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Reload Thread: box formulas.

  1. #1
    HotCarl's Avatar
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    box formulas.

    i dont wanna use programs to calculate my boxes anymore.

    i searched but all i see is program links.

    can anybody point me towards any websites that tell ya the formulas and stuff so you can do em yourself?



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    Quote Originally Posted by bcleachd View Post
    can i fit 100 spoke 15 inch rims standard offset on a 95 dodge neon 4 door?




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    Re: box formulas.

    Sealed enclosure:

    Vb = Vas/([Qtc/Qts]^2-1)
    Fb = (Qtc/Qts)*Fs
    F3 = Fb*((1/Qtc^2-2+((1/Qtc^2-2)^2+4)^0.5)/2)^0.5

    Ported enclosure:

    Vb = 20*Qts^3.3*Vas
    Fb = (Vas/Vb)^0.31*Fs
    F3 = (Vas/Vb)^0.44*Fs




  3. #3
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    Re: box formulas.

    good start. what about port length and junk like that?



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    Quote Originally Posted by bcleachd View Post
    can i fit 100 spoke 15 inch rims standard offset on a 95 dodge neon 4 door?

  4. #4
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    Re: box formulas.

    Port length

    Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av)

    Av is the cross-sectional area of the port (in square inches),
    Lv is the length of the port (in inches) and
    Vb is the enlcosure's net volume (in cubic inches).


    Square area of a circle = Pi*r^2
    Square area of a rectangle = H * W

    Guess the rest depends on what you mean by "junk like that".




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    Re: box formulas.

    Sealed enclosure:

    Vb = Vas/([Qtc/Qts]^2-1)
    Fb = (Qtc/Qts)*Fs
    F3 = Fb*((1/Qtc^2-2+((1/Qtc^2-2)^2+4)^0.5)/2)^0.5

    Ported enclosure:

    Vb = 20*Qts^3.3*Vas
    Fb = (Vas/Vb)^0.31*Fs
    F3 = (Vas/Vb)^0.44*Fs

    I don't mean to sound like a complete noob, but what do all of those abriviations stand for in all of those equations? I have never really understood that.




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  7. #7
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    Re: box formulas.

    Quote Originally Posted by MikeyB
    I don't mean to sound like a complete noob, but what do all of those abriviations stand for in all of those equations? I have never really understood that.
    Vb = net enclosure volume
    Fb = box resonant frequency
    F3 = -3db point in the frequency response of the system
    Qtc = the total "Q" of the system (driver in the enclosure)
    Qts = total Q of the driver (in the T/S parameters)
    Fs = resonant frequency of the driver (in the T/S params)
    Vas = volume of air that when compressed to 1m^3 exhibits the same compliance as the suspension of the driver (in the T/S params)


    Fb in the port length calculation is the desired tuning frequency.




  8. #8
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    Re: box formulas.

    Thanks guys, very appreciated.




  9. #9
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    Re: box formulas.

    oh man, your a huge help squeak. thanks a ton.



    |9855|Pro60's|8002|IDmax|NINe.1|

    HotCarl's Myspace

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    Quote Originally Posted by bcleachd View Post
    can i fit 100 spoke 15 inch rims standard offset on a 95 dodge neon 4 door?

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