Building a custom box for 2 soundqubed 12s

[Dcoils101]

I've got 2 soundqubed HDS 2.1 12" subwoofers. 600w RMS each. Designing a custom enclosure. Currently just in a prefab tuned to 43hz with not enough port area. 1.6 net airspace per sub. It sounds surprising well. Not peaky. Plays musically and with good frequency response, playing with a fairly flat response between 45 and 75hz. 

But I know these subs need a much better box. I'm looking for recommendations. I've got about 36"w 28"d x 13.75"h to work with as maximum dimensions. I'm thinking I want to use 3/4" birch plywood. 1/2" baffle, subs flush mounted, aero port with 56sq inches of port area, tuned to 35hz. Manufacturer recommended 4 foot net airspace after accounting for the port volume and subwoofer displacement. I want to go a little smaller, I want about 3.75 net cubic ft internal airspace including port and sub displacement. 

 

Help with designs and recommendations would be appreciated.

[ckeeler11]

You could go 13.75"H x 36"W x 20"D. For port you will need an 8.5" port for 56sq. in. not sure where you would get that. You can go 8" which will give you 50 sq. in. and length of 23" for tuning of 35Hz.. Volume would be 3.8 cu. ft. before bracing and sub so you should be right there at 3.75.