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HotCarl
12-05-2005, 06:24 PM
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?

squeak9798
12-05-2005, 07:06 PM
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

HotCarl
12-05-2005, 07:24 PM
good start. what about port length and junk like that?

squeak9798
12-05-2005, 07:29 PM
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".

MikeyB
12-05-2005, 07:33 PM
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.

kuijo
12-05-2005, 07:35 PM
http://caraudio.com/vb/showthread.php?t=106885

squeak9798
12-05-2005, 07:36 PM
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.

MikeyB
12-05-2005, 07:38 PM
Thanks guys, very appreciated.

HotCarl
12-05-2005, 10:12 PM
oh man, your a huge help squeak. thanks a ton.