Electrical audio signal processing systems and devices – Loudspeaker feedback
Patent
1993-12-13
1995-04-18
Kuntz, Curtis
Electrical audio signal processing systems and devices
Loudspeaker feedback
381194, 381199, H04R 300
Patent
active
054085330
ABSTRACT:
A motional feedback loudspeaker system wherein the loudspeaker distortion is reduced by a negative feedback signal derived from the back electromotive force induced by the motion of the voice-coil within the magnet field. It is essential that the feedback signal be a linear function of the loudspeaker cone motion, and this is achieved by locating the voice-coil within a uniform elongated cylindrical magnetic field of substantially constant flux density and having an axial length substantially greater than the axial length of the voice-coil. Therefore the voice-coil is underhung so as to remain immersed within the uniform field even at peak displacements of the voice-coil during maximum excursions of the speaker cone. The uniform elongated magnetic field is preferably provided by a cylindrical radially polarized magnet of neodymium. In order to sense the back electromotive force due to the voice-coil motion the speaker is located within a bridge network so that the magnitude of voltage imbalance across the bridge is proportional to the cone velocity. A difference amplifier senses this voltage from which is derived the feedback signal which is fed degeneratively into an early amplification stage. This negative feedback reduces the nonlinear distortion of the loudspeaker, and also improves the transient response and frequency response.
REFERENCES:
patent: 5321762 (1994-06-01), Stuart
Loudspeakers, G. A. Briggs, 1958, p. 64.
Cheng, David K., Field and Wave Electromagnetics, p. 197, 1983.
Kelly Mark D.
Kuntz Curtis
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