WO2008002049A1 - Electrostatic speaker having ventilative diaphragm - Google Patents
Electrostatic speaker having ventilative diaphragm Download PDFInfo
- Publication number
- WO2008002049A1 WO2008002049A1 PCT/KR2007/003076 KR2007003076W WO2008002049A1 WO 2008002049 A1 WO2008002049 A1 WO 2008002049A1 KR 2007003076 W KR2007003076 W KR 2007003076W WO 2008002049 A1 WO2008002049 A1 WO 2008002049A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- diaphragm
- fixed electrode
- electrostatic speaker
- speaker
- korean paper
- Prior art date
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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
- H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
- H04R31/003—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor for diaphragms or their outer suspension
-
- 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
- H04R19/02—Loudspeakers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R7/00—Diaphragms for electromechanical transducers; Cones
- H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
Definitions
- the present invention relates to an electrostatic speaker, and more particularly, to an electrostatic speaker having a ventilative diaphragm capable of improving a low frequency characteristic and reproducing a natural sound.
- Electrostatic speakers generate sound pressure when a driving signal is input to a fixed electrode and a DC bias voltage is applied to a diaphragm.
- the diaphragm is charged with a higher voltage than the fixed electrode, and when an audio signal is transmitted to the fixed electrode, an electrostatic field is generated in response to the audio signal.
- the variable electrostatic field generated around the fixed electrode interacts with a fixed electrostatic field of the diaphragm which causes the diaphragm to be both pulled and pushed, resulting in the generation of sound.
- the electrostatic speakers include a single ended speaker having a diaphragm and a single fixed electrode that are arranged in parallel to each other, and a double ended speaker having a diaphragm and a pair of fixed electrodes arranged at both sides of the diaphragm.
- Figs. 1 and 2 show the schematic structure of a general single ended speaker.
- the speaker includes a sound generator 10 having a diaphragm 12 and a fixed electrode 14, and a plurality of holes 14a are formed in the fixed electrode 14.
- insulating supports 18 are formed between both ends of the diaphragm
- the level of an audio signal input from an amplifier is increased by an audio frequency transformer TF.
- One output node of the transformer TF is connected to the fixed electrode 14, and the other output node thereof is connected to a negative pole node of a bias voltage source V .
- An positive pole node of the bias voltage source V is connected to the diaphragm 12. The bias voltage source V makes the speaker charged and maintained
- the diaphragm 12 has a consistent voltage and a consistent charging capacity in an equilibrium state, and a voltage V is applied between the diaphragm 12 and the fixed electrode 14.
- the voltage between the fixed electrode 14 and the diaphragm 12 varies according to an amplified audio signal, and then the balance between attractive force and repulsive force applied to the diaphragm 12 is upset, which causes the diaphragm 12 to move, resulting in the generation of sound.
- Fig. 3 shows the schematic structure of a general double ended speaker.
- the double ended speaker is formed by adding one fixed electrode to the sound generator of the single ended speaker, in order to improve the driving force of the diaphragm. That is, the double ended speaker includes a sound generator 20 having two fixed electrodes 24 and 26. In this way, the double ended speaker reduces the distortion of sound and increases the level of sound pressure.
- the bias voltage V is applied between a diaphragm 22
- the diaphragm 22 receives the attractive force from one of the two fixed electrodes 24 and 26 and the repulsive force from the other fixed electrode to vibrate, thereby generating sound.
- a plurality of holes 24a and 26a are formed in the fixed electrodes 24 and 26, respectively, and insulating support members 28 are formed between the diaphragm 22 and the fixed electrodes 24 and 26.
- the diaphragm used for the electrostatic speaker should have high surface resistance such that positive charges that are charged with a high voltage can be stably maintained in the diaphragm, and should appropriately prevent the discharge between the diaphragm and the electrodes caused by a high voltage applied to the diaphragm.
- the diaphragm should have a strong initial tensile strength in order to prevent the diaphragm from being attracted to the electrode when no signal is input and the positive charge on the diaphragm from being discharged.
- the diaphragm for an electrostatic speaker is formed as follows: a petrochemical polymer film, such as a thin polyester film having a relatively strong tensile strength, is stretched to be adhered to a frame; a heterogeneous material, such as nylon or PVC, is coated on one surface of the polyester film in order to reduce low-frequency resonation within an audible frequency range; and high-resistance conduction coating and antistatic coating using a diluted solution of graphite powder is performed on the other surface of the polyester film.
- a petrochemical polymer film such as a thin polyester film having a relatively strong tensile strength
- a heterogeneous material such as nylon or PVC
- the diaphragm obtained in this way is non-ventilative, and has the following problems. That is, when the intensity of a signal input to the fixed electrode increases and the diaphragm is close to the fixed electrode, a ground effect is generated.
- the ground effect means that, when an object rapidly approaches the ground, high air resistance occurs between the ground and the object within a specific range of distance from the ground, which prevents the object from approaching the ground.
- flying objects such as a helicopter and a GEV (ground effect vehicle)
- GEV ground effect vehicle
- the generated air hits the ground, causing the air between the helicopter and the ground to be compressed.
- the compressed air serves as a cushion that helps the helicopter to hover.
- This effect is called the ground effect, which saves the power of the helicopter.
- the height incurred by the ground effect corresponds to the diameter of a main rotor while the helicopter is hovering.
- Fig. 4 is a graph illustrating the relationship between the ratio of the height of the rotor to the diameter of the rotor (horizontal axis) and the ratio of an increment in the thrust of the rotor (vertical axis).
- the increment in the thrust of the rotor is about 20% when the ratio of the height of the rotor to the diameter of the rotor is 0.25.
- the increment in the thrust of the rotor drastically decreases to about 7% when the ratio of the height of the rotor to the diameter of the rotor is 0.5.
- the increment in the thrust of the rotor is 0 when the ratio of the height of the rotor to the diameter of the rotor is 1.25, and the helicopter is not affected by the ground effect.
- a method of increasing the ratio of the holes to the fixed electrode (the number of holes per unit area) or a method of increasing the distance between the diaphragm and the fixed electrode may be considered.
- an area in which electrostatic attractive force is generated is reduced, and the electrostatic attractive force is weakened, which results in a reduction in reproduction sound pressure.
- the electrostatic attractive force is weakened, and thus reproduction sound pressure is lowered.
- the speaker needs to have a characteristic of radially and uniformly spreading sound.
- the movement of the diaphragm of the electrostatic speaker is done as the planar vibration, it is difficult to naturally spread sound due to the directivity of a high-pitched sound.
- a panel is formed in a semi-cylindrical shape having a length corresponding to the height of a human being, or when the length of the panel is smaller than the height of the human being, the panel is inclined backward so as to be the same height of the listener's ear where the sound is spread.
- the diaphragm is formed in a semi-cylindrical shape, it is difficult to perfectly realize a radial and uniform sound spread.
- a method of additionally providing an electrical delay circuit to operate the diaphragm like a spherical surface has been proposed. However, this method has problems in that the size of a speaker increases, the structure of the speaker becomes complicated, and the amount of data to be processed increases. Disclosure of Invention Technical Problem
- An object of the invention is to provide an electrostatic speaker capable of reducing air resistance and the ground effect occurring between a diaphragm and a fixed electrode, while satisfying all characteristics required for the electrostatic speaker, thereby obtaining a uniform frequency reproduction characteristic over the entire frequency range.
- Another object of the invention is to provide an electrostatic speaker including a diaphragm that can be easily manufactured by using a thermoplastic adhesive.
- Still another object of the invention is to provide an electrostatic speaker having a diaphragm that can be simply manufactured at low manufacturing costs.
- Yet another aspect of the invention is to provide an electrostatic speaker having a diaphragm that can radially and uniformly spread sound without complicating the structure of a speaker and increasing the amount of data to be processed.
- an electrostatic speaker includes a diaphragm and a sound generator that includes one fixed electrode or a pair of fixed electrodes that are arranged at a predetermined gap from the diaphragm.
- a plurality of ventilation holes are formed in the diaphragm.
- the diaphragm may be made from Korean paper.
- a plurality of holes may be formed in the fixed electrode, and portions of the diaphragm corresponding to the plurality of holes may be non-ventilative.
- a concave-convex portion may be formed on the surface of the fixed electrode facing the diaphragm.
- the diaphragm When the diaphragm is made from Korean paper, the diaphragm may be formed in a hemispherical shape, and the fixed electrode may also be formed in a hemispherical shape at a predetermined gap from the diaphragm.
- a plurality of holes may be formed in the fixed electrode, and the distance between the holes and the distance between the diaphragm and the holes may be set in a high frequency band such that the ground effect does not occur between the fixed electrode and the diaphragm.
- an electrostatic speaker capable of reducing the ground effect occurring between a diaphragm and a fixed electrode to increase an output sound pressure, while satisfying all characteristics required for the electrostatic speaker, thereby obtaining a uniform frequency reproduction characteristic over the entire frequency range.
- portions except for a portion in which the ground effect mainly occurs are made non- air-permeable, which makes it possible to increase an output sound pressure and further improve a frequency reproduction characteristic.
- a concave-convex portion is formed on the surface of the fixed electrode, which makes it possible to reduce the ground effect and decrease the size and thickness of an electrostatic speaker.
- the diaphragm is made from Korean paper having high thermal resistance, and thus the diaphragm can be easily adhered to a frame in a high temperature environment.
- Korean paper satisfies all physical properties required for an electrostatic speaker, which makes it possible to simplify a process of manufacturing a diaphragm for an electrostatic speaker and reduce the overall manufacturing cost.
- the diaphragm made from the Korean paper is formed in a hemispherical shape, which makes it possible to perfectly realize a uniform and radial sound spread.
- Figs. 1 and 2 are diagrams schematically illustrating the structure of a single ended speaker.
- Fig. 3 is a diagram schematically illustrating the structure of a double ended speaker.
- Fig. 4 is a graph illustrating the ground effect.
- Fig. 5 is an enlarged view illustrating the surface of Korean paper according to an embodiment of the invention.
- Fig. 6 is a diagram illustrating a chemical formula of the Korean paper according to the embodiment of the invention.
- Fig. 7 is graphs illustrating frequency characteristics of an electrostatic speaker according to an embodiment of the invention.
- Fig. 8 is a diagram schematically illustrating an electrostatic speaker according to another embodiment of the invention.
- Fig. 9 is a diagram schematically illustrating an electrostatic speaker according to still another embodiment of the invention.
- Fig. 10 is a diagram schematically illustrating an electrostatic speaker according to yet another embodiment of the invention.
- a first embodiment of the invention is characterized by a ventilative diaphragm for an electrostatic speaker.
- a ventilative diaphragm for an electrostatic speaker In the case of a non-ventilative diaphragm according to the related art, when a diaphragm is as close to a fixed electrode as it is affected by a ground effect, an increase in the pressure between the diaphragm and the fixed electrode due to the ground effect is directly transmitted to the non-ventilative diaphragm, which causes a reduction in sound pressure in a low frequency band due to the ground effect.
- the ventilative diaphragm when the pressure between the ventilative diaphragm and the fixed electrode increases due to the ground effect, the effect of the increased pressure on the ventilative diaphragm is reduced by fine holes formed in the ventilative diaphragm. Therefore, the ventilative diaphragm is less affected by the sound pressure that is lowered due to the ground effect in a low frequency band than the non-ventilative diaphragm according to the related art.
- a ventilative diaphragm according to Example 1 is obtained as follows. A polyester film is stretched to be adhered to a fixed frame, and a heterogeneous material, such as nylon or PVC (polyvinyl chloride), is coated on one surface of the polyester film in order to reduce low-frequency resonation within an audible frequency range. Then, high-resistance conduction coating and antistatic coating using a diluted solution of graphite powder is performed on the other surface of the polyester film.
- a heterogeneous material such as nylon or PVC (polyvinyl chloride)
- the fine holes are formed in a general non-ventilative diaphragm to form a diaphragm having ventilation characteristic, which makes it possible to reduce the effect of the increased pressure between the diaphragm and the fixed electrode due to the ground effect.
- Example 2 is characterized in that a diaphragm is made from Korean paper.
- the inventors have studied a new diaphragm material for solving various problems of the diaphragm for an electrostatic speaker according to the related art.
- the inventors' study found that Korean paper, which is a Korean traditional paper, had a high degree of ventilation and formability, while satisfying all physical characteristics required for a diaphragm for an electrostatic speaker (a high tensile strength, high resistance, and a characteristic of maintaining a tensile state at a temperature that enables thermal adhesion).
- the Korean paper is a bast fiber obtained from, sources, such as Broussonetia kazinoki (paper mulberry), Moras (mulberry tree), Edgeworthia papyrifera, and Wikstroemia trichotoma.
- sources such as Broussonetia kazinoki (paper mulberry), Moras (mulberry tree), Edgeworthia papyrifera, and Wikstroemia trichotoma.
- a method of manufacturing the Korean paper includes: a process of placing a bundle of material, such as paper mulberries upright into a container, boiling it until the bark can be easily stripped from the paper mulberries, stripping the bark from the paper mulberries, and drying the bark of the paper mulberries; a process of soaking the bark in water, extracting only bast fibers from the bark, boiling the bast fibers in lye for about three hours or more, and squeezing water from the bast fibers using a compressor; and a process of soaking the bast fibers of the paper mulberries in clean water, mixing liquid squeezed from sunset-hibiscus with the water such that the bast fibers can be uniformly dispersed in the water, and straining a paper solution using a mesh.
- Fig. 5 is an enlarged view of the surface of the Korean paper
- Fig. 6 is a diagram illustrating a chemical formula of the Korean paper.
- the Korean paper consists of cellulose, which is a straight-chained polymer obtained by polymerizing several thousands of glucoses, and cellulose molecules form a fibril, and the fibril is coupled to a compound, such as hemicellulose (polymer having various kinds of saccharides, which are similar to glucose, coupled thereto) or lignin, to form a fibrous tissue.
- a compound such as hemicellulose (polymer having various kinds of saccharides, which are similar to glucose, coupled thereto) or lignin, to form a fibrous tissue.
- the Korean paper is manufactured by the hydrogen bond between the cellulose molecules in addition to the physical mixture of these fibers.
- the hydrogen bond occurs since an oxygen atom attracts a hydrogen nucleus in a plurality of hydroxyl groups within a molecule, while having extra electrons.
- the strength of the hydrogen bond is weaker than that of a covalent bond, but since the hydrogen bond occurs between a great number of long polymers, the overall strength of the hydrogen bond is strong.
- the length of fibers of the Korean paper is large and the width of the fibers is small, the bonding strength between the fibers is strong.
- fibril forming the fabric of the cellulose is arranged in the axial direction, the strength of the fiber is strong.
- the length of the bast fiber of the paper mulberry is in the range of 3.33 to 17.08 mm (average length is 8.72 mm)
- the width thereof is in the range of 15.1 to 43.6 D (average width is 23.3 D)
- the lumen width thereof is in the range of 3.4 to 29.7 D (average lumen width is 11.7 D)
- the extension rate thereof is in the range of 4 to 8 %.
- the Korean paper has a high extension rate and a strong strength, similar to leather due to the long length and the structure of the bast fiber of the paper mulberry, which is a main ingredient of the Korean paper, and variation in the characteristics of the bast fiber during a manufacturing process. Therefore, the diaphragm made from the Korean paper can be maintained in a high-tension state, and can be prevented from being attached to the electrode when no signal is supplied. As a result, it is possible to prevent positive charges of the diaphragm to being discharged.
- the diaphragm made from the Korean paper has higher heat resistance than a petrochemical polymer film according to the related art, the diaphragm is little damaged by a high- voltage arc discharge. Therefore, it is possible to apply a higher charging voltage to the diaphragm as compared to the related art, and thus improve the sensitivity of an electrostatic speaker. In addition, it is possible to increase the ratio of a high output sound pressure to an input signal.
- a process of manufacturing the diaphragm with the Korean paper is easier than a process of manufacturing a petrochemical polymer film according to the related art.
- the above-mentioned three processes are needed to manufacture the diaphragm made of the polyester film that has been widely used, but only one process of adhering the Korean paper in a tensile state to the frame is needed to manufacture the diaphragm according to Example 2.
- the Korean paper has better characteristics than the existing diaphragm while satisfying physical characteristics required for the electrostatic speaker, and the Korean paper makes it possible to simplify a manufacturing process.
- Example 2 is characterized in that the ventilative Korean paper is used for the diaphragm of the electrostatic speaker to improve the characteristics of the non- ventilative diaphragm according to the related art.
- FIG. 7 illustrating the experimental result of operational characteristics of an electrostatic speaker having the diaphragm made from the Korean paper, that is, the relationship between a sound pressure and a frequency, according to Example 2, and the experimental result of operational characteristics of an electrostatic speaker having the non-ventilative diaphragm according to the related art.
- the sound pressure is remarkably improved in a low frequency band according to Example 2. That is, as can be seen from the comparison between the ventilative diaphragm according to Example 2 shown at "(a)" in Fig. 7 and the non- ventilative diaphragm based on the related art shown at "(b)" in Fig. 7, when an input signal having the same intensity Is is input, the sound pressure is improved by about 3 dB according to Example 2, which corresponds to a 40% increase in the input energy.
- a second embodiment is characterized in that a portion of the diaphragm that is made from the Korean paper has a ventilation characteristic in order to overcome the ground effect.
- a deposit such resin or starch, or paint, such as varnish, may be coated on the portion 72a of the diaphragm corresponding to the holes 74a of the fixed electrode 74.
- a deposit such resin or starch, or paint, such as varnish, may be coated on the portion 72a of the diaphragm corresponding to the holes 74a of the fixed electrode 74.
- holes of both electrodes face each other in order to balance the sound pressure.
- a third embodiment is characterized in that a concave- convex portion 84b is formed on the surface of a fixed electrode 84 that faces a diaphragm 82.
- the concave-convex portion 84b formed on the fixed electrode 84 disturbs the boundary layer to generate a warm current that enables a smooth air flow. Therefore, the width of the boundary layer is reduced, which prevents the ground effect from being noticeable.
- the ventilative diaphragm according to this embodiment when the ventilative diaphragm according to this embodiment is applied, the ground effect is further reduced due to the ventilation characteristic of the diaphragm, which makes it possible to further improve the sound pressure.
- a fourth embodiment is characterized in that a diaphragm made from the Korean paper is formed in a hemispherical shape.
- a diaphragm made from the Korean paper is formed in a hemispherical shape.
- the diaphragm made from the Korean paper when used for the electrostatic speaker, it is not necessary to add a complicated electrical circuit required to reproduce an artificial spherical wave.
- the diaphragm made from the Korean paper makes it possible to reproduce a natural sound due to the characteristics of the Korean paper.
- This embodiment is characterized in that the diaphragm made from the Korean paper is formed in a spherical shape such that the sound can be radially spread. As described above, since the Korean paper has high formability, it can be formed in a spherical shape.
- Fig. 10 shows a sound generator 90 of an electrostatic speaker having the hemispherical diaphragm made from the Korean paper according to this embodiment.
- a diaphragm 92 is formed in a hemispherical shape, and two electrodes 94 and 96 are also formed in hemispherical shapes corresponding to the shape of the diaphragm at a regular interval from the diaphragm 92. Therefore, the electrostatic speaker according to this embodiment does not need to have a specific device for radially spreading the sound, unlike the related art, and can improve imperfect radiational characteristics of the semi-cylindrical diaphragm according to the related art.
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Multimedia (AREA)
- Manufacturing & Machinery (AREA)
- Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/305,622 US8284967B2 (en) | 2006-06-28 | 2007-06-26 | Electrostatic speaker having ventilative diaphragm |
CN200780023864.3A CN101485211B (en) | 2006-06-28 | 2007-06-26 | Electrostatic speaker having ventilative diaphragm |
JP2009515314A JP5081906B2 (en) | 2006-06-28 | 2007-06-26 | An electrostatic speaker having a breathable vibrating membrane |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR20060058359 | 2006-06-28 | ||
KR10-2006-0058359 | 2006-06-28 | ||
KR1020070013000A KR100850872B1 (en) | 2006-06-28 | 2007-02-08 | An electrostatic speaker having a ventilative diaphragm |
KR10-2007-0013000 | 2007-02-08 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2008002049A1 true WO2008002049A1 (en) | 2008-01-03 |
Family
ID=38845769
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/KR2007/003076 WO2008002049A1 (en) | 2006-06-28 | 2007-06-26 | Electrostatic speaker having ventilative diaphragm |
Country Status (1)
Country | Link |
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WO (1) | WO2008002049A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010098712A (en) * | 2008-10-15 | 2010-04-30 | Kotatsu Kokusai Denshi Kofun Yugenkoshi | Method and electronic device for driving capacitance electro-acoustic transducer |
US9288583B2 (en) | 2012-03-30 | 2016-03-15 | Sumitomo Riko Company Limited | Speaker |
CN117714954A (en) * | 2024-02-05 | 2024-03-15 | 隆回涵丰电子科技有限公司 | Vibrating diaphragm assembly and sound equipment |
Citations (3)
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 |
JPH08298697A (en) * | 1995-04-26 | 1996-11-12 | Sony Corp | Speaker, cone paper for speaker and production of cone paper |
US6584206B2 (en) * | 2000-10-25 | 2003-06-24 | Sony Corporation | Speaker apparatus |
-
2007
- 2007-06-26 WO PCT/KR2007/003076 patent/WO2008002049A1/en active Application Filing
Patent Citations (3)
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 |
JPH08298697A (en) * | 1995-04-26 | 1996-11-12 | Sony Corp | Speaker, cone paper for speaker and production of cone paper |
US6584206B2 (en) * | 2000-10-25 | 2003-06-24 | Sony Corporation | Speaker apparatus |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010098712A (en) * | 2008-10-15 | 2010-04-30 | Kotatsu Kokusai Denshi Kofun Yugenkoshi | Method and electronic device for driving capacitance electro-acoustic transducer |
US8379882B2 (en) | 2008-10-15 | 2013-02-19 | Htc Corporation | Method and electronic device for driving a capacitance electro-acoustic transducer |
US9288583B2 (en) | 2012-03-30 | 2016-03-15 | Sumitomo Riko Company Limited | Speaker |
CN117714954A (en) * | 2024-02-05 | 2024-03-15 | 隆回涵丰电子科技有限公司 | Vibrating diaphragm assembly and sound equipment |
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