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Some measurements (current setup with the SVS 20-39PCi)

Discussion in 'Subwoofers' started by nelmr, Dec 14, 2010.

  1. nelmr

    nelmr Active Member

    Well I played with the REW program and the RS Meter as the mic using the correction file for the meter.

    This is with the 20-39PCi and the two main front speakers. I am curious how the bass graphs will work as I play around with the HSU and SVS seperately as well as combined.

    Measurements sweeping signals for the bass:
    [​IMG]

    Avearge RTA fullrange
    [​IMG]

    Waterfall plots for bass:
    [​IMG]

    Waterfall plot for fullrange:
    [​IMG]
     
  2. nelmr

    nelmr Active Member

    By the way what is up with the waterfall plot in full range with regards to the higher frequencies. Is that what a comb filter effect is?
     
  3. Flint

    Flint "Do you know who I am?" Superstar

    Waterfall measures the decay rate for sounds sent to the speaker. Longer decay rates are caused by:
    1) the speaker system might be slow to stop generating sound (woofer flopping about)
    2) driver might have resonances which ring beyond the electrical excitetation
    3) the room reverb and echo is causing the sound to bounce around for awhile before the acoustic energy fully disperses
     
  4. nelmr

    nelmr Active Member

    Thanks for what the waterfall graphs can help measure. What about the bumping, pointy, comb/step like pattern (even for the faster decays). What does that indicate?
     
  5. Flint

    Flint "Do you know who I am?" Superstar

    In general, most of the bumpy frequency response nonlinearities above 500Hz is from comb filtering (assuming the speakers are very good). Comb filtering can be caused by reflections off walls, cabinet edge diffraction, dual parallel driver interaction, and sometimes from a single driver operating at higher frequencies where their wavelengths are shorter than the diameter of the driver piston.
     
  6. nelmr

    nelmr Active Member

    Maybe it's time to build those OC703 panels. I have had the OC in the garage for years. I've just been to lazy to buy the wood and build the panels. I even have the cloth and the polyester quilt padding.
     

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