After thinking about it, I wondered if doubling the amount of drivers helped to smooth out the room response even more. Not sure though.
My understanding is that it's the separation between drivers (or between driver and port) which helps to smooth out the response. A bit like having two subs in slightly different parts of the room.
I suspect this is why the SVS cylinder subs seem to sound a bit smoother than their response curves would indicate; the ports are about three feet away from the woofer...
A final sweep of the room shows me +/-3db from 14Hz to 100Hz.
Wow...
