based padding below the sill to isolate it somewhat from the floor (a scrap of wood flooring sound padding does the trick nicely).

B. physically position the door to the "exterior" wall (..the interior portion being the HT room). Because the "interior" wall "extras" add to the walls depth , and because of the door mounting, the door should appear recessed from the "interior", and normal from the "exterior". Make sure that no section of the interior wall paneling touches the door frame (i.e. leave a small gap). You'll fill that gap with caulk. The extension can be hidden with some molding, but again - make sure the molding is applied so that it isn't rigidly connected to the door frame. (..I know - clear as mud. )

One final thing I should have mentioned before..

Stay away from traditional lighting fixtures that cut into ceilings. "Pot" lighting is horrible - acoustically speaking. Instead consider track lighting where only a small hole is needed for wiring. Also consider AC venting and wrapping ducts considerably more than you normally would (..also don't use metal plates - use plastic instead). Of course any holes you cut (like lighting, wall plates, AC, etc.) should also have caulking around them to seal the room.

[KJP]

Master Hnadbook is the best $26 you can spend on this project.

[Paul H]

Good info gang, keep some ideas coming - I'll check that book.

I'm still not sure on the ceiling. I want/need the sound isolation so I can't go with an acoustic tile only. Framing a new ceiling under the ceiling joists would require (educated guess) 2x6 framing, costing about 8" of headroom that I'm not anxious to give up.

Has anyone insulated the joist space and installed double drywall? If so, how were the results on the floor immediately above?

Thanks,

[cjd]

If you do the ceiling right you do not have to drop it more than an inch or two below the normal ceiling. But that assumes no drywall on the "real" ceiling, and the new ceiling has the beams oriented the same way and floated up into the space between joists.

C

[Paul H]

If you do the ceiling right you do not have to drop it more than an inch or two below the normal ceiling. But that assumes no drywall on the "real" ceiling, and the new ceiling has the beams oriented the same way and floated up into the space between joists.

C

Interesting ... :T

[howburger]

I skimmed my previously existing 5/8" drywall with mud and sanded, primed and added another layer of 5/8" with 2-3 tubes of Green Glue per sheet between layers. I also added a pre-hung solid core door with positive weatherstripping all the way around, not just the sweep at the bottom. I caulked the bottom of the walls to the floor. I wish that I had done some SPL measurements inside and out before I started, but I just dove in before I thought of it. I can tell you though, when I'm sitting in the theater now and have someone close the door, it gets very quiet inside. I have a 4 x 15" IB array and it has reduced the low frequency that used to permeate my neighbor's walls(his bedroom wall is 10' from my theater wall). Now he almost never hears it unless I'm watching something like "War of the Worlds" with frequencies into the teens. I can now listen to music at levels up to 70 - 80 decibels with my wife in bed directly above the theater, without the IB hooked up of course.

Harold

[JimS]

Stay away from traditional lighting fixtures that cut into ceilings. "Pot" lighting is horrible - acoustically speaking. Instead consider track lighting where only a small hole is needed for wiring. Also consider AC venting and wrapping ducts considerably more than you normally would (..also don't use metal plates - use plastic instead). Of course any holes you cut (like lighting, wall plates, AC, etc.) should also have caulking around them to seal the room.

I certainly second these thoughts - in my previous house I soundproofed a room in the basement for drum practice room & rehearsals (got to cheat quite a bit since it was a "bonus" room with cinderblock on 3 out of 4 sides and no venting). I could play at relatively loud levels late at night without disturbing the rest of the house, but if the door was even cracked a bit for ventilation the sound (especially bass) carried almost as if the room wasn't treated.

I don't remember the source since it was long ago, but when I worked on that project I recall seeing a cite that if you leave even a few square inches open it negates much of the rest of the soundproofing effort - so keep that caulk gun handy!!

[bigburner]

I think that Art Ludwig's page is mandatory reading for this sort of question. If you've seen it before, now is a good time to revisit it. I know I've gone through it on more than one occasion.

http://www.silcom.com/~aludwig/

Excellent site thanks Joe.

Nigel.

[Scottg]

I don't remember the source since it was long ago, but when I worked on that project I recall seeing a cite that if you leave even a few square inches open it negates much of the rest of the soundproofing effort - so keep that caulk gun handy!!

Thats why sealing the room is issue #1 :T

..or when in doubt.. caulk the sh!t out of it! (..and use a lossy caulk that won't dry-out over time.)

[coolerbin]

I have a room which will be HT room, three walls are concerate, do I need to put double drywall on these three walls?

[Dennis H]

I have a room which will be HT room, three walls are concerate, do I need to put double drywall on these three walls?

No just on the wall that's open to the rest of the house.

[royceb]

Good info gang, keep some ideas coming - I'll check that book.

I'm still not sure on the ceiling. I want/need the sound isolation so I can't go with an acoustic tile only. Framing a new ceiling under the ceiling joists would require (educated guess) 2x6 framing, costing about 8" of headroom that I'm not anxious to give up.

Has anyone insulated the joist space and installed double drywall? If so, how were the results on the floor immediately above?

Thanks,

I used John's Manville Sound Control between the joists. I installed a drop tile ceiling instead o drywall, but the results are very satisfying. The only sound that escapes is deep bass. I can listen to much of my music collection without disturbing my wife if she is watching TV directly above me in the family room.

[Paul H]

Has anyone used a solid core wood door? Is it similar for sound attenuation to an exterior steel door?

[Chris D]

Yes, my theater was built with all these things and more, including the solid core door. Works like a charm.

[Scottg]

Has anyone used a solid core wood door? Is it similar for sound attenuation to an exterior steel door?

It can be better - the "key" however is the seal around the door.