US3798374A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Sound reproducing system utilizing motional feedback
Assignee: Individual
•
Filing: 1972-04-03
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Granted: 1974-03-19
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Expires: 1992-04-03
Abstract
Abstract A sound reproducing system utilizes motional feedback to reduce loudspeaker distortion and to extend the loudspeaker''s frequency response. The system substantially comprises an amplifier which is jointly responsive to the input source signal and to a feedback signal, a moving-coil loudspeaker including a main electromagnetic structure which is responsive to the amplifier''s output signal for effecting axial speaker-cone motion, motional sensing means for providing a signal which is functionally related to axial cone velocity, and an equalizer exhibiting a predetermined nonlinear attenuation versus frequency characteristic and which is responsive to the motional signal for providing the feedback signal. The feedback signal is degeneratively applied to the amplifier which, in turn, forces the loudspeaker to respond linearly to the input source signal and thereby provide a uniform sound energy output. It is a feature of the present invention that the loudspeaker cone exhibits a substantially constant acceleration at low frequencies and a substantially constant velocity at higher frequencies.
Inventors
- 👤 S Meyers
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:33
CPC Classifications
H; H04; H04R; H04R3/00; H04R3/002
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
119 words
A sound reproducing system comprising: first amplifying means jointly responsive to a source signal and to a first feedback signal; first sound energy producing means responsive to said first amplifying means; first means for sensing the sound energy output of said first producing means; and first equalizIng means exhibiting a predetermined nonlinear attenuation versus frequency times a constant characteristic and being responsive to said first sensing means for providing said first feedback signal, said characteristic having a positive slope over the lower portion of a first frequency range and a zero slope over the rest of said first frequency range; whereby said first sound energy producing means radiates a substantially uniform sound energy output over said first frequency range.
Claim 2
Dependent Claim
119 words
A sound reproducing system comprising: first amplifying means jointly responsive to a source signal and to a first feedback signal; first sound energy producing means responsive to said first amplifying means; first means for sensing the sound energy output of said first producing means; and first equalizIng means exhibiting a predetermined nonlinear attenuation versus frequency times a constant characteristic and being responsive to said first sensing means for providing said first feedback signal, said characteristic having a positive slope over the lower portion of a first frequency range and a zero slope over the rest of said first frequency range; whereby said first sound energy producing means radiates a substantially uniform sound energy output over said first frequency range.
Claim 3
Dependent Claim
59 words
The sound reproducing system of claim 1 wherein said first sound energy producing means is a loudspeaker of the moving-coil type including a cone and a voice coil, said voice coil responding to said first amplifying means for axially driving said cone; and said first sensing means responds to the motion imparted to said cone by said voice coil.
Claim 4
Dependent Claim
25 words
The sound reproducing system of claim 2 wherein said first sensing means responds to the axial velocity imparted to said cone by said voice coil.
Claim 5
Dependent Claim
51 words
The sound reproducing system of claim 3 wherein said first sensing means includes a coil which is mechanically coupled to said cone and which interacts with an associated magnetic field to produce an electrical signal which is functionally related to the axial velocity imparted to said cone by said voice coil.
Claim 6
Dependent Claim
69 words
The sound reproducing system of claim 2 wherein said cone exhibits a velocity versus frequency characteristic which is substantially approximated by a first straight line having a slope of -6 db/octave and by a second straight line having a slope of 0 db/octave, said lines intersecting where 0.476 Rf is approximately equal to 1.5, R being the effective radius of said loudspeaker cone and f the operating frequency thereof.
Claim 7
Dependent Claim
104 words
The sound reproducing system of claim 4 further including: in association with said voice coil, a first permanent magnet, a first inner pole piece, and a first outer pole piece, which in combination form the main electromagnetic structure of said loudspeaker; in association with said sensing coil, a second permanent magnet, a second inner pole piece, and a second outer pole piece, which in combination form said motional sensing means; and an appropriately shaped non-magnetic electrically conductive metallic member which is rigidly attached to said second outer pole piece and which is located between said second outer pole piece and said main electromagnetic structure.
Claim 8
Dependent Claim
92 words
The sound reproducing system of claim 4 further including: in association with said voice coil, a first permanent magnet, a first inner pole piece, and a first outer pole piece, which in combination form the main electromagnetic structure of said loudspeaker; in association with said sensing coil, a second permanent magnet, a second inner pole piece, and a second outer pole piece, which in combination form said motional sensing means; and an appropriately shaped non-magnetic, electrically conductive metallic member mechanically securing said second inner pole piece to said first inner pole piece.
Claim 9
Dependent Claim
56 words
The sound reproducing system of claim 2 wherein said cone exhibits a substantially constant acceleration over a low frequency region and a substantially constant velocity over a high frequency region, said regions meeting where 0.476 Rf is approximately equal to 1.5, R being the effective radius of said loudspeaker cone and f the operating frequency thereof.
Claim 10
Dependent Claim
21 words
The sound reproducing system of claim 1 wherein said first sound energy producing means is a loudspeaker of the electrostatic type.
Claim 11
Dependent Claim
24 words
The sound reproducing system of claim 1 also comprising linear amplifying means serially interposed between said first sensing means and said first equalizing means.
Claim 12
Dependent Claim
71 words
The sound reproducing system of claim 2 wherein said first equalizing means exhibits an attenuation versus frequency characteristic which is substantially approximated by a first straight line having a slope of +6 db/octave And by a second straight line having a slope of 0 db/octave, said lines intersecting where 0.476 Rf is approximately equal to 1.5, R being the effective radius of said loudspeaker cone and f the operating frequency thereof.
Claim 13
Dependent Claim
59 words
The sound reproducing system of claim 2 wherein said first equalizing means exhibits an attenuation versus frequency characteristic which is substantially approximated by a curve which is concave upward at its lower end and is concave downward at its upper end with an intervening slope approaching 6 db/octave and an ultimate slope at the upper end approaching 0 db/octave.
Claim 14
Dependent Claim
36 words
The sound reproducing system of claim 1 further comprising: second amplifying means responsive to said source signal; filtering means responsive to said second amplifying means; and second sound energy producing means responsive to said filtering means.
Claim 15
Dependent Claim
36 words
The sound reproducing system of claim 1 further comprising a plurality of identical sound energy producing means which are responsive to said first amplifying means and which are identical to said first sound energy producing means.
Claim 16
Dependent Claim
103 words
The sound reproducing system of claim 1 further comprising: second amplifying means jointly responsive to said source signal and to a second feedback signal; second sound energy producing means responsive to said second amplifying means; second means for sensing the sound energy output of said second sound energy producing means; and second equalizing means exhibiting a predetermined nonlinear attenuation versus frequency characteristic and being responsive to said second sensing means for providing said second feedback signal, whereby said second sound energy producing means radiates a substantially uniform sound energy output over a frequency range which does not overlap with said first frequency range.
Claim 17
Dependent Claim
141 words
A sound reproducing system comprising: an amplifier jointly responsive to an input source signal and to a feedback signal; a loudspeaker of the moving-coil type including a cone and a voice coil, said voice coil responding to said amplifier for axially driving said cone; means for sensing the axial velocity of said cone; and an equalizer exhibiting a predetermined nonlinear attenuation versus frequency characteristic and being responsive to said sensing means for providing said feedback signal, whereby said cone exhibits a velocity versus frequency times a constant characteristic which is substantially approximated by a first straight line having a slope of -6 db/octave and by a second straight line having a slope of 0 db/octave, said lines intersecting where 0.476 Rf is approximately equal to 1.5, R being the effective radius of said loudspeaker cone and f the operating frequency thereof.
Claim 18
Dependent Claim
141 words
A sound reproducing system comprising: an amplifier jointly responsive to an input source signal and to a feedback signal; a loudspeaker of the moving-coil type including a cone and a voice coil, said voice coil responding to said amplifier for axially driving said cone; means for sensing the axial velocity of said cone; and an equalizer exhibiting a predetermined nonlinear attenuation versus frequency characteristic and being responsive to said sensing means for providing said feedback signal, whereby said cone exhibits a velocity versus frequency times a constant characteristic which is substantially approximated by a first straight line having a slope of -6 db/octave and by a second straight line having a slope of 0 db/octave, said lines intersecting where 0.476 Rf is approximately equal to 1.5, R being the effective radius of said loudspeaker cone and f the operating frequency thereof.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |