View Full Version : Double checking my numbers

08-06-2007, 10:34 PM
I am trying to design a box for a friend that has 2 15" Power Acoustik Fubar's. The specs on them are that it needs a ported box at around 3 cu.ft and I was going to tune it for around 34hz. I read the tutorial on the top on this section about doing it with WinISD and so thats what I did.

For net volume I used: 6.0 cu.ft

Port area: 3 inches wide by 15 inches high


My max dimensions were: 40 inches wide and 16.5 inches high

Product of remaining two sides:660

Using WinISD I got a Port Length of: 10.55 inches

I used that to figure out my port displacement:

((3+.75)*15*10.55) / 1728 = 0.34

Then I came up with my gross volume:

Net Volume(6.0)+Port Displacement(0.34)+Sub Displacement(.123)=6.157

Then I solved for my remaining side:

S= (6.157 * 1728) / 660 =16.120 inches

So we got:

Internal Dimensions:

40 inches wide x 16.120 deep x 16.5 inches high

Net Volume:


Port Area:

3 inches x15 inches

Port Length:


Am I doing good so far?

This is my first time using this way to do it. I usally use the calculator on Subwoofertools.com.

Thanks in advance for any help.

08-07-2007, 10:00 AM
using the formula in my sig i came up with....

if using 6.0cu' net, port area of 45sq" and tuning of 34hz....port length is 12" add the end correction factor (if port shares a wall with the box) of 1.5" (1/2 the port's width) to get a 13.5" long port.

the displacement of the port would be.....

12.75 L (don't count the 3/4" for the face of the box since we're already using int. dims.) x 3.75 W (also the same with the port wall that shares a box side) x 15 H = 717.18 / 1728 = .42cu'

so we're at 6.42cu for total net volume....add you sub disp. which you said was .123 now we have 6.54cu' box.

using you max dims., now play with the numbers to get 6.54.

08-07-2007, 03:56 PM
thanks alot for the help