Patent
1979-08-17
1981-06-30
Robinson, Thomas A.
H04R 304
Patent
active
042764432
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. Features of the present invention are that: the velocity shaped signal from the velocity feedback equalizer is degeneratively applied to the frequency equalizer-power amplifier combination which, in turn, forces the loud speaker to respond linearly to the input source signal and thereby provide a uniform sound energy output; the velocity-frequency equalization effect is limited to that frequency range over which the loud speaker cone operates substantially as a rigid member; the velocity feedback equalizer loss characteristic exhibits a positive slope over the low frequency and rigid member operating frequency range of the cone, and a zero slope over the high frequency range of the cone; the frequency equalizer loss characteristic exhibits a zero slope over the low frequency range of the cone, a positive slope over the rigid member operating frequency range of the cone, and a zero slope over the high frequency range of the cone; and the power amplifier gain characteristic exhibits a zero slope over the low frequency range of the cone, a negative slope over the rigid member operating frequency range of the cone, and a zero slope over the high frequency range of the cone. An advantage of the present invention is that it allows use of relatively small loud speakers and loud speaker enclosures.
REFERENCES:
patent: 3798374 (1974-03-01), Meyers
patent: 3821473 (1974-06-01), Mullins
patent: 3878748 (1975-04-01), Spence
patent: 4025722 (1977-05-01), Karron
"The Philips Motional Feedback System", undated trade circular distributed by North American Philips Corp.
Oliveras R. Martin
Robinson Thomas A.
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