In pictures: Dissecting the Onkyo Liverpool Series...
The subwoofer back plate has a bevy of options. An adjustable low-pass cut-off is available, as well as a differing output level and phase switch. The subwoofer also allows audio passthrough to a second subwoofer for greater impact. A 150W amplifier handles the subwoofer's power.
In pictures: Dissecting the Onkyo Liverpool Series MS5LX