Abstract: A sound reproducing system utilizes motional feedback and an improved integrated magnetic structure for reducing loudspeaker distortion; for reducing acoustic coupling between the radiated sound energy output and the cone motion sensing structure thereby reducing unwanted feedback signals; and for reducing obstruction of the radiated sound energy output by the cone motion sensing structure thereby minimizing undesirable alteration of the radiated tonal quality. The loudspeaker includes a cone, a frame, and flexible webs. The main electromagnetic structure includes a rear cylindrical iron pole piece, an annular cylindrical permanent magnet, an inner annular cylindrical iron pole piece, a main voice coil bobbin, a main voice coil, and a front annular cylindrical iron pole piece.

Abstract: A pitch sensor for facilitating more accurate tuning of instruments comprises: a reference pitch pulse generator, a saw-tooth generator, a sensing probe, a probe output amplifier, a modulator, and ouput means. The reference pitch pulse generator further comprises an oscillator, a divider chain, gates, and first and second pulse drivers. According to a specific embodiment of the present invention, the sensing probe is a magnetic probe, the oscillator is a crystal oscillator, the divider chain is a decimal divider chain, and the output means is a speaker. Accordingly, the saw-tooth generator is responsive to the reference pitch pulse generator; the probe output amplifier is responsive to the magnetic probe; the modulator is jointly responsive to the saw-tooth generator and to the probe output amplifier; and the speaker is responsive to the modulator. A feature of the present invention is the use of the saw-tooth generator to drive the modulator.

Abstract: A sound reproducing system utilizes motional feedback and velocity-frequency equalization to reduce loud speaker distortion. The system substantially comprises a frequency equalizer-power amplifier combination which is jointly responsive to the input source signal and to a velocity feedback equalizer; the loud speaker structure which is responsive to the frequency equalizer-power amplifier combination; a cone motion sensing structure which is responsive to the motion of the loud speaker cone; an auxiliary amplifier which is responsive to the cone motion sensing structure; and the velocity feedback equalizer which is responsive to the auxiliary amplifier.

Abstract: A sound reproducing system utilizes motional feedback and an integrated magnetic structure to reduce loud speaker distortion. The loud speaker structure of such system comprises a main electromagnetic structure and a cone motion sensing structure. The main electromagnetic structure includes a cup-shaped cylindrical iron outer pole piece, a solid cylindrical permanent magnet, a solid cylindrical iron inner pole piece, a main voice coil, a thin cylindrical bobbin, a cone, a speaker frame, and flexible webs. The cone motion sensing structure includes a hollow cylindrical iron outer sleeve, a hollow cylindrical copper outer sleeve, a disc-shaped non-magnetic support, a hollow cylindrical copper inner sleeve, a solid cylindrical iron rod, a feedback coil, a thin feedback bobbin, and a conical member connecting the feedback bobbin to the voice coil bobbin. A stability control network is connected to the feedback coil for suppressing any supersonic transmission peaks appearing in the motional feedback signal.