Using three 4 '' aeroports is not gonna really give you enough port area. I would go with around 80 square inches of port area with that 15. If its a daily box I'd go about 4.5-5cubes after displacement of port and woofer, and your tuning of 33hz should be nice for some SQL. I use 3.5 cubes after displacement tuned to 35hz for my XXX 12 with 45 square inches of port(too small but haven't had time to rebuild this box). My competition box that I'm putting up a 148.9 legal with is a lil over 6 cubes after displacements and will soon be going from 121 to 150 square inches of port tuned to about 60hz(haven't decided exactly where to tune yet I'm still playing with the vehicle). Hopefully that gives you an idea of where to start. Good luck man.
Dad, Electrical Engineer, MBA
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