help with venting

[slicks5150]

I have the dimensions for my box which are as follows
height 14.5"
width 25"
depth 19"
3/4" board
which comes to 3.09389ft^3 which is perfect for me now how do I determine how long and how wide and ETC. . . to make my vent all the calculators that I find are for port size(i.e. they all same port diameter) but I dont want a round port what is the formula or a link to a calculator for vent size???? I want to tune it at 30hz ( the sub is an atlas12) any help would be greatly appreciated.

[tommyk90]

Did you figure in that you are going to have port and sub displacement as well?

What is the exact box size you are looking for?

[slicks5150]

I want the box to be 3ft^3 . which I figured would work out being that I was at 3.09389 do I need to adjust maybe to 20" deep .
I just found something out. if I have 3ft^3 with the dimensions I listed then the vent would need to be 12" high width would be 2" and the length would be 18.91" to tune at 30hz does this sound about right?
now if this is correct than I would need to go to 20"deep or my vent would be right up against the back of my box at 18.91"s (depth was at 19"s)
I tried to calculate the height of the vent to be at 13 inches but I came up with 20.74"s deep which is to deep thats at a 2" width at 1.5 " width I came up with 15.07" deep but the calculator I used said the ratio should be 1:8 which it is not at 1.5 inches. . . . any insite as to what my problem is here .