Originally Posted by bladez View Post
I hadn't considered a passive radiator. I have seen them, but know very little about them. Do they function in place of a port? The only problem is the only place on the box for it is behind a center console so there's no room
I would suggest to review your install and box thoughts.
External ports looks like a leaf blower or an overweight armadillo.

And whether external or internal it is going to be at least ~1 ft^3 of volume based upon their specs.

There is only 1 way to zero out the need for extra volume and still have the box a 4th order box.

It is your call.