SUB 618 is bass-reflex active subwoofer featuring a 600W RMS Class D Power Amplifier with SMPS Technical Data Speaker Type Active Subwoofer Acoustical data Frequency Response [-10dB] - 35 - 130 Hz Max SPL (1 m) 133 dB Directivity omnidirectional LF 18" LF Voice Coil 2.5" Amplifier Amp Technology SM..