Building walls fit for good sound

Discussion in 'Home Theater Projects' started by Lanny_B, Dec 28, 2003.

  1. Lanny_B

    Lanny_B Second Unit

    Nov 24, 2001
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    I was looking on my new Digital Video Essentails disc, and it showed a diagram of what would be good building materials for a wall, though I haven't yet been able to find any more detail on it.


    I'm finishing a room in my basement for a home theater setup. It's a small room, but hopefully should work. It's a room that's about 10' wide, 17' long, and 8' high. The front and back walls have already been sheetrocked.

    I'm kind of confused what I'm seeing here. So, questions are:
    1. which side of this diagram is the front and which is the side that I don't see?

    2. With the soundcore, does it matter if I only have that on the two side walls, and not the front and back since they're already done? Plus, the right side wall will have doorway spaces in it, as well as a big space where I'm building a shelf that has rear access on the other side of the wall. So there's not much drywall that will be on the right side, is what I'm saying.

    3. I'm actually not sure what I'm seeing with the staggered stud wall there. Am I supposed to leave the zigzag spaces there like that, or is that just showing it pulled apart?

    4. What about insulation? Is there anything about filling those with insulation?
  2. Bob McElfresh

    Bob McElfresh Producer

    May 22, 1999
    Likes Received:
    Hi Lanny. Your question is a bit advanced for the Basics area. I'm going to move your post to a place where more of the HT room builders hang out.
  3. Bobby

    Bobby Auditioning

    Oct 9, 2003
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    The view that the picture shows is a top-down view on a bit of an angle. The studs you see there are staggered and are NOT 'pulled apart' at all. The fact that the inside edges of both sets of studs are not touching the opposite side of the wall is exactly what you want. The top and bottom plates in the diagram ARE pulled apart from the top and bottom of the wall.

    The idea here is to isolate (sound-wise) one side of the wall from the other. Most walls are composed of upright 2x4's, usually 16" apart, nailed in between the top and bottom plate which are also 2x4's. Using a 2x4 for the plates (top and bottom) means that you have one set of studs, 16 inches apart, where both edges of the upright 2x4's are flush with the edges of the plate as they are obviously the same width.

    With staggered studding, instead of using 2x4 plates, you will use a minimum of a 2x6, top and bottom. Along with the wider plates you will also use double the amount of upright 2x4 studs. One set of studs will be flush with one edge of the plate (say, the inside wall of the theatre) and the other set of studs will be flush with the opposite edge of the plate (the outside wall of the theatre).

    The idea here is that when you fasten sheetrock to each side of the wall, they are NOT fastened to the same set of studs, thus sound will not travel as well from one side of the wall to the other. In a regular wall the sheetrock on both sides of the wall are fastened to the same studs thus sound resonates through the studding from one side of the wall to the other.

    Hope this makes sense. [​IMG]

    To answer your questions:

    1. The 'front' of the diagram (lets call it the inside wall of the theatre) is the side with the 5/8" plywood + 1/8" soundcore + 5/8" drywall. The opposite side (wall outside the theatre, the one you can't see in the diagram) has just the 5/8" drywall.

    2. Applying the soundcore to 2 out of 4 walls (assuming a 4 wall room) is kinda pointless in my opinion because the sound will still travel through the untreated walls. You'd be better off adding another layer of sheetrock on the walls that are already finished. (And perhaps the soundcore in between?). As far as doorways, you need a way to get in/out of the room so I wouldn't worry about them. You could install solid core doors and some weather stripping to help contain the sound in the theatre but that's about it.

    3. Yes, the 'zig-zag spaces' are exactly what the staggered studding looks like and the studs are not 'pulled apart' in the diagram. Notice that the sheetrock/covering layer on either side of the wall is fastened to their own set of studs - that's the idea.

    4. You would usually insulate in between each set of studs to help with the soundproofing. I'm not exactly sure if you would insulate both sides independently - my guess is that it would be better but again it's double the insulation.

    Hope this helps a bit. [​IMG]

    PS. I'm not sure what you would do with the walls that are already sheetrocked. It IS possible to stagger a wall that is a regular 2x4 plate. You would add the difference of the width on the plates and throw up another set of studs but yours is already sheetrocked. You could build another wall in front of the other walls but that may take more time than removing the existing sheetrock plus you'll lose a bit of space.

    Personally, I would probably just leave the walls as they are, not stagger the remaining walls, and just double up the sheetrock all around. I'm working on my theatre now and I did stagger the studs but I was starting from scratch without any walls and it was more or less just to see, or rather hear, the difference. I'm not convinced that I really needed it but I'm sure I'll be happy I did it in the long run.

    Good luck!

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