Whoa, I was looking up instrument loudspeakers on google and came by this:
http://www.instituteofbass.com/product_spotlight/This makes me wonder if something tricky can be done with the WO as well.
At first glance, this makes no sense to me. This theory may work in cylinder heads, where 4+ smaller valves amount to more flow than a single large valve, but I thought one of the necessities of creating lower frequencies was starting with a cone surface that could create them to begin with! Low frequencies seem lower pitches when played very loudly, but... well you get my drift. What is really going on in those cabinets with all the 5" drivers?
All I can figure is they're using multiple drivers to create larger SPL since there is as they said more effective cone area, but making up for the lack of actual low frequency reproduction from the driver cones by using a transmission line or folded horn of sorts.