The Edifier R1850DB are powered bookshelf speakers designed to work independently from receivers or amplifiers. These speakers have a built-in amplifier with an option for a subwoofer output so you may transform a bookshelf setup into a 2.1 sound system. Connections include 2 RCA, 1 optical, and 1 coaxial connection. Use RCA for connecting to turntables and using the included RCA to AUX for AUX connections. Optical cable included is great for computers. Woofer size is 4-inch while the silk dome tweeters are 19mm.