SVS: Procedure on how to check for room nulls?

Discussion in 'Archived Threads 2001-2004' started by Curtis_Edwards, Aug 15, 2001.

  1. Curtis_Edwards

    Curtis_Edwards Stunt Coordinator

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    Can someone be so kind as to describe the steps needed in order to detect room nulls? Please also list equipment that would be needed?
    Thanks in advance.
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    -- CUE
    "Without Struggle There Is No Progress!!"
     
  2. Dennis Jacob

    Dennis Jacob Agent

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    One of the easiest is to place the subwoofer where you want to sit. Then walk around your room to see where you should place the sub. This cheats to a certain degree, but could be the most convenient. You'll need a test tone to play while you move around. Good Luck
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  3. Stephen Dodds

    Stephen Dodds Second Unit

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    All you need is an SPL meter (the Radio Shack will do) and a test CD (www.stryke.com).
    Even easier, order the RABOS kit from www.infinityspeakers.com. It comes with a calibrated SPL meter, a good CD and good instructions.
    Then you establish a reference level, and start playing the different frequencies. Note the peaks, and the nulls and you get a response curve.
    The reverse positioning mentioned above is a good way of finding the best spot.
    An easier way is to stick the sub in a corner, which will excite the most room modes, and then use an EQ to flatten the peaks. Boosting nulls does not work.
    Steve
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    Steve's Toys
     
  4. JohnMM

    JohnMM Stunt Coordinator

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    Is there a test CD similar to the one at stryke.com that I can get at Amazon (where I have some credits)?
    Also, I have AVIA and I have tried using one of the tests to do this - the one where it sweeps through the frequencies - but the tones go by too quickly to read the SPL meter. Is there a different test on AVIA that I have missed to do this?
     
  5. Steve_D

    Steve_D Second Unit

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    Here's the one I use from Amazon. I use Track 25 to help establish a zero db point for my mains, and then tracks 49-65 to calibrate my sub for 2 channel. Just remember the bass tracks are recorded -12 db in reference to the other tracks.
    The actual surround stuff is for Dolby Pro Logic but I don't use those, except some of the sound effects like the tractor, cows, and subway station are cool.
    There are plenty of sweeps and narrow band noise tracks as well.
    http://www.amazon.com/exec/obidos/AS...198414-6762951
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    [Edited last by Steve_D on August 15, 2001 at 06:35 PM]
     
  6. JohnMM

    JohnMM Stunt Coordinator

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    Steve_D, thanks for the info and link.
     
  7. BruceD

    BruceD Screenwriter

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    John,
    To better understand the big picture of what you are trying to accomplish, you should visit the etfacoustic site, where they go through an extensive demo room example of tuning the bass response in a room. This is very informative.
    www.etfacoustic.com
    The software they offer runs on a PC and is pretty inexpenxive ($149). I have been using it for the last year and learning much about room/speaker tuning.
    BruceD
     
  8. Bob McElfresh

    Bob McElfresh Producer

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    Hey Bruce. Nice link. Thanks [​IMG]
     

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