Bluetooth Bookshelf Speakers with Sub-WooferMost 2. 1 systems include tiny satellite speakers and make up for the small sound from satellites with their sub woofer. With the S350DB you get both a massive sub woofer and fully featured bookshelf speakers. Connect your sources via Bluetooth, RCA, optical, coaxial or AUX with these. Take full control of your audio with the side panel controls on the side of one of the bookshelf speakers. 3 knobs are located on the side that effect the bass, treble