Ok well, I'm building this box for my HDC315 but using different calculators I get different numbers and every person tells me a different number also. So could someone who is certain they can get me the right numbers do the math out for me and see what they get? And then I can work on changing things up a bit to fit my needs.

My goals
3.8-4 cubes after all displacements
64sq" of port space
dimensions - 16.5hx41wx16.5d(17.25 with double baffle)

Here's my box

Net Cubic Feet: 3.8cu/ft
Tuning: 36.5hz
Port: 67.5sq"

17.25h (Including the double baffle.) x 41w x 16.5d (Top of box where sub will be mounted.)

Port Dimensions
w = 4.5"
h = 15"
l1 = 9.75"
l2 = 8"

Cut Sheet *Inches

Front Plate: 41 x 15
Back Plate: 41 x 15
Top Plate 2x: 41 x 16.5 (Double baffle)
Bottom Plate: 41 x 16.5
Right Plate: 15 x 15
Left Plate: 15 x 15
Port L1: 9.75 x 15
Port L2: 8x15
Angle Cuts 3x: 45 degree small triangles (For smooth port)

Box Plan