I have the dimensions for my box which are as follows
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.