Small and thin dynamic speaker with a diameter of 1.1 inches (28 mm) and a thickness of 0.2 inches (5 mm). (Nominal Impedance 8 ohms) Equipped with a magnet and voice coil as well as a Hi-Fi speaker. The minimum resonance frequency is 650 Hz, and it is difficult to play bass but it is more suitable than a ceramic type for beeping sound for the playback of voice like a radio. The impedance is 8 ohms, so it is not as easy as a ceramic mold. It is best to use a small power amplifier IC with an output of about 100 mW.