Patent US3773976A successfully refreshed from Google Patents.
US3773976A
Expired / Lapsed
US
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Electrostatic loudspeaker and amplifier
Assignee: ALEXANDER MICHAEL T
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Filing: 1972-06-05
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Granted: 1973-11-20
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Expires: 1992-06-05
Abstract
Abstract An electrostatic loud speaker system is shown which combines a balanced transducer, an amplifier and an enclosure each of unique construction which together permit the reproduction of frequencies over the full audio range. The electrostatic transducer is shown surrounded by an enclosure that has an outlet passage preferably significantly smaller than the transducer and an acoustic lens preferably guides the sound through the narrow outlet into a wave form of circular cross-section. By these provisions a low resonant frequency for the speaker and wide dispersal of the directional high frequencies are achieved in an enclosure of limited size. The fixed electrodes of the transducer are of substantial thickness and are formed of high dielectric constant material, achieved preferably by molding a lower K matrix with additives raising K and lowering volumetric resistivity. The amplifier is formed of series-connected active devices, one controlled by the other. A third active device amplifies the audio signal. Its output is connected to control the first of the series-connected devices and the output terminal of the amplifier is connected through a resistive feedback path to the output of the third device. A further feedback system employs a carrier wave applied to the diaphragm of the transducer. The resulting signal on the electrodes is differentiated and negatively fed back to damp speaker response at low frequency resonance.
Inventors
- 👤 H Beveridge
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 18:51
CPC Classifications
H; H04; H04R; H04R3/00; H04R3/002; H03; H03F; H03F1/00; H03F1/34; H03F1/36; H03F3/00; H03F3/181; H03F3/183; H04R19/00; H04R19/02
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
208 words
An electrostatic loudspeaker comprising the combination of a balanced transducer, an amplifier and an enclosure, said transducer comprising a pair of electrodes between which is mounted a diaphragm, said electrodes being apertured members having a thickness greater than about three times the air gap between the electrode and the diaphragm in mid-position and a dielectric constant greater than about thirty said amplifier connected to drive said transducer and comprising a pair of active devices connected in series, the first controlling the second, an output terminal connected between said active and a third active device comprising a constant current source connected to receive and amplify the audio signal, the output of said third active device connected to control the first said series-connected active devices, and the output terminal of said amplifier connected through a resistive feedback path to the output of said third active device, and said enclosure surrounding said transducer and adapted to contain the backwardmoving sound emitted from one side of said transducer and an aircolumn-defining outlet passage for foward-moving sound emitted from the other side of said transducer, said outlet passage comprising a series of side by side channels curving together from said transducer to a throat region and then curving apart to disperse the sound.
Claim 2
Dependent Claim
208 words
An electrostatic loudspeaker comprising the combination of a balanced transducer, an amplifier and an enclosure, said transducer comprising a pair of electrodes between which is mounted a diaphragm, said electrodes being apertured members having a thickness greater than about three times the air gap between the electrode and the diaphragm in mid-position and a dielectric constant greater than about thirty said amplifier connected to drive said transducer and comprising a pair of active devices connected in series, the first controlling the second, an output terminal connected between said active and a third active device comprising a constant current source connected to receive and amplify the audio signal, the output of said third active device connected to control the first said series-connected active devices, and the output terminal of said amplifier connected through a resistive feedback path to the output of said third active device, and said enclosure surrounding said transducer and adapted to contain the backwardmoving sound emitted from one side of said transducer and an aircolumn-defining outlet passage for foward-moving sound emitted from the other side of said transducer, said outlet passage comprising a series of side by side channels curving together from said transducer to a throat region and then curving apart to disperse the sound.
Claim 3
Dependent Claim
36 words
The electrostatic transducer of claim 1 wherein said electrode comprising an apertured plate cast of a matrix material and a dispersion of an additive having a dielectric constant substantially greater than that of said matrix material.
Claim 4
Dependent Claim
70 words
The electrostatic transducer of claim 1 including means producing a feedback signal to said amplifier for combating a low frequency response peak comprising a single carrier wave generator connected to said diaphragm, a pair of pick-up circuits connected respectively to said electrodes, a displacement detector circuit responsive to said pick-up circuits and means to produce the differential of the displacement signal and apply it to the input of said amplifier.
Claim 5
Dependent Claim
40 words
The electrostatic transducer of claim 1 wherein said output channels have inlets disposed immediately adjacent said electrode and said channels collectively define a throat having an effective cross-section area less than one half the sound emitting area of said electrode.
Claim 6
Dependent Claim
40 words
The transducer of claim 4 where said channels are defined by a set of walls which converge toward each other to said throat and then diverge from each other to outlets which collectively distribute the sound over a semicircular arc.
Claim 7
Dependent Claim
124 words
In an electrostatic loudspeaker system comprising an electrostatic transducer, a power source for applying to said transducer a polarizing voltage, and an audio amplifier for applying to said transducer an audio signal, the improvement wherein said audio amplifier comprises the combination of a pair of active devices connected in series, the first controlling the second, an output terminal of said amplifier connected between said active devices, and a third active device comprising substantially a constant current generator connected to receive and amplify the audio signal, the output of said third active device connected to control the first of said series connected active devices, and the output terminal of said amplifier connected through a resistive feedback path to the output of said third active device.
Claim 8
Dependent Claim
124 words
In an electrostatic loudspeaker system comprising an electrostatic transducer, a power source for applying to said transducer a polarizing voltage, and an audio amplifier for applying to said transducer an audio signal, the improvement wherein said audio amplifier comprises the combination of a pair of active devices connected in series, the first controlling the second, an output terminal of said amplifier connected between said active devices, and a third active device comprising substantially a constant current generator connected to receive and amplify the audio signal, the output of said third active device connected to control the first of said series connected active devices, and the output terminal of said amplifier connected through a resistive feedback path to the output of said third active device.
Claim 9
Dependent Claim
30 words
The loudspeaker system of claim 6 wherein the input of said second of said series connected active devices is directly connected across the resistive load of the first active device.
Claim 10
Dependent Claim
75 words
The electrostatic loudspeaker of claim 6 having two electrodes, one on each side of the diaphragm, including a second amplifier constructed according to the aforementioned amplifier, wherein the output terminal of one of said amplifiers is connected to said diaphragm, the ouTput terminal of the second of said amplifiers is connected to both electrodes, and phase inverter means is provided to invert the audio input of one of said amplifiers with respect to the other.
Claim 11
Dependent Claim
131 words
The electrostatic loudspeaker system of claim 6 wherein each of said active devices comprises elements performing the functions respectively of cathode, grid and plate, the plate element of the first active device connected through a resistor to the amplifier output terminal and the cathode element of the second active device, the cathod element of the first active device and the plate element of the second active device connected across a DC potential in excess of one thousand volts, the plate element of the second device being positive, the plate element of the first active device being connected to the grid element of the second active device, and the grid element of the first active device connected to the plate of said third active device and to feedback from said output terminal.
Claim 12
Dependent Claim
57 words
The electrostatic loudspeaker system of claim 9 wherein an element performing the function of a zener diode is also connected between the output terminal and the plate element of said first active device, across said resistor, thereby preventing said resistor from limiting the amount of current which said first active device can supply to said output terminal.
Claim 13
Dependent Claim
16 words
The electrostatic loudspeaker system of claim 9 wherein said first and second active devices comprise pentodes.
Claim 14
Dependent Claim
63 words
The electrostatic loudspeaker system of claim 11 wherein said transducer has a capacitance on the order of 3,000 pf requiring peak current in excess of 100 ma. with a polarizing voltage on the order of 4,000 volts, said pentodes having a transconductance (Gm) on the order of 1,000 ohms and the resistance of said feedback path is on the order of 2 megohms.
Claim 15
Dependent Claim
40 words
The electrostatic loudspeaker system of claim 6 having two electrodes, one on each side of the diaphragm, wherein said power source is connected to apply said polarizing voltage across said electrodes and said output terminal is connected to said diaphragm.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-19 | 1977-05-21 | 1977-11-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-19 | 1981-05-21 | 1981-11-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-19 | 1985-05-21 | 1985-11-20 | $7700.00 | Window Closed / Lapsed |