CN108271108B

CN108271108B - Electrostatic loudspeaker structure

Info

Publication number: CN108271108B
Application number: CN201611263676.5A
Authority: CN
Inventors: 边仿
Original assignee: Kunshan Haifeiman Technology Group Co ltd
Current assignee: Kunshan Haifeiman Technology Group Co ltd
Priority date: 2016-12-30
Filing date: 2016-12-30
Publication date: 2023-04-07
Anticipated expiration: 2036-12-30
Also published as: WO2018121701A1; CN108271108A

Abstract

The invention relates to an electrostatic loudspeaker structure, comprising a tensioned diaphragm and two pole plates with openings, wherein conductive electrode layers are formed on the two pole plates, and the electrostatic loudspeaker structure is characterized in that: the polar plate comprises a metal mesh grid and an annular rigid frame; the periphery of the metal woven mesh is fixed on the rigid frame and keeps a tension state, and the metal woven mesh is electrically connected with a signal wire; the two polar plates are positioned on two sides of the vibrating diaphragm and are in mirror symmetry along the vibrating diaphragm. The advantages are that: the wire diameter of the high-number metal woven mesh is extremely small, so that acoustic wave diffraction is facilitated, acoustic transmission loss is extremely small, and the electric field uniformity of the metal woven mesh is higher. The round metal wire does not have the wedge, so that the creepage requirement of the electrostatic loudspeaker is reduced.

Description

Electrostatic loudspeaker structure

Technical Field

The invention relates to the technical field of loudspeakers, in particular to an electrostatic loudspeaker structure.

Background

The current electroacoustic speakers are classified into an equal magnetic speaker, a moving coil speaker, a piezoelectric speaker and an electrostatic speaker by a driving method.

Electrostatic loudspeakers are often considered to provide high quality audio reproduction, primarily for advanced headphones and sound boxes. The conventional electrostatic speaker is based on the principle that two fixed electrode plates (usually pcb, metal plate, and metal plate with an insulating layer) with openings are clamped by a conductive diaphragm to form a capacitor, and the diaphragm is driven to vibrate and radiate sound by supplying dc bias voltage to the diaphragm and applying ac voltage to audio frequency of the two electrodes and by using electrostatic force generated by positive and negative electric fields. In order to reduce the vibration quality of the diaphragm, the structure of the diaphragm mostly adopts an insulating film, and an extremely thin electric conductive coating layer, such as metal and semiconductor, is plated on the surface layer of the insulating film.

Compared with the most common moving-coil loudspeaker, the vibrating diaphragm of the electrostatic loudspeaker is extremely thin and light, and the inertial motion of the vibrating diaphragm can be almost ignored, so that the electrostatic loudspeaker has better transient response and stronger detail expression; meanwhile, the sounding area of the loudspeaker is very large, the total area of the vibrating diaphragm is more than ten times of that of the traditional moving coil loudspeaker, the sound field and the sound image of the electrostatic loudspeaker are larger in listening sensation, and meanwhile, the sound is loose and natural.

Under ideal conditions, the electrostatic loudspeaker needs two polar plates to enable air pushed by the vibrating diaphragm to pass through with the lowest resistance as possible so as to enhance the sound permeability of the polar plates, and the polar plates are required to have larger aperture ratio; meanwhile, it needs to generate a strong and uniform electrostatic field between two plates to drive the diaphragm to move linearly, and further to drive as much air flow as possible to achieve sufficient sound intensity, which requires that the plate electrodes are as uniform as possible, and the lower the aperture ratio, the better. In short, the aperture ratio of the polar plate is improved, the intensity of an electrostatic field is reduced while the acoustic resistance is reduced, and the uniformity is poor; on the other hand, the sound permeability is deteriorated, and both cannot be considered. The current conventional method is to uniformly perforate the polar plate, and the perforation rate is about 20-40.

In addition, the electrostatic speaker is easily damaged when it is in an environment with high humidity or dust, and some users using the electrostatic earphone may even be equipped with a special moisture-proof box for storage. This is because: when the electrostatic loudspeaker is in a high-voltage working state during sounding, the polar plate and the vibrating diaphragm are easy to adsorb dust; when the film is in an environment with high humidity for a long time, the coating is easy to strip the vibrating diaphragm. In order to increase the environmental adaptability of the electrostatic loudspeaker, a thinner dust cover is added on part of the electrostatic loudspeaker at present to seal the polar plate and the vibrating diaphragm. Referring to fig. 1, the reference numbers in the figure denote: the polar plate 1, the vibrating diaphragm 2, the vibrating diaphragm frame 3, the film frame 4 and the film 5, wherein the film 5, the polar plate 1, the vibrating diaphragm frame 3 and the film frame 4 surround together to form a closed space.

Although in theory, the acoustic wave can pass through the barrier almost without loss when the thickness of the barrier is much less than the wavelength of the acoustic wave. As can be seen from fig. 1, the diaphragm 2 divides the closed space into two cavities. Although sound waves emitted by the diaphragm 2 can pass through the membrane 5, the vibration of the diaphragm 2 substantially changes the volume of the cavity and pushes air to move, thereby driving the membranes 5 on both sides to vibrate together. In this case, the diaphragm 2 is vibrated by the driving diaphragm 5 to reduce the amplitude, and the diaphragm 5 also constitutes a new sound source, increasing the sound pollution of the speaker and deteriorating the sound quality.

Disclosure of Invention

The invention aims to provide an electrostatic loudspeaker structure and an earphone with the same, aiming at the defects of the prior art structure.

In order to achieve the above object, the speaker according to the embodiment of the present invention is implemented by the following technical solutions:

the utility model provides an electrostatic loudspeaker structure, includes by two polar plates of tensioned vibrating diaphragm and trompil, two polar plates on all be formed with electrically conductive electrode layer, its characterized in that: the polar plate comprises a metal mesh grid and an annular rigid frame; the periphery of the metal woven net is fixed on the rigid frame and keeps a tension state, and the metal woven net is electrically connected with the signal wire; the two polar plates are positioned on two sides of the vibrating diaphragm and are in mirror symmetry along the vibrating diaphragm.

The inner sides of the polar plates facing the vibrating diaphragm are fixedly provided with at least one insulating clamping piece, and the clamping pieces of the two polar plates correspond to and clamp the vibrating diaphragm one by one so that the vibrating diaphragm is a plane in a static state.

The number of the clamping pieces on the polar plate is not less than two, the distance between any two elastic pads on the polar plate and the distance from any one elastic pad to the rigid frame are not less than 2cm.

The open porosity of the metal woven mesh is between 30 and 70 percent.

The open pore rate of the metal woven mesh is between 35 and 65 percent.

The wire diameter of the metal woven net is not more than 0.12mm, and the mesh number is not less than 100 meshes.

The rigid frame is formed by an epoxy glass cloth laminated board.

The rigid frame is a metal frame having an insulating layer.

The inner edge of the inner side of the rigid frame is plated with a metal conducting ring which is connected end to end and is in a closed ring shape, and the periphery of the metal mesh grid is fixed on the metal conducting ring in an electrical connection mode.

The metal frame material is selected from one of high damping alloy or aluminum alloy.

The electrostatic loudspeaker structure further comprises a dust cover, the dust cover comprises an even thin film enclosing into a closed cavity, and the vibrating diaphragm and the two polar plates are located in the closed cavity.

The thin film is an elastic film with the thickness of 50-1000 microns, and the tension of the elastic film is not more than 1/10 of that of the diaphragm.

The tension of the film is not more than 1/30 of the tension of the diaphragm.

The membrane is adhered to and supported by the rigid frame.

Compared with the prior art, the invention has the beneficial effects that:

1. the grids of PCB and punched metal plates must be guaranteed not to break during processing, so there is a physical limit to the size of the grids. The wire diameter of the high-number metal woven mesh is far smaller than the grid size of the PCB polar plate and the punched metal polar plate, so that the acoustic wave diffraction is facilitated, and the acoustic transmission loss is extremely low. And the electric field uniformity of the metal woven net is higher.

2. When the conventional pcb plate and the punched metal plate are used as pole plates, the opening part is provided with a wedge-shaped wedge of 90 degrees. During operation, charges are concentrated at the wedge, and the noise is easily generated by discharging. And the round metal wires of the metal woven mesh do not have the wedges, so that the creepage requirement of the electrostatic loudspeaker is reduced.

3. The polar plate is additionally provided with the clamping piece for clamping the vibrating diaphragm, so that the noise caused by the fact that the vibrating diaphragm contacts the electrode when the loudspeaker works is avoided.

4. The dustproof cover structure is optimized, the film thickness on the dustproof cover is controlled, and the mode that the elastic film and the tension of the film are reduced is adopted, so that the damage of the dustproof cover to the tone quality is reduced.

Drawings

The above features and advantages of the present invention will become more apparent and readily appreciated from the following description of the exemplary embodiments thereof taken in conjunction with the accompanying drawings.

Fig. 1 is a schematic structural view of a conventional electrostatic speaker with a dust cover;

FIG. 2 is a schematic diagram of an outer side structure of a plate according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an inner side surface structure of a plate according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a loudspeaker according to an embodiment of the present invention;

fig. 5 is a graph of the auditory spectrum of a human ear.

Detailed Description

The invention is described in further detail below with reference to the attached drawing figures to facilitate understanding by those skilled in the art:

referring to fig. 2-4, the electrostatic speaker disclosed in the present invention includes an audio signal line 6, an electrically conductive diaphragm 2, a diaphragm frame 3, and two pole plates, wherein an electrically conductive electrode layer is formed on the pole plates, the diaphragm frame 3 is made of an insulating material, and the periphery of the diaphragm 2 is fixed on the diaphragm frame 3 and is tensioned. When the loudspeaker works, the vibrating diaphragm is forced to vibrate by the electrostatic force generated by the positive and negative electric fields by supplying the vibrating diaphragm 2 with direct-current bias voltage and giving alternating-current voltage to the polar plate. The diaphragm vibrates to produce sound based on a vibration factor (frequency, amplitude, and phase dependent). The sound caused by the diaphragm 2 penetrates at least the openings in the pole plate and thus radiates the sound into the outer space.

The difference from the prior art is that: the polar plate of the embodiment adopts a metal woven mesh. The structure is as follows:

each plate is formed by a metal mesh 7 and an annular rigid frame 8. The periphery of the metal mesh 7 is fixed to the rigid frame 8 and held in tension, while the metal mesh 7 is electrically connected to the audio signal line 6 to serve as a pole plate for generating an electric field when the speaker is operated. The two rigid frames 8 clamp the diaphragm frame 3 and the upper diaphragm 2, and the first polar plate and the second polar plate are located on two sides of the diaphragm and are in mirror symmetry along the diaphragm 2.

In a preferred embodiment, the rigid frame 8 is formed from fiberglass PCB board, model FR-4. The substrate of FR-4 employs an epoxy glass cloth laminate on which metal wires are printed. When the invention is applied, the structure is as follows: the inner edge of the inner side of the rigid frame 8 is plated with a metal conductive ring 9 which is connected end to end and is in a closed ring shape, and the periphery of the metal mesh 7 is fixed on the metal conductive ring 9 in an electrical connection manner, which can be welding, bonding, etc. The metal conductive ring 9 also has a lead 10, and the lead 10 is electrically connected to the audio signal line 6.

In another preferred embodiment, the rigid frame 8 is formed by a metal frame having an insulating layer. Similarly, the inner edge of the inner side of the rigid frame 8 is plated with a metal conductive ring 9 which is connected end to end and is in a closed ring shape, and the periphery of the metal mesh grid 7 is fixed on the metal conductive ring 9 in an electrical connection manner.

The material of the metal frame may be an aluminum alloy. In the scheme, the rigid frame is an aluminum-based PCB (printed Circuit Board), namely an aluminum-based copper-clad plate, and consists of a copper foil, a heat conduction insulating layer and a metal substrate. The circuit printing mode and the fixing mode of the metal mesh grid 7 are the same as those of a glass fiber PCB. The processing technology of the aluminum-based PCB and the glass fiber PCB as the rigid frame is mature, and the cost is relatively low. Compared with a glass fiber PCB, the aluminum-based PCB has higher strength, and the natural frequency of the metal frame can be far higher than 20KHz, so that the sound pollution is effectively reduced.

The metal frame can be made of high-damping alloy, and the generation of resonance can be effectively reduced through the high-damping performance of the metal frame.

In order to strengthen the rigid frame 8 and increase the natural frequency of the rigid frame 8, an integral internal support structure may be provided inside the annular rigid frame 8, as shown in fig. 2-3.

The metal mesh 7 has a structure with a high mesh number and a high aperture ratio. The open porosity should be between 30-70%. The wire diameter of the metal mesh 7 is not more than 0.12mm, and the mesh number is not less than 100 meshes.

The following are parameters of the woven metal mesh 7 in several specific embodiments:

a 100-mesh plain metal woven net with the wire diameter of 0.100mm and the opening rate of 37 percent;

a 100-mesh plain metal woven net with the wire diameter of 0.080mm and the aperture ratio of 47 percent;

a 100-mesh plain metal woven net with the wire diameter of 0.025mm and the aperture ratio of 81 percent;

120-mesh plain metal woven net with wire diameter of 0.080mm and opening rate of 39 percent;

a 120-mesh plain metal woven net with the wire diameter of 0.040mm and the aperture ratio of 65 percent;

a 140-mesh plain metal woven net with the wire diameter of 0.060mm and the aperture ratio of 45 percent;

a 140-mesh plain metal woven net with the wire diameter of 0.030mm and the aperture ratio of 70 percent;

180-mesh plain metal woven mesh with wire diameter of 0.050mm and aperture ratio of 42%;

180-mesh plain metal woven net with wire diameter of 0.025mm and opening rate of 68%;

200 mesh plain metal mesh grid with 0.051mm wire diameter and 35% hole opening rate;

200 mesh plain metal mesh with wire diameter of 0.025mm and opening rate of 64%;

a 250-mesh plain metal woven mesh with the wire diameter of 0.040mm and the opening rate of 37 percent;

a 250-mesh plain metal woven net with the wire diameter of 0.030mm and the aperture ratio of 50 percent;

300-mesh plain metal woven net with wire diameter of 0.030mm and opening rate of 41 percent;

300 mesh plain woven metal mesh with wire diameter of 0.025mm and opening rate of 49%;

the 400-mesh plain metal woven net has the wire diameter of 0.025mm and the opening rate of 37 percent.

Through comparison between a trial sample of an applicant and an electrostatic loudspeaker with a conventional electrode, the extensibility of a sound field and a high frequency is better than that of the electrostatic loudspeaker with the conventional electrode when the electrode is made of a metal woven net. And when the opening rate is between 35% and 65%, the sound performance is particularly excellent.

The process is limited, and the grids of the punched PCB, the metal punched plate and the punched metal plate with the insulating layer must be guaranteed not to be broken during processing, so that the size of the grids has physical limit. While the wire diameter of the high-number metal woven net can reach 0.25mm or even lower. When propagating, the sound wave can continue around an object whose size is close to or smaller than the wavelength, which is called diffraction. And for example, the wire diameter of 0.05mm is used, and the corresponding acoustic wave wavelength is 6.67MHz and is far higher than 20KHz audible by human ears. Therefore, the metal mesh grid 7 is used as a polar plate, which is beneficial to sound wave diffraction, and the sound transmission loss is extremely small.

In addition, when the punched PCB, the metal punched plate, or the punched metal plate with an insulating layer is used as a polar plate, the aperture size is large and the uniformity of the electric field is not good in order to increase the aperture ratio. On the premise of the same aperture ratio, the aperture and the wire diameter of the metal mesh grid are much smaller, and the uniformity of an electric field is higher.

For punched PCBs and metal plates, having a thickness such that the acoustically transparent opening substantially corresponds to a circular channel having a length, sound waves are reflected, diffracted and coherent within the channel and at the channel periphery, resulting in sound degradation.

In addition, when the conventional pcb plate and the metal punching plate are used as polar plates, a wedge-shaped wedge of 90 degrees is inevitably arranged at the opening position of the polar plates. When the device works, charges are concentrated at the wedge part, and the noise is easily generated by discharging. Although the metal punching plate with the insulating layer avoids the problems, for the electrostatic loudspeaker, the output sound pressure level is in direct proportion to the distance between the vibrating diaphragm and the polar plate, so that the distance between the polar plate and the vibrating diaphragm is very small, the electrostatic loudspeaker inevitably has insufficient low frequency inductance due to the small amplitude of the vibrating diaphragm, the insulating layer obviously sacrifices the amplitude of the vibrating diaphragm, and the arrangement of the insulating layer outside the polar plate is not an ideal scheme.

The wedge is not arranged on the round metal wire of the metal woven mesh, so that the problem of the discharge of the wedge can be avoided, and the creepage requirement of the electrostatic loudspeaker is reduced.

The metal mesh grid 7 is also provided with a clamping piece 11. Referring to fig. 2, at least one insulating clamping member 11 is fixedly arranged on the inner side of the metal mesh grid 7 facing the diaphragm 2, and the clamping members 11 on the two pole plates correspond to each other one by one and clamp the diaphragm 2. The diaphragm 2 is flat in a rest state. The clamping element 11 acts as a support point for the diaphragm 2 and divides the vibration of the diaphragm 2. Therefore, the vibrating diaphragm 2 can be effectively prevented from contacting the polar plate to generate noise when vibrating, and even damaging the loudspeaker. The number and distribution of the clamping members 11 on each metal mesh 7 should be selected according to the tension and amplitude of the diaphragm 2 and the distance from the diaphragm 2 to the plate. The clamping piece 11 is arranged too densely, so that the amplitude of the vibrating diaphragm 2 is greatly reduced, and low-frequency deterioration is caused; when the distance between two adjacent clamping pieces 11 is too large, the amplitude of the vibrating diaphragm 2 between the two adjacent clamping pieces exceeds the distance between the vibrating diaphragm 2 and the polar plate, so that the vibrating diaphragm 2 beats the polar plate when working. Therefore, the distance between any two clamping pieces 11 on the metal woven mesh 7 and the distance from any one clamping piece 11 to the rigid frame are not less than 2cm.

In addition to the above improvement, the electrostatic speaker structure in this embodiment further includes a dust cover, which includes a uniform thin film 12 enclosing a closed cavity, and the diaphragm 3 and the two pole plates are located in the closed cavity. In a particular embodiment, the membrane 12 is adhered to the rigid frame 8 and supported by the rigid frame 8, while the rigid frame 8 and the diaphragm frame 3 are tightly sealed, thereby forming an enclosed space.

Preferably, the membrane 12 is an elastic membrane having a thickness of between 50 and 1000 microns and a tension of not more than 1/10 of the tension of the diaphragm 2. It is further preferred that the tension of the membrane 12 is no more than 1/30 of the tension of the diaphragm. The membrane 12 is thus in a tensioned state, but the tension is at least an order of magnitude smaller than that of the diaphragm 2, while having a better ductility. As can be seen from FIG. 5, the sensitive region of the human ear is concentrated between 500Hz-5 KHz. When the diaphragm 2 vibrates, although the cavity volumes on both sides of the diaphragm 2 are rapidly changed, the thin film 12 is in a slow expansion/contraction state, and the vibration frequency is greatly reduced. Avoids the sensitive sound pollution of human ears.

In addition, in order to protect the diaphragm 2 of the electrostatic speaker, the electrostatic speaker may further be provided with a protective mesh 13, and the protective mesh 13 is a metal woven mesh fixed to the outer side of the rigid frame 8.

It should be noted that the above-mentioned embodiments are provided for further detailed description of the present invention, and the detailed description of the present invention is not deemed to be limited thereto, and those skilled in the art can make various modifications and variations on the above-mentioned embodiments, and those modifications and variations fall within the scope of the present invention.

Claims

1. The utility model provides an electrostatic loudspeaker structure, includes by two polar plates of tensioned vibrating diaphragm and trompil, two polar plates on all be formed with electrically conductive electrode layer, its characterized in that: the polar plate comprises a metal mesh grid and an annular rigid frame; the periphery of the metal woven mesh is fixed on the rigid frame and keeps a tension state, and the metal woven mesh is electrically connected with a signal wire; the two polar plates are positioned on two sides of the vibrating diaphragm and fixedly provided with at least one insulated clamping piece towards the inner side of the vibrating diaphragm along the metal woven mesh in mirror symmetry with the vibrating diaphragm, the clamping pieces on the two polar plates correspond to each other and clamp the vibrating diaphragm one by one, so that the vibrating diaphragm is a plane in a static state, the number of the clamping pieces on the metal woven mesh is not less than two, the distance between any two elastic pads on the polar plates, and the distance from any one elastic pad to the rigid frame are not less than 2cm; the aperture ratio of the metal mesh grid is between 35 and 65 percent, the wire diameter of the metal mesh grid is not more than 0.10mm, the mesh number is not less than 100 meshes, so that the uniformity of an electric field is higher, the sound wave diffraction is more facilitated, and the sound transmission loss is extremely small; the rigid frame is formed by an epoxy glass cloth laminated board; the rigid frame is a metal frame which is provided with an insulating layer; the inner edge of the inner side of the rigid frame is plated with a metal conducting ring which is connected end to end and is in a closed ring shape, and the periphery of the metal mesh grid is fixed on the metal conducting ring in an electrical connection mode; the metal frame material is selected from one of high damping alloy or aluminum alloy; the electrostatic loudspeaker structure further comprises a dust cover, the dust cover comprises a uniform thin film enclosing to form a closed cavity, the vibrating diaphragm and the two polar plates are both located in the closed cavity, the thin film is an elastic film with the thickness of 50-1000 microns, the tension of the thin film on the position, corresponding to the vibrating diaphragm, of the dust cover is not more than 1/10 of the tension of the vibrating diaphragm or not more than 1/30 of the tension of the vibrating diaphragm, and the thin film is adhered to the rigid frame and supported by the rigid frame.