USB input SD card Bluetooth 4.2 Aux in FM radio Frequency Response of the Satellite: 180 Hz to 20 kHz Satellite Impedance: 4 Ω Satellite Output Power (RMS): 5W x 2 Size of the subwoofer's driver: 5 15 W is the subwoofer's output power (RMS). Impedance of the subwoofer: 4 Ω 50 W is the total system power. 25 W is the pure system power (RMS).