port lengths?

hey,

just a quick question on port lengths.

I built a ported box for my freinds 12in rockford punch sub. I followed the specs fro m rockford which call for 2.0 cu feet with a 4" port 10.75 long. So i sent my freind to get the port but all they had was 2" ones. I typed in the new info in the calc on this website but there saying the port should only be 2 inches.

Is this right??? seems kind of small for a port.

thanks guys

You will need to use four 2" ports to equal the opening area of one 4" port.  You should consider getting acquainted with the relatively easy-to-use WinISD Pro when designing enclosures.  See the sticky on this forum.

Here's how you calculate square inch opening area of a circle:  pi R squared.

pi is always 3.14 (accepted figure, although the numbers after the decimel point go on forever...)

R is radius of the circle, or half the diameter.

A 4" port is a diameter of 4", or a radius of 2".

• Square the radius, meaning multiply it times itself
• Multiply the result by 3.14
• The result for a 4" port is 12.56"
• The result for a 2" port is 3.14".
• 12.56 / 3.14 = 4.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.