Wall Linings

Discussion in 'Archived Threads 2001-2004' started by Fred Seger, Mar 9, 2001.

  1. Fred Seger

    Fred Seger Stunt Coordinator

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    Not sure if this belongs in this section of the forum or not? But it is DIY.
    I'm moving my home entertainment system from the first floor to my basement. I call it an "entertainment system" because it isn't a true "home theater yet". I just bought a projector though, so I'm getting closer.
    The basement is totally unfinished - concrete walls all the way around. I want to finish the walls to reduce unwanted echoes and reverberations. My business makes custom styrofoam products. I've already make sound panels for customers. They look like a bunch of small pyramids in a grid.
    Is this a good lining for my HT?
    The price is right ( free - it is my business)
    I would probably hide the panels with black sheets or curtains.
    Thanks again.
     
  2. Greg Monfort

    Greg Monfort Supporting Actor

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    Styrofoam isn't a good audio absorber. The product you describe sounds like a diffusor.
    Get a copy of Owens-Corning's "Noise Control Design Guide" for wall/floor/ceilings.
    Speaker placement: http://www.dolby.com/tech/L.mn.0002.5.1Guide.s.pdf
    BTW, angling walls to complement this layout will dramatically reduce the need for bass traps, as well as building a vertical 'peak' into the back wall further reduces the possibility of standing waves. If you can swing it, a rising ceiling from the screen wall helps too.
    If not, then room dims should be some golden or acoustic ratio, to minimize modes. An excellentt treatise is H-K's White Papers. http://www.harman.com/search/results...00&search=when
    For viewing distances and much more: http://www.hometheatervillage.com/vi...y/library.html
    GM
    ------------------
    Loud is beautiful, if it's clean
     
  3. Arthur Falkler

    Arthur Falkler Auditioning

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    As long as the styrofoam doesn't squeak when the bass hits, that sounds like a great idea!
    Man, I hate the sound of styrofoam...
    ASFIII
     
  4. Richard Greene

    Richard Greene Stunt Coordinator

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    I would seriously consider avoiding the basement.
    If you must move there, the correct solution is to build
    an isolated plasterboard "room", including the walls, floor and ceiling, to keep your sound away from the concrete down there. Concrete makes standing waves much worse than 1/2" plasterboard and flexible wood floors.
    Another poster made several errors in his post
    that I've corrected below:
    (1) Angling walls does not reduce standing waves.
    It merely makes them more difficult to calculate
    compared with an ordinary rectangular room.
    (2) The golden ratio dimensions (0.62x by 1.0x by 1.62x)
    do not minimize room modes. they merely spread out the
    standing waves so two or more don't overlap, as in a square room or cubical room.
     
  5. Greg Risley

    Greg Risley Second Unit

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    Fred I was wondering what you guys charged to make those little pyramid diffusers. I've seen the acoustical ones for big bucks and your way seems like it may be more economical. Maybe I can throw a little buiseness your way or you can point in the right direction here in Austin, TX.
    Thanks
    Greg
     
  6. Greg Monfort

    Greg Monfort Supporting Actor

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    >Another poster made several errors in his post
    that I've corrected below:
    (1) Angling walls does not reduce standing waves.
    It merely makes them more difficult to calculate
    compared with an ordinary rectangular room.
    (2) The golden ratio dimensions (0.62x by 1.0x by 1.62x)
    do not minimize room modes. they merely spread out the
    standing waves so two or more don't overlap, as in a square room or cubical room.
    =====
    (1) Please elaborate, as standing waves require parallel surfaces to propogate, as does 'slap' echo. Non-parallel surfaces cause reflections, reducing in amplitude with each reflection, like a billiard ball caroming around the cushions. Big difference.
    (2) Ok, what's the difference? If none overlap, that's minimizing them, as they are reduced to the fewest number, however many that may be.
    GM
    ------------------
    Loud is beautiful, if it's clean
     
  7. Richard Greene

    Richard Greene Stunt Coordinator

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    Greg, I wanted to send you an e-mail but I'm new hear and
    have no idea how that's done, so I'll reply below:
    Greg wrote:
    "(1) Please elaborate, as standing waves require parallel surfaces to propogate, as does 'slap' echo. Non-parallel surfaces cause reflections, reducing in amplitude with each reflection, like a billiard ball caroming around the cushions. Big difference."
    RG replies:
    Non-parallel surfaces do reduce flutter echo at higher frequencies but that's more of a problem in larger rooms
    and auditoriums rather than in typical small to medium-sized home listening rooms.
    I wish it were true that standing waves require parallel surfaces. Standing waves simply require reflective
    surfaces. A spherical room, for example, would not only have standing waves, it would be the worst possible shape for a room (or the interior of a speaker enclosure) even though no surfaces are "parallel". Every reflection from every angle would have the same surface-to-surface dimension, so ALL modes would overlap. Also bad would be a cubical room where all three axial room modes would overlap.
    Greg wrote:
    "(2) Ok, what's the difference? If none overlap, that's minimizing them, as they are reduced to the fewest number, however many that may be.
    RG replies:
    If no room modes overlap, they should be less audible than
    if two or more modes do overlap. The quantity of room resonances will not change with different room dimensions.
    So using the "golden ratio" dimensions for a listening room will not reduce the number of modes.
     
  8. James Mudler

    James Mudler Stunt Coordinator

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  9. Greg Monfort

    Greg Monfort Supporting Actor

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    >Greg, I wanted to send you an e-mail but I'm new
    hear and
    have no idea how that's done, so I'll reply below:
    ====
    Click on the second icon in the bar of the poster to
    send email, but this should be done 'out in the open'
    anyway IMO as I don't think anyone else reading the
    thread should be left 'hanging', so to speak. [​IMG]
    ====
    >Greg wrote:
    "(1) Please elaborate, as standing waves require
    parallel surfaces to propogate, as does 'slap' echo.
    Non-parallel surfaces cause reflections, reducing in
    amplitude with each reflection, like a billiard ball
    caroming around the cushions. Big difference."
    RG replies:
    Non-parallel surfaces do reduce flutter echo at
    higher frequencies but that's more of a problem in
    larger rooms
    and auditoriums rather than in typical small to
    medium-sized home listening rooms.
    ====
    This doesn't jive with my measurements of the two
    home LEDE listening rooms I've done, neither of which
    are large, nor does it agree with the info in "Sound
    System Engineering", Don & Carolyn Davis, which
    pointed me in this direction. It's discussed in the
    White Papers too.
    ====
    >I wish it were true that standing waves require
    parallel surfaces. Standing waves simply require
    reflective
    surfaces.
    ====
    Are we talking about the same thing? Standing waves
    don't decay, reflections do. Before/after
    measurements of the rooms shows a marked reduction in
    modes/amplitude. One room is laid out ~ like is shown
    on pg. 217, and the other on pg. 223, except
    bookcases are used in lieu of RPG diffusors.
    ====
    > A spherical room, for example, would not only have
    standing waves, it would be the worst possible shape
    for a room (or the interior of a speaker enclosure)
    even though no surfaces are "parallel". Every
    reflection from every angle would have the same
    surface-to-surface dimension, so ALL modes would
    overlap.
    ====
    Correct, a sphere has an infinite number of
    'parallel' surfaces.
    ====
    > Also bad would be a cubical room where all three
    axial room modes would overlap.
    ====
    Correct.
    ====
    >Greg wrote:
    "(2) Ok, what's the difference? If none overlap,
    that's minimizing them, as they are reduced to the
    fewest number, however many that may be.
    RG replies:
    If no room modes overlap, they should be less audible
    than
    if two or more modes do overlap. The quantity of room
    resonances will not change with different room
    dimensions.
    So using the "golden ratio" dimensions for a
    listening room will not reduce the number of modes.
    ====
    Right, I see now that mine was poorly phrased. Haste
    makes for mistakes. My bad. [​IMG] Minimizing amplitude
    of the various modes was the point. It's all
    explained in the White Paper.
    GM
    ------------------
    Loud is beautiful, if it's clean
     

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