Low frequency acoustic device

Abstract

The present invention provides a low-frequency acoustic device, comprising a first shell and a second shell, wherein a first opening is provided at a first end of the first shell, the second shell is provided inside the first shell, a sound guide groove is provided at the second shell, and the second opening is connected and corresponds to the first opening; the first shell and the second shell are closed and connected, and an inner cavity is formed between the first shell and the second shell; a first audio driver is provided at a second end of the second shell, a second audio driver is provided at a third end of the second shell, the first audio driver and the second audio driver are symmetrically arranged face to face, a rear cavity of the first audio driver is connected to a rear cavity of the second audio driver, and the first audio driver and the second audio driver play at the same phase; a passive radiator is provided at the fourth end of the first shell. The symmetrical design of the audio driver, the sound guide groove design, the cavity design and the passive radiator increase the sound pressure in the low-frequency band, reduce the distortion in the low-frequency band, control the directivity, and reduce the volume.

Description

Technical Field

[0001] The invention relates to the technical field of acoustics, in particular to designing a low-frequency acoustic device. Background Art

[0002] Existing subwoofers include the following designs: First, a single speaker and bass reflex tube design. This design enhances the low-frequency effect through the bass reflex tube. The structure is simple and the cost is low, but the bass reflex tube is prone to airflow noise, the low-frequency distortion is large, and the low-frequency lower limit is limited.

[0003] Second, the dual-drive push-pull design uses two drive units installed back to back and played in anti-phase. This design allows the harmonic distortion produced by the two speakers to cancel each other out, which can reduce distortion. However, since the speaker has a 180-degree phase difference, the sound on both sides is inconsistent, resulting in extremely strong directivity. Its directivity cannot be controlled, resulting in uneven sound field distribution.

[0004] Third, dual-drive push-push design. This design uses two drive units installed back to back and play in the same phase. Since the drive units are installed back to back, their movement directions are inconsistent, which can effectively reduce the vibration of the cabinet, and the superposition of sound energy improves the low-frequency output efficiency. However, this design is omnidirectional and cannot control the directivity. In a larger space, the low-frequency energy distribution is uneven, which affects the listening experience of the speaker.

[0005] Fourth, a single speaker and passive radiator design uses a passive radiator instead of a bass reflex tube. This design does not have the airflow noise of the bass reflex tube and has a smooth low-frequency response. However, the low-frequency extension capability of a single passive radiator is limited, making it difficult to take into account both low-frequency volume and clarity.

[0006] Fifth, slot loaded design, this design usually has two speakers facing each other, and the sound comes out from the slot. The slot in the slot loaded design is larger and narrower, which can optimize the output of low frequencies, make the air flow more smoothly, reduce the eddy effect of low frequencies, and control the directivity. However, due to the setting of two speakers, the volume of the speaker with slot loaded design is larger and the space utilization rate is low. Summary of the invention

[0007] The purpose of the present invention is to provide a low-frequency acoustic device with large low-frequency volume, less distortion, controllable audio directivity and small device volume.

[0008] To achieve the first objective of the present invention, the present invention provides a low-frequency acoustic device, comprising a first shell and a second shell, wherein the first end of the first shell is provided with a first opening, the second shell is arranged inside the first shell, the second shell is provided with a sound guiding groove, the sound guiding groove is provided with a second opening, the second opening of the sound guiding groove is connected and corresponds to the first opening; the first shell and the second shell are closed and connected, and an inner cavity is formed between the first shell and the second shell; the second end of the second shell is provided with a first audio driver, the third end of the second shell is provided with a second audio driver, the first audio driver and the second audio driver are symmetrically arranged face to face, the rear cavity of the first audio driver is connected with the rear cavity of the second audio driver, and the first audio driver and the second audio driver play at the same phase; the fourth end of the first shell is provided with a passive radiator.

[0009] It can be seen from the above scheme that since the first audio driver and the second audio driver are symmetrically arranged and play at the same phase, the sound energy of the first audio driver and the second audio driver is superimposed in the sound guide groove when they are working, and a double resonance peak is generated in the 40-80Hz frequency band, the sound pressure in the low frequency band is increased, the distortion in the low frequency band is reduced, and the low frequency output efficiency is improved. And since a sound guide groove is provided, the sound guide groove is a groove loading design, since the sound is transmitted through the sound guide groove, and by controlling the groove width of the sound guide groove, the directivity of the sound transmitted by the first audio driver and the second audio driver is controllable. Since the back cavity of the first audio driver is connected to the back cavity of the second audio driver, the first audio driver and the second audio driver can share the back cavity, so that the volume of the low-frequency acoustic device is reduced. And a passive radiator is provided, while balancing the pressure in the inner cavity, since the first audio driver and the second audio driver share the passive radiator, the volume of the low-frequency acoustic device is further reduced.

[0010] In a further solution, the first diaphragm of the first audio driver and the second diaphragm of the second audio driver are symmetrically arranged face to face, and the first diaphragm of the first audio driver and the second diaphragm of the second audio driver are arranged face to face with the sound guide groove.

[0011] It can be seen that when the first diaphragm of the first audio driver and the second diaphragm of the second audio driver are working, the sound energy can be superimposed in the sound guiding groove, thereby making the superposition effect of the sound energy better and improving the sound propagation efficiency.

[0012] In a further solution, the back of the first audio driver faces the first wall of the first shell, the back of the second audio driver faces the second wall of the first shell, and the first wall and the second wall are arranged opposite to each other.

[0013] It can be seen that the back of the first audio driver and the first wall of the first shell form a back cavity of the first audio driver, and the back of the second audio driver and the second wall of the first shell form a back cavity of the second audio driver, so that the back cavity of the first audio driver and the back cavity of the second audio driver are symmetrically arranged to meet the dual-drive push-push design.

[0014] In a further embodiment, the cross-sectional area of ​​the second opening of the second shell is smaller than the cross-sectional area of ​​the first opening.

[0015] In a further solution, a connecting portion is provided at the second opening of the second shell, the connecting portion connects the first shell and the second shell, and the surface of the connecting portion is an arc surface.

[0016] It can be seen that the cross-sectional area of ​​the second opening of the second shell is smaller than the cross-sectional area of ​​the first opening, so that when the sound is transmitted from the sound guide groove to the external space, the sound propagation route is optimized, so that the directivity of the sound can be further expanded.

[0017] In a further solution, a symmetry plane between the first audio driver and the second audio driver passes through the passive radiator, and a center point of the passive radiator is arranged on the symmetry plane between the first audio driver and the second audio driver.

[0018] It can be seen that this arrangement enables the passive radiator to be arranged at the point with the maximum pressure in the inner cavity, so that the passive radiator can better balance the pressure of the air in the box.

[0019] In a further solution, the first opening is arranged on the third wall of the first shell, the passive radiator is arranged on the fourth wall of the first shell, and the third wall is arranged opposite to the fourth wall.

[0020] It can be seen that the first opening is arranged opposite to the passive radiator to avoid mutual interference with the sound propagating in the direction of the opening.

[0021] In a further embodiment, the sound-conducting groove is not connected to the inner cavity.

[0022] It can be seen that the sound-conducting groove is not connected to the inner cavity, so that the inner cavity is in a closed state. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural diagram of an embodiment of a low-frequency acoustic device of the present invention.

[0024] Figure 2 It is a cross-sectional view of an embodiment of a low-frequency acoustic device of the present invention from a first viewing angle.

[0025] Figure 3 It is a cross-sectional view of the low-frequency acoustic device embodiment of the present invention from a second viewing angle.

[0026] Figure 4It is a cross-sectional view of the low-frequency acoustic device embodiment of the present invention from a third viewing angle.

[0027] Figure 5 It is a structural diagram of a second shell, a first audio driver and a second audio driver of an embodiment of a low-frequency acoustic device of the present invention.

[0028] Figure 6 It is a structural diagram from another perspective of the second shell, the first audio driver and the second audio driver of the embodiment of the low-frequency acoustic device of the present invention.

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0030] The low-frequency acoustic device provided by the present invention combines a dual-drive push-push design, a slot-loading design and a passive radiator design, so that when the sound energy is superimposed and extended in the low-frequency band, the directivity of the sound can be controlled. And due to the setting of the passive radiator, while balancing the inner cavity pressure, the volume of the low-frequency acoustic device is further reduced.

[0031] See also Figure 1 , Figure 2 and Figure 3 The low-frequency acoustic device includes a first shell 1, a first end of which is provided with a first wall 13, a second wall 14, a third wall 11 and a fourth wall 12, which surround the first shell 1. The first wall 13 is arranged opposite to the second wall 14, and the third wall 11 is arranged opposite to the fourth wall 12. A first opening 151 is arranged on the third wall 11 of the first shell 1.

[0032] See also Figure 3 The low-frequency acoustic device is further provided with a second shell 22 , which is arranged inside the first shell 1 . The second shell 22 is provided with a sound guide groove 21 , and a second opening 211 of the sound guide groove 21 is connected and corresponds to the first opening 151 .

[0033] The first shell 1 is hermetically connected to the second shell 22 , and an inner cavity 111 is formed between the first shell 1 and the second shell 22 .

[0034] See also Figure 4 , wherein a connecting portion 221 is provided at the second opening 211 of the second shell, and the connecting portion 221 connects the first shell 1 and the second shell 22. Specifically, the connecting portion makes a smooth transition between the first opening 151 and the second opening 211 of the sound guide groove 21. Further, the surface of the connecting portion 221 is a curved surface.

[0035] When the cross-sectional area of ​​the sound guiding groove 21 of the second shell 22 is smaller than the cross-sectional area of ​​the first opening 151 , so that the sound can be transmitted from the sound guiding groove to the external space, the route of sound propagation is optimized.

[0036] The second end of the second shell 22 is provided with a first audio driver 31, and the third end of the second shell 22 is provided with a second audio driver 32. The first audio driver 31 and the second audio driver 32 are symmetrically arranged face to face, and the back volume of the first audio driver 31 is connected with the back volume of the second audio driver 32. Specifically, the back of the first audio driver 31 faces the first wall 13 of the first shell 1, and the back of the second audio driver 32 faces the second wall 14 of the first shell 1. The first wall 13 and the second wall 14 are arranged opposite to each other. The first audio driver 31 and the second audio driver 32 play at the same phase.

[0037] Since the rear cavity of the first audio driver 31 and the rear cavity of the second audio driver 32 are symmetrically arranged and installed in opposite directions, the first audio driver 31 and the second audio driver 32 output vibration forces in opposite directions when they are working, and the cabinet vibration caused by the first audio driver 31 and the second audio driver 32 can be offset. In addition, the rear cavity of the first audio driver 31 and the rear cavity of the second audio driver 32 are symmetrically arranged, and the first audio driver 31 and the second audio driver 32 play in the same phase, so the first audio driver 31 and the second audio driver 32 meet the dual-drive push-push design.

[0038] Furthermore, the first audio driver 31 and the second audio driver 32 are audio drivers of the same specification, so that when the first audio driver 31 and the second audio driver 32 move in the same phase, the sound energy is superimposed on the sound guiding groove 21 .

[0039] The first audio driver 31 and the second audio driver 32 move in the same phase, which also causes the sound waves to be superimposed in the same phase in the sound guide groove 21, thereby increasing the sound pressure in the low frequency band. The rear cavity of the first audio driver 31 is connected to the rear cavity of the second audio driver 32, thereby reducing the influence of the heating of the audio driver on the acoustic performance.

[0040] See also Figure 4 , Figure 5 and Figure 6 Specifically, the first diaphragm 311 of the first audio driver 31 and the second diaphragm 321 of the second audio driver 32 are symmetrically arranged face to face, and the first diaphragm 311 of the first audio driver 31 and the second diaphragm 321 of the second audio driver are arranged facing the sound guide groove 21.

[0041] Among them, the sound guide groove 21 adopts a groove loading design. In the groove loading design, the first audio driver 31 and the second audio driver 32 are arranged on both sides of the sound guide groove 21, and the first diaphragm 311 of the first audio driver 31 and the second diaphragm 321 of the second audio driver 32 are symmetrically arranged, and the groove width of the sound guide groove 21 is set to 5%-10% of the diameter of the audio driver, thereby reducing the airflow sound of the sound and forming a symmetrical acoustic channel.

[0042] The sound-guiding groove 21 and the cavity 111 produce a Helmholtz resonance effect to form a resonant system. The formula for the resonant frequency is: , where c is the speed of sound, S is the cross-sectional area of ​​the second opening 211 of the sound-guiding groove 21, and V b is the volume of the inner cavity 111, and L is the depth of the sound guiding groove 21. The groove width (W) of the sound guiding groove 21 can be used to adjust the groove cross-sectional area of ​​the second opening 211 of the sound guiding groove 21, and the groove depth of the sound guiding groove 21 can be adjusted to change the resonant frequency f of the resonant system. h , thereby optimizing the sound in the low frequency band.

[0043] The calculation formula of the cavity volume of the inner cavity 111 is: , where V as is the equivalent volume of the audio driver, Q tc is the target system Q of the audio driver. Q ts It is the overall quality factor of the audio driver, with a typical value of 0.3-0.5.

[0044] The calculation formula of the groove width of the sound guide groove 21 is: , where V b is the volume of the inner cavity 111, f c is the target low-frequency cutoff frequency, S d is the diaphragm area of ​​the audio driver and c is the speed of sound.

[0045] A passive radiator 41 is provided at the fourth end of the first shell 1. The symmetric plane of the first audio driver 31 and the second audio driver 32 passes through the passive radiator 41. The center point of the passive radiator 41 is set on the symmetric plane of the first audio driver 31 and the second audio driver 32. Since the first opening is set on the third wall of the first shell, the passive radiator 41 is set on the fourth wall of the first shell 1, and the third wall 11 and the fourth wall 12 are arranged opposite to each other. Since the first audio driver 31 and the second audio driver 32 are symmetrically arranged face to face, the two audio drivers are installed in reverse, and when the two audio drivers are in motion, the pressure generated by the corresponding rear cavity will be offset on the symmetric plane of the first audio driver 31 and the second audio driver 32, so the maximum pressure point is on the symmetric plane of the first audio driver 31 and the second audio driver 32, and the passive radiator is set on the symmetric plane to balance the pressure more effectively. The first audio driver 31 and the second audio driver 32 share a passive radiator, saving space for the low-frequency acoustic device.

[0046] In this embodiment, the resonant frequency (f pr ) is the resonant frequency of the audio radiator (f s ), thereby achieving the low frequency band extension to 0.7 times the drive unit resonant frequency. Among them, the calculation formula for the resonant frequency of the passive radiator is Among them, M pr is the equivalent mass of the passive radiator, C pr is the compliance of the passive radiator. By adjusting the equivalent mass and compliance of the passive radiator, its resonant frequency can be changed.

[0047] The calculation formula for the equivalent mass of a passive radiator is: . Where ρ0 is the air density, w0=2πf s .f s is the resonant frequency of the audio radiator. The effective area of ​​the passive radiator (S pr ) is the diaphragm area of ​​the audio driver (S d ) is 1.2-1.5 times.

[0048] The formula for calculating the compliance of a passive radiator is: Among them, V b is the volume of the inner cavity 111, γ is the specific heat ratio of air, P0 is the standard atmospheric pressure, S d is the diaphragm area of ​​the audio driver.

[0049] Since the first audio driver and the second audio driver are symmetrically arranged and move in the same phase, the sound energy of the first audio driver and the second audio driver is superimposed in the sound guide groove when they are working, and a double resonance peak is generated in the 40-80Hz frequency band, the sound pressure in the low-frequency band is increased, the distortion in the low-frequency band is reduced, and the low-frequency output efficiency is improved. And since a sound guide groove is provided, the sound guide groove is a groove-loaded design, and since the sound is transmitted through the sound guide groove, the directionality of the transmitted sound is controllable. Since the back cavity of the first audio driver is connected to the back cavity of the second audio driver, the back cavity that can be shared by the first audio driver and the second audio driver can be reduced, so that the volume of the low-frequency acoustic device is reduced. And a passive radiator is provided to further reduce the volume of the low-frequency acoustic device while balancing the pressure in the inner cavity.

[0050] The above are only preferred embodiments of the present invention, but the design concept of the invention is not limited thereto. Without departing from the concept of the present invention, more other equivalent embodiments may be included. It is obvious to those skilled in the art that various changes, readjustments and substitutions can be made without departing from the protection scope of the present invention.

Claims

1. A low frequency acoustic device, characterized in that: The device comprises a first shell and a second shell, wherein a first end of the first shell is provided with a first opening, the second shell is provided inside the first shell, the second shell is provided with a sound guide groove, the sound guide groove is provided with a second opening, and the second opening of the sound guide groove is connected and corresponds to the first opening; The first shell is hermetically connected to the second shell, and an inner cavity is formed between the first shell and the second shell; A first audio driver is disposed at the second end of the second shell, and a second audio driver is disposed at the third end of the second shell, the first audio driver and the second audio driver are symmetrically disposed face to face, a rear cavity of the first audio driver is connected to a rear cavity of the second audio driver, and the first audio driver and the second audio driver play at the same phase; A passive radiator is disposed at the fourth end of the first shell.

2. The low-frequency acoustic device according to claim 1, characterized in that: The first diaphragm of the first audio driver and the second diaphragm of the second audio driver are symmetrically arranged face to face, and the first diaphragm of the first audio driver and the second diaphragm of the second audio driver are arranged facing the sound guide groove.

3. The low-frequency acoustic device according to claim 2, characterized in that: The back of the first audio driver faces the first wall of the first housing, the back of the second audio driver faces the second wall of the first housing, and the first wall is arranged opposite to the second wall.

4. The low-frequency acoustic device according to claim 1, characterized in that: A cross-sectional area of ​​the second opening of the second shell is smaller than a cross-sectional area of ​​the first opening.

5. The low-frequency acoustic device according to claim 4, characterized in that: A connecting portion is disposed at the second opening of the second shell, the connecting portion connects the first shell and the second shell, and the surface of the connecting portion is an arc surface.

6. The low-frequency acoustic device according to any one of claims 1 to 5, characterized in that: A symmetry plane between the first audio driver and the second audio driver passes through the passive radiator; The center point of the passive radiator is arranged on a symmetry plane between the first audio driver and the second audio driver.

7. The low-frequency acoustic device according to claim 6, characterized in that: The first opening is arranged on the third wall of the first shell, the passive radiator is arranged on the fourth wall of the first shell, and the third wall is arranged opposite to the fourth wall.

8. The low-frequency acoustic device according to any one of claims 1 to 5, characterized in that: The sound guiding groove is not connected with the inner cavity.

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