A speaker unit with an acoustic resistance adjustment function

Abstract

The utility model discloses a loudspeaker unit with sound resistance regulation function. The diaphragm of the unit is a folded ring type rectangular diaphragm; wherein, the folded ring type rectangular diaphragm comprises 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 hole reticular layer; the outer side of the fine hole reticular layer is covered with an intermediate film, and the covering ratio of the intermediate film is 30% to 70%. The utility model provides a channel for heat dissipation. The intermediate film is covered on the outer side of the fine hole reticular layer, and the covering ratio is 30% to 70%. When the sound wave is transmitted from the diaphragm to the fine hole reticular layer and then spreads outward, the intermediate film will change the propagation path of the sound wave. Due to the partial covering of the intermediate film, it will make the sound wave encounter different medium interfaces (the interface between the intermediate film and air) in the propagation process, thereby generating reflection and transmission phenomena, which is equivalent to adjusting the sound resistance and making the energy distribution of the sound wave more reasonable.

Description

Technical Field

[0001] This utility model relates to the field of loudspeaker technology, and in particular to a loudspeaker unit with acoustic impedance adjustment function. Background Technology

[0002] Currently, the heat dissipation design of most loudspeakers is still imperfect. When a loudspeaker is operating, especially at high power output, the voice coil generates a significant amount of heat. Existing loudspeaker heat dissipation mainly relies on the slight displacement of the diaphragm to drive airflow, and the magnet and frame conducting heat to the external environment through their material properties. However, this heat dissipation method is inefficient and cannot dissipate heat in a timely manner. Heat accumulation inside the loudspeaker leads to increased voice coil temperature, accelerating the aging of the voice coil insulation material and reducing loudspeaker performance and lifespan. Simultaneously, high temperatures can also demagnetize the magnet, further weakening the loudspeaker's performance stability. Furthermore, current adjustable acoustic impedance solutions mainly rely on two structures: perforated plate acoustic resistors, which adjust acoustic impedance by changing the aperture ratio, but this increases the length of the airflow path, introduces the Helmholtz resonant cavity effect, and produces new acoustic coloration at specific frequencies between 500Hz and 1kHz; and smart material variable damping layers, which can change damping in real time using electrical signals, but the material response speed is slow (>10ms) and power consumption is high, making it difficult to use for dynamic control across the entire frequency range. Utility Model Content

[0003] In view of this, the purpose of this utility model is to provide a loudspeaker unit with a fine mesh, which can solve at least one of the technical problems mentioned in the background art.

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

[0005] The folded rectangular diaphragm includes a folded ring area and a hollow portion disposed 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, the coverage ratio of the intermediate film being 30% to 70%.

[0006] In the above technical solution, the microporous mesh layer has numerous uniformly sized micropores. During the operation of the speaker unit, the diaphragm vibrates continuously, generating heat. These micropores provide channels for heat dissipation, allowing air to flow through them between the diaphragm and the microporous mesh layer, creating convection. When the diaphragm vibrates, the surrounding air is moved, and heat is carried away through the micropores, thus achieving heat dissipation. An interlayer membrane covers the outside of the microporous mesh layer, with a coverage ratio of 30% to 70%. When sound waves travel from the diaphragm to the microporous mesh layer and then propagate outwards, the interlayer membrane alters the propagation path. Due to the partial coverage by the interlayer membrane, it causes the sound waves to encounter different medium interfaces (the interface between the interlayer membrane and the air) during propagation, resulting in reflection and transmission. This effectively adjusts the acoustic impedance, making the energy distribution of the sound waves more rational. Part of the sound waves are reflected back to the diaphragm and microporous mesh layer area, while the other part is successfully transmitted. This balance between reflection and transmission prevents sound waves from losing too much energy prematurely, while also preventing them from radiating outwards in an overly concentrated manner, thus making sound propagation more uniform and efficient.

[0007] From the perspective of the overall vibration system, the vibration characteristics of the folded rectangular diaphragm and the acoustic characteristics of the perforated mesh layer need to be matched with the acoustic impedance of the external sound field. The presence of the interlayer diaphragm can, to some extent, bridge the acoustic impedance difference between the diaphragm-perforated mesh layer combination and the external sound field. For example, if the acoustic impedance of the external sound field is low (such as in an open space), the interlayer diaphragm can appropriately increase the acoustic impedance of the system through its coverage ratio, allowing sound waves to be transmitted more smoothly from the diaphragm-perforated mesh layer system to the external space, reducing sound wave reflection losses at the interface, and improving the overall efficiency and sound quality of the loudspeaker.

[0008] In some embodiments, the pore diameter of the microporous mesh layer is 0.05–0.3 mm.

[0009] In the above technical solution, the interlayer membrane coverage ratio is 30% to 70%, which works in conjunction with the aperture diameter of 0.05–0.3 mm to adjust the acoustic impedance. The interlayer membrane partially covers the aperture, changing the sound wave propagation path and energy distribution. Its coverage ratio determines the ratio of sound wave reflection to transmission, while the aperture diameter affects the ease with which sound waves pass through the aperture and its propagation characteristics. When the aperture diameter is small (close to 0.05 mm), the sound waves encounter greater resistance when passing through the aperture. In this case, the coverage ratio of the interlayer membrane can be appropriately adjusted to increase the coverage ratio, further enhancing sound wave reflection and scattering, redistributing sound wave energy in the diaphragm and aperture mesh layer region, improving low-frequency response performance, and making the bass more powerful and robust. When the aperture diameter is large (close to 0.3 mm), sound waves pass through the aperture relatively easily, and the coverage ratio of the interlayer membrane can be appropriately reduced to allow the sound waves to transmit more smoothly. At the same time, the larger aperture size increases the radiation efficiency of high-frequency sound waves, making the high-frequency sound clearer and brighter, thereby achieving a wide frequency response range and balanced timbre performance.

[0010] When the speaker is operating, the synergistic effect of the interdiaphragm and the perforated mesh layer dynamically adjusts the acoustic impedance to adapt to audio signals of different frequencies and power. When low-frequency signals are input, the interdiaphragm enhances low-frequency sound pressure by reflecting and scattering sound waves, resulting in fuller bass. Simultaneously, the heat dissipation function of the perforated mesh layer ensures stable diaphragm vibration, preventing heat buildup caused by large low-frequency vibration amplitudes and maintaining stable bass output. When high-frequency signals are input, the perforations in the perforated mesh layer provide a smooth propagation path for high-frequency sound waves, while the interdiaphragm, by appropriately covering the perforations, optimizes the directionality and energy distribution of high-frequency sound waves, preventing them from being too diffuse or too strong. This results in delicate, transparent, and layered high-frequency sound, allowing the entire speaker to output high-quality sound at different frequencies.

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

[0012] In the above technical solutions, stainless steel has relatively high thermal conductivity, which can quickly conduct the heat generated by the diaphragm vibration to the surface of the fine-pore mesh layer, and then achieve efficient air convection heat dissipation through the fine pores. Its excellent thermal stability ensures that it will not deform or change its performance due to temperature changes within the speaker's operating temperature range, guaranteeing stable heat dissipation performance. Stainless steel also has high strength and hardness, providing reliable protection for the diaphragm against external mechanical shocks and vibrations, while the fine-pore structure maintains good heat dissipation function, ensuring long-term stable operation of the diaphragm.

[0013] Polyester has a low density, resulting in a lightweight, fine-pore mesh layer that barely affects the diaphragm's vibration characteristics, thus contributing to improved high-frequency response performance of the loudspeaker. While its heat dissipation efficiency is not as high as that of stainless steel, it is sufficient for everyday use and provides more balanced heat dissipation at low frequencies. Polyester's flexibility allows it to adapt to diaphragm deformation during vibration, making it less prone to breakage or damage. The pores change rhythmically with diaphragm vibration, promoting the expulsion of hot air and the intake of cold air, enhancing heat dissipation. Simultaneously, it buffers and regulates sound wave propagation, resulting in a smoother sound.

[0014] Nylon is lightweight, and its fine-pore mesh layer reduces the overall mass of the diaphragm, improving high-frequency response. Its good tensile strength and abrasion resistance, combined with the stable shape and performance of the pores during vibration, ensures even heat dissipation. The smooth surface of nylon facilitates airflow, reducing acoustic impedance. Combined with an interlayer with appropriate coverage, it optimizes acoustic impedance matching, improving sound clarity and layering. Nylon is resistant to chemical corrosion and aging; its unobstructed pores ensure stable heat dissipation even after long-term use, guaranteeing a good heat dissipation environment for the diaphragm and extending the speaker's lifespan.

[0015] Stainless steel has a high density and good rigidity. When the fine-pore mesh layer is combined with the interlayer, it enhances the overall rigidity of the composite structure, making the reflection and scattering of sound waves more pronounced during propagation. The coverage ratio of the interlayer is 30% to 70%, and the acoustic impedance can be adjusted on this basis to a higher level, which is suitable for scenarios that require enhanced low-frequency sound pressure and improved low-frequency response.

[0016] Polyester and nylon materials have low density and good flexibility. The combination of the fine-pore mesh layer and the interlayer is relatively lightweight and soft, resulting in strong sound wave transmission. The coverage ratio of the interlayer can adjust the acoustic impedance within a moderate range. The fine-pore mesh layer made of polyester material, in conjunction with the interlayer, allows for a more balanced acoustic impedance in the mid-to-high frequency range, making the sound clear and bright; while nylon material provides smooth acoustic impedance adjustment across the entire frequency range, resulting in richer sound layers.

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

[0018] In the above technical solution, the PET film is soft, smooth, and has a certain degree of elasticity, which can change the sound wave propagation path and energy distribution. Its coverage ratio is 30% to 70%, and its acoustic impedance adjustment range is moderate, balancing reflection and transmission to produce clear and distinct sound. While the PET film has moderate thermal conductivity, its heat dissipation effect is improved when combined with a microporous mesh layer, preventing heat accumulation, ensuring stable acoustic performance, and enhancing the reliability of the loudspeaker.

[0019] The 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, adjusts acoustic impedance to a higher level, improves low-frequency response, and makes bass deeper and more powerful. The metal layer provides electromagnetic shielding, reduces electromagnetic interference, and improves sound purity. Simultaneously, the metal's good thermal conductivity, combined with the fine-pore mesh layer, further ensures speaker performance, making it suitable for high-fidelity and high-power applications.

[0020] The PEN diaphragm possesses high mechanical strength and thermal stability, capable of withstanding vibrations and temperature variations during speaker operation, ensuring stable acoustic impedance adjustment performance. Its smooth surface reduces resistance during sound wave propagation, resulting in excellent high-frequency sound wave transmission and a wideband response. The PEN diaphragm exhibits good dimensional stability, resisting deformation under various environmental conditions, ensuring a stable interlayer coverage ratio and consistent acoustic impedance adjustment. Combined with a heat-dissipating perforated mesh layer, acoustic performance is optimized, making it suitable for scenarios requiring high sound quality stability.

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

[0022] In the above technical solutions, in the low-frequency range, appropriately thickening the interlayer membrane can enhance sound wave reflection and scattering, thereby increasing low-frequency sound pressure; in the mid-to-high frequency range, thinning the interlayer membrane facilitates sound wave transmission, making the sound clear and bright. For example, an interlayer membrane with a thickness of 12-15 μm can effectively balance low-frequency enhancement and mid-to-high frequency clarity, resulting in distinct sound layers. Combined with the pore diameter (0.05–0.3 mm) of the fine-pore mesh layer, an interlayer membrane thickness of 8-20 μm can achieve wideband acoustic impedance matching. Finer pores (0.05–0.15 mm) paired with a 15-20 μm interlayer membrane are suitable for low-frequency optimization; coarser pores (0.15–0.3 mm) paired with an 8-12 μm interlayer membrane are beneficial for mid-to-high frequency enhancement, achieving a balanced frequency response.

[0023] Increasing the thickness of the interlayer slightly reduces heat dissipation efficiency because it covers part of the heat dissipation channels in the porous mesh layer. However, the impact is minimal in the 8-20 μm thickness range and can be compensated for by optimizing the pore diameter and distribution. For example, appropriately increasing the pore diameter or density can enhance heat dissipation, ensuring timely heat dissipation from the speaker and maintaining stable acoustic impedance adjustment performance. Different interlayer materials exhibit varying heat dissipation performance at thicknesses of 8-20 μm. PET film provides moderate heat dissipation, PET / metal composite film provides good heat dissipation but requires control of the metal layer thickness, and PEN film provides excellent heat dissipation with minimal impact from increased thickness. When selecting an interlayer material, both heat dissipation and acoustic impedance adjustment requirements must be considered. For example, thicker PEN film or PET / metal composite film is suitable for high-power speakers, balancing both heat dissipation and acoustic impedance adjustment performance.

[0024] When a loudspeaker is operating, the thickness of the interdiaphragm affects the dynamic balance between acoustic impedance adjustment and heat dissipation. Under high-power input and low-frequency signal conditions, the demand for acoustic impedance adjustment is high, resulting in significant heat generation. In this case, appropriately thickening the interdiaphragm can meet the acoustic impedance adjustment requirements while simultaneously preventing heat accumulation through the efficient heat dissipation of the fine-pore mesh layer. An interdiaphragm thickness within the range of 8-20 μm ensures long-term stability in both acoustic impedance adjustment and heat dissipation performance. An excessively thin interdiaphragm is susceptible to mechanical damage and environmental influences, leading to rapid performance degradation; an excessively thick interdiaphragm negatively impacts heat dissipation and high-frequency sound wave transmission. A thickness range of 8-20 μm, combined with different materials, ensures stable acoustic performance of the loudspeaker during long-term use, meeting the demands of high-quality audio playback.

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

[0026] In the aforementioned technical solution, the double cantilever surround design provides the diaphragm with more stable support and a more uniform displacement distribution during vibration. Compared to the traditional single cantilever surround, the double cantilever structure effectively reduces the segmented vibration modes of the diaphragm at low frequencies, allowing the diaphragm to move more easily in a unified mode, thereby improving low-frequency radiation efficiency and enhancing low-frequency response. Its symmetrical structure allows for better control of diaphragm vibration, resulting in a richer and more powerful low-frequency sound with less distortion. In the high-frequency range, the double cantilever surround allows the diaphragm to vibrate more naturally, reducing phase distortion and amplitude attenuation near the high-frequency cutoff frequency. By optimizing the surround's geometry and stiffness distribution, the diaphragm maintains effective vibration over a wider frequency range, thereby improving the speaker's high-frequency extension, making the high-frequency sound clearer and brighter, and reproducing more high-frequency details.

[0027] The surround area should comprise 10%–25% of the total diaphragm area to achieve a balance in acoustic performance. A smaller surround area (close to 10%) results in a relatively larger effective vibrating area for the diaphragm, which is beneficial for increasing sound pressure level and making the sound louder. However, an excessively small surround area may lead to insufficient diaphragm support, affecting vibration stability and low-frequency response. Conversely, a larger surround area (close to 25%), while sacrificing some effective vibrating area, significantly enhances the diaphragm's support and control capabilities, improving low-frequency response and sound clarity. Therefore, within the 10%–25% area range, optimization can be performed according to different acoustic needs to achieve the optimal balance between sound pressure level and sound quality.

[0028] The area ratio of the surround region works synergistically with the heat dissipation function of the perforated mesh layer and the acoustic impedance adjustment function of the interlayer. At an appropriate area ratio, the surround region provides stable mechanical support for the diaphragm, allowing it to better perform its acoustic properties under the influence of the perforated mesh layer and the interlayer. For example, when the surround region area is 15%-20%, the diaphragm vibration ensures sufficient sound pressure level output while matching the acoustic impedance adjustment of the interlayer, making sound wave propagation more efficient and uniform. Simultaneously, the heat dissipation function of the perforated mesh layer effectively ensures the temperature stability of the diaphragm during operation, further enhancing the overall performance of the loudspeaker.

[0029] The area ratio of the surround region has a significant impact on the diaphragm's vibration modes. Within the range of 10% to 25%, the surround region effectively controls the diaphragm's vibration modes and reduces the occurrence of higher-order modes. When the surround region area is small, the diaphragm's vibration modes are relatively simple, mainly exhibiting piston-like vibration, which is beneficial for improving high-frequency directivity and sound pressure level consistency. As the surround region area increases, the constraint effect of the surround strengthens, and the diaphragm's vibration modes gradually shift towards a more complex distribution. However, this shift is controllable, allowing for the optimization of mid- and high-frequency acoustic characteristics while maintaining low-frequency performance. For example, when the surround region area is around 18%, the diaphragm's vibration modes achieve a good balance between low, mid, and high frequencies, resulting in a fuller and more natural sound.

[0030] Furthermore, the area ratio of the surround region needs to be matched with the thickness and material of the interlayer diaphragm to achieve optimal vibration control and acoustic performance. For example, when the surround region area is large, a thicker (15-20 μm) PEN film can be selected as the interlayer diaphragm to enhance acoustic impedance adjustment capability. Simultaneously, the high mechanical strength and thermal stability of the PEN film, together with the surround region, constrain the diaphragm's vibration, improving vibration stability. Conversely, when the surround region area is small, a thinner (8-12 μm) PET film or PET / metal composite film can be used to reduce the influence of the interlayer diaphragm on diaphragm vibration, allowing the diaphragm to vibrate more flexibly. At the same time, the acoustic impedance adjustment function of the interlayer diaphragm optimizes the clarity and layering of the sound.

[0031] In some embodiments, the intermediate membrane and the diaphragm are bonded together by micro-contact hot pressing, mechanical bump fitting, or glue.

[0032] In the above technical solution, micro-contact thermo-pressing composite uses localized high temperature and pressure to form intermolecular bonds between the intermediate diaphragm and the diaphragm in a tiny area, resulting in a tight and highly stable connection. This avoids acoustic defects caused by adhesive aging or mechanical loosening at the connection point, improves the consistency of acoustic impedance adjustment, and optimizes sound clarity and layering. The low thermal resistance at the connection point and high heat dissipation efficiency facilitate heat conduction from the diaphragm to the microporous 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 a long period, ensuring durable acoustic performance.

[0033] Mechanical bump interlocking achieves a tight connection through bump embedding. The mechanical interlocking structure of the bumps provides strong support and vibration resistance, ensuring that the connection is not easily loosened by external forces or vibrations, thus guaranteeing the stability of the acoustic impedance adjustment structure. The bumps can reflect some sound waves, working in conjunction with the intermediate diaphragm acoustic impedance adjustment to enhance low-frequency sound pressure and sound fullness. As vibration transmission paths, the bumps allow diaphragm vibrations to be efficiently transmitted to the intermediate diaphragm, improving sound wave transmission efficiency. The regular arrangement of the bumps ensures consistent acoustic performance, avoids sound wave interference or diffraction, and allows sound to propagate evenly, improving sound quality uniformity and reliability.

[0034] The adhesive fixing process is simple and easy to operate, suitable for interlayer membranes and diaphragms of various complex shapes and materials, and easily accommodates designs with different acoustic impedance adjustment requirements. After curing, the adhesive forms a uniform, flexible layer that adapts to sound wave vibrations, reduces acoustic impedance mismatch, and improves sound clarity and fidelity. Selecting a suitable adhesive can ensure excellent environmental adaptability at the joint, resisting temperature and humidity changes and chemical corrosion, guaranteeing long-term stable operation of the speaker in harsh environments. The viscoelasticity of the adhesive can absorb some vibrational energy, reducing resonance and noise, and improving sound purity.

[0035] In some embodiments, a silicone transition layer is provided between the intermediate membrane and the microporous mesh layer.

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

[0037] In some embodiments, the silicone transition layer comprises a first silicone layer, a second silicone layer, and a third silicone layer sequentially from the fine-pore mesh layer side to the intermediate film side; wherein 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.

[0038] In the above technical solution, the high porosity of the first silicone layer allows for a larger vibration space when sound waves pass through, which helps in the transmission and enhancement of low-frequency sound waves. As the porosity gradually decreases, the second and third silicone layers gradually improve the reflection of sound waves and the focusing of high-frequency sound waves, making the 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 for a larger vibration space for low-frequency sound waves during propagation, thereby enhancing the low-frequency response. As the sound wave propagates towards the intermediate membrane, the porosity of the second and third silicone layers gradually decreases, which gradually enhances the reflection of sound waves and the focusing of high-frequency sound waves, improving the clarity and directionality of the sound. Through the multi-layer silicone structure, more precise acoustic impedance matching can be achieved. The porosity and thickness of each silicone layer can be adjusted according to the frequency characteristics of the sound waves, making the transmission of sound waves between different media smoother, reducing sound wave reflection and scattering, and improving the transmission efficiency and fidelity of the sound waves.

[0039] The multi-layered structure of the silicone transition layer effectively isolates and manages vibrations. The high porosity of the first silicone layer absorbs and disperses vibrations from the fine-pore mesh layer, reducing the impact of vibrations on the intermediate membrane. As sound waves propagate towards the intermediate membrane, the second and third silicone layers gradually enhance the reflection and focusing of sound waves, making the sound transmission clearer and more natural. The multi-layered silicone structure allows for the adjustment of sound wave reflection and scattering characteristics. The porosity and thickness of each silicone layer can be adjusted according to acoustic requirements, resulting in different reflection and scattering effects between different layers. Through proper design, sound wave interference and diffraction can be reduced, improving sound clarity and consistency. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is an exploded three-dimensional structural diagram of an embodiment of the speaker unit with fine mesh of this utility model;

[0042] Figure 2 This is an exploded side view of an embodiment of the speaker unit with a fine mesh according to this utility model;

[0043] Figure 3 This is a top view schematic diagram of an embodiment of the speaker unit with fine mesh of this utility model. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are only for illustrating the present invention and do not limit the scope of the present invention. Similarly, the following embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0045] Example 1

[0046] Please see Figures 1 to 3 A loudspeaker unit with acoustic impedance adjustment function includes: an interlayer diaphragm 1, a perforated mesh layer 2, a diaphragm 3, a voice coil 4, a magnet 5, a support 6, and a magnetic return assembly 7. The diaphragm 3 of the unit is a folded rectangular diaphragm; wherein the folded rectangular diaphragm 3 includes a folded region 31, and a hollow portion 32 disposed at the center of the folded region 31; the hollow portion 32 is covered with a perforated mesh layer; an interlayer diaphragm 1 is covered on the outer surface of the perforated mesh layer 2, and the coverage ratio of the interlayer diaphragm 1 is 30% to 70%.

[0047] In this embodiment, the equivalent acoustic resistance (R) of the entire hollow section is precisely controlled by adjusting the coverage ratio (β) of the intermediate film. total The entire perforated section (covered with a fine mesh layer and partially covered with an intermediate membrane) can be considered as two parallel acoustic channels:

[0048] 1. Area of ​​channel A (the region not covered by the intermediate membrane): A open = (1 - β) * A mesh The total acoustic impedance R in this area open = R mesh / (1 - β); R mesh =The entire fine porous network layer (A) mesh (Area) Total acoustic impedance when uncovered and unobstructed; β = Intermediate membrane coverage ratio. R mesh The material, porosity, thickness, and total area A of the network layer itself mesh Decision. R mesh / (1-β) is because acoustic resistance is inversely proportional to the effective ventilation area. When only a portion of the area is (1-β) * A mesh When open, its resistance is greater than that of the entire area A. mesh All open R mesh The time required is greater. 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 R of the open channel... open = R mesh / 0.5 = 2 * R mesh .

[0049] 2. Area of ​​channel B (the region covered by the intermediate membrane): A covered = β * A mesh The total acoustic impedance R in this area covered = R membrane R membrane =Acoustic resistance of the area covered by the intermediate membrane. In this design, it is desirable for the area covered by the intermediate membrane to be as "sealed" as possible, meaning that air should have difficulty passing through. This means R membrane It should be much larger than R mesh Ideally, R membrane Approaching infinity (∞) indicates complete obstruction. In reality, even "sealed" diaphragms may have minor leaks or their inherent flexibility may introduce some acoustic impedance, but the design goal is still to make their acoustic impedance very high. membrane It depends on the density, stiffness, tension, and edge sealing of the diaphragm material. If the diaphragm is porous, its acoustic resistivity r needs to be calculated. s_mem Thickness d mem Then R membrane = (r s_mem * d mem ) / A covered But the usual goal is to design it as r s_mem * d mem Maximize, so that R membrane great.

[0050] 3. Overall equivalent acoustic impedance (R) total Channel A (R) open ) and channel B (R covered This represents an acoustic parallel relationship. The total volume velocity U flowing through the hollow section... total = U open + U covered The formula for calculating the total impedance of parallel acoustic resistors is: 1 / R total =1 / R open + 1 / R covered Substitute into the expression above:

[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 Very large, so 1 / R membrane This term is very small, relative to (1 - β) / R mesh This can be ignored. Therefore, the formula simplifies to: 1 / R total ≈ (1 - β) / R mesh Taking the reciprocals of both sides, we get the simplified formula: R total ≈ R mesh / (1 - β)

[0055] Based on the above theoretical model, the optimal coverage ratio can be obtained by performing the following calculations according to actual needs.

[0056] (1) Measure or calculate the basic acoustic resistance (R) mesh ): It is necessary to know the entire fine porous network layer (A) mesh The total acoustic impedance (Area) without any intermediate membrane covering. Method: Using an impedance tube or dual-microphone transfer function method, measure the acoustic impedance of the sample containing only the perforated mesh layer to directly obtain its acoustic impedance R in the target frequency range. mesh (Usually, the average value of the mid-to-low frequencies is taken, because acoustic impedance adjustment mainly affects these frequency bands). If the material parameters of the mesh layer (porosity φ, flow resistivity σ - Rayls / m, thickness d) are known, then R mesh = (σ * d) / A mesh The flow resistivity σ usually requires experimental measurement or consulting a material database. For regular meshes, σ can be estimated using a formula.

[0057] (2) Determine the target acoustic impedance range (R) min R max Based on the design requirements of the loudspeaker system (such as desired Qts, low-frequency response flatness, and transient response), determine the minimum (R) that the entire hollow section is expected to achieve. min ) and maximum (R) max Equivalent acoustic impedance. For example, R min This may correspond to the complete removal of the intermediate membrane (β=0), in which case R total_min = R mesh R max The goal is to achieve maximum damping by covering the intermediate membrane.

[0058] (3) Evaluation of intermediate membrane performance (R membrane Design or select the intermediate membrane material / structure with the goal of maximizing the acoustic resistance R of the covered area. membraneAs large as possible. If the diaphragm is completely sealed and infinitely rigid, then R membrane ≈ ∞. In fact, it's possible to test the acoustic resistance when a small piece of the interlayer membrane covers a small hole of known area. Ensure its R... membrane >>R mesh (e.g., >10 times R) mesh If R membrane If the value is not large enough, the simplified formula will have increased errors, and the adjustment effect will be worse.

[0059] (4) Calculate the required coverage ratio range (β) min ,β max ): Using 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), therefore β min = 0. If the intermediate membrane design cannot completely remove (β) min If R > 0), then R min ≈R mesh / (1 - β min Considering non-ideal factors (R) membrane (Finite size): For greater precision, 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 equation, we obtain a more accurate β. min and β max .

[0065] (5) Assess coverage ratio range (β) min ,β max The rationality of β: the calculated β max It should be in the range of 0.3 to 0.7 (30% to 70%) or near that. Too low (β) max <<0.3) leads to the objective R max Not big enough, or basic R mesh If R is too small, the adjustment range is insufficient, and the maximum damping effect is not obvious. The only solution is to increase R. mesh (Use a denser / thicker mesh), or increase R max The target value is too high (β_max >> 0.7), causing the target value R to be too low. max Too large, or base R mesh Too large. High resistance can only be achieved by covering most of the area, potentially leading to a significant reduction in the effective radiation area and a severe decrease in sensitivity. Increased risk of segmentation vibration in the intermediate membrane increases distortion. Increased stroke / complexity of the adjustment mechanism reduces Rresistance. mesh (Use a looser / thinner mesh), or reduce R max Objective. If it cannot be changed, the side effects of a high coverage ratio must be accepted, and the intermediate membrane must be optimized (e.g., by increasing tension / stiffness).

[0066] (6) Select the initial / working point coverage ratio (β) initial If the position of the intermediate membrane can be dynamically adjusted, the coverage ratio can be adjusted at β. min to β max Variation over time. If a fixed optimal value is required, choose β. initial In β min to β max Between. Usually, the midpoint is chosen (e.g., (β)). min +β max ) / 2), or the β value corresponding to the design target of the total Q value (Qts) of the system. Combined with the speaker T / S parameters (Thiele / Small parameters) simulation or calculation, find the R value that makes the system Qts reach the design target (e.g., 0.707 for the Butterworth response). total Then, we can deduce β in reverse.

[0067] In this embodiment, the physical meaning of the 30%-70% coverage ratio based on the above inference is that within this range, a change in β can cause R... total Significant change (the change factor is large enough). In the β = 0.4–0.6 interval, R0.5 total The change with β is relatively linear and easy to control. Avoid β approaching 1 (covering almost the entire area), which leads 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 leads to a weak adjustment effect.

[0068] In this embodiment, the pore diameter of the fine-pore mesh layer is 0.05–0.3 mm. The reason for selecting this range is as follows:

[0069] I. Consideration of the range of fine pore diameter

[0070] Too small an aperture (<0.05mm) will cause severe high-frequency attenuation, especially when the aperture is less than 0.05mm. Even with a high porosity design, the sound impedance (r) of a single aperture will be significantly reduced. a The extremely high aperture value leads to excessive attenuation of mid-to-high frequency (>2kHz) energy, resulting in a muffled sound lacking detail. Furthermore, this extremely small aperture is close to the economic limit of current precision manufacturing, making it prone to clogging and requiring special treatments such as oleophobic and hydrophobic coatings. An aperture that is too large (>0.3mm) will result in insufficient acoustic impedance, rendering the control meaningless. At this point, r... a The value is very small; even with low porosity, the total acoustic resistance (R0) is low. a It may be difficult to effectively dampen the vibration in the central region of the diaphragm or suppress wind noise. The effect of suppressing higher-order modes in the central region will be worse. It may also affect the directivity and frequency response smoothness due to obvious diffraction or scattering of sound waves.

[0071] From the perspective of acoustic resistance principles, fine-mesh mesh creates resistance to airflow, which manifests as acoustic resistance. Acoustic resistance is the acoustic impedance (Z). a The real part of the acoustic impedance r is similar to that of a resistor. a When the orifice is small (its diameter is much smaller than the wavelength) and the flow rate is low, the approximate formula is:

[0072]

[0073] in: It is the air viscosity coefficient (approximately 1.8e-5 Pa). (s@20°C) The thickness (mm) of the fine-mesh material. Let r be the radius of the fine hole (mm). Therefore, r... a and Inversely proportional, a slight decrease in aperture results in a sharp increase in acoustic resistance per aperture. Total acoustic resistance Ra ≈r a / σ, a high porosity σ (numerous and densely packed pores) results in a lower total acoustic resistance. Smaller pore sizes require higher pore density to maintain a reasonable porosity; otherwise, the acoustic resistance will be too high.

[0074] II. The Influence of Porosity

[0075] Porosity represents the proportion of open area to total area. Pore size and porosity together determine acoustic resistance (Ra). a Harmony quality (M) a Sound quality (M) a Analogous to inductance, it is related to the air quality inside the hole. ( (This refers to air density). Within the target operating frequency band (mid-frequency to high-frequency), the fine-mesh mesh should primarily exhibit pure resistivity (R). a (Dominant) requires sufficiently small pores and reasonable porosity to avoid M a Excessive porosity introduces unnecessary inertia. A porosity range of 30%-70% is recommended. Too low a porosity results in poor sound transmission and increased weight; too high a porosity leads to low acoustic impedance and weak structural strength. Using a hexagonal close-packed pore array is a commonly used and efficient design.

[0076] III. Acoustic Filter Characteristics and Cutoff Frequency of Fine-Mesh Mesh

[0077] In this case, the fine-mesh mesh is equivalent to a first-order low-pass acoustic filter. Its cutoff frequency ( Approximate to Related. Substituting into the formula, we can see that... Roughly the same as Proportional. Changes in aperture affect R. a and M a The effects are different, and thus affect By selecting the pore size and porosity, the frequency point at which the fine-pore mesh begins to significantly attenuate high frequencies can be precisely set. For example: target ≈15kHz, which may require an aperture of approximately 0.15mm. Target ≈ 8kHz, may require an aperture of approximately 0.08mm (smaller aperture, lower cutoff frequency).

[0078] IV. The Control Effect of Fine Mesh on Airflow and Noise

[0079] During large-amplitude diaphragm vibrations, especially at low frequencies and high dynamic ranges, a high-speed airflow forms behind the central perforated area. The fine-perforated mesh can disperse this high-speed airflow into low-speed micro-airflows, reducing the Reynolds number. The parameters denoted by v (flow velocity) and d (characteristic size, here the aperture) are key for determining laminar / turbulent flow. Smaller apertures drastically reduce d, so even if the flow velocity v decreases only slightly due to flow diversion, the Reynolds number (Re) will drop significantly. Therefore, smaller channels have a higher critical Re (easier to maintain laminar flow), and the viscous effect of the orifice wall is stronger, directly consuming turbulent energy. Smaller apertures result in stronger flow diversion and more significant noise suppression. However, excessively small apertures can lead to excessive acoustic impedance and audible high-frequency attenuation, requiring a balance between noise suppression and high-frequency extension.

[0080] V. Improvement of Directivity by Fine-Mesh Mesh

[0081] At higher frequencies, rectangular diaphragms are prone to beaming. A fine-mesh array transforms the central acoustic radiation into a dense array of point sources, distributed on a plane with spacing much smaller than the wavelength. The spherical waves radiated by each point source interfere with each other, and the dense array of point sources causes the sound waves to diffuse over a wide angle. Compared to piston radiation, high-frequency directivity attenuation is gentler, thus improving the high-frequency beaming phenomenon of rectangular diaphragms. The aperture spacing is a key factor, determined by both aperture diameter and porosity. With a fixed porosity, the smaller the aperture diameter, the smaller the aperture spacing needs to be to maintain porosity. To effectively improve directivity, the aperture spacing must be much smaller than the wavelength of the target improvement frequency. For example, for 10kHz (wavelength 34mm) audio, an aperture spacing of ≤8.5mm is recommended, ideally ≤5.7mm. An aperture diameter of 0.05-0.3mm combined with a reasonable porosity (30-70%) can easily achieve a sufficiently small aperture spacing, effectively improving directivity in the range of several kHz to tens of kHz.

[0082] VI. The Influence of Fine-Mesh Mesh on Diaphragm Modes

[0083] Compared to circles, rectangles are more prone to generating segmented vibrations (higher-order modes) at low frequencies, with the central region being a high-frequency area and exhibiting low piston-like efficiency. A central perforated area with a fine mesh can remove inefficient / harmful mass; the perforation directly removes some mass, and the fine mesh closely adheres to the diaphragm, covering the perforated area. This is equivalent to applying a distributed viscoelastic damping layer to the active segmented vibration region. When the diaphragm vibrates at its center, it drives air through the fine mesh, reducing the acoustic resistance R. a The vibration energy is converted into heat energy and dissipated. The high rigidity of the mesh material can also constrain the local deformation of the diaphragm below.

[0084] Based on the above discussion, it can be seen that there are two directions for choosing the aperture:

[0085] (1) Based on the goal (Low-pass effect): If you want good high-frequency extension ( For frequencies >18kHz, select 0.2 - 0.3mm. If a balance is desired ( ~12-18kHz), select 0.15 - 0.2mm. If you prioritize mid-frequency purity / strong noise reduction ( ~8-12kHz), select 0.1 - 0.15mm. For extreme noise reduction / focus on mid-frequency ( <8kHz), select 0.05 - 0.1mm.

[0086] (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 with reduced damping / noise suppression), low porosity increases R a and M a (Strong damping but reduced efficiency may affect low frequencies).

[0087] Based on aperture spacing (directivity): Ensure aperture spacing ( (The highest frequency wavelength where improved directivity is desired), for example, a target of 10kHz. <8.5mm. For a pore size of 0.15mm, with a hexagonal arrangement and a porosity of approximately 50%, The aperture is approximately 0.17mm, which meets the requirements. The aperture size has little impact on the directionality, as long as the aperture density is high enough.

[0088] Furthermore, the fine-aperture mesh acts as a low-pass acoustic filter. The small aperture causes early and dramatic high-frequency attenuation, requiring the target frequency band to remain flat before attenuation. The small aperture effectively suppresses the "popping" sound (wind noise) generated by airflow behind the diaphragm, especially during transient large amplitude vibrations. The dense mesh can slightly diffuse sound waves, improving high-frequency directivity. However, apertures <0.05mm are difficult to manufacture, prone to clogging, and have low strength; apertures >0.3mm are insufficient to provide adequate acoustic impedance.

[0089] In this embodiment, the thickness of the perforated mesh layer is 0.02–0.10 mm, with a maximum range of 0.04–0.06 mm (full-frequency unit). The specific reasons are as follows: the acoustic impedance Ra of the perforated mesh consumes acoustic energy, leading to increased attenuation with increasing frequency; the inertia Ma of the air within the pores hinders the transient response, causing tailing distortion; and the periodic scattering of sound waves by the perforated array causes frequency response peaks and valleys. Based on this, the following parameter optimization countermeasure strategy is proposed.

[0090]

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

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

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

[0094] Based on the requirements of the fine-mesh layer in the design (diameter 0.05–0.3 mm, thickness 0.02–0.10 mm), and considering the speaker application scenarios (requiring good acoustic transmission, certain mechanical strength, lightweight, and environmental resistance) and manufacturing costs, the following three materials are very suitable choices:

[0095] Stainless steel microporous mesh: Stainless steel possesses high strength and rigidity, maintaining shape stability even at extremely thin thicknesses, resisting deformation, sagging, or cracking, and capable of withstanding the vibration stress of the speaker diaphragm. Furthermore, it is corrosion-resistant, high-temperature resistant, and aging-resistant, exhibiting stable performance and a long lifespan in various environments. Etching, weaving, or electroforming processes can precisely manufacture the required aperture and thickness (etched or woven thin meshes of 0.02-0.1mm are feasible). The regular mesh structure results in minimal distortion when sound waves pass through. Although stainless steel is relatively more expensive than polymer materials, its durability and stability reduce later maintenance and replacement costs. The cost of mass-producing etched or precision-woven meshes is controllable, making its overall cost-effectiveness excellent for speaker units requiring high performance and long lifespan. It is a mid-to-high-end but cost-effective choice.

[0096] Polyester film microporous mesh is extremely lightweight, significantly lighter than metal mesh, and has minimal impact on the vibration quality and sensitivity of the speaker diaphragm. Polyester film (such as PET) is the cheapest 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 perforated sections. Furthermore, the film itself has low acoustic impedance, resulting in good acoustic performance after perforation. This material and processing cost are highly competitive, making it the first choice for those seeking high cost-effectiveness and lightweight design. It is ideal for cost-sensitive products requiring large-scale production.

[0097] Nylon braided mesh boasts excellent flexibility and drape, easily conforming to complex curved surfaces (such as the slight curvature of a diaphragm) and offering good installation adaptability. Nylon filaments are inexpensive to produce, and the microfiber weaving process is mature, resulting in cost-effective large-scale production. With both raw material and weaving process costs being low, it is an economical choice. It is particularly suitable for applications where extreme lightweighting is not critical, but good fit and low cost are required.

[0098] For the highest strength, stability, and lifespan, choose stainless steel microporous mesh. Although the unit cost is slightly higher, its reliability and durability offer a long-term cost advantage for demanding products. For extreme lightweighting and lowest cost, choose polyester film microporous mesh. This is the most economical solution while having minimal impact on speaker performance (sensitivity). For good flexibility, easy installation, and low cost, choose nylon woven mesh. It is low-cost, easy to install, and its acoustic performance meets requirements.

[0099] From a manufacturing perspective, stainless steel mesh primarily uses precision etching or ultra-fine filament weaving. Polyester mesh mainly uses laser drilling or chemical etching. Nylon mesh uses ultra-fine fiber precision weaving. All three materials achieve good acoustic transmittance when meeting the required porosity and aperture. Stainless steel mesh may exhibit very slight diffraction at high frequencies, but the impact is usually minimal. Polyester and nylon meshes typically have lower acoustic impedance. In extreme environments (high temperature, high humidity, corrosion), stainless steel offers a more significant stability advantage. Under normal conditions, polyester and nylon are sufficient. Considering the bonding compatibility and process between the mesh layer and the diaphragm (usually polymer materials or paper), polyester and nylon are more compatible with adhesives. In actual mass production decisions, samples are typically made for acoustic testing (frequency response, distortion), mechanical testing (vibration fatigue), and cost calculation. Ultimately, the most suitable material is selected based on the product's positioning (high-end, mid-range, entry-level). All three are practically proven, meet the requirements of the solution, and are cost-effective.

[0100] In this embodiment, the unit voice coil is 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 schemes are given:

[0101] Option A: Copper-clad aluminum wire (CCAW) voice coil + internal magnet circuit

[0102] Wire diameter: Φ0.08–0.12mm (high-frequency unit) / Φ0.15–0.20mm (full-range unit); Number of layers: single or double layer (power > 20W); Frame: aluminum-magnesium alloy (lightweight and thermally conductive) or Kapton (high temperature resistant); Advantages include lightweight (density ≈ 3.0g / cm³): offsetting the added mass of the fine mesh and improving high-frequency extension (> 18kHz); High conductivity (≈ 70% IACS): reducing resistance loss and improving efficiency by 10–15%; Lower cost than pure copper voice coils, offering the best cost performance.

[0103] Option B: Edgewound voice coil + double magnetic gap design; cross-section: rectangular (width-to-height ratio 1:2~1:3, such as 0.2×0.4mm); magnetic circuit: T-iron + double neodymium magnetic rings (magnetic flux density ≥1.2T); its advantages are high fill rate, more efficient driving of rigid fine-hole mesh; better heat dissipation, and 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 better rigidity / weight, 3 times better resistance to lateral deformation, perfectly matching the high rigidity requirements of fine-pore mesh; Reduces thermal mismatch, with an expansion coefficient close to that of metal fine-pore mesh, and a lifespan of >1000h@40°C.

[0105] In this embodiment, the intermediate film is made of PET film, PET / metal composite film, or PEN film. The selection principle for the intermediate film material is as follows:

[0106] 1. High areal density (area mass) and low air permeability: Ensures sound resistance R in the covered area. membrane Much higher than the acoustic impedance R of the mesh layer mesh (satisfies R) membrane >>R mesh Acoustic resistance is positively correlated with mass inertia: surface density σ (Unit: kg / m²) The higher the value, the greater the inertial drag on air vibrations. Furthermore, air permeability needs to be close to zero: to prevent airflow penetration, otherwise it will significantly reduce R... membrane For this reason, the following materials are preferred:

[0107] ①PET (Polyethylene terephthalate): Areal density is controllable (common thickness 6–20 μm, σ≈8–27 g / m²) 2 ), easy to achieve high R membrane Furthermore, it is almost airtight (air permeability <0.1 cm³ / cm² / s), meeting sealing requirements.

[0108] ② Metallized composite films (e.g., PET metallized): The areal density is further reduced (metallized layer thickness 20–50 nm), but rigidity is enhanced. R The membrane is higher. The aluminum coating completely blocks air permeability and improves high-frequency acoustic impedance stability.

[0109] 2. High rigidity and resistance to deformation: Suppresses segmentation vibration and avoids resonance interference from the covered area itself, thus preventing acoustic impedance adjustment. When the coverage ratio is >50%, the membrane area increases, and the risk of segmentation vibration rises sharply. The material's bending stiffness needs to be sufficiently high. In this case, PEN or PET aluminized film is preferred (especially when the coverage ratio is ≥60%).

[0110] 3. Low tension dependence and dimensional stability: Traditional elastic membranes (such as rubber) require high tension to maintain flatness, but tension changes with temperature / humidity, leading to R... membrane Drift. Materials with low coefficient of thermal expansion (CTE) such as PET and PI can be selected. Alternatively, a pre-tensioned composite film, such as a PET / aluminum foil / PET three-layer composite, can be used. The aluminum foil layer (CTE ≈ 23 ppm / °C) can offset the shrinkage of PET and maintain tension stability.

[0111] 4. For lightweight design and drive compatibility coverage of 70%, the mass of the interlayer diaphragm should be less than 10% of the diaphragm mass to avoid inertial load affecting the high-frequency response. (Assuming diaphragm mass...) m dia =1g, coverage area 70%, maximum allowable intermediate membrane 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 (12 μm) is an option: σ ≈17g / m 2

[0112] Based on the above, the following solutions can be referenced for the coordinated design of material and coverage ratio.

[0113] Option 1: PET base film (coverage ratio 30–60%) is low-cost, has mature technology, and balances areal density and stiffness. Thickness selection is based on coverage ratio: β ≤ 40% → thin (6–8 μm), β = 40–60% → standard (12–15 μm). Adding a nano-silica coating improves rigidity without increasing mass.

[0114] Option 2: PET-Aluminum Composite Film (Coverage 50–70%): 8 μm PET + 30 nm aluminum layer + 5 μm PET protective layer. Areal density is only 18 g / m², but bending stiffness is approximately 5 times that of pure PET. The aluminum layer completely blocks air permeability. membrane →∞ is closer to the ideal model. Suitable for applications requiring extreme acoustic impedance or wideband adjustment at high coverage ratios.

[0115] Option 3: PEN membrane (coverage 40–70%, high-frequency acoustic impedance preferred) high modulus ( E (≈6GPa), high temperature resistance, and low sound loss factor. Applicable to scenarios requiring acoustic impedance adjustment to >2 kHz (such as full-range units).

[0116] The core logic for selecting the interlayer membrane material is: to achieve the highest R ratio with the minimum areal density under the constraint of coverage ratio. membrane And bending stiffness. PET is an economical and reliable benchmark choice, with 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 requirements.

[0117] In this embodiment, the thickness of the interlayer membrane is 8-20 μm. If the interlayer membrane is a PET membrane with a thickness of 8-20 μm, the optimal operating point is 12±2 μm (acoustic resistance-mass-stiffness balance at 50% coverage). If the interlayer membrane is a PET-aluminum composite membrane, the thickness is 6-12 μm PET + 30-100 nm Al. If the interlayer membrane is a PEN membrane, the thickness is 6-15 μm.

[0118] In this embodiment, the surround region adopts a double cantilever surround, and the area of ​​the surround region is 10%-25%. Based on the special structure of this acoustic impedance-adjustable loudspeaker (rectangular diaphragm + central acoustic impedance adjustment region), the surround design needs to meet three 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 region). Based on this, several surround shapes are compared as follows:

[0119]

[0120] Based on the above comparison, the double cantilever folded ring was selected. The stroke linearity of the double cantilever folded ring is ≤0.7, which can reduce corner stress by 80% (compared to a semi-circular ring), avoiding tearing at the four corners of the rectangular shape. The resonance quality factor Qms <1.5 (measured value), far from the acoustic impedance adjustment frequency range (50-500 Hz).

[0121] Based on the selected shape, the area of ​​the folded region is further selected for the folded material. The minimum area of ​​the folded region needs to be calculated under the following constraints:

[0122] 1. Mechanical constraints (to avoid excessive stress):

[0123]

[0124] In the formula, Magnetic gap flux density (typically 1 T) Voice coil length (m) Material yield strength (IIR: 8 MPa)

[0125] 2. Acoustic constraints (impedance matching):

[0126]

[0127] Based on the above constraints, the area of ​​the fold ≥ max( , (and not less than 10% of the total diaphragm area).

[0128] In this embodiment, the intermediate membrane and the diaphragm are fixed by micro-contact thermoforming, mechanical bump bonding, or adhesive. It should be noted that adhesive fixing is the simplest method, but typical adhesives increase in density after curing, easily leading to an increase in the effective mass of the intermediate membrane, and adhesive seeps into the mesh; therefore, this method is the least recommended. The preferred method is micro-contact thermoforming, which has the advantage of zero added mass and zero mesh clogging. The second-best option is mechanical bump bonding, suitable for long-stroke low-frequency units. The last-best option is an adhesive, which can use a formulation of MS-based + 40 vol% hollow microspheres, which can alleviate the above problems.

[0129] In this embodiment, a silicone transition layer (not shown in the figure) is provided between the intermediate film and the microporous mesh layer. Designing a transition layer or special coupling structure, such as a transition layer with a gradually changing aperture or thickness, between the intermediate film and the microporous mesh allows sound waves to propagate more smoothly from one medium to another, reducing energy loss and distortion caused by poor coupling. It can effectively solve the impedance mismatch problem when sound waves propagate in different acoustic impedance media (rigid microporous mesh → flexible film), thereby reducing reflection loss and distortion. To meet the above requirements, the following aspects are required: (1) The transition layer must meet the acoustic impedance gradual matching, such as the high acoustic impedance (high rigidity) of the microporous mesh (stainless steel / polyester) → the low acoustic impedance (high flexibility) of the intermediate film (PET / PEN). (2) The transition layer must achieve a continuous gradual change in acoustic impedance to avoid the reflection of sound waves at the interface (similar to the principle of anti-reflective coating in optics). (3) Suppress resonance and standing waves, and eliminate local resonance and high-frequency standing waves caused by impedance abrupt changes (common in rigid-flexible interfaces). (4) To maintain structural stability, it is necessary to be compatible with existing processes (hot pressing / gluing) and not to increase the mass or thickness too much.

[0130] Based on the above settings, the comparison materials are as follows:

[0131]

[0132] For the reasons mentioned above, microporous elastomers such as silicone are chosen because the porosity can be controlled by the foaming rate (30%-70%), allowing for a continuous and gradual change in acoustic impedance. Its high damping characteristics (loss factor tanδ>0.3) can absorb interfacial vibration energy. It can be fabricated as a liquid precursor, precisely coated, and then cured.

[0133] In this embodiment, the silicone transition layer sequentially comprises a first silicone layer, a second silicone layer, and a third silicone layer from the microporous mesh layer side to the intermediate film side; wherein 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 adopted, as shown in the gradient structure example (from the microporous mesh towards the intermediate film).

[0134]

[0135] This solution can improve frequency response smoothness, reducing fluctuations caused by interface reflections by 3–5 dB in the 1–5 kHz frequency band. Furthermore, it can reduce distortion, suppress local standing waves, and improve transient response.

[0136] The above description is only a part of the embodiments of this utility model, and does not limit the scope of protection of this utility model. Any equivalent device or equivalent process transformation made based on the content of this utility model specification and drawings, or direct or indirect application in other related technical fields, are similarly included in the patent protection scope of this utility model.

Claims

1. A loudspeaker unit with acoustic impedance adjustment function, characterized in that, The diaphragm of the unit is a folded ring rectangular diaphragm; The folded rectangular diaphragm includes a folded ring area and a hollow portion disposed at the center of the folded ring area; the hollow portion is covered with a fine porous mesh layer; an intermediate film is covered on the outer side of the fine porous mesh layer, and the coverage ratio of the intermediate film is 30% to 70%.

2. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, The pore diameter of this fine-porous mesh layer is 0.05-0.3 mm.

3. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, The fine-pore mesh layer is made of stainless steel, polyester, or nylon.

4. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, The intermediate membrane is made of PET film, PET / metal composite film, or PEN film.

5. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, The thickness of the intermediate film is 8-20 μm.

6. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, The folded ring region adopts a double cantilever folded ring, and the area of ​​the folded ring region is 10%-25%.

7. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, The intermediate membrane and the diaphragm are bonded together by micro-contact hot pressing, mechanical protrusion embedding, or glue.

8. A loudspeaker unit with acoustic impedance adjustment function as described in claim 1, characterized in that, A silicone transition layer is provided between the intermediate membrane and the microporous mesh layer.

9. A loudspeaker unit with acoustic impedance adjustment function as described in claim 8, characterized in that, The silicone transition layer comprises, from the fine-pore mesh layer side to the intermediate film side, a first silicone layer, a second silicone layer, and a third silicone layer in sequence; wherein 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.

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