winISD help!

Discussion in 'Amps [BG]' started by thebassbuilder, Mar 19, 2014.


  1. thebassbuilder

    thebassbuilder

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    Calling all speaker builders. I downloaded winISD and I am just now learning how to use this program (I think). I want to know if I am missing something here. When I enter all the info needed from the spec sheet on the speaker and go to the box disign section it tells me I need a box volume of 3.87ft. I know I was recomended by DukeLeJeune to use about a 1ft box. Just wanting to know how to calculate a smaller box volume? Also the port size it gives me is crazy. It will say 4" dia and 1/2" length. So I am all confused. I am reading the help section but have not found anything yet. Let me know if I am missing something or need to try a different program.
     
  2. Passinwind

    Passinwind Charlie Escher Supporting Member

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    Which version did you download? If you use Windows 7 or 8 you should go with WinISD 0.7.0.900 .

    Go to the Box screen and enter the cab volume you want to model, plus the number of ports and port diameter. Hit enter and you should see a model reflecting those specs.
     
  3. thebassbuilder

    thebassbuilder

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    Thank you!
     
  4. BbbyBld

    BbbyBld

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    I think it does that because it starts with the optimal box volume for the speaker that is based on the Vas spec. Air acts as a spring when enclosed. Vas is the volume of air that matches the spring force of the speaker suspension. You will get maximum performance when you match the Vas spec. Lots of speakers work just fine when you don't match Vas. The other thing is that a lot of these programs optimize for maximum low frequency extension, which is not always what you want. Duke most likely has experience with the speaker and knows what it will do in a 1 cube box.

    That probably wouldn't be unreasonable if you were using 1/2" plywood. If you increase the diameter, the length will increase. You can also keep the same diameter, or go down in diameter, except use more than one port, which will add length.
     
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  6. thebassbuilder

    thebassbuilder

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    Thanks for the info. On the port section of winISD it has a box that you cannot change that says mach: and has a number in the box below it. What is this referring to?
     
  7. BbbyBld

    BbbyBld

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    That has to do with the air velocity of the port. The port will "chuff" or make noise if the air velocity is too high. WinISD has a pull-down function on the graph window that is called rear port air velocity. It's plotted as a function of frequency. Under the signal tab, change your power level to the max power level you plan on running. This affects the predicted air velocity. Ideally, the air velocity will be under 10 on the graph across the frequency spectrum, but that's being super anal. In reality, higher air velocity is okay depending on frequency and is sometimes a good thing, but I won't tell you much more about that. :ninja: Try to keep all of it under 30 or 40 by experimenting with port sizes and you should be alright. I think some versions of winISD throw out a mach warning and may not have the velocity plot.

    Obviously, a wider port, or multiple ports will have lower air velocity. A larger cabinet will also have lower air velocity. A longer port will have higher air velocity than a shorter one.
     
  8. thebassbuilder

    thebassbuilder

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    I am glad people like your self are here to help newbies like my self out. Thank you!
     
  9. bgavin

    bgavin Supporting Member

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    OP,
    Vent chuffing is determined at the maximum usable input power.

    Link to S2010 Max Power

    This link shows the S2010 driver in a 1.1 cubic feet net volume test box.
    Moving down from the high frequencies, the max power dips to 103w at 88 Hz.
    This is input power maximum for this particular driver.

    Move farther down in frequency to find the lowest frequency at 103w.
    This is approximately 52 Hz.
    If you move down to 41 Hz, you will find the driver will only accept 23w or so.

    Link to S2010 Vent Velocity

    This link shows the vent velocity in msec, at the 103w maximum input power.
    17msec is 5% MACH, or the agreed-upon velocity for no chuffing.
    Increasing the vent area or vent count changes this number.
    WinISD will automatically calculate the vent length for you.
     
  10. chiplexic

    chiplexic

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    I forget which version but it will warn you about Mach velocity by showing the Mach number in "green" for a good speed and "red" for a no,no speed.
     

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