EP1194004A1 - Dispositif acoustique électrostatique - Google Patents

Dispositif acoustique électrostatique Download PDF

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Publication number
EP1194004A1
EP1194004A1 EP00402687A EP00402687A EP1194004A1 EP 1194004 A1 EP1194004 A1 EP 1194004A1 EP 00402687 A EP00402687 A EP 00402687A EP 00402687 A EP00402687 A EP 00402687A EP 1194004 A1 EP1194004 A1 EP 1194004A1
Authority
EP
European Patent Office
Prior art keywords
diaphragm
electrode
acoustic device
electrostatic
main portion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00402687A
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German (de)
English (en)
Inventor
Geuk Yeon Kim
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thomson Licensing SAS
Original Assignee
Thomson Licensing SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson Licensing SAS filed Critical Thomson Licensing SAS
Priority to EP00402687A priority Critical patent/EP1194004A1/fr
Priority to AU2002212288A priority patent/AU2002212288A1/en
Priority to PCT/EP2001/011212 priority patent/WO2002028142A2/fr
Publication of EP1194004A1 publication Critical patent/EP1194004A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers

Definitions

  • the present invention relates to an electrostatic acoustic device and especially to an electrostatic acoustic device having a first electrode for applying an electrical field, a diaphragm with a main portion, a peripheral portion and an elastic portion between the main portion and the peripheral portion and fixing means for fixing the peripheral portion of the diaphragm to the first electrode, wherein the main portion of the diaphragm is movable by the electrical field.
  • Electrostatic acoustic devices in this context primarily include electrostatic loudspeakers or microphones.
  • a typical electrostatic loudspeaker known in the art is shown in FIG. 1.
  • sound pressure can be produced in correspondence with a driving signal by impressing a bias voltage, for instance direct current biasing, with the driving signal.
  • a bias voltage for instance direct current biasing
  • the driving signal 1 output from a power amplifier is boosted several times via a step-up transformer 2 an output signal of which is output to a speaker element 5.
  • This speaker element 5 consists of stationary electrodes 6, 7 which are electrode plates having multiple holes, or perforations, therein. These stationary electrodes 6, 7 are arranged opposing each other with a prescribed distance therebetween.
  • the output signal of the step-up transformer 2 is impressed between these stationary electrodes 6, 7.
  • the speaker element 5 includes a diaphragm 8 forming the conductive fine filter on the polyester film for example, and maintains this diaphragm 8 between the stationary electrodes 6, 7.
  • the bias voltage of several kV is formed by boosting the commercial power source at a high voltage bias circuit 3 and is applied between a secondary side middle tap of the step up transformer 2 and the diaphragm 8.
  • the circuit 3 for forming the bias voltage impresses the bias voltage to the diaphragm 8 via resistor 4 having a prescribed resistance value.
  • the sound pressure corresponding to the driving signal can be provided by elastically vibrating the diaphragm with this driving force F.
  • ⁇ is the dielectric constant which, in this case, is 8.85 * 10 -12 [F/m]
  • S is made up of the electrode area [m 2 ]
  • E 0 and E are bias voltage [V] and voltage of driving signal [V] respectively
  • d is a distance between the electrodes [m].
  • the driving force F expressed by the above equation is produced on the entire diaphragm equally. Since the diaphragm is homogeneous and its outer circumference is fixedly hold, it is deformed to a circular arc shape and elastically vibrated as shown by the arrow in FIG. 2.
  • spacers may be employed for limiting the diaphragm movement to avoid that the diaphragm touches the stationary electrodes.
  • the bass response is limited by such spacers.
  • the diaphragm is stretched in a frame and, therefore, is flat essentially. Due to such diaphragm shape, sherical dispersion is poor.
  • a loudspeaker may have the shape of a portion of a cylinder.
  • the horizontal and vertical profile of such loudspeaker are shown in FIG. 3 again the arrows indicate the movement of the diaphragm.
  • DE-A-196 41 503 describes an electrostatic loudspeaker with circular dispersion characteristic.
  • the electrodes and the diaphragm have the shape of a half ball.
  • the periphery of the diaphragm is fixed to a ring by gluing.
  • the object of the present invention to provide an electrostatic acoustic device enhanced electro-acoustic efficiency, whereby the diaphragm of the device does not touch the electrodes.
  • an electrostatic acoustic device having a first electrode for applying an electrical field, a diaphragm with a main portion, a peripheral portion and an elastic portion between the main portion and the peripheral portion and fixing means for fixing the peripheral portion of the diaphragm to the first electrode, wherein the main portion of the diaphragm is movable by the electrical field, and wherein the elastic portion of the diaphragm is deformed during movement of the diaphragm, whereas the shape of the main portion of the diaphragm is essentially maintained, when substantially constant surface force is applied to the entire surface of the diaphragm by the electrical field.
  • the elastic portion is deformable easier than other portions of the diaphragm.
  • the elastic portion is deformed and the main portion of the diaphragm maintains its shape.
  • the movement of the diaphragm is very linear, i.e. parallel to the electrodes, compared to the prior art. Consequently a loudspeaker using such technique has a better linear response.
  • high sound pressure level is obtainable since the air volume vibrated by the diaphragm is similar to that of US-A-5,471,540.
  • the electrostatic acoustic device further includes a second electrode positioned opposite to the first electrode, wherein the diaphragm is fixed between the first and the second electrode.
  • the electrode or the electrodes as well as the diaphragm each may have the shape of a spherical, cylindrical or pyramidal dome. Such shape of the diaphragm would increase the low frequency range and high frequency range for reproduction, since these specific shapes strengthen the diaphragm tremendously. Additionally, thinner or lighter material can be used for the diaphragm compared to the prior art.
  • dome shape of the diaphragm is the wide spatial dispersion and the easiness of production and handling of such diaphragm.
  • FIG. 4 includes a sectional view of an electrostatic loudspeaker on the left side, a perspective view in the middle and a topview of the inventive loudspeaker on the right side.
  • the inventive loudspeaker of FIG. 4 is built up with a first electrode 6, a second electrode 7 and a diaphragm 8 therebetween. Both electrodes are provided with throughholes so that the air vibrated by the diaphragm 8 can pass the electrodes 6 and 7.
  • the diaphragm 8 is fixed between the electrodes 6 and 7 by fixing means 10. Thus, a parallel structure of the electrodes 6 and 7 and the diaphragm 8 is obtained.
  • the fixing means 10 includes two fixing rings which also serve as spacers between the electrodes 6 and 7 and the diaphragm 8, respectively.
  • the diaphragm 8 is sandwiched between the two fixing rings.
  • the fixing means 10 is realized by two identical, electrically insulating rings.
  • the fixing means 10 may also include ring sections, pins, bolts or the like. This means that the diaphragm may be fixed on a couple of points of its circumference.
  • the diaphragm 8 may also include tongues at its periphery for fixing the diaphragm 8 to the fixing means 10.
  • the fixing rings shown in FIG. 4 are integrally formed with the electrodes 6 and 7, so that the diaphragm 8 may be clamped between the electrodes, wherein electric insulation is provided by coating the electrodes 6 and 7 and/or the diaphragm 8.
  • the fixing means may be part of one or both of the electrodes 6 and 7.
  • the main part of the diaphragm 8 corresponds to a sphere section. At the periphery of the sphere section there is provided a collar. This collar is integral with the sphere section and represents an elastic portion 9. The function of this elastic portion 9 will be described in connection with FIG. 5, 6 and 7.
  • FIG. 4 show a spherical dome shaped loudspeaker.
  • a shaped loudspeaker has an improved spherical dispersion characteristic.
  • loudspeakers with a flat diaphragm have poor spatial dispersion.
  • loudspeakers of the one forth cylinder type have good horizontal but bad vertical dispersion.
  • the shape of the dome may also be that of a pyramid, cone, ellipsoid, hyperboloid or the like.
  • the advantage of the dome shaped diaphragm 8 is on the one hand that, as already mentioned, the spherical dispersion of the acoustic emission is improved compared to flat or cylindrical loudspeakers.
  • the dome shape of the diaphragm 8 improves its mechanical strength. Therefore, the thickness of the diaphragm can be reduced to 0,02 mm or less.
  • Such a thin diaphragm may be realized by a transparent mylar film which is very flexible. Additionally, lighter material for the diaphragm can be employed because of the inherent strength of the dome shape diaphragm.
  • a further advantage of the dome shaped diaphragm 8 is that it must not be stretched between the electrodes to be kept centered between them.
  • the dome shaped diaphragm has to be fixed only perpendicular to the surface or the diaphragm by spacers, for example. Thus, no or only very low central forces perpendicular to the moving direction are applied to the dome shaped diaphragm 8, so that the degree of freedom for choosing the material of the diaphragm is enlarged.
  • FIG. 5 shows the operation of the electrostatic loudspeaker according to the present invention.
  • Both electrodes 6, 7 and the diaphragm 8 have nearly the same shape.
  • the diaphragm 8 is centered between the electrodes 6 and 7.
  • the dome shaped diaphragm 8 linearly moves between the first and the second electrode. Due to the enhanced mechanical strength of the diaphragm obtained by the dome shape the main part of the diaphragm within the elastic portion 9 does not change its shape essentially.
  • the elastic portion 9 is very flexible in the direction of the center axis of the loudspeaker, i.e. vertical in the figure.
  • the main portion and the flexible portion 9 of the diaphragm have different flexibilities in the direction of the center axis although both portions are of the same material.
  • the reason for this difference is that the elastic portion 9 is aligned perpendicular to the center access, whereas the portions of the dome have at least components parallel to the center axis.
  • FIG. 6 shows a further embodiment of the present invention.
  • the elastic portion 9 of the diaphragm 8 is corrugated in the form of one sine wave. Such shape of the elastic portion 9 enhances the flexibility particularly in the direction perpendicular to the center axis of the loudspeaker.
  • FIG. 7 shows still another embodiment of the present invention including an elastic portion 9 having the shape of one half of a sine wave.
  • This shape also improves the flexibility of the diaphragm 8 so that the parallellity of the movement of the diaphragm with respect to the electrodes 6 and 7 is improved compared to the embodiment of FIG. 5.
  • the peripheral portion 11 of each electrode is formed parallel to the elastic portion 9 of the diaphragm 8. Such a form of the peripheral portion 11 serves for preventing touching of the electrode by the diaphragm more effectively.
  • the arrow in the figure indicates the amplitude of the vibration movement of the diaphragm 8.
  • the corrugation shape of the elastic portion 9 of the diaphragm 8 is described as one sine wave or half of a sine wave.
  • the corrugation of the elastic portion 9 may be realized by any other profile like half circular or zigzag.
  • this elastic portion enables parallel movement of the dome shaped main portion of the diaphragm 8 so that higher sound pressures and better spatial dispersion can be obtained compared to the prior art.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
EP00402687A 2000-09-29 2000-09-29 Dispositif acoustique électrostatique Withdrawn EP1194004A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP00402687A EP1194004A1 (fr) 2000-09-29 2000-09-29 Dispositif acoustique électrostatique
AU2002212288A AU2002212288A1 (en) 2000-09-29 2001-09-27 Electrostatic acoustic device
PCT/EP2001/011212 WO2002028142A2 (fr) 2000-09-29 2001-09-27 Dispositif acoustique electrostatique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP00402687A EP1194004A1 (fr) 2000-09-29 2000-09-29 Dispositif acoustique électrostatique

Publications (1)

Publication Number Publication Date
EP1194004A1 true EP1194004A1 (fr) 2002-04-03

Family

ID=8173886

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00402687A Withdrawn EP1194004A1 (fr) 2000-09-29 2000-09-29 Dispositif acoustique électrostatique

Country Status (3)

Country Link
EP (1) EP1194004A1 (fr)
AU (1) AU2002212288A1 (fr)
WO (1) WO2002028142A2 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892927A (en) * 1973-09-04 1975-07-01 Theodore Lindenberg Full range electrostatic loudspeaker for audio frequencies
EP0616485A1 (fr) * 1993-03-16 1994-09-21 Walter Schmid Transducteur électrostatique
US5471540A (en) * 1992-10-24 1995-11-28 Sony Corporation Electrostatic loudspeaker having stationary electrodes formed as multiple sheets insulated from each other
NL9400923A (nl) * 1994-06-08 1996-01-02 Cornelis Ruijtenberg Transducent van een elektrostatische luidspreker en werkwijze voor het vervaardigen van een geisoleerde statorplaat van een dergelijke transducent.
DE19641503A1 (de) * 1996-10-09 1998-05-20 Norman Gerkinsmeyer Elektrostatischer Lautsprecher mit wahlweiser Rundstrahlcharakteristik

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892927A (en) * 1973-09-04 1975-07-01 Theodore Lindenberg Full range electrostatic loudspeaker for audio frequencies
US5471540A (en) * 1992-10-24 1995-11-28 Sony Corporation Electrostatic loudspeaker having stationary electrodes formed as multiple sheets insulated from each other
EP0616485A1 (fr) * 1993-03-16 1994-09-21 Walter Schmid Transducteur électrostatique
NL9400923A (nl) * 1994-06-08 1996-01-02 Cornelis Ruijtenberg Transducent van een elektrostatische luidspreker en werkwijze voor het vervaardigen van een geisoleerde statorplaat van een dergelijke transducent.
DE19641503A1 (de) * 1996-10-09 1998-05-20 Norman Gerkinsmeyer Elektrostatischer Lautsprecher mit wahlweiser Rundstrahlcharakteristik

Also Published As

Publication number Publication date
WO2002028142A3 (fr) 2002-09-19
AU2002212288A1 (en) 2002-04-08
WO2002028142A2 (fr) 2002-04-04

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