This is a very high power passive sub of bandpass design as only Dr. Geddes can do it.  But the best part of buying a Geddes sub is the setup analysis that is provided.  With every sub comes a run of a complex room/sub fitting algorithm.  Bass is completely room dependent and just buying a sub (or several) will not ensure a satisfactory response in any given room.  Now you can have the subs custom fit to your room!  (Photo not current - sub now has three larger ports on the sides.)