Sony MEX-M70BT Marine CD & USB Car Motorcycle Receiver w/Bluetooth NFC (Certified Refurbished) Max power output: 55 watts x 4 at 4 ohms Power Ad Hoc: CEA2006 Standard Power: 17 Watts RMS per channel into 4 Ohms, 4 channels driven from 20Hz to 20 kHz with less than 1% THD+N. Speaker Impedance: 4-8 Ohms Audio Format(s) Supported: MP3/WMA/WMA files1