They have a 100V and 8 OHM driver built in making them compatible with almost any system. Please make sure that you set the speaker to 8OHM if you are using a standard low impedance Hi-Fi system. Water resistant PP cone main driver Rotary selector switch for 100V line tappings or 8 ohms operation Weatherproofed IP54 1M hard-wired speaker cable attached to the rear of the unit Mounting bracket included Optional mounting by M6 screw sockets Available in white or black finish 100V Tappings 1.5W, 3W, 6W Power RMS (8 Ohms) 30W, Max 60W.