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need more help please.....

Discussion in 'Home Cinema Building DIY' started by go5, May 11, 2003.

  1. go5

    go5
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    okay so I just used winISD to input some driver information and got some results that maybe I need some help with.

    I received a 33.5 l volume for the design.

    the dimenisions are as follows:

    w - 0.363 m = 14.37 "
    h - 0.559 m - 22.09 "
    d - 0.232 m - 9.21 "

    can i minipulate these numbers as long as they equal the same total ( take 4 inches from the h and add it to the d? )

    22 seems a little high to me, maybe I am wrong and it is exactly right.

    also 33.5 l = 1.2 cubic feet. 1.2 cubic feet give aprox 14" by 14" by 10.7 ". How is that so off of the other dimensions?

    hope all this makes sense and forgive me if it does not.

    Thanks

    Mike
     
  2. MikeK

    MikeK
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    The program isn't really designed specifically for subwoofers, it's for speakers in general. If you asked for the optimum box dimensions, it's given you what's known as "the golden ratio" for internal dimensions, which are 1.6 x 1.0 x 0.6.
    Note that it gives these as H(1.6) x W(1.0) x D(0.6), but it really doesn't matter - most manufacturers use H(1.6) x D(1.0) x W(0.6) anyway to cut baffle (front panel - ie where you actually mount the driver) diffraction by making the speaker narrower - that's if they bother with this ratio at all, that is - it's not a hard and fast rule, just a guide, a sort of starting point!


    You can use any shape you want really, but it's probably best to avoid a cube (remember it's only the internal dimensions which count as far as this is concerned), any box with two of the 3 dimensions the same, and any where one of the dimensions is an exact multiple of another. Various other things can be done as well, such as non parallel internal walls and curved walls etc - the theory is all around reducing internal reflected waves!


    Also, if it's a sealed alignment, don't worry too much about the exact volume - try altering it a few litres either way and see how little it affects the response.

    Also, don't forget the volume of the actual driver and amp, plus any internal bracing (which take up space inside the box). And lastly, don't overlook the effect of stuffing the box with acoustic wadding - it can add a sizable amount to the "effective" volume of the box - 20% is not untypical (make sure you keep the stuffing away from the driver though, so it can't interfere mechanically with the cone's motion - a particular problem to think about with sealed downfiring subs).
     
  3. go5

    go5
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    thanks for the info....

    I have researched and received so many different factors and differences from so many sources. Is there any really good program, way of calculating, giguring out , etc to design an enclosure. I think I have a good idea than nope maybe not.

    Any sure things out there?

    Thanks in advance
     
  4. RichardH

    RichardH
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    In WinISD, alter the dimension you want to change (e.g. the 22"0, press Enter, and the third dimension will be recalculated for you.
     

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