WinISD and sensitivity ratings?

Discussion in 'Amps and Cabs [BG]' started by The_Lucek, Jul 30, 2018.

  1. The_Lucek


    May 21, 2011
    Hey guys. I'm looking at speakers for a 2x15 build that I will be pairing with a tube 200w head. Since I will be limited on power I went looking for biggest sensitivity.
    To stop beating around the bush and just get to it, the ratings I'm seeing on winISD and the graphs posted by manufacturers is not identical. It's about 1 to 2 dB lower on winISD than the graphs show.
    Who am I to trust here? Is winISD going bonkers with the math, or are the people selling speakers polishing them up a bit?

    So far I've looked into the FaitalPRO 15pr400 but a bit less sensitive than the 3015. Being on the old continent I got some more choices, and I find the Beyma 15MI100 interesting.
  2. BadExample


    Jan 21, 2016
    The 3015 sensitivity I believe is measured out of cab. Check the data sheet foot notes to be sure. Yhe box controls the cone, so less sensitivity might be a compromise for better mechanical power handling.
  3. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    Data sheet charts show response with the driver literally mounted in a wall, so they're only accurate above 150 Hz or so. Data sheet SPL figures are usually an average across a wide portion of the cab bandwidth, where as a bass player you're main concern is in the lows. WinISD is what you should use to compare drivers below 250 Hz, data sheets above that.
    The_Lucek and agedhorse like this.
  4. ThisBass


    Aug 29, 2012
    15PR400 manufacturer rating sensitivity 1W/1m 99dB
    predicted sensitivity (BassBox pro)
    response chart modelling 1Watt/1Meter

    Kappalite 3015 manufacturer rating sensitivity 1W/m 100.8dB
    predicted sensitivity (BassBox pro)
    response chart modelling 1Watt/1Meter

    15MI100 manufacturer rating sensitivity 1W/1m 100dB
    predicted sensitivity (BassBox pro)
    response chart modelling 1Watt/1Meter

    Not sure the MI100 was really suitable for (modern) bass guitar application, except for coffee house gigs where there is no need for deep lows or if amp power is a limiting factor on a larger stage.
    Last edited: Jul 30, 2018
    The_Lucek likes this.
  5. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I wrote my own speaker modeling program, starting from what I thought was the underlying physics principles. (You can find it at my "non commercial" web page, but there are much better programs for actual useful speaker design). So far so good. My program consistently predicts sensitivity higher than WinISD. I believe this is due to a difference in how my program and WinISD convert "1 Watt" into a corresponding input voltage. Computing sensitivity the way I think WinISD does it, I get the same results. But I like my method better. ;)

    The difference hasn't been big enough for me to worry about in my designs, and is a detail where our respective approaches are both documented, so an expert could weigh in on whose method is preferable. But it points to possible modeling differences between programs, and meanwhile, there's also the measured curve.
    The_Lucek and dralionux like this.
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    As you have seen, there are different ways to conpute sensitivity, both power and voltage will give the same value if nominal impedance is used but different values if actual impedance versus frequency is used.

    These days, most manufacturers use the nominal impedance method because the difference is usually pretty small.
  7. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    That's what I do in my program. My main rationale is that I don't really care about power, but about the voltage driving the speaker terminals, because voltage gain is what's constant with frequency when an amp is flat.

    At least, that's a good enough model for me to think my way through my own DIY speaker designs.

    Output current just goes along for the ride. Until it doesn't, but that's your job to deal with. ;)
    agedhorse likes this.
  8. The_Lucek


    May 21, 2011
    Wow! What a plethora of pro responses! Thanks fellas for helping me clear things up! Really appreciated!
    Kro likes this.
  9. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    WinISD electro-mechanical parameters has no entry for Z, only for Re and Le. It uses Re to calculate sensitivity, so the voltage drive figure is going to be lower than expected. For the 3015, for instance, it calculates one watt as a 2.3v signal. It's a program quirk that you get used to. I always change the entry in the signal tab to the appropriate voltage, 2.8 for 8 ohms, 2 for 4 ohms, etc.
    The_Lucek, fdeck and agedhorse like this.
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