Posted by Wayne Parham [ 67.66.228.132 ] on October 23, 2004 at 14:00:32:

In Reply to: Two Pi with off-sized speaker box posted by brian.goodman on October 23, 2004 at 13:22:52:

Use the formula below to calculate the port size. For the Alpha 10's used in two π's, you'll want to tune the box to 40Hz.

Here's a little BASIC program that will calculate the formulas for you, if you can still find an old BASIC interpreter around somewhere.

10 INPUT"Enclosure Volume";VE
20 INPUT"Diameter of Port";PD
30 INPUT"Length of Port";PL
40 VB=VE*1728:PI=3.1415926535:AP=PI*((PD/2)^2):LC=PL+((8*PD)/(3*PI))
50 FR=(13548/(2*PI))*(AP/(VB*LC))^.5
60 PRINT"Fr =";FR;"Hz."
70 GOTO 10

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