hey,

im building a ported box for 2 12 inch swiss audio spl1290's.

i am trying to figure out what the length of the port should be but i just cant get it....im using this equation

Lv = [(1.463*10^7R^2)/(Fb^2*Vb)] - 1.463

ive searched and searched and read the entire sticky in this forum but i keep coming up with an outragously large number...

the box before the port is going to be

34.5 inches long

19 inches deep

and 14 inches high

andthe port is going to be 3 inches tall

i want it to be ported to 36 hrtz

the internal cubic feet is 4.5 giving each one about 2.25 cubic feet

im going to have the subs on the top of the box firing upwards and the port in the front like near the ground...

so using that formula i came up with that the

square root ((heightxwidth)/pie) because its a vented port.

square root ((3x33)/3.14) 33 beacsue tahts the inside measurment.

so i got 5.613615478.......thats the part that replaces the r casue its a vented box.

so....

Lv = [(1.463*10^7R^2)/(Fb^2*Vb)] - 1.463

Lv= [(1.463*10,000,000*31.51267873)]

--------------------------------------------- -1.463

(36^2)*(4.5)

Lv= [461030489.8]

------------------- -1.463

5832

Lv= [79051.87]-1.463

lv=79050.40 now obviously thats wayyyyy to big for the box???

anyone have any idea what im doing wrong??? like units wrong? the only one i can think of is the Vb i ahve it at 4.5 thats cuboc feet, should that be in inches or something, ikd im reallly confused.

thanks

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