SOUND TRANSDUCER CONTAINING DUAL VOICE COILS

摘要

A sound transducer (10) includes a frame (2); a diaphragm (14) resiliently mounted to the frame; a voice coil (28) for actuation of the diaphragm in response to a signal; and a further coil (30) fixedly mounted to the frame and arranged to produce an opposing magnetic field to the voice coil in response to the signal. The frame has an axial post (20), the voice coil being wound on a former (24) provided around the axial post, and the further coil being fixedly mounted on the axial post. The voice coil and the further coil are arranged so that their two magnetic fields are in opposite directions, thereby increasing the efficiency of the transducer. The transducer is also provided with amplification circuitry (32), for example, an integrated circuit (34), which is mounted on a heat sink (38). A filter (36) is also provided. In an alternative embodiment, the transducer can be provided without the amplification circuitry, or the amplification circuitry can be used with known sound transducers. In yet another embodiment, the transducer can be provided with a second further coil, which further increases the efficiency of the transducer. The amplification circuitry can also include phase-shifting means, which enhances the perceived sound quality.