Lightweight but powerful FEA-optimized neodymium magnet Extremely high BL factor and Xmax for outstanding LF output 15 mm Xmax, 60 mm peak-to-peak excursion before damage 6.0" split winding copper voice coil on fiberglass former Ventilated voice coil gap reduces power compression B&C's 21SW152 21" pro subwoofer speaker boasts an oversized 6.0" voice coil, neodymium motor, 2,000 watts RMS power handling capacity, and 15 mm Xmax (60 mm peak-to-peak excursion before damage).