Patent ID: 8073187

Claim:
A speaker comprising: a cylindrical bobbin; a support structure adapted to support said bobbin for sliding motion in an axial direction of said bobbin; a magnetic path formation frame having a magnet and a magnetic path formation member that cooperates with the magnet to form a cylindrical magnetic gap, said bobbin being disposed coaxially with the magnetic gap, and a magnetic field that passes through interior and exterior of said bobbin being formed in the magnetic gap; a control coil wound around said bobbin; and first and second coils wound around one end side and another end side of said bobbin, respectively, with said control coil disposed between said first and second coils, wherein the magnetic field is formed to be opposite in direction between the one end side and the other end side of said control coil, and the magnetic field is formed such that when a constant electric current flows through said control coil, a Lorentz force acts on said control coil in a direction of forcing back said bobbin slidingly moved from a predetermined position.