Genelec's Active Home Theater subwoofers, the HTS4B delivers tight and powerful bass down to 18 Hz. The subwoofer shares the same design layout with one magnetically shielded active loudspeaker driver and two passive radiators. the HTS3B has a 12" driver and passive radiators powered by a 200 W amplifier. It has a frequency response from 18 Hz to 120 Hz and the maximum SPL output is 113 dB and 117 dB respectively.