other than the JL Audio website formula, here is a modified formula that OLD_SCHOOL gave to me that i wrote in lamens math with a more detailed description so that it was possible to understand without using all the Lv\Av\Fb\Vb terms that arent described very well.

SO;

say the box is 1 cubic foot

the port is 4x12

and its tuned to 36hz

this is where to get the informtion to put into the formula;

the cross section would be (4*12) 48in^2.

the net volume would be (12*12*12) 1728in^3.

and the square root of 36 would be 6.

this IS the formula;

and remember...Code:x = cross sectional area of port (inches^2) y = net volume of box after displacements (inches^3) z = tuning frequency of port (hz) PL= Port length (inches) x[1.84 * 10^8] ____ _______________ - .823 * \/ x PL = y[z\.159^2]

do all math on TOP

do all math on BOTTOM

SUBTRACT .823*square root of X from the quotient of the numerator and denomenator (use dictionary.com if you dont know those words)

the awnser is the port length.

***THANKS TO OLD_SCHOOL FOR HELPING WITH THIS****

this way was eaiser for me.

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