need port sizes

My calculations are always based on a standard 4" diameter round port (standard for me as that's what I usually use.)  At 4". the port needs to be 2.6" long for his 5 CUFT enclosure and a 35Hz tuning frequency.  That is 12.56 sqin of port area.  His 4X8" opening is 32 sqin of port area.  That's why I said it was too large.

But, if the openings are already cut, 32 sqin (or about the same as a 6.5" round port) comes out to be 10.3" long.

Q: Is it bad to have a port that is too short?

A: Although a port is used to get the correct tuning in a box, it is not good to have a ports that are too short. By too short I mean you want the port to be equal to or longer than the depth of you subwoofer.

Q: Is there a difference in performance between a circle and a slotted port?

A: No, you will get the same performance out of a box and the same tuning frequency aslong as you have the same port opening size and depth. You will need to remember tocalculate the displacement of the thickness of the wood being used as compared to theplastic of the circle ports in the box.

Q: How far from the wall of my box does my port need to be?

A: You want to have the port the same distance away from the box as the diameter of the port or more.