Speaker and speaker apparatus
A speaker capable of properly adjusting a spring characteristic with which a voice coil is driven and capable of being driven in large amplitude. When a position control coil wound around a bobbin is at a reference position, both ends of the coil cross a magnetic gap formed between external and internal yokes by a predetermined length and Lorentz forces acting on the front and rear ends are balanced. When the voice coil moves in either forward or rearward direction, lengths of the magnetic gap crossed by the front and rear ends of the control coil are different therebetween, and the vector sum of Lorentz forces acting on the position control coil is opposite in direction from the movement of the voice coil, whereby the voice coil is stably held at the reference position.
1. 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.
2. The speaker according to claim 1 , wherein said control coil is disposed between magnetic gaps in which the magnetic field is formed in opposite directions.
3. The speaker according to claim 1 , wherein said control coil is disposed so as to overlap at both ends thereof magnetic gaps in which the magnetic filed is formed in opposite directions.
4. A speaker apparatus, comprising:
a speaker having a cylindrical bobbin and a control coil wound around the bobbin; and
a circuit adapted to supply said control coil with a constant electric current,
wherein said speaker includes 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; 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,
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.
5. The speaker apparatus according to claim 4 , wherein said control coil is disposed between magnetic gaps in which the magnetic field is formed in opposite directions.
6. The speaker apparatus according to claim 4 , wherein said control coil is disposed so as to overlap at both ends thereof magnetic gaps in which the magnetic filed is formed in opposite directions.
7. The speaker apparatus according to claim 4 , further including:
an output unit adapted to amplify an electric current supplied thereto and to supply said first and second coils with the amplified electric current in opposite directions.