external, like coming out of the box?take the mounting flange off and screw it onto the box from the inside thru the sub cutout. Assemble the rest of the aero as usual
Like a ~18 inch port where ~9 inches is in the box and ~9 inches is sticking out. I want to build a couple 4th order boxes for my 8's to test. I was really planning on using pvc. I've never built a box with anything but slot ports.