Reason I say footprint, you can design subs that support low end extension with very little distortion, problem is, it is some massive box the size of a coffee table, or the enclosure might be tuned to certain frequency, any below it is horrible. Designing an enclosure that can take care of the lowend without hogging up the room is my main concern. So come on Sunfire build an 15" or 18" sub, they seem to be farther than everyone else with this design.