View Full Version : port formula

11-11-2004, 12:18 AM
i was reading on another forum that the formula was 1.463x10^8....blah,blah...
i've always used 1.84...this is what jmac told me. who is right???

11-11-2004, 12:19 AM
Big Mac.

11-11-2004, 12:22 AM
JL Audio agrees with Jmac

11-11-2004, 12:35 AM
thats guys...gotta go spread the good news. or just rub in someone else was wrong!!!

11-12-2004, 03:06 AM
heres the response i got. someone help me interpert.

The speed of sound in air @ 18 degrees centigrade is 1.347*10^4 inches per second that value squared is 1.815*10^8 that squared value divided by 4*pi is 1.45*10^7. The particular equation he is referring to assumes that the port diameter is in inches. The equation you may be using could assume the port diameter is in some other type of unit.

11-12-2004, 05:00 AM
there's two equations I've found:

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


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

so your 1.84 is not in the same context as the 1.463 and shouldn't be considered "right" over a different system of equations.