Acoustics in a HTR

Discussion in 'Home Theater Projects' started by Brian Osborne, Oct 13, 2005.

  1. Brian Osborne

    Brian Osborne Stunt Coordinator

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    I'm going to be doing a HTR myself in the basement of my new house.
    I'm looking for a little advise on how to set up and construct for the best sound.
    The room finished is going to be 16x20 and will have a door to completely close off the room. The TV, front speakers, sub and all components will be hidden in the front wall.
    I planned on building a wood floor over the concrete of the basement. Doing this for a couple reasons. One so I can have the second row of seats on a riser, and second to allow me to install an in floor sub.
    I will be installing carpet in the room.
    I had planned on drywall in the room, walls and ceiling, but I'm afraid of what might happen to the sound with so many hard surfaces. Someone once told me that much of the problems associated with hard surface noise could be remedied by building walls crooked. Tip the back wall forward 1 or 2 degrees, and tipping the side walls back 1 or 2 degrees. Is there any truth to that?
    Another thought I had is to add columns to the room. I've seen this in some other HTRs, even ones some of the members have. Does this help break up the sound and avoid echoes?
    I have until Dec 2nd to get my plans finalized. Any suggestions would be appreciated.
     
  2. drobbins

    drobbins Screenwriter

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    Flat surfaces, like the walls, will reflect sound kind of like a mirror. Tilting will only reflect the sound in a different direction. Non-flat surfaces, like bowed walls or columns, will diffuse the sound waves in different directions. The sound is still there but not as a distinct echo. Acoustic panels, carpet, curtains, etc.. will absorb the sound waves.

    In my first theater I made up some acoustic panels out of rigid fiberglass insulation. You can see them on the walls here I liked the way they (deadened) the room some. Even with the theater turned off, I used to like to sit in there and get peace & quiet. During a movie, the sound was crisp. I got mixed reviews on the looks of these panels though. So, in my second theater I did not use them. While the room was empty, it had a terrible echo. A textured ceiling, carpet, curtains and the seating stopped a noticeable echo. I don't think the sound is as crisp though. I need to figure a way to make better looking panels.
    Dave


    PS. Why won't the forum let me type (dead) with out the ( )? When I do it comes out like this - % ".
     
  3. Brad E

    Brad E Second Unit

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    dead
     
  4. Brad E

    Brad E Second Unit

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    Worked for me.[​IMG]
     
  5. chris_everett

    chris_everett Second Unit

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    Non-parallel walls can help prevent standing waves from forming, which I imagine is where the "build crooked walls" comes from. I'm not sure how much 1 or 2 degrees will help though. Things that do matter:

    1. Basic room dimensions. Search for "Room mode calculator" and you will find a little program that gives you put in your rooms width, length and height, and it will show you your problem frequencies. With the right dimensions you will minimize your problems.

    2. Absorbtion. You want to have at least some of your wall surfaces to absorb sound rather than reflect it. You can accomplish this with any number of commercial or DIY products. (Accoustic foam, Rigid fiberglass, etc.)

    3. Diffustion. As drrobbins said, If you can prevent sound from reflecting in a "linear" way, that will also help. Any number of design details, i.e. columns, molding, risers, stages, and so forth can give you a lot here without having some sort of actual diffuser "product"

    In my theater, I put accoustic foam on the ceiling, and a strip around the walls at ear level. At higher frequencies the room sounds great, but I do have a 50hz standing wave because of the room dimensions. (which I was suck with)
     
  6. Brian Osborne

    Brian Osborne Stunt Coordinator

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    I suppose I'll start with the columns and the carpeted stage and see what else needs to be added to improve the sound to where I'd like it.
    I think that putting the DVD shelving built into the back wall would help a lot too.
    Thanks for the help

    dead

    worked for me too..
     
  7. drobbins

    drobbins Screenwriter

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    Let me try again
    Dead
    dead % " (dead)

    Well 3 out of 5 worked?

    Dave
     
  8. drobbins

    drobbins Screenwriter

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    Brian,
    Sorry about that " Issue" thing. I did a start thread in the test area and I am still having issues.

    Anyway, here is a
    link to a cool calculator that helps with room sizes and seating locations.

    Dave
     
  9. Brian Osborne

    Brian Osborne Stunt Coordinator

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    Thanks, I'll download it and play around when I get off work.
     

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