How SQUARE is a SQUARE room?

Discussion in 'Archived Threads 2001-2004' started by Phil de Bruin, May 13, 2002.

  1. Phil de Bruin

    Phil de Bruin Auditioning

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    Okay - so if a room is perfectly square, or have one dimension exactly twice another - you may encounter resonances that may colour the sound. But just how 'perfectly square' does a room have to be?

    Are we talking within a half a foot? An inch? What about if the room in question is pretty god damn square, but the wall protrudes in the middle due to a fireplace? How much difference is that going to make?

    Comments!?? :)

    /nightdog35/images/filmreel.gif
     
  2. John Desmond

    John Desmond Stunt Coordinator

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    The closer you get to "square" the worse will be your problems. Same thing with multiple dimensions being multiples of each other. So a room that is 8*8*8 will be real bad. Since we're talking about long wavelengths, I would think the 8* 9*8 isn't going to be much better.
     
  3. Dustin B

    Dustin B Producer

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    The room doesn't have to be square or have one dimensione exactly twice the other. Any rectangular room will have 3 axial room modes (plus a bunch of others I don't understand yet). The reason square rooms are said to be the second worst possible shape (cube being the worst) is now two of those 3 axial room modes are the same, resulting in one frequency and it's harmonics being boosted or cut twice.
     
  4. Richard Greene

    Richard Greene Stunt Coordinator

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    Example for 18' x 16' x 8' room

    showing axial room modes up to 80Hz.):

    565/18 = 31Hz (and 31Hz. x 2 = 62Hz.)

    565/16 = 35Hz. (and 35Hz. x 2 = 71Hz.)

    565/8 = 71Hz.

    Assuming room modes are 5Hz. wide there is the potential

    for boomy bass at these frequencies:

    29 to 33Hz (31Hz. mode)

    33 to 37Hz. (35 Hz. mode)

    60 to 64Hz. (62Hz. mode)

    69 to 73Hz. (71Hz. mode)

    69 to 73Hz. (71Hz. mode)

    Analysis:

    The 31Hz. and 35Hz. modes are adjacent modes that may sound like one broad bass frequency peak from 29 to 37Hz.

    The two 71Hz. modes are stacked = potential bass boom

    The 62Hz. and 71Hz. modes are close enough so

    they may sound like one broad bass frequency peak from

    60 to 73Hz.
     

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