For low frequency response with maximum output, Dayton Audio's PSS555-8 21" professional subwoofer is an unbeatable value. This massive driver is capable of incredible displacement with excellent efficiency and power handling. Featuring a 4-1/2" voice coil, powerful ferrite motor, extensive venting, rigid treated paper cone, and rugged cast aluminum frame the PSS555-8 is capable of incredible low frequency response at breathtaking SPL levels.