Thanks. It's more precise to the parameters of the sub. Also If one of the subs were to go out, I can remove the box and replace the sub without having to mess with the other sub. I did have specs for a dual ported box but it would have required me to put the speaker terminals on the top of the box since the ports are the side opposed to the ports being on the bottom with the single boxes. It would have been easier to build the dual box, I just opted for the seperates.