Why you should compensate when using the RS SPL meter

Discussion in 'Speakers & Subwoofers' started by Stephen Dodds, Sep 21, 2003.

  1. Stephen Dodds

    Stephen Dodds Second Unit

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    Ever wondered what the Radio Shack SPL meter frequency response looks like in graphic form?

    [​IMG]


    Cheers

    Steve
     
  2. Dave Milne

    Dave Milne Supporting Actor

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    Yikes! Not good...

    It's kinda hard to read the scale, though... is it 5dB per division?
    What did you use for a reference?
    Have you tried the cap mod to the RS to flatten the low end?
     
  3. VinhT

    VinhT Second Unit

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    I would be very interested in learning how you tested the meter. Also, a few questions.

    1) What weight setting does that graph represent?

    2) Did you test the analog or digital meter?

    3) Could you post a larger image of the graph or give some information regarding the scaling used?

    4) Could use you please use the Export Data function of TrueRTA and send me the file of the SPL meter's response? I would like to create a more accurate correction chart than the one that is usually referenced on this forum. Or, if you could create a correction file for use with TrueRTA, it would be greatly appreciated by many people. Thank you!
     
  4. Edward J M

    Edward J M Cinematographer

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    The RS meter is either C-Weighted or A-Weighted.

    We all use C-Weighted for monitoring and measuring speakers; the A-Weighted scale filters frequecies below about 500 Hz.

    Even so, the C-Weighted scale is hardly linear in the bass region; it is a complex log10 function and is -0.5 dB at 80 Hz, -2 dB at 40 Hz, -6 dB at 20 Hz, and -14 dB at 10 Hz.

    To compound this, the RS meter adds its own inherent inaccuracy on top of the C-Weighted scale, hence the development of the "RS Correction Factors" which correct for both the C-Weighted scale and the meter inaccuracies.

    If you really want to see what your system is doing, you need a professional grade mic that has a linear (i.e., unweighted) response, and a spectrum analyzer software program.

    Regards,

    Ed
     
  5. Stephen Dodds

    Stephen Dodds Second Unit

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    The divisions are 5dB. That is actually the correction applied by TrueRTA. I just flipped it to give a response reading.

    Just for interest sake here is the Behringer ECM 8000 correction, unflipped. To get the actual response flip it horizontally.

    [​IMG]
     

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