The Bowers & Wilkins CT8 SW is a passive subwoofer designed to be used with each CT8 LR speaker you may have in your system. The main purpose is to reinforce the low frequencies of your front facing speaker & provide a lower range of 13 Hz without affecting the dynamics & imaging. The 15" Rohacell driver ensures the best quality sounds while managing those low frequencies with ease. The 70-litre enclosure is built using Bowers & Wilkins matrix-braced construction for extra reinforcement.