Magnetic suspension transducer

Abstract

An improved electrodynamic acoustic transducer eliminates or reduces the need for flexible or elastic materials to suspend an internal magnetic element by using both static and dynamic signal-dependent magnetic fields to control its movement. In one implementation, the transducer has a magnet that moves within a surrounding tube. This tube in turn supports one or more electromagnetic coils that generate a dynamic signal-dependent magnetic field that causes the internal magnetic element to vibrate. The surrounding tube also supports one or more magnets whose location on the tube is fixed and whose magnetic fields provide appropriate restoring forces acting on the internal magnetic element. These fixed magnets may be replaced or supplemented by ferromagnetic materials. This transducer may provide sound and infrasonic vibration by coupling the internal magnetic element to other radiating elements or by being placed in close proximity to or in actual contact with the pinna or meatus of the human ear when used in headphones or earphones, for example, and it also may provide sound through the direct vibration of the air in contact with the surface of the internal magnetic element. When direct atmospheric coupling is not required, the transducer may be assembled in a sealed enclosure.