The S900 is a 2.0 active bookshelf speaker for home audio and desktop monitoring. A 4-inch mid-woofer and a 1-inch silk-dome tweeter cross over at 2.6 kHz, and the MDF cabinet is tuned to suppress internal standing waves. Inputs cover Bluetooth 5.3, optical, RCA and 3.5 mm, so it connects directly to a TV, computer or phone. Independent volume and tone knobs sit on the side of the master unit, so day-to-day adjustment never requires an app.