The PSRX728S is a high power subwoofer system containing two 2268H neodymium magnet, patented* Differential Drive®, 18" woofers in a front-loaded, vented enclosure. The enclosure is designed to present a minimum frontal area. The system offers complete input connection flexibility for compatibility with a variety of cabling schemes. A recessed, external switch allows selection of either contacts +1/-1 or +2/-2. By relocating an internal connector, it is also possible to drive each woofer discretely from a separate amplifier channel. The enclosure is constructed of top quality birch plywood and coated in PROEL AUDIO’s rugged DuraFlex™ finish. Each woofer is housed in an isolated chamber and the enclosure is heavily braced to maximize low-frequency performance. The attractive CNC machined, 16-gauge steel grille is internally lined with acoustically transparent foam to provide additional driver protection and give a very professional appearance. *U.S. Patent 5,748,760; other U.S. and foreign patents pending. Specifications: Frequency Range (-10 dB): 27 Hz – 220 Hz Frequency Response (±3 dB): 33 Hz – 220 Hz Input Connection Modes: Switchable, +1/-1 or +2/-2 Internally selectable, Parallel or Discrete Recommended Crossover Frequencies: 80 Hz, 24 dB / octave HPF 80 Hz, 24 dB / octave LPF Power Rating (Continuous 1 / Program / Peak): Parallel: 1600 W / 3200 W / 6400 W Maximum SPL2 : 136 dB SPL peak Sensitivity (1w @ 1m): 98 dB SPL LF Driver: 2 x PROEL AUDIO 2268H 457 mm (18 in) Differential Drive woofer with neodymium-magnet and dual voice-coils Nominal Impedance: Parallel: 4 ohms Discrete: 8 ohms x 2 Active Tunings: dbx DriveRack, all models. Settings available at Enclosure: Rectangular, 18 mm, 13-ply birch plywood Finish: Black DuraFlex finish Grille: Powder coated, black, 16-gauge perforated steel with acoustical transparent charcoal foam backing. Removable PROEL AUDIO badge and punched  logo. Input Connectors: Neutrik® Speakon® NL-4 (x2) Dimensions (H x W x D): 602 mm x 1067 mm x 838 mm (23.7 in x 42 in x 33 in) Net Weight: 76 kg (166.5 lb) Optional Accessories: SRX728S-CVR: Pull-over padded cover