Room modes

Discussion in 'Pro Audio' started by Ken Platt, Aug 19, 2003.

  1. Ken Platt

    Ken Platt Guest

    As we plan to open a new room this fall we would really like to make it
    sound as nice as it can right off the hop (duh). The dimentions are 46.6'
    long x 12.7' wide x 11' high. After doing some research into room modes I'm
    still a little confused. Am I right that multiple modes at the same
    frequency(ies) are the real killers? Do I also need to be concerned about
    modes bunched closely together. From what I can ascertain with my limited
    knowledge, it seems I have big problems from 300-400Hz and lesser problems
    at about 80-125Hz. assuming I'm correct (am I...PLEASE?) can anyone suggest
    a good solution on the cheap DIY (thank god one of the partners is a general
    contractor!) and or a good resource (online preferably) for trapping at
    these frequencies. Thanks for any help
    Ken
     
    Ken Platt, Aug 19, 2003
    #1
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  2. Ken Platt

    Bob Smith Guest

    Room modes bunched together closer aren't good for the room sound.

    Here is a place to start:

    http://www.realtraps.com/facts.htm

    bobs

    Bob Smith
    BS Studios
    we organize chaos
    http://www.bsstudios.com
     
    Bob Smith, Aug 19, 2003
    #2
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  3. Yes bunched up modes are problems... Does your room haves to be those exact
    dimentions??? or can they be slightly changed??? Changing the size of the
    room can drasticly change the modes...
     
    Ryan Richards \(Diesel Breath\), Aug 20, 2003
    #3
  4. Ken Platt

    Rob Adelman Guest

    I was thinking this as well. Sound waves at audible frequencies are the
    size that they are. You can't "scale them down" to go along with the
    other scaled down parameters. This would seem to make such an experiment
    meaningless.

    -RA
     
    Rob Adelman, Aug 22, 2003
    #4
  5. Ken Platt

    Scott Dorsey Guest

    No, wavelength is inversely proportional to frequency. The way a 5 KHz
    wave propagates around a room is exactly the same way a 50 KHz wave propagates
    around a 1/10 scale model of the room. So you can use ultrasonic sources
    for testing scale models out.

    The Beranek book has a very nice discussion of this.
    --scott
     
    Scott Dorsey, Aug 22, 2003
    #5
  6. Ken Platt

    mikethespark Guest

    I think you will find that the BBC has done extensive work in scaling down
    studio models for analysis and agree with Scott's answer.

    Regards, Mike
     
    mikethespark, Aug 23, 2003
    #6
  7. Ken Platt

    Kenny Guest

    IF you are going to multiply the frequencies by 10 and build a scale model
    at 1/10 then okay.
    But, I am talking reality here. The guy who needs help with his room is not
    going to do this.

    Let's try to stay on the planet earth... where real people live.


    I know from experience that recording spaces are very hard to analyze
    using time alignment and TEF equipment.

    The reason is the relatively slow speed sound travels.
    The human ear can't even tell there is a delay until sound travels over 40
    feet.

    Think about it...
    If you are analyzing a large space, like and auditorium. 200 feet.
    and a step in a wall is causing a frequency to bounce hard back at the mics.
    You wont ever see it on a TEF screen unless it is 40 feet away. from the
    mic.
    Then is looks like a slap echo at it's favorite frequency.

    A room that is 12 x 12 x 48 is going to be a bad room period.
    it is a long echo chamber with sides that are equally divided into the
    length.
    the worst possible combination.

    Kenny
     
    Kenny, Aug 23, 2003
    #7
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