Hi all,
I have a problem. Instead of buying a plastic port and calculating the length for a vent in a bass reflex enclosure I would like to transpose the equation and determine the diameter of the port using the thickness of the wood as a constant. The normal equation for calculating that I was given by SY is:
L = ((2118*D^2)/(Fb^2*Vb)) - 0.85*D
If I rearrange it like this:
D = ((2118*L^2)/(Fb^2*Vb)) - 0.85*L
Will I get the correct answer? I'm not bad at math and I think it is correct but I want to be sure. Can anyone help?
G
I have a problem. Instead of buying a plastic port and calculating the length for a vent in a bass reflex enclosure I would like to transpose the equation and determine the diameter of the port using the thickness of the wood as a constant. The normal equation for calculating that I was given by SY is:
L = ((2118*D^2)/(Fb^2*Vb)) - 0.85*D
If I rearrange it like this:
D = ((2118*L^2)/(Fb^2*Vb)) - 0.85*L
Will I get the correct answer? I'm not bad at math and I think it is correct but I want to be sure. Can anyone help?
G
To check your work, plug in D into the first equation, then plug the resulting L into the second and you should come up with the same D as you plugged into the first.
-------------solution below------------------
FYI, your equation uses millimeters for port dimensions and liters for box volume. I think the constant, given as 2118, should be closer to 2650.
Given an equation:
0=k*Dv^2/(Fb^2*Vb)-0.85*Dv-Lv
(look familiar? - that's the quadratic equation)
0=ax^2+bx+c
x = -b/(2*a) +/- sqrt(b^2-4*a*c)/(2*a)
Thus, there are two solutions for D, but one is most likely negative and not possible 😉 It is also possible that (b^2-4*a*c) is negative, in which case, you can't tune with a simple port.
-------------solution below------------------
FYI, your equation uses millimeters for port dimensions and liters for box volume. I think the constant, given as 2118, should be closer to 2650.
Given an equation:
0=k*Dv^2/(Fb^2*Vb)-0.85*Dv-Lv
(look familiar? - that's the quadratic equation)
0=ax^2+bx+c
x = -b/(2*a) +/- sqrt(b^2-4*a*c)/(2*a)
Thus, there are two solutions for D, but one is most likely negative and not possible 😉 It is also possible that (b^2-4*a*c) is negative, in which case, you can't tune with a simple port.
Thank's for your help Ron. I think that I'm going to go ahead and use a tubular port in the rear of the cabinets after all. I think that attempting to use only the thickness of the wood as "Lv" would make the resulting diameter too small and result in port turbulence and chuffing. Thank you very much for your reply.
G
G
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