Why are #'s different in LspCAD vs WinISD

Discussion in 'Archived Threads 2001-2004' started by Harold A, Feb 18, 2001.

  1. Harold A

    Harold A Stunt Coordinator

    Dec 16, 2000
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    I am using these programs to try and design a sealed Shiva Sub. The numbers I get between the 2 programs for a -3db down point is way different. I checked and made sure the sub parameters are the same for both. This is my first attempt at a DIY sub. I want the deepest bass extension I can get with a sealed sub. The box will be 16"x16" by ?? height. The height will be adjusted to what it needs to be to get the box volume I need. I assume I want the biggest box that is feasible say around 3ft tall in my case.
    Why are the numbers between the programs so differnt?
  2. Greg Monfort

    Greg Monfort Supporting Actor

    May 30, 2000
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    For one thing, WINISD has errors in it, and is worth every penny you paid for it. Secondly, depending on the program, it may have (probably has) one of several condensed versions for the various formulas.
    As an example, the original duct length formula is as long as your arm, so the more parameters that are lumped together as constants, the greater the error. They CYA by saying that it's necessary to do final tuning per some procedure, since the condensed formulas err on the longish side.
    I use BoxPlot for quick comparisons since it appears to use the Margolis/Small formulas which I used for many years before all the ~inexpensive programs came out. For in-room power response and fine tuning, I use Lspcad, which appears to use the full tilt boogie formulas.
    Loud is beautiful, if it's clean

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