square/round port help (yes I searched first)

[blazin_yeti87]

Hey all, new to the forum and require a little info.

First, build info:

'03 cavalier 2dr

sub is a Treo Engineering SSX 15

Amp is American bass XD3000

Will have single 220a Alt.

Will have 1-2 batteries in the trunk.

Looking to build a box with a square or round port(open to either) where the sub and port fire into the car. looking to do sub slightly left off centre and port to the right.

Available space is 34.25"W, 17.5"H, and 16-18"D. Treo recommends 3.5cu.ft net, 50sq.in port, 25.25in length, F3=29.4Hz.

I have always done slot ported but I would like to try square/round port this time around. I'm not asking for someone to do all the leg work and design me a box, more looking for help doing the port.

Thanks in advance