It is a driven 1-way bass-reflex design to extends the frequency response down to 27 Hz. It has two bass-reflex chambers designed around two 21-inch/4.5-inch voice coil high spec dual voice coil drive units and ultra-wide ports that drastically reduce low-frequency turbulence to deliver exceptional low frequency performance. The SW221 is designed to streamline setup a deliver maximun result in minimum time uniting features unique to deliver solutions for rental and installations systems. The SW221 can only be used in ground stacked configurations in conventional left/right setups as well as arranged in a cardioid subwoofer configurations. The cabinet is constructed of 18mm ply Baltic birch and have an impact and weather resistant paint finish (Polyurea Protection), properly braced for the intended use. The front of the cabinet are protected by a hex-stamped rugged steel grille and each side panel incorporate four recesed handlers. The connectors are Neutrik NL4. Four 100mm wheels are available as optional accesorie to mounted at the rear. SW221 providing a coste efective solution for professional of touring, integrator and installers delivers an intelligent and flexible system to at any budget.