Easy way to measure T/S parameters

Posted In: Subwoofers 101

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    simon5 on #159


    Usually, the most important T/S parameters are mostly easy to measure except Vas.
    Re, Fs, Qes, Qms and Qts are easy to measure.

    Usually you measure Vas with delta-compliance because it’s more accurate.
    Other method we hear a lot about is delta-mass.

    In this URL, they talk about an easier method. I’d like to know if this method is good or not.
    Better than delta-compliance? Better than delta-mass?


    Measuring Vas (equivalent air compliance)
    To measure Vas, use a good solid enclosure of known volume that’s about a cube of the nominal speaker size. Determine the total volume, including the speaker cut-out and that trapped by the cone with the speaker mounted on the outside of the box for easy access. Measure the resonant frequency in this situation as well as the free air space resonant frequency.

    Vas = Vb((Fb/Fs)^2 – 1)


    Vb is the volume trapped by the speaker and box
    Fb is the resonance frequency of speaker and box

    simon5 on #2559

    I was expecting an answer fast from John or Deon hehe!

    Sorry guys I know you’ve got alot of work to do, I should quiet down a bit 😉

    dB on #2560

    John Straede has it correct.

    simon5 on #2561

    Thanks! It is better than delta-compliance? Better than delta-mass?

    dB on #2562

    What he is describing is delta compliance.

    simon5 on #2563

    Oh ok, thanks!

    I was thinking delta-compliance needed two enclosures and check the difference between the two.

    I wonder why people used delta-mass in the first place… this seems easier.

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