The port and the subs should be on the same side (Yes, that is the speaker baffle). This allows the sub and the port to couple acoustically. In instances where you can't, then the opposite wall would be the next best thing. 2 evenly spaced (unlike the picture) braces should be placed equidistant from the middle and sides internal internal braces would be fine. Like this (but spaced as noted and with the sub placement in mind, at least one in the middle):
1 large flared round port is best as it is poses the least friction for moving the air and the dual flares like a Precision port or aero port, reduce chuffing (wind noise or farting)
Precision Port 6" Flared Port Tube KitThe unique flared-end construction of the Precision Port™ system enables it to outperform any standard port tube on the market. Conventional tubes suffer from nasty turbulence at the entrance and exit of the port, producing unwanted noise and poor sound...
For the two of the BlackBrick subs you're going to use tune to 32Hz:
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The following measurements' include considerations for the woofer, port and brace displacements.
Slot loaded box:
4"Wx10"Hx14"D slot loaded box:
You'll need a 5.75 internal cubic feet. I always recommend a 3/4 inch roundover edge on the extremal port area.
6"Dx10"L Round flared precision port port box:
You'll need a 5.5 internal cubic foot box.
For determining how to cut the port length, follow these guideline.
* - The value for Flare Length Port Required is the overall length of the flared port. If you specified more than one port for the Number of Ports value the Flare Length Port Required value will be for each port.
* - For the 6" Precision Ports cut the center tube 6 inches shorter than the Flare Length Port Required value.