With a subwoofer, you enjoy extra deep bass during your favorite movie or series. It's a powerful speaker that only produces the low bass tones. You add it to your television or home cinema set for a complete home cinema experience. Go for an active subwoofer with a built-in preamplifier if you don't want to buy a separate amplifier. The Sonos Sub G3 or the Harman Kardon Citation Sub S are good choices. Check if your soundbar is compatible with the rest of your devices. You can only connect Bose subwoofers to a couple of Bose soundbars, for example.