Question on Analysing Drivers with WINISD.

Discussion in 'Archived Threads 2001-2004' started by Anthony AC, Mar 4, 2003.

  1. Anthony AC

    Anthony AC Extra

    Dec 17, 2002
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    Hello People, well seeing as you're the experts. [​IMG]

    I want to embark on the wonderful world of DIY subs, and have come across these two drives (specs below) and don't understand why the supposedly "cheaper" driver seems to model "better". Or is it that I don't know how to read the stats (most likely). The more expensive driver gives a flatter curve yet the cheaper drive has a louder SPL with a smaller Xmax. Is it due to the efficiencies or is it something else?

    Driver X:
    Sensitivity - SPL - 1Watt @ 1 metre: 88.17
    Voice Coil Resistance (Re): 3.5 Ohms
    Resonant Frequency (Fs): 25.58Hz
    Mechanical Q Factor (Qms): 3.843
    Electrical Q Factor (Qes): 0.458
    Total Q Factor (Qts): 0.409
    Equivalent Volume (Vas): 93.42 Lt
    Cone Area: 0.049 Sq m
    Xmax: 10.5mm

    Driver Y:
    Sensitivity - SPL - 1Watt @ 1 metre: 93.0 (note WINISD says 90.8)
    Voice Coil Resistance (Re): 3.5 Ohms
    Resonant Frequency (Fs): 21.6Hz
    Mechanical Q Factor (Qms): 12.29
    Electrical Q Factor (Qes): 0.294
    Total Q Factor (Qts): 0.288
    Equivalent Volume (Vas): 220 Lt
    Cone Area: 0.0494 Sq m
    Xmax: 6.0mm

    WINISD says that Driver Y has a higher SPL down to 24Hz and then both drivers are approx. equal below that.

    I have modelled both with the following, 125 L enclosure tuned to 21.5Hz, 2 x 82mm vents - 487mm long. Driver Y has a -3dB @ 35.4 Hz and Driver X has a -3db @ 21.3 Hz, yet Driver Y is supposedly louder.

    Your thoughts and advice would be appreciated.

    Thanks, Anthony.
  2. Henry_W

    Henry_W Stunt Coordinator

    May 7, 2002
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    I'll leave the 'why's' from a technical standpoint to others - I am fresh into this my self. I have noticed that a lower QTS will generally show low end anomilies in bass reflex designs (that is your driver Y).

    As to SPL - With WINISD, Boxplot and Unibox they depend on math to get the answer and my experience is that they are all accurate in their application of the formulas. Real SPL is a measured event, however, manufacturers use many different methods to measure - many setups are designed to meet their marketing strategy. Without test equipment to validate, I would stick with the programs determination of SPL for box building.

    Lastly, speaker price is not always the right measure, but the general rule is that price increases with quality...

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