Loudspeaker unit with acoustic resistance adjusting function

Abstract

The invention discloses a loudspeaker unit with an acoustic resistance adjusting function. The vibrating diaphragm of each unit is a folding ring type rectangular vibrating diaphragm; wherein the folding ring type rectangular vibrating diaphragm comprises a folding ring area and a hollow part arranged at the center of the folding ring area; the hollow part is covered with a fine-hole net-shaped layer; the outer side face of the fine-hole net-shaped layer is covered with a middle film, and the covering ratio of the middle film ranges from 30% to 70%. The fine-hole net-shaped layer provides a channel for heat dissipation. The middle film covers the outer side of the fine-hole net-shaped layer, and the covering ratio is 30%-70%. When sound waves are transmitted from the vibrating diaphragm to the fine-hole net-shaped layer and then propagated outwards, the intermediate diaphragm can change the propagation path of the sound waves. Due to partial covering of the middle film, sound waves can meet different medium interfaces (an interface between the middle film and air) in the propagation process, so that reflection and transmission phenomena are generated, namely, acoustic resistance is adjusted, and energy distribution of the sound waves is more reasonable.

Description

Technical Field

[0001] The present invention relates to the technical field of loudspeakers, and in particular to a loudspeaker unit with an acoustic impedance adjustment function. Background Art

[0002] Currently, the heat dissipation design of most speakers is incomplete. When a speaker is operating, especially at high power output, the voice coil generates a significant amount of heat. Existing speakers primarily dissipate heat by relying on the tiny displacement of the diaphragm to drive air flow, and by transferring heat from the magnet and frame to the external environment through their inherent material properties. However, this heat dissipation method is inefficient and fails to dissipate heat promptly. Heat accumulation within the speaker causes the voice coil temperature to rise, accelerating the aging of the voice coil insulation, reducing speaker performance and lifespan. High temperatures can also demagnetize the magnet, further weakening the speaker's performance stability. Furthermore, current adjustable acoustic impedance solutions rely primarily on two structures. Perforated plate acoustic resistors adjust the acoustic impedance by varying the porosity, but this increases the airflow path length, introducing a Helmholtz resonant cavity effect and generating new sound coloration at specific frequencies between 500Hz and 1kHz. Smart material variable damping layers can adjust the damping in real time using electrical signals. However, the material's slow response speed (>10ms) and high power consumption make them difficult to use for full-band dynamic control. Summary of the Invention

[0003] In view of this, an object of the present invention is to provide a speaker unit with a fine-pore mesh, which can solve at least one of the technical problems mentioned in the background technology.

[0004] According to one aspect of the present invention, there is provided a speaker unit with a fine-mesh mesh, wherein the diaphragm of the unit is a folded-ring rectangular diaphragm;

[0005] Among them, the folded ring rectangular diaphragm includes a folded ring area and a hollow part arranged at the center of the folded ring area; the hollow part is covered with a fine-porous mesh layer; the outer side of the fine-porous mesh layer is covered with an intermediate film, and the coverage ratio of the intermediate film is 30% to 70%.

[0006] In the above technical solution, the fine-porous mesh layer has a large number of uniformly sized pores. During operation of the speaker unit, the diaphragm continuously vibrates and generates heat. These pores provide a channel for heat dissipation, allowing air to flow through the pores and form convection between the diaphragm and the fine-porous mesh layer. When the diaphragm vibrates, the surrounding air is drawn in, and heat is carried away by the air through the pores, thereby achieving heat dissipation. The intermediate membrane covers the outer surface of the fine-porous mesh layer, with a coverage ratio of 30% to 70%. When sound waves are transmitted from the diaphragm to the fine-porous mesh layer and then propagate outward, the intermediate membrane changes the propagation path of the sound waves. Due to the partial coverage of the intermediate membrane, the sound waves encounter different medium interfaces (the interface between the intermediate membrane and the air) during propagation, resulting in reflection and transmission. This effectively adjusts the acoustic impedance, resulting in more efficient energy distribution of the sound waves. Part of the sound wave is reflected back to the diaphragm and fine-porous mesh layer area, while the remaining part is smoothly transmitted. This balance between reflection and transmission can avoid the premature loss of a large amount of sound wave energy, while also preventing the sound waves from radiating outward too concentratedly, making the propagation of sound more uniform and efficient.

[0007] From the perspective of the vibration system as a whole, the vibration characteristics of the rectangular diaphragm and the acoustic characteristics of the fine-porous mesh layer need to match the acoustic impedance of the external sound field. The presence of the intermediate membrane can, to a certain extent, bridge the acoustic impedance difference between the diaphragm-fine-porous mesh layer combination and the external sound field. For example, if the acoustic impedance of the external sound field is small (such as in an open space), the intermediate membrane can appropriately increase the system's acoustic impedance through its coverage ratio, allowing sound waves to be transmitted more smoothly from the diaphragm-fine-porous mesh layer system to the external space, reducing the reflection loss of sound waves at the interface, and improving the overall efficiency and sound quality of the speaker.

[0008] In some embodiments, the pore diameter of the fine-porous mesh layer is 0.05-0.3 mm.

[0009] In the above-mentioned technical solution, the interlayer coverage ratio ranges from 30% to 70%, synergistically regulating acoustic impedance with the pore diameter of 0.05–0.3mm. The interlayer partially covers the pores, altering the sound wave propagation path and energy distribution. Its coverage ratio determines the ratio of sound wave reflection to transmission, while the pore diameter influences the ease with which sound waves pass through the pores and their propagation characteristics. When the pore diameter is small (closer to 0.05mm), sound waves encounter greater resistance when passing through the pores. In this case, the interlayer coverage ratio can be adjusted appropriately. Increasing the coverage ratio further enhances sound wave reflection and scattering, redistributing sound wave energy between the diaphragm and the pore mesh layer, improving low-frequency response and delivering richer, more powerful bass. When the pore diameter is larger (closer to 0.3mm), sound waves pass through the pores more easily, and the interlayer coverage ratio can be reduced appropriately, allowing sound waves to transmit more smoothly. The larger pore size also increases the radiation efficiency of high-frequency sound waves, making high-frequency sounds clearer and brighter, thereby achieving a wide frequency response range and balanced timbre.

[0010] When the speaker is working, the synergistic effect of the middle membrane and the fine-pored mesh layer can dynamically adjust the acoustic impedance to adapt to audio signals of different frequencies and power. When low-frequency signals are input, the middle membrane enhances the low-frequency sound pressure by reflecting and scattering sound waves, making the bass fuller. At the same time, the heat dissipation function of the fine-pored mesh layer ensures the stable vibration of the diaphragm, avoids heat accumulation caused by large low-frequency vibration amplitude, and maintains stable bass output. When high-frequency signals are input, the pores of the fine-pored mesh layer provide a smooth propagation channel for high-frequency sound waves. The middle membrane optimizes the directionality and energy distribution of high-frequency sound waves by appropriately covering the pores, avoiding excessive dispersion or excessive intensity of high-frequency sound waves, making the high-frequency sound delicate, transparent and layered, allowing the entire speaker to output high-quality sound at different frequencies.

[0011] In some embodiments, the fine-porous mesh layer is made of stainless steel, polyester, or nylon.

[0012] In this technical solution, stainless steel's relatively high thermal conductivity allows it to quickly transfer heat generated by the diaphragm's vibration to the surface of the fine-pored mesh layer, where it is then efficiently dissipated through air convection. Its excellent thermal stability means that within the speaker's operating temperature range, it will not deform or change performance due to temperature fluctuations, ensuring stable heat dissipation. Stainless steel's high strength and hardness provide reliable protection for the diaphragm, shielding it from external mechanical shock and vibration. At the same time, the finely structured pores maintain excellent heat dissipation, ensuring long-term stable operation of the diaphragm.

[0013] Polyester has a low density, and the resulting fine-pored mesh layer is lightweight, barely affecting the diaphragm's vibration characteristics, helping to improve the speaker's high-frequency response. While its pores aren't as efficient as stainless steel in dissipating heat, they meet the cooling needs of everyday use and provide a more balanced heat dissipation effect at low frequencies. Polyester's flexibility allows it to adapt to the deformation of the diaphragm during vibration, making it less susceptible to breakage or damage. The pores regularly change with the diaphragm's vibrations, facilitating the expulsion of hot air and the intake of cool air, enhancing heat dissipation. They also buffer and regulate sound wave propagation, resulting in a softer sound.

[0014] Nylon is lightweight, and its fine-pored mesh layer reduces the diaphragm's overall mass and enhances high-frequency response. It also offers excellent tensile strength and abrasion resistance, and its pores maintain their shape and performance during vibration, ensuring uniform heat dissipation. Nylon's smooth surface facilitates air flow and reduces acoustic resistance. Combined with an interlayer with an appropriate coverage ratio, it optimizes acoustic impedance matching, enhancing sound clarity and depth. Nylon is chemically and aging-resistant, maintaining unobstructed pores and stable heat dissipation over extended use, ensuring optimal heat dissipation for the diaphragm and extending the speaker's lifespan.

[0015] Stainless steel has high density and excellent rigidity. When combined with the interlayer, the fine-pored mesh layer enhances the overall rigidity of the composite structure, enhancing the reflection and scattering of sound waves during propagation. The interlayer's coverage ratio ranges from 30% to 70%, allowing for adjustable acoustic impedance. Adjusting this to a higher level is ideal for applications requiring enhanced low-frequency sound pressure and improved low-frequency response.

[0016] Polyester and nylon materials offer low density and excellent flexibility. The combination of the fine-mesh layer and the interlayer is relatively light and soft, offering high sound wave transmission. The interlayer's coverage ratio adjusts the acoustic impedance to a moderate range. The polyester fine-mesh layer combined with the interlayer ensures a more balanced acoustic impedance across the mid- and high-frequency ranges, resulting in clear and bright sound. Nylon provides smooth acoustic impedance adjustment across the entire frequency range, enriching the sound with richer layers.

[0017] In some embodiments, the intermediate film is made of PET film, PET / metal composite film, or PEN film.

[0018] In this technical solution, the PET film is soft, smooth, and has a certain degree of elasticity, which can modify the propagation path and energy distribution of sound waves. Its coverage ratio ranges from 30% to 70%, and its acoustic impedance is adjustable within a moderate range, balancing reflection and transmission for clear and distinct sound. While PET film has average thermal conductivity, when combined with the heat-dissipating fine-pored mesh layer, it improves heat dissipation, prevents heat accumulation, ensures stable acoustic performance, and enhances speaker reliability.

[0019] PET / metal composite film combines the flexibility of PET film with the high reflectivity and conductivity of metal. The metal layer enhances sound wave reflection and scattering, adjusting acoustic impedance to a higher level, improving low-frequency response and making bass more powerful and resonant. The metal layer also provides electromagnetic shielding, reducing electromagnetic interference and enhancing sound purity. Furthermore, the metal's excellent thermal conductivity, combined with the fine-porous mesh layer to dissipate heat, further safeguards speaker performance and is suitable for high-fidelity and high-power applications.

[0020] The PEN membrane boasts high mechanical strength and thermal stability, withstanding the vibrations and temperature fluctuations experienced during speaker operation, ensuring stable acoustic impedance adjustment. Its smooth surface reduces resistance to sound wave propagation, enhances high-frequency sound transmission, and provides excellent broadband response. The PEN membrane also exhibits excellent dimensional stability and resists deformation under varying environmental conditions, ensuring a stable interlayer coverage ratio and consistent acoustic impedance adjustment. Combined with a heat-dissipating fine-pored mesh layer, it optimizes acoustic performance, making it suitable for applications requiring high-quality, stable sound quality.

[0021] In some embodiments, the thickness of the intermediate film is 8-20 μm.

[0022] In the above technical solution, in the low-frequency band, appropriately thickening the intermediate membrane can enhance sound wave reflection and scattering, thereby increasing low-frequency sound pressure; in the mid- and high-frequency bands, thinning the intermediate membrane is conducive to sound wave transmission, making the sound clear and bright. For example, an intermediate membrane with a thickness of 12-15μm can better balance low-frequency enhancement and mid- and high-frequency clarity, making the sound layered. Combined with the pore diameter of the fine-pored mesh layer (0.05-0.3mm), an intermediate membrane thickness of 8-20μm can achieve broadband acoustic impedance matching. Finer pores (0.05-0.15mm) paired with an intermediate membrane of 15-20μm are suitable for low-frequency optimization; coarser pores (0.15-0.3mm) paired with an intermediate membrane of 8-12μm are conducive to mid- and high-frequency enhancement, achieving a balanced frequency response.

[0023] Increasing the thickness of the interlayer will slightly reduce the heat dissipation efficiency because it covers part of the heat dissipation channels of the porous mesh layer. However, the impact is small in the thickness range of 8-20μm and can be compensated by optimizing the pore diameter and distribution. For example, appropriately increasing the pore diameter or density can enhance heat dissipation, ensuring that the heat of the speaker is dissipated in a timely manner and ensuring stable acoustic impedance adjustment performance. Interlayers of different materials have different heat dissipation performance at thicknesses of 8-20μm. PET film has moderate heat dissipation, PET / metal composite film has good heat dissipation but the thickness of the metal layer needs to be controlled, and PEN film has excellent heat dissipation and is less affected by increased thickness. When selecting the material of the interlayer, it is necessary to comprehensively consider the heat dissipation and acoustic impedance adjustment requirements. For example, high-power speakers should use thicker PEN film or PET / metal composite film to take into account both heat dissipation and acoustic impedance adjustment performance.

[0024] When the speaker is operating, the thickness of the interlayer membrane affects the dynamic balance between acoustic impedance regulation and heat dissipation. When high power input and low-frequency signals are predominant, the need for acoustic impedance regulation is high and heat generation is high. In this case, appropriately thickening the interlayer membrane can meet the acoustic impedance regulation needs, while relying on the efficient heat dissipation of the fine-pored mesh layer to prevent heat accumulation. An interlayer thickness within the range of 8-20μm can ensure long-term stability in acoustic impedance regulation and heat dissipation performance. An interlayer that is too thin is susceptible to mechanical damage and environmental influences, resulting in rapid performance degradation; an interlayer that is too thick can affect heat dissipation and high-frequency sound wave transmission. A thickness range of 8-20μm, combined with different materials, can ensure stable acoustic performance of the speaker during long-term use and meet the needs of high-quality audio playback.

[0025] In some embodiments, the folding ring area adopts a double cantilever folding ring, and the area of ​​the folding ring area is 10%-25%.

[0026] In the above technical solution, the double-cantilever surround design can provide the diaphragm with more stable support and more uniform displacement distribution when vibrating. Compared with the traditional single-cantilever surround, the double-cantilever structure can effectively reduce the split vibration mode of the diaphragm during low-frequency vibration, making it easier for the diaphragm to move in an overall mode, thereby improving the low-frequency radiation efficiency and enhancing the low-frequency response capability. Its symmetrical structure can better control the vibration of the diaphragm, making the low-frequency sound richer and more powerful, with less distortion. In the high-frequency band, the double-cantilever surround can allow the diaphragm to vibrate more naturally, reducing phase distortion and amplitude attenuation near the high-frequency cutoff frequency. By optimizing the geometry and stiffness distribution of the surround, the diaphragm can maintain effective vibration over a wider frequency range, thereby improving the high-frequency ductility of the speaker, making the high-frequency sound clearer and brighter, and able to reproduce more high-frequency details.

[0027] The surround area accounts for 10%-25% of the total diaphragm area to achieve a balance in acoustic performance. When the surround area is small (close to 10%), the effective vibration area of ​​the diaphragm is relatively large, which is conducive to improving the sound pressure level and making the sound louder. However, an overly small surround area may lead to insufficient support for the diaphragm, affecting the stability of vibration and low-frequency response. When the surround area is large (close to 25%), although some effective vibration area will be sacrificed, it can significantly enhance the support and control capabilities of the diaphragm, improve low-frequency response and sound clarity. Therefore, within the area ratio range of 10%-25%, optimization can be carried out according to different acoustic requirements to achieve the best balance between sound pressure level and sound quality.

[0028] The area ratio of the surround works in synergy with the heat dissipation function of the fine-porous mesh layer and the acoustic impedance adjustment function of the intermediate membrane. At an appropriate area ratio, the surround provides stable mechanical support for the diaphragm, allowing the diaphragm to better exert its acoustic performance under the action of the fine-porous mesh layer and the intermediate membrane. For example, when the area of ​​the surround is 15%-20%, the vibration of the diaphragm can not only ensure sufficient sound pressure level output, but also match the acoustic impedance adjustment of the intermediate membrane, making the propagation of sound waves more efficient and uniform. At the same time, the heat dissipation function of the fine-porous mesh layer can also effectively ensure the temperature stability of the diaphragm during operation, further improving the overall performance of the speaker.

[0029] The surround's area ratio has a significant impact on the diaphragm's vibration mode. Within a 10%-25% area ratio, the surround can effectively control the diaphragm's vibration mode and reduce the occurrence of high-order modes. When the surround's area is small, the diaphragm's vibration mode is relatively simple, primarily piston-like, which helps improve high-frequency directivity and sound pressure level consistency. As the surround's area increases, the surround's restraining effect strengthens, and the diaphragm's vibration mode gradually shifts to a more complex distribution. However, this shift is controllable, ensuring low-frequency performance while optimizing the acoustic characteristics of mid- and high-frequency frequencies. For example, when the surround's area is around 18%, the diaphragm's vibration mode achieves a good balance between low, mid-, and high frequencies, making the sound fuller and more natural.

[0030] In addition, the area ratio of the surround area needs to match the thickness and material of the intermediate film to achieve optimal vibration control and acoustic performance. For example, when the surround area is large, a thicker (15-20μm) PEN film can be selected as the intermediate film to enhance the acoustic resistance adjustment capability. At the same time, the high mechanical strength and thermal stability of the PEN film can be used together with the surround area to constrain the vibration of the diaphragm and improve vibration stability. When the surround area is small, a thinner (8-12μm) PET film or PET / metal composite film can be used to reduce the impact of the intermediate film on the vibration of the diaphragm, allowing the diaphragm to vibrate more flexibly. At the same time, the acoustic resistance adjustment function of the intermediate film can optimize the clarity and layering of the sound.

[0031] In some embodiments, the intermediate film and the diaphragm are fixed by micro-contact hot pressing, mechanical bump embedding, or glue.

[0032] In this technical solution, micro-contact hot-pressing lamination uses localized high temperature and high pressure to form molecular bonds between the interlayer and diaphragm in a tiny area, resulting in a tight and highly stable connection. This prevents acoustic defects caused by glue aging or mechanical loosening at the joint, improves the consistency of acoustic impedance regulation, and optimizes sound clarity and layering. The joint has low thermal resistance and high heat dissipation efficiency, facilitating heat transfer from the diaphragm to the fine-porous mesh layer for dissipation, ensuring stable speaker performance. The micro-contact area will not loosen or fatigue due to vibration, and can stably withstand vibration stress over the long term, ensuring long-term acoustic performance.

[0033] Mechanical dot interlocking utilizes embedded dotted points to achieve a tight connection. The interlocking structure of the dotted points provides strong support and vibration resistance, ensuring that the joint is not easily loosened by external forces or vibration, and ensuring the stability of the acoustic impedance adjustment structure. The dotted points partially reflect sound waves, working in conjunction with the acoustic impedance adjustment of the interlayer membrane to enhance low-frequency sound pressure and sound richness. The dotted points act as a vibration transmission path, efficiently transferring diaphragm vibration to the interlayer membrane, improving sound wave transmission efficiency. The regular arrangement of the dotted points ensures consistent acoustic performance, preventing sound wave interference or diffraction, and evenly disseminating sound, enhancing sound quality uniformity and reliability.

[0034] The glue-based fixing process is simple and easy to use, suitable for interlayers and diaphragms of various complex shapes and materials, and easily adaptable to designs with varying acoustic impedance requirements. Once cured, the glue forms a uniform, flexible layer that adapts to sound wave vibrations, reduces acoustic impedance mismatch, and improves sound clarity and fidelity. Choosing the right glue ensures excellent environmental adaptability at the joint, resisting temperature and humidity fluctuations and chemical corrosion, ensuring long-term stable operation in harsh environments. The glue's viscoelastic properties absorb some vibration energy, reducing resonance and noise, and enhancing sound purity.

[0035] In some embodiments, a silica gel transition layer is provided between the intermediate film and the fine-porous mesh layer.

[0036] In the above technical solution, the silicone transition layer has excellent elasticity and damping properties, effectively absorbing and isolating vibrations between the fine-porous mesh layer and the intermediate membrane. When the diaphragm vibrates, the generated mechanical vibrations are transmitted through the intermediate membrane to the silicone transition layer. The high damping properties of the silicone convert vibration energy into heat and dissipate it, thereby reducing vibration transmission between the different layers and preventing acoustic interference and distortion caused by vibration coupling. The elastic properties of the silicone transition layer enable it to form an excellent acoustic match with the intermediate membrane and fine-porous mesh layer. It can adjust the propagation speed and direction of sound waves to a certain extent, ensuring smoother transmission between the different media. By adjusting parameters such as the thickness and hardness of the silicone transition layer, specific acoustic effects can be achieved. For example, appropriately increasing the thickness of the silicone transition layer can enhance low-frequency attenuation and achieve more transparent high-frequency performance; while appropriately increasing the hardness of the silicone can enhance the brightness and impact of the sound, meeting the listening preferences and specific acoustic needs of different users.

[0037] In some embodiments, the silicone transition layer includes a first silicone layer, a second silicone layer and a third silicone layer in sequence from the fine-porous mesh layer side to the intermediate membrane side; wherein the porosity of the first silicone layer is greater than that of the second silicone layer, and the porosity of the third silicone layer is greater than that of the third silicone layer.

[0038] In the above technical solution, the first silicone layer with a higher porosity allows sound waves to vibrate more freely, helping to transmit and enhance low-frequency sound waves. As the porosity gradually decreases, the second and third silicone layers gradually improve sound wave reflection and focus high-frequency sound waves, making sound transmission more precise and clear. The multi-layer silicone structure helps optimize the transmission of low-frequency sound waves and the focusing of high-frequency sound waves. The high porosity of the first silicone layer allows low-frequency sound waves to vibrate more freely during propagation, thereby enhancing low-frequency response. As the sound waves propagate toward the intermediate membrane, the porosity of the second and third silicone layers gradually decreases, enhancing sound wave reflection and focusing high-frequency sound waves, improving sound clarity and directionality. The multi-layer silicone structure achieves more precise acoustic impedance matching. The porosity and thickness of each silicone layer can be adjusted according to the frequency characteristics of the sound waves, ensuring smoother sound wave transmission between different media, reducing reflection and scattering, and improving sound wave transmission efficiency and sound fidelity.

[0039] The multi-layered structure of the silicone transition layer effectively isolates and manages vibration. The high porosity of the first silicone layer absorbs and disperses vibrations from the fine-mesh layer, reducing their impact on the intermediate membrane. As sound waves propagate toward the intermediate membrane, the second and third silicone layers gradually enhance their reflection and focusing, resulting in clearer and more natural sound transmission. The multi-layered silicone structure modulates the reflection and scattering properties of sound waves. The porosity and thickness of each silicone layer can be adjusted to meet acoustic requirements, resulting in varying reflection and scattering effects between layers. Through appropriate design, sound interference and diffraction can be reduced, improving sound clarity and consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 This is an exploded schematic diagram of the three-dimensional structure of an embodiment of a loudspeaker unit with a fine-mesh mesh according to the present invention;

[0042] Figure 2 This is an exploded side view of a loudspeaker unit with a fine mesh according to an embodiment of the present invention;

[0043] Figure 3 It is a top view schematically showing an embodiment of a loudspeaker unit with a fine-mesh mesh according to the present invention. DETAILED DESCRIPTION

[0044] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and are not intended to be exhaustive. All other embodiments obtained by those of ordinary skill in the art without creative effort are intended to fall within the scope of protection of the present invention.

[0045] Example 1

[0046] See also Figures 1 to 3 A speaker unit with acoustic impedance adjustment function includes: an intermediate membrane 1, a porous mesh layer 2, a diaphragm 3, a voice coil 4, a magnet 5, a bracket 6, and a magnetic return assembly 7. The diaphragm 3 of the unit is a rectangular ring-shaped diaphragm; the ring-shaped rectangular diaphragm 3 includes a ring region 31 and a hollow portion 32 disposed at the center of the ring region 31; the hollow portion 32 is covered with a porous mesh layer; the outer surface of the porous mesh layer 2 is covered with an intermediate membrane 1, and the coverage ratio of the intermediate membrane 1 is 30% to 70%.

[0047] In this embodiment, the equivalent acoustic resistance (R total ). The entire hollow part (covered with a fine-porous mesh layer and partially covered with an intermediate membrane) is regarded as two parallel acoustic channels:

[0048] 1. Area of ​​channel A (area not covered by the intermediate film): A open =(1-β)*A mesh ; The total acoustic resistance R of the area open =R mesh / (1-β); R mesh = the entire reticular layer (A mesh The total acoustic resistance when the surface is not covered or blocked; β = the coverage ratio of the intermediate film. R mesh The material, porosity, thickness and total area A of the mesh layer itself mesh Decision. mesh / (1-β) is because the acoustic resistance is inversely proportional to the effective ventilation area. mesh When open, its resistance is greater than the entire area A mesh All open R mesh Specifically, the resistance is 1 / (1-β) times the original. For example, β = 0.5 (half is covered), the open area is halved, and the acoustic resistance of the open channel R open =R mesh / 0.5=2*R mesh .

[0049] 2. Area of ​​channel B (area covered by the intermediate film): A covered=β*A mesh ; The total acoustic resistance R of the area covered =R membrane . R membrane = acoustic resistance of the area covered by the intermediate film. In this solution, it is hoped that the area covered by the intermediate film is as "sealed" as possible, that is, it is difficult for air to pass through. This means that R membrane Should be much larger than R mesh Ideally, R membrane Approaching infinity (∞) indicates complete blocking. In reality, even a "sealed" diaphragm may have tiny leaks or the flexibility of the diaphragm itself may introduce some acoustic impedance, but the design goal is still to make its acoustic resistance very high. membrane Depends on the density, stiffness, tension and edge sealing of the diaphragm material. If the diaphragm is porous, its own acoustic resistivity r needs to be calculated. s_mem , thickness d mem , then R membrane =(r s_mem *d mem ) / A covered But usually the goal is to design s_mem *d mem Extremely large, making R membrane great.

[0050] 3. Overall equivalent acoustic resistance (R total ): Channel A (R open ) and Channel B (R covered ) is the acoustic parallel relationship. The total volume velocity U flowing through the hollow part total =U open +U covered The total impedance of the parallel acoustic resistance is calculated as: 1 / R total =1 / R open +1 / R covered Substituting into the above expression:

[0051] 1 / R total =1 / [R mesh} / (1-β)]+1 / R membrane};

[0052] 1 / R total =(1-β) / R mesh +1 / R membrane};

[0053] Simplification under the core design goal (R membrane >>R mesh )

[0054] Because R membrane is very large, so 1 / R membraneThis term is very small relative to (1-β) / R mesh can be ignored. Therefore, the formula is simplified to: 1 / R total ≈(1-β) / R mesh ; Take the reciprocal of both sides to get the simplified formula: R total ≈R mesh / (1-β)

[0055] Based on the above theoretical model, the following calculations can be performed according to actual needs to obtain the optimal coverage ratio:

[0056] (1) Measure or calculate the basic acoustic resistance (R mesh ): Need to know the entire pore network layer (A mesh Method: Use an impedance tube or a dual-microphone transfer function method to measure the acoustic impedance of a sample equipped only with the fine mesh layer, and directly obtain its acoustic resistance R in the target frequency range. mesh (Usually the average value of mid- and low-frequency is taken, because the acoustic impedance adjustment mainly affects these frequency bands). If the material parameters of the mesh layer (porosity Resistivity σ-Rayls / m, thickness d), then R mesh =(σ*d) / A mesh The flow resistivity σ usually requires experimental measurement or reference to a material database. For a regular pore network, σ can be estimated using the formula.

[0057] (2) Determine the target acoustic resistance range (R min , R max ): According to the design requirements of the speaker system (such as the desired Qts, low frequency response flatness, transient response), determine the minimum (R min ) and maximum (R max ) equivalent acoustic resistance. For example, R min This may correspond to the complete removal of the intermediate film (β=0), at which point R total_min =R mesh . R max is the maximum damping that one hopes to achieve by covering the middle membrane.

[0058] (3) Evaluation of interlayer performance (R membrane ):Design or select the intermediate membrane material / structure, the goal is to make the acoustic resistance R of the coverage area membrane As large as possible. If the diaphragm is completely sealed and has infinite rigidity, then R membrane ≈∞. In fact, the acoustic impedance of a small piece of the intermediate film covering a small hole of known area can be tested. Ensure that its R membrane >>R mesh (e.g. >10 times R mesh ). If Rmembrane If it is not large enough, the error of the simplified formula will increase and the adjustment effect will deteriorate.

[0059] (4) Calculate the required coverage ratio range (β min , β max ): Use the simplified formula R total ≈R mesh / (1-β): To achieve R max ≈R mesh / (1-β max )=>β max ≈1-(R mesh / R max ); To achieve R min ≈R mesh / (1-β min )=>because R min =R mesh (When β=0), so β min = 0. If the middle film design cannot be completely removed (β min >0), then R min ≈R mesh / (1-β min ). Considering non-ideal factors (R membrane If more precision is required, use the full formula: R total =1 / [(1-β) / R mesh +1 / R membrane ]; solve for β with respect to R total The expression:

[0060] (1-β) / R mesh +1 / R membrane =1 / R total

[0061] (1-β) / R mesh =1 / R total -1 / R membrane

[0062] 1-β=R mesh *(1 / R total -1 / R membrane )

[0063] β=1-R mesh *(1 / R total -1 / R membrane )

[0064] R min and R max Substituting into the above formula, we can get a more accurate β min and β max .

[0065] (5) Evaluate the coverage ratio range (β min , β max ) rationality: the calculated β max Should be in the range of 0.3 to 0.7 (30% to 70%) or nearby. Too low (β max <<0.3) resulting in target R max Not big enough, or the base R mesh Too small, resulting in insufficient adjustment range and insignificant maximum damping effect. You can only increase R mesh}(use a denser / thicker mesh), or increase R max Target. Too high (β_max>>0.7) leads to target R max Too large, or the base R mesh Too large. Only when most of the area is covered can high resistance be achieved, which may result in a significant reduction in the effective radiation area and a serious decrease in sensitivity. The risk of self-splitting vibration of the intermediate film increases, leading to distortion. The increase in the travel / complexity of the adjustment mechanism leads to a reduction in R mesh (use a looser / thinner mesh), or lower R max Goal: If this cannot be changed, accept the side effects of high coverage ratio and optimize the interlayer (e.g. increase tension / stiffness).

[0066] (6) Select the initial / operating point coverage ratio (β initial ): If the position of the intermediate film can be dynamically adjusted, the coverage ratio can be adjusted in β min to β max If you need to fix an optimal value, choose β initial In β min to β max Usually choose the midpoint (such as (β min +β max ) / 2), or the β value corresponding to the design target of the system total Q value (Qts). Combined with the simulation or calculation of the speaker T / S parameters (Thiele / Small parameters), find the R that makes the system Qts reach the design target (such as 0.707 for Butterworth response). total , and then reverse β.

[0067] In this embodiment, based on the above inference, the physical meaning of the coverage ratio of 30%-70% is that within this range, the change of β can cause R total Significant change (the change multiple is large enough). In the range of β = 0.4 to 0.6, R total The change with β is relatively linear and easy to control. Avoid β approaching 1 (covering almost all the area), which will lead to a sharp drop in sensitivity, diaphragm vibration problems, and a heavy burden on the adjustment mechanism; avoid β approaching 0 (covering too little area), which will result in weak adjustment effect.

[0068] In this embodiment, the pore diameter of the fine mesh layer is 0.05-0.3 mm. The reasons for this selection are as follows:

[0069] 1. Consideration of pore diameter range

[0070] Apertures that are too small (<0.05mm) will result in severe attenuation of high frequencies. Especially when the aperture is less than 0.05mm, even with a high porosity design, the sound resistance of a single hole (r a ) value is also extremely large, causing excessive attenuation of mid- and high-frequency energy (>2kHz), resulting in a muffled sound and lack of detail. Furthermore, this extremely small aperture approaches the economic limit of current precision manufacturing and is prone to clogging, requiring special treatment such as oleophobic and hydrophobic coatings. An aperture that is too large (>0.3mm) will result in insufficient acoustic resistance, rendering the control meaningless. a The value is very small, even if the porosity is low, the total acoustic resistance (R a ) may not be able to effectively damp the vibration of the center area of ​​the diaphragm or suppress wind noise, and the effect of suppressing high-order modes in the center area may be reduced. It may also cause significant diffraction or scattering of sound waves, affecting the directivity and frequency response smoothness. From the perspective of acoustic resistance, the fine mesh produces resistance to air flow, which manifests as acoustic resistance. Acoustic resistance is the acoustic impedance (Z a ) is similar to the real part of resistance. The acoustic resistance of a single circular hole is r a In the case of small pores (pore diameter is much smaller than the wavelength) and low flow rate, the approximate formula is

[0071] r a ≈(8*η*t) / (π*r 4 )

[0072] Where: η is the air viscosity coefficient (about 1.8e-5Pa·s@20℃), t is the thickness of the fine mesh material (mm), and r is the pore radius (mm). a and Inversely proportional, the acoustic resistance of a single hole increases sharply when the aperture decreases slightly. a ≈r a / σ, the higher the porosity σ (many and dense pores), the lower the total acoustic resistance. Small pores require a higher pore density to maintain a reasonable porosity, otherwise the acoustic resistance will be too high.

[0073] 2. The influence of porosity

[0074] Porosity refers to the ratio of open area to total area. Pore size and porosity together determine the acoustic resistance (R a ) and sound quality (M a ). Sound quality (M a ) analog inductance, related to the quality of the air in the hole. M a ≈ρ0*t / (π*r 2 *σ)( is the air density). In the target operating frequency band (medium frequency to high frequency), the fine mesh should be mainly pure resistive (R a Dominant), the pores need to be small enough and the porosity reasonable to avoid M a Too large a porosity introduces unnecessary inertia. The recommended porosity range is 30%-70%. Too low results in poor acoustic permeability and increased weight; too high results in low acoustic impedance and weak structural strength. A hexagonal, closely packed pore array is a common and efficient design.

[0075] 3. Acoustic filter characteristics and cutoff frequency of fine mesh

[0076] In this case, the fine mesh is equivalent to a first-order low-pass acoustic filter. Its cutoff frequency (f c ) is similar to Substituting into the formula, we can see that f is roughly proportional to 1 / r. The effect of aperture change on R a and M a The impact of different, thus affecting f c By selecting the pore size and porosity, the frequency point (f c ). For example: target f c ≈15kHz, which may require an aperture of about 0.15mm. Target f c ≈8kHz, may require an aperture of about 0.08mm (smaller aperture, lower cutoff frequency).

[0077] 4. The control effect of fine mesh on airflow and noise

[0078] When the diaphragm moves with large amplitude, especially at low frequencies and large dynamics, a high-speed airflow forms behind the central hollow area. The fine-pore mesh can disperse the high-speed airflow into low-speed micro-airflow, reducing the Reynolds number (Reynolds number Re=(ρ*v*d) / η, v is the flow velocity, and d is the characteristic dimension (here is the aperture)), which is a key parameter for judging laminar flow / turbulent flow. The fine pores reduce d sharply, and even if the flow velocity v is not reduced much due to diversion, Re will drop significantly. Therefore, small channels have a higher critical Re (easier to maintain laminar flow), and the viscosity effect of the inner wall of the small hole is stronger, which directly consumes turbulent energy. The smaller the aperture, the stronger the diversion effect and the more significant the noise suppression effect. However, too small an aperture will lead to excessive acoustic resistance and audible high-frequency attenuation, and a balance needs to be struck between noise suppression effect and high-frequency extension.

[0079] 5. Improvement of directivity by fine mesh

[0080] At higher frequencies, rectangular diaphragms are prone to beaming. A fine-pore mesh transforms the sound radiation from the central area into an array of countless dense point sources, distributed on a plane with spacing far smaller than the wavelength. The spherical waves radiated by each point source interfere with each other, and the dense point source array diffuses the sound waves over a wide angle. Compared to piston radiation, the high-frequency directivity decays more gradually, improving the beaming phenomenon of rectangular diaphragms. The pore spacing is a key factor, determined by both pore diameter and porosity. At a fixed porosity, the smaller the pore diameter, the smaller the pore spacing must be to maintain the same porosity. To effectively improve directivity, the pore spacing must be significantly smaller than the wavelength of the target frequency. For example, for 10kHz (34mm wavelength) audio, a pore spacing of ≤8.5mm is recommended, and ideally ≤5.7mm is ideal. A pore diameter of 0.05-0.3mm combined with a reasonable porosity (30-70%) can easily achieve a sufficiently small pore spacing, effectively improving directivity in the kHz to 10s range.

[0081] 6. The influence of fine mesh on diaphragm mode

[0082] Compared with the circle, the rectangle is more likely to excite split vibration (high-order mode) at low frequency. The central area is the high-incidence area and the piston motion efficiency is low. The center hollowing and fine mesh can remove inefficient / harmful mass. The hollowing directly removes part of the mass. The fine mesh is close to the diaphragm and covers the hollow area, which is equivalent to applying a distributed viscoelastic damping layer in the active area of ​​split vibration. When the center of the diaphragm vibrates, the air is driven through the fine mesh, and the acoustic resistance R a The vibration energy is converted into heat energy for dissipation, and the high rigidity of the mesh material can also restrain the local deformation of the diaphragm below.

[0083] Based on the above discussion, there are two directions for the selection of aperture:

[0084] (1) Based on the target f c (Low-pass effect): If you want good high-frequency extension (f c >18kHz), choose 0.2-0.3mm. If you want balance (f c ~12-18kHz), choose 0.15-0.2mm. If you focus on mid-frequency purity / strong noise suppression (f c ~8-12kHz), choose 0.1-0.15mm. If you want extreme noise suppression / focus on mid-frequency (f c <8kHz), select 0.05-0.1mm.

[0085] (2) Based on porosity: After selecting the pore size, adjust the porosity (usually 40%-60%) to fine-tune R a and M a , high porosity reduces R a and M a (transparent but damping / noise suppression reduced), low porosity increases R a and M a(The damping is strong but the efficiency is reduced, which may affect the low frequency).

[0086] Based on hole spacing (directivity): Ensure hole spacing d c-c <<λ min / 4(λ min is the highest frequency wavelength where you want to improve directivity), for example, if the target is 10kHz, d c-c <8.5mm. For 0.15mm pore size, hexagonal arrangement, and porosity of about 50%, d c-c ≈0.17mm, which meets the requirements. The aperture selection has little effect on the directivity, as long as the aperture density is high enough.

[0087] Furthermore, a fine-pore mesh acts as a low-pass acoustic filter. Small apertures cause early and dramatic high-frequency attenuation, and the target frequency band must remain flat before attenuation. Small apertures effectively suppress the "puffing" sound (wind noise) produced by airflow behind the diaphragm, especially during transient high-amplitude conditions. A densely packed mesh of small holes can slightly diffuse sound waves, improving high-frequency directivity. However, apertures <0.05mm are difficult to process, prone to clogging, and lack strength, while apertures >0.3mm struggle to provide sufficient acoustic resistance.

[0088] In this embodiment, the thickness of the fine mesh layer is 0.02-0.10 mm. The maximum range is 0.04-

[0089] 0.06mm (full-frequency unit). The specific reasons are as follows: the fine pore mesh acoustic resistance Ra consumes sound energy, causing attenuation to increase with increasing frequency; the air inertia Ma in the pores hinders transient response and causes tailing distortion; the periodic pore array scatters sound waves, causing peaks and valleys in the frequency response. Based on this, the following parameter optimization countermeasure strategy is proposed

[0090] question Optimization mechanism Control parameters Excessive high-frequency attenuation Increase the cutoff frequency fc Reduce thickness t and increase aperture d Blurred sound field Reduce sound quality Thinning t, increasing porosity σ Frequency peaks and valleys Breaking the diffraction interference condition Non-periodic hole array, high hole density Transient procrastination Balancing Ra and diaphragm damping requirements Exact match Ra∝1 / m

[0091] Based on the above strategies, the setting is 0.04–0.06mm.

[0092] In this embodiment, the fine-pored mesh layer is made of stainless steel, polyester, or nylon.

[0093] In this embodiment, the fine-pored mesh layer is made of stainless steel, polyester, or nylon.

[0094] Based on the requirements for the fine-pored mesh layer in the solution (diameter 0.05–0.3mm, thickness 0.02–0.10mm), combined with the speaker application scenario (must have good acoustic transparency, certain mechanical strength, lightweight, and environmental resistance) and manufacturing cost considerations, the following three materials are very suitable choices:

[0095] Stainless steel microporous mesh: Stainless steel has high strength and rigidity. It can maintain a stable shape even at extremely thin thicknesses, is not prone to deformation, sagging or cracking, and can withstand the vibration stress of the speaker diaphragm. In addition, it is corrosion-resistant, high-temperature-resistant, and aging-resistant, with stable performance in various environments and a long service life. Etching, weaving, or electroforming processes can accurately produce the required pore size and thickness (0.02-0.1mm etching or woven thin mesh is feasible). In addition, the mesh structure is regular, and the distortion when sound waves pass through is small. Although the cost of stainless steel is relatively high compared to polymer materials, its durability and stability reduce the cost of subsequent maintenance and replacement. The cost of large-scale production of etched mesh or precision woven mesh is controllable, and its overall cost-effectiveness is excellent in speaker units that require high performance and long life. It is a medium-to-high-priced but cost-effective option.

[0096] Polyester film microporous mesh is extremely lightweight, significantly lighter than metal mesh, and has minimal impact on the vibration mass and sensitivity of the speaker diaphragm. Polyester film (such as PET) is inexpensive, the lowest cost of the three materials. Laser drilling or chemical etching processes are mature and cost-effective for large-scale production. It is also easy to cut, shape, and bond, facilitating assembly into the diaphragm's hollowed-out area. Furthermore, the film's inherent low acoustic impedance ensures excellent acoustic performance after perforation. Both the material and processing costs are extremely competitive, making it a top choice for cost-effective and lightweight products. It is well-suited for cost-sensitive, mass-produced products.

[0097] Nylon braided mesh offers excellent flexibility and drape, easily conforming to complex curves (such as the slight curvature of a diaphragm), and offers excellent installation adaptability. Nylon filaments are low-cost raw materials, and the microfiber weaving process is mature, making large-scale production cost-effective. The low cost of both raw materials and the weaving process makes it an economical and affordable option. It's particularly suitable for applications that don't demand extreme lightweighting but require excellent conformability and low cost.

[0098] For maximum strength, stability, and longevity, choose stainless steel microporous mesh. While the cost per piece is slightly higher, its reliability and durability offer long-term cost advantages in demanding applications. For ultimate lightweighting and minimal cost, choose polyester film microporous mesh. This is the most economical solution, while also minimizing the impact on speaker performance (sensitivity). For excellent flexibility, easy conformability, and low cost, choose nylon woven mesh. It offers low cost, easy installation, and satisfactory acoustic performance.

[0099] From a manufacturing perspective, stainless steel mesh is primarily precision-etched or woven with ultrafine wire. Polyester mesh is primarily laser-punched or chemically etched. Nylon mesh is precision-woven with ultrafine fibers. All three materials offer excellent acoustic permeability, provided the required porosity and pore size are met. Stainless steel mesh may exhibit very slight diffraction at high frequencies, but the impact is generally minimal. Polyester and nylon meshes generally offer lower acoustic impedance. In extreme application environments (high temperature, high humidity, and corrosion), stainless steel offers a significant stability advantage. In more general environments, polyester and nylon are sufficient. Considering the bonding compatibility and process between the mesh and the diaphragm (usually made of polymer or paper), polyester and nylon are more compatible with adhesives. In actual mass production decisions, prototypes are typically produced for acoustic testing (frequency response, distortion), mechanical testing (vibration fatigue), and cost analysis. Ultimately, the most suitable material is selected based on the product's positioning (high-end, mid-range, or entry-level). All three options are proven, meet the requirements, and are cost-effective.

[0100] In this embodiment, the unit voice coil adopts a copper-clad aluminum wire voice coil, a flat wire voice coil, or a honeycomb structure voice coil. Based on the above three voice coils, the following three solutions are given:

[0101] Solution A: Copper Clad Aluminum Wire (CCAW) Voice Coil + Internal Magnetic Circuit

[0102] Wire diameter: Φ0.08–0.12mm (high-frequency unit) / Φ0.15–0.20mm (full-frequency unit); number of layers: single or double (power>20W); frame: aluminum-magnesium alloy (lightweight and thermally conductive) or Kapton (high temperature resistant); the advantage is lightweight (density ≈3.0g / cm 3 ): offsets the additional mass of the fine mesh and improves high-frequency extension (>18kHz); high conductivity (≈70% IACS): reduces resistive losses and improves efficiency by 10-15%; the cost is lower than that of pure copper voice coils, with the best cost performance.

[0103] Option B: Flat wire voice coil (Edgewound) + dual magnetic gap design; cross section: rectangular (width-to-height ratio 1:2-1:3, such as 0.2×0.4mm); magnetic circuit: T-iron + dual neodymium magnetic ring (magnetic flux density ≥1.2T); the advantages are high fill rate and more efficient driving of rigid fine-mesh mesh; better heat dissipation and the ability to suppress even-order harmonic distortion (THD < 0.5% @ 1kHz).

[0104] Option C: Honeycomb voice coil (high-end option); Process: Laser-welded hexagonal aluminum wire mesh skeleton; Advantages include good rigidity / weight ratio, 3x increased resistance to lateral deformation, and a perfect match for the high rigidity requirements of fine-mesh mesh; Reduced thermal mismatch, close to the expansion coefficient of metal fine-mesh mesh, and a lifespan of >1000h@40℃.

[0105] In this embodiment, the material of the intermediate film is PET film, PET / metal composite film or PEN film.

[0106] The material selection principles for the interlayer are as follows:

[0107] 1. High surface density (surface quality) and low air permeability: ensure the sound resistance R of the covered area membrane Much higher than the mesh layer acoustic resistance R mesh (Satisfy R membrane >>R mesh ). The acoustic resistance is positively correlated with mass inertia: surface density σ (unit: kg / m 2 ) the higher the inertial resistance to air vibration. In addition, the air permeability should be close to zero: avoid airflow penetration, otherwise it will significantly reduce R membrane For this reason, the following materials are preferred:

[0108] ①PET (polyethylene terephthalate): surface density is controllable (common thickness 6-20μm, σ≈8-27g / m 2 ), easy to achieve high R membrane . And it is almost airtight (air permeability <0.1cm 3 / cm 2 / s), meeting the sealing requirements.

[0109] ② Metallized composite film (such as PET aluminum coating): The surface density is further reduced (the aluminum coating layer is 20-50nm thick), but the rigidity is enhanced, and RmembraneRmembrane is higher. The aluminum coating completely blocks air permeability and improves the stability of high-frequency acoustic resistance.

[0110] 2. High rigidity and deformation resistance: This suppresses segmentation vibration and prevents self-resonance in the coverage area from interfering with acoustic impedance regulation. When the coverage ratio exceeds 50%, the diaphragm area increases, and the risk of segmentation vibration increases dramatically. The material must have sufficient bending stiffness. In this case, PEN or PET aluminized film is preferred (especially when the coverage ratio is ≥60%).

[0111] 3. Low tension dependence and dimensional stability: Traditional elastic films (such as rubber) require high tension to maintain flatness, but the tension will change with temperature / humidity, resulting in R membrane Drift. Choose materials with a low coefficient of thermal expansion (CTE), such as PET and PI. Alternatively, use a pre-tensioned composite film, such as a PET / aluminum foil / PET three-layer composite. The aluminum foil layer (CTE ≈ 23ppm / °C) offsets PET shrinkage and maintains stable tension.

[0112] 4. Lightweight and driver compatibility When the coverage ratio is 70%, the mass of the intermediate film must be less than 10% of the mass of the diaphragm to avoid inertial load affecting high-frequency response. Assuming the diaphragm mass m dia =1g, coverage area 70%, upper limit of the allowable intermediate film mass: mmax =0.1×1×0.7=0.07g. If the coverage area A mesh =5cm 2 , upper limit of surface density: σ max =0.07 / 5×10 -4 =140g / m 2 Based on this material, PET (12μm) can be selected: σ≈17g / m 2

[0113] Based on the above, the following solutions can be used for collaborative design of material recommendation and coverage ratio:

[0114] Option 1: PET base film (coverage ratio 30-60%) has low cost, mature technology, and balanced surface density / rigidity. Thickness selection is based on coverage ratio: β≤40% → thin (6-8μm), β=40-60% → standard (12-15μm), adding nano-silica coating: improves rigidity without increasing mass. Option 2: PET-aluminum composite film (coverage ratio 50-70%): 8μm PET + 30nm aluminum layer + 5μm PET protective layer. Surface density is only 18g / m 2 , but the bending stiffness is ≈ 5 times that of pure PET. The aluminum layer completely blocks the air permeability, R membrane →∞ is closer to the ideal model. Suitable for applications requiring extreme acoustic impedance or wideband modulation at high coverage ratios. Option 3: PEN membrane (40-70% coverage ratio, high-frequency acoustic impedance priority) features high modulus (E≈6 GPa), high temperature resistance, and low acoustic loss factor. Suitable for applications requiring acoustic impedance modulation extending to >2 kHz (e.g., full-range drivers).

[0115] The core selection logic of the interlayer material is: to achieve the highest R with the minimum surface density under the coverage ratio constraint. membrane and flexural stiffness. PET is an economical and reliable benchmark choice, offering balanced performance when coverage is ≤60%. PET-aluminum composite film is the optimal solution when coverage is >60%, balancing lightweight and ultra-high acoustic impedance. PEN is suitable for high-frequency extension needs.

[0116] In this embodiment, the thickness of the intermediate film is 8-20 μm. If the intermediate film is a PET film, the thickness is 8-20 μm, and the optimal working point is: 12±2 μm (acoustic resistance-mass-rigidity balance when the coverage ratio is 50%). If the intermediate film is a PET-aluminum composite film, the thickness is 6-12 μm PET + 30-100nm Al. If the intermediate film is a PEN film, the thickness is 6-15 μm.

[0117] In this embodiment, the surround area uses a double cantilever surround, and the surround area is 10%-25%. Based on the special structure of the acoustic impedance adjustment speaker (rectangular diaphragm + central acoustic impedance adjustment area), the surround design must meet the following requirements: high linear displacement (to ensure low distortion under large stroke), suppression of edge resonance (to avoid interference with the acoustic impedance adjustment frequency band), and acoustic impedance matching (to work in conjunction with the central acoustic impedance area). Based on this, several folding shapes are compared as follows:

[0118] shape Stroke linearity Stress distribution Resonance suppression Suitable for rectangular diaphragms Semicircular (Single Roll) Low (β < 30%) stress concentration Poor (Q>5) Poor (corner deformation) Sinusoidal Middle (β<50%) relatively uniform Medium (Q≈3) middle Double Roll High (β < 70%) Optimal Excellent (Q<1.5) optimal Stepped high High manufacturing difficulty excellent generally

[0119] Based on the above comparison, we chose the double cantilever surround. The double cantilever surround has a stroke linearity of ≤0.7, which can reduce stress at the corners by 80% (compared to a semicircular shape), preventing the corners from tearing. The resonance quality factor Qms is <1.5 (measured value), which is far away from the acoustic impedance adjustment frequency band (50-500Hz).

[0120] Based on the selected shape, the fold material is further selected for the fold area. To calculate the minimum fold area, the following constraints need to be set:

[0121] 1. Mechanical constraints (avoid excessive stress):

[0122]

[0123] Where, B is the magnetic gap flux density (typically 1T), l e Voice coil length (m), σ y Material yield strength (IIR: 8MPa)

[0124] 2. Acoustic constraints (impedance matching):

[0125]

[0126] Based on the above constraints, the ring area ≥ max (A s1 , A s2 ), and not less than 10% of the total diaphragm area.

[0127] In this embodiment, the intermediate film and the diaphragm are fixed by micro-contact hot pressing composite or mechanical bump interlocking or glue. It should be pointed out that glue fixation is the simplest way, but the density of typical glue increases after curing, which easily leads to an increase in the effective mass of the intermediate film, and the glue penetrates into the mesh, so this solution is least recommended. The preferred solution is micro-contact hot pressing composite, which has the advantages of zero additional mass and zero mesh blockage. The second-choice solution is mechanical bump interlocking, which is suitable for large-stroke low-frequency units. The last-choice adhesive can adopt the formula: MS base + 40vol% hollow microspheres, which can alleviate the above problems.

[0128] In this embodiment, a silicone transition layer (not shown) is provided between the intermediate film and the fine-porous mesh layer. A transition layer or a special coupling structure is designed between the intermediate film and the fine-porous mesh, such as a transition layer with a gradient pore size or gradient thickness, so that the sound wave can propagate more smoothly from one medium to another, reducing the energy loss and distortion caused by poor coupling. It can effectively solve the impedance mismatch problem when the sound wave propagates in different acoustic impedance media (rigid fine-porous mesh → flexible film), thereby reducing reflection loss and distortion. To meet the above requirements, the following requirements are met: (1) The transition layer must meet the acoustic impedance gradient matching, such as the high acoustic impedance (high rigidity) of the fine-porous mesh (stainless steel / polyester) → the low acoustic impedance (high flexibility) of the intermediate film (PET / PEN). (2) The transition layer must achieve a continuous gradient of acoustic impedance to avoid reflection of the sound wave at the interface (similar to the principle of anti-reflection coating in optics). (3) Resonance and standing waves are suppressed, and local resonance and high-frequency standing waves caused by impedance mutations (common at rigid-flexible interfaces) are eliminated. (4) Maintaining structural stability requires compatibility with existing processes (hot pressing / gluing) without increasing excessive mass or thickness.

[0129] Based on the above settings, the comparison materials are as follows:

[0130]

[0131] For these reasons, microporous elastomers such as silicone rubber are selected because their porosity (30%-70%) can be controlled by the foaming rate, achieving a continuous gradient of acoustic impedance. Their high damping properties (loss factor tanδ > 0.3) absorb interfacial vibration energy. They can be made into liquid precursors and cured after precise coating.

[0132] In this embodiment, the silicone transition layer includes a first silicone layer, a second silicone layer, and a third silicone layer in order from the fine-pored mesh layer side to the intermediate membrane side; the porosity of the first silicone layer is greater than that of the second silicone layer, which is greater than that of the third silicone layer. In this embodiment, to achieve a three-dimensional spatial gradient of acoustic impedance, a layered composite design can be used. An example of a gradient structure (from the fine-pored mesh to the intermediate membrane) is:

[0133]

[0134] This solution can improve the smoothness of the frequency response and reduce the fluctuation caused by interface reflection by 3-5dB in the 1-5kHz frequency band. It can also reduce the distortion rate, suppress local standing waves, and improve transient response:

[0135] The above descriptions are only some embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A speaker unit with acoustic impedance adjustment function, characterized in that: The diaphragm of the unit is a rectangular diaphragm with a folded ring; The rectangular diaphragm includes a folded ring area and a hollow portion arranged at the center of the folded ring area; the hollow portion is covered with a fine mesh layer; the outer surface of the fine mesh layer is covered with an intermediate film, and the coverage ratio of the intermediate film is 30% to 70%; The material of the intermediate film is PET film, PET / metal composite film or PEN film; The thickness of the intermediate film is 8-20 μm.

2. A speaker unit with acoustic impedance adjustment function according to claim 1, characterized in that: The pore diameter of the fine-porous mesh layer is 0.05-0.3 mm.

3. The speaker unit with acoustic impedance adjustment function according to claim 1, characterized in that: The fine-pored mesh layer is made of stainless steel, polyester or nylon.

4. The speaker unit with acoustic impedance adjustment function according to claim 1, characterized in that: The folding ring area adopts a double cantilever folding ring, and the area of ​​the folding ring area is 10%-25%.

5. The speaker unit with acoustic impedance adjustment function according to claim 1, characterized in that: The intermediate film and the diaphragm are fixed by micro-contact hot pressing, mechanical convex point interlocking or glue.

6. The speaker unit with acoustic impedance adjustment function according to claim 1, characterized in that: A silica gel transition layer is provided between the intermediate film and the fine-pored mesh layer.

7. The speaker unit with acoustic impedance adjustment function according to claim 6, characterized in that: The silica gel transition layer includes a first silica gel layer, a second silica gel layer and a third silica gel layer in sequence from the fine-porous mesh layer side to the intermediate membrane side; wherein the porosity of the first silica gel layer is greater than that of the second silica gel layer, which is greater than that of the third silica gel layer.

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