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Frequency Measurments

Discussion in 'Archived Threads 2001-2004' started by Mike J LeBlanc, Feb 14, 2002.

  1. Mike J LeBlanc

    Mike J LeBlanc Auditioning

    Joined:
    Jan 26, 2002
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    Just set up my Rava sub place it in the corner of my 20x15 room took frequency measurments from 20 160 hz using Stryke's Basszone Test CD and Radioshack meter The numbers have been corrected. The measurment drop off quite a bit below 40hz. I noticed others on this forum with frequency Measurments higher down below 40hz. Was wondering what I could do to to get these numbers up.
    Do I need to get an equalizer and bring all the other frequencys down to flatten them out?
    You can look at frequency Measurments here. Entered the numbers in a excel spread sheet I downloaded from this fourm http://www.pineriver-mn.com/graph.htm
    Thanks
    Mike
     
  2. Richard Greene

    Richard Greene Stunt Coordinator

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    The first thing to do is to apply correction factors to the Rat Shack sound meter. I use the following factors:

    20Hz add 6dB

    22Hz. add 4dB

    25Hz. add 2.5dB

    28Hz. add 2dB

    32Hz. add 1.5dB

    36Hz. add 1dB

    40Hz. add 1dB

    from 45 to 2,000Hz. the meter

    is accurate enough so no correction

    factors are needed.

    I prefer the slow frequency sweep (track 5) on the Stryke

    Basszone CD for measuring overall bass frequency response deviations at my listening position. The sine wave tones are okay but are not spaced closely enough -- a standing wave frequency response peak that happens to be half way between two of the sine wave tones would not be FULLY excited by either sine wave tone = some smoothing of the frequency response curve.

    The next thing to do is to experiment with the sub's

    low-pass filter to see if you can improve the frequency response without buying an equalizer. I believe the Rava

    has a 12db/octave low-pass filter -- try the lowest

    possible crossover frequency and measure the sub's frequency response again. Then try a higher frequency.

    If you ever want to upgrade your low-pass filter to

    24dB/octave, you can set the crossover frequency control on the sub at 70Hz. and buy a pair of FMOD 12dB/octave

    low pass filters to plug into the input jack(s) of your subwoofer. Cascading two 70Hz.(down 3dB at 70Hz.) 12dB/octave low-pass filters results in a 24dB/octave filter (down 6dB at 70Hz.) 24dB/octave filters help keep male voices away from the subwoofer where they rarely sound good.
     

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