JBL Professional 500-watt Dual 15-Inch Two-Way Portable Loudspeaker, Black (JRX125) Two JBL 15 in LF Drivers with a 64 mm (2.5 in) Edge Wound Ribbon Voice Coils - for greater efficiency and Power handling Ferro-fluid Cooled Compression Driver with Titanium diaphragm improves HF performance Tough acoustically Superior enclosure constructed using 19mm MDF for improved LF performance JBL advanced Crossover Network for sound shaping and SonicGuard protects the HF driver from excesses Quasi 3 way crossover design for extra bass from the two 15" woofers