I was bored with the same-o round ports, so I calculated the surface area of a 4" round port- of which 3 were required for this 10 cubic foot enclosure. The measurements I came up with were approximately 5-1/2" per side for the triangle, and 3-1/2" per side for the square. I put a 1/2" radius on the inside of the bezel openings and I'll let you be the judge for the results. There is no wind noise from the ports and I am a happy camper! I used a Dayton DCS450 18" driver and a Dayton SA240 subwoofer amplifier. The results are as you would imagine.