In a speaker, a magnet 23 is disposed at a mid position of a voice coil bobbin 25 mounted on a cone 34. A couple of voice coils 28 and 29 are put around the circumferential outer surface of the voice coil bobbin 25 at the positions thereof facing one end and the other end of the magnet 23. A magnet 32 is disposed within the voice coil bobbin 25, and develops two magnetic fields in a state that the first and second voice coils 28 and 29 are located between the one and other ends of the first magnet 23. Dampers 26 and 27 support the voice coil bobbin 25 at positions such that the voice coil bobbin 25 is axially vibratory. Those positions are located on both sides of and symmetrical with respect to those portions of the voice coil bobbin 25 which are respectively wound with the voice coils 28 and 29.