Theater in unfinished basement space

**bpape** · **06-19-09, 03:30 PM**

Fiberglass and mineral wool are the most common and cost effective. For bass control and rear wall, look at the coefficients for something that has good bottom end performance but rolls off absorption as you go up in frequency.

For reflection panels, they don't need to reach as deep but they should be absorptive all the way up.

Bryan

**patchesj** · **06-20-09, 11:56 AM**

Pictures of the raw space. Pay no attention to the sheet hanging on the wall or the futon... Were very important test/demo tools to gain approval for the project.... Borrowed SD Epson projector from the office and played a few DVDs over the weekend to get buy in from the rest of the household..

Looking into room from open area in basement
Looking into room towards "rear" wall
Towards front wall from inside HVAC/Mech room
Again, towards rear of room
From outside room looking at stairwell

**Ted White** · **06-20-09, 01:45 PM**

Quote:

patchesj wrote:

It is structural, but I think adding additional studs would be OK?

Adding the new staggered studs to a load bearing wall is fine. This will not reduce any load bearing capacity.

http://www.soundproofingcompany.com/...Wall-Guide.pdf

As Bryan said, ventilation is a big consideration.

**patchesj** · **06-21-09, 08:08 AM**

Quote:

Ted White wrote:

Adding the new staggered studs to a load bearing wall is fine. This will not reduce any load bearing capacity.

http://www.soundproofingcompany.com/...Wall-Guide.pdf

As Bryan said, ventilation is a big consideration.

For ventilation, I'm thinking that keeping the air handler for that room independant will help with isolation. Perhaps a 300 to 400 cfm inline fan can be tied to a 12v trigger and pull air from the rest of the basement and dump it in the front of the theater. A "return vent" back by the projector can go to a mdf baffle system and back to the open basement.
Posted via Mobile Device

**bpape** · **06-21-09, 09:08 AM**

That can be done certainly - provided the rest of the basement has enough exchange to keep up with the heat.

Bryan

**Ted White** · **06-21-09, 10:05 AM**

Quote:

patchesj wrote:

For ventilation, I'm thinking that keeping the air handler for that room independant will help with isolation. Perhaps a 300 to 400 cfm inline fan can be tied to a 12v trigger and pull air from the rest of the basement and dump it in the front of the theater. A "return vent" back by the projector can go to a mdf baffle system and back to the open basement.
Posted via Mobile Device

The issues are air volume (CFM) and isolation. Air ducts muct be surrounded by absorption and mass to contain sound. Drywall and fiberglass

**patchesj** · **06-21-09, 02:05 PM**

The basement is about 2700 sq ft, probably 1800 or so in an open area outside the theater. It is on it's own hvac zone so if we keep that at a reasonable temp, the air exchange into the theater should keep it comfortable.
I need to figure out how much air we would need to move in there. I can't imagine it would be more than 300 cfm. Using an independant fan and duct work would allow me to build an mdf box under the stairs for supply and one in the mechanical room for the return. Should minimize sound transmission to the rest of the basement, and eliminate it from using the other hvac ducts to get upstairs. I think...
Posted via Mobile Device

**Space** · **06-21-09, 04:01 PM**

"Given that one of the existing walls is already 2x6, can I just stagger 2x4s using the same top/sill plates? Basically have them stick out 1/2 inch past the existing studs? Is there an effective way to decouple the "new" ceiling joists from that wall? Maybe just connect them only to the new studs?"

On the load bearing wall in question, wouldn't it benefit you over all to build a separate 2X4 wall that is not connected to any of the existing structure? All the little bit here and little bit there of trying to decouple from the load wall still tie the new wall and the new ceiling right back to it. Especially when you try to attach joists overhead, you will find this an issue with good connections being made as the smaller wall dimensions suggested will not allow proper attachment of the joist.

Nevermind the load bearing part of it, the 2X6 wall has compression blocking that makes another connection >besides< the existing connection that the wood I-beams are already making.

Your concerns that this is going to be a source of transmission are not unfounded, it already is a source being as rigid as it is and doing what it is doing, e.g. supporting most likely another wall directly over head.

It's a straight line to the top of the house

**Ted White** · **06-22-09, 09:11 AM**

Building a second wall is better for many reasons if practicality will allow it

**bpape** · **06-22-09, 09:20 AM**

Absolutely if space considerations will allow it.

Bryan

**patchesj** · **06-24-09, 03:56 PM**

Yep, I think a second wall is the way I should go. That will isolate all 4 walls and the ceiling from anything else, except the concrete floor.
Posted via Mobile Device

**patchesj** · **07-01-09, 07:15 PM**

Does anyone have information or diagrams that would show how to construct two walls next to each other (room in a room), with a doorway? Which wall do you attach the door frame too? How do you keep the frame and trim from becoming a bridge between walls? I'm going to go with a single 36" door instead of the original french door design. Is an "exterior" door with weather striping the way to go?

Thanks

**bpape** · **07-01-09, 07:18 PM**

Use a solid core wood door with seals. Attach the door to the inner wall to prevent it from vibrating the outer structure.

You can use 2 passing 1x4's that overlap but do not touch each other and then caulk the gap. Nobody will ever know it's not attached except you.

Don't drywall either of the 2 inner facing surfaces - only the surfaces that face the theater room and the other room.

Bryan

**patchesj** · **07-01-09, 07:24 PM**

With the thick wall (I'll have a 2x6 and 2x4 wall), do you use doors with a 10" jamb?

**bpape** · **07-01-09, 10:23 PM**

No need. Standard door on the inner wall. Just make a plate to fake a jamb around the other one and have it slide around the other one.

Bryan

**Space** · **07-02-09, 07:41 PM**

Quote:

patchesj wrote:

Does anyone have information or diagrams that would show how to construct two walls next to each other (room in a room), with a doorway? Which wall do you attach the door frame too? How do you keep the frame and trim from becoming a bridge between walls? I'm going to go with a single 36" door instead of the original french door design. Is an "exterior" door with weather striping the way to go?

Thanks

One door per wall is often recommended to create a soundlock.

This is a vital area to maintain isolation. Doors and windows can be big leaks of sound and require as much attention to detail as anything in the project, often more detail.

Solid core doors require medium to heavy weight type hinges and based on this fact alone, the jamb requirements are considerable.

Plumb framing with 1 inch door jamb material solidly placed against the framing and adequate sized and length screws is a requirement to maintain this door over its anticipated life span.

A threshold is recommended as well. No door knobs...no holes of any kind in the door really. A pull handle and closure work well but the closure is not a requirement, depending on the weight of the actual door.

**Ted White** · **07-09-09, 11:01 AM**

Actually, if you are going to be successful at compressing the door seals you will certainly want a doorknob with standard lockset. Otherwise the door will bounce open. The hole for the doorknob is not a significant flanking path, especially with dual communicating doors.

Look at solid core doors. Generally particleboard or MDF filled, although mineral core is also available. Better to look at a "flush" door slab (no recessed panels that create thin spots).

As Bryan said you can build extension jambs to accomodate the wall depth. You don't need to buy a super deep door jamb.

Sing the top hinge screws through the door jamb into the side 2x4 framing. You'll need to replace the short screws they give you

**Space** · **07-09-09, 06:08 PM**

"Actually, if you are going to be successful at compressing the door seals you will certainly want a doorknob with standard lockset."

A door closer would be far more effective..

Especially in a double wall configuration, where extreme amounts of effort/cash have been put into keeping sound in and or out. It would be akin to shooting ones self in the hand to use a door knob, certainly worth two bullets if you use a knob on each door of a back-to-back door setup.

**Ted White** · **07-09-09, 06:12 PM**

Quote:

Space wrote:

A door closer would be far more effective..

I couldn't disagree more. You need to see the type of pressure a properly sealed door exerts. A positive lock is required.

And you over-estimate the flanking potential of the lockset hole.

**Space** · **07-09-09, 07:57 PM**

Plus magnetic sealing strips....

A hole will allow airborne sound somewhere to go, I am not sure how flanking fits into that.

**Ted White** · **07-09-09, 08:07 PM**

I'm thinking acoustic door, which uses compression seals. You're thinking exterior door, which (sometimes) use magnetic seals. Compression seals are better for acoustics, if there's a choice available.

The bugger is that an exterior door has nice seals, but lightweight, foam-filled slab.

The interior solid core door has the massive door slab, but no seals on the jambs.

So it's common to get a cheap interior solid core pre-hung, and replace the stops (moulding) with a compression gasket system. The threshold can be ommitted as well.

Yields a heavy, well sealed door. Go to Lowe's and get 2 and build the airlock.

**Space** · **07-09-09, 11:46 PM**

Quote:

Ted White wrote:

I'm thinking acoustic door, which uses compression seals. You're thinking exterior door, which (sometimes) use magnetic seals. Compression seals are better for acoustics, if there's a choice available.

The bugger is that an exterior door has nice seals, but lightweight, foam-filled slab.

The interior solid core door has the massive door slab, but no seals on the jambs.

So it's common to get a cheap interior solid core pre-hung, and replace the stops (moulding) with a compression gasket system. The threshold can be ommitted as well.

Yields a heavy, well sealed door. Go to Lowe's and get 2 and build the airlock.

I already mentioned that holes are not good when so much has gone into a build up to this point.

The thinking is that if a man will build a room with the utmost attention to detail then there is nothing left but one place that sound will gain passage, in this case using your reference, it will be the door knob hole...which is no concern because all the other areas have been maintained to the inth degree.

Which usually is a difficult thing to achieve for even the most professional installer.

What you are trying to say, and what you are saying are mixed.

For a better understanding of what I am thinking of and how it is a benefit to people that attempt diy back-to-back or door installs of any kind in an sound environment where attention to detail is required:
http://www.johnlsayers.com/phpBB2/vi...s+and+doorknob

Brien Holcombe
http://www.buildthisroom.com

**patchesj** · **07-10-09, 08:07 AM**

Well, certainly some interesting comments regarding the door. Not being an acoustical engineer, I can only add my "common sense" logic. To me sound is pressure and vibration, so if we are trying to prevent sound leakage (and conversely keep ambient noise out) we need to make the room as air tight as possible (pressure) and isolate interior surfaces from exterior surfaces to prevent transference of the mechanical movements (vibration). Again, not being a professional with access to test equipment, my mind tells me that I'm going to have a larger issue with vibrations across the door slab (lack of isolation and mass) than pressure migration via the door hole. I can see the argument for both problems and agree they will both exist. However, being a home owner and not a studio manager I need to take the most cost effective route as well as applying a bit of aesthetic design.

I am not sure how well received a double door setup with closers on both vs door knobs would be accepted by the more sane non-audiophile members of the household (and general public)

Can we agree that in the best case studio design where I would be the only person using the doorway the no knob design is better, but in a "home theater/music room" it might push the edge of acceptable design?

To throw fuel on the fire.... My primary focus on sound isolation is between the theater room and the floor above (and rest of primary living area of the house). The area immediately outside the theater door is probably the least of my worries. That space is about 1000 sq ft of "non-living" area, located under the breakfast room/living room on the 1st floor. There is a work out room that will be attached to the open space as well as a basement bedroom/bathroom with a door about 35 feet away from the theater door.

**Ted White** · **07-10-09, 09:53 AM**

Walls for dedicated rooms will typically score an STC 55-60. Common solid core doors will score in the high 20s to low 30s. And they're big holes. So we concern ourselves with doors.

Very massive (very expensive) commercial acoustic doors with proper gaskets can move the door to the high 40s. They have doorknobs.

A simple communicting door system (as previously described) to create an airlock can also hit high 40s, and higher, with better low frequency performance for a fraction of the cost of this commercial door. We presume that they are each hung in a decoupled wall.

So the numbers (acoustic and $$) warrant at least a look at the airlock idea. This will be less of an issue if the sound passing through the single closed door is entering a room with absorption, drywall on all walls and ceiling, etc. Sound will still enter the ceiling joists overhead, so make it as difficult as possible.

Ideally certainly you would not have a doorknob, but the acoustic door world at large hasn't apparently figured out a way to have an automatic door closer supply sufficient pressure to compress the seal bulbs and also allow you push the door back out easily.

What I mentioned earlier was that a doorknob with metal covers on both sides isn't an open hole. And it has a cross section quite a bit smaller than a single gang outlet, which the NRC has tested to not be significant when closed off.

**patchesj** · **07-10-09, 10:02 AM**

Quote:

Ted White wrote:

Walls for dedicated rooms will typically score an STC 55-60. Common solid core doors will score in the high 20s to low 30s. And they're big holes. So we concern ourselves with doors.

Very massive (very expensive) commercial acoustic doors with proper gaskets can move the door to the high 40s. They have doorknobs.

A simple communicting door system (as previously described) to create an airlock can also hit high 40s, and higher, with better low frequency performance for a fraction of the cost of this commercial door. We presume that they are each hung in a decoupled wall.

So the numbers (acoustic and $$) warrant at least a look at the airlock idea. This will be less of an issue if the sound passing through the single closed door is entering a room with absorption, drywall on all walls and ceiling, etc. Sound will still enter the ceiling joists overhead, so make it as difficult as possible.

Ideally certainly you would not have a doorknob, but the acoustic door world at large hasn't apparently figured out a way to have an automatic door closer supply sufficient pressure to compress the seal bulbs and also allow you push the door back out easily.

What I mentioned earlier was that a doorknob with metal covers on both sides isn't an open hole. And it has a cross section quite a bit smaller than a single gang outlet, which the NRC has tested to not be significant when closed off.

Do you have any links or pictures of the door knobs you are describing? From an aesthetic view, I would like to keep the "exterior" door and door knob the same style as everything else in the house. The "interior" door doesn't really matter, the theater room is going to look different enough...

Currently we have solid core doors with a 2-raised panel design, and lever style handles.

Advertisement