KJ03 is a passive speaker and requires an amplifier or receiver to produce sound. It cannot be connected directly to a turntable, computer, or phone. The KJ03 is equipped with a 2-inch full range speaker, which is particularly good for mid to high frequencies. It can be used as a subwoofer sub speakers, DIY speakers. KJ03 can connect car CDs and mini amplifiers. It can be used as desktop, bookshelf or wall mountable speakers, meeting multi-purpose needs. Amplifier is required and not included. Material: Wooden body Full range speaker: 2 inch Impedance: 4 Ohm Rated Power: 10W Frequency response: 85Hz - 20KHz Size: 3.74 inch x 2.95 inch x 5.71 inch Weight: 535g