The S.9 utilizes an active-passive configuration; one of the 10-inch drivers is controlled by the 350 watt amplifier, while the passive driver reinforces the active driver. This additional surface effectively doubles the air moving capacity of the design. The result is more dynamic, prodigious bass across the entire room while reaching over a half octave below the S.5 model. Both speaker level and subwoofer (line) level inputs are provided for the most flexible connectivity, and the controls let you dial in the subwoofer to blend perfectly into your system.