Series II enclosure delivers the enhanced efficiency and higher output of a vented enclosure, without the distracting noise or “chuffing” generated by a port. The patented Slipstream port dramatically reduces port noise at high sound pressure levels by minimizing airflow turbulence. With high-roll surrounds, proprietary cone design, and long excursion, Series II enclosure deliver deep, powerful bass, with greater accuracy than conventional ported boxes. And the exclusive SSI™ (Smart Selectable Impedance) switch lets you choose 2- or 4-ohm impedance for maximum configuration flexibility. It’s everything you want in a compact, easily installed enclosure.