Every design I see on the net uses two woofers, facing in opposing directions, wired out of phase, so the cones are traveling in the same absolute direction (as opposed to relative to the driver basket).I assume they're facing in the opposite direction so that the output on either side of the baffle is compose of the wave from one driver front and one driver rear - keeping things symmetric.
What I’m wondering is why the use of two drivers? Is it that without two drivers this symmetry of output is lost? Or is it simply that you can halve the necessary driver excursion by splitting it between two drivers?
Or put another way, would one huge driver with a long Xmax do just as well?
Any insight would be appreciated.