JP2009164676A - Passive radiator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive passive radiator having a small depth space, which has high efficiency of reproducing low sounds and can stably reproduce low sounds of high sound pressure. <P>SOLUTION: The passive radiator is configured so that the outer peripheral portion of a diaphragm 2 is supported only by a roll-like edge 1 without using a damper; the center of gravity G of the entire vibration system including the mass of the diaphragm 2 and an effective vibration mass of the edge 1 is set near the center 1c of the amplitude of a support portion, with respect to the diaphragm for the edge 1; the mass distribution density in the inner peripheral portion 2a of the diaphragm is increased; and the vibrating system is prevented from rolling, without increasing the stiffness of the support system. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a passive radiator used for bass reflex speakers and kelton speakers for stereo reproduction of stereo and multi-channel sound reproducing devices.

  In recent years, along with the popularization of home theater playback devices and the like in ordinary homes, there has been a demand for the realization of a low-frequency sound reproduction speaker that can reproduce low-frequency sound with high sound pressure while being low-cost and small. Generally, the bass reproduction speaker is a bass reflex type speaker or a kelton type speaker, and uses a port to enhance the bass. However, it is known that wind noise noise is generated from the port when low sound is reproduced with high sound pressure.

  Therefore, if a bass-reflex speaker using a passive radiator is used instead of a port, or a kelton speaker using a passive radiator is used instead of a port, wind noise noise of the port can be eliminated.

  FIG. 13 is a cross-sectional view showing the configuration of the conventional bass reflex speaker, and FIG. 14 is a cross-sectional view showing the configuration of the conventional kelton speaker. In FIGS. 13 and 14, driver units 118 and 128 and passive radiators 117 and 127 are attached to cabinets 119 and 129, respectively.

  However, passive radiators are large and have a large number of parts compared to ports, which increases costs and requires space. In addition, there are many cases where stable vibration and low sound reproduction cannot be achieved because the diaphragm tends to roll when the amplitude is large. So it was not used much.

  On the other hand, for example, a passive radiator described in Patent Document 1 has been proposed as a passive radiator in which the number of parts is reduced. FIG. 11 is a cross-sectional view showing a configuration of a conventional passive radiator described in Patent Document 1. As shown in FIG.

  In FIG. 11, the surface portion 92c of the diaphragm 92 is formed integrally with the edge 91 and is made of a foam material. A back plate 92d is attached to the back side of the surface portion 92c of the diaphragm, and is made of resin or cardboard. The edge 91 is attached to the frame 93. With this configuration, since the diaphragm 92 is supported only by the edge 91 and no damper is used, the cost can be reduced and the depth space can be reduced.

  On the other hand, as a passive radiator that prevents rolling of the diaphragm at a large amplitude, for example, a passive radiator as described in Patent Document 2 has been proposed. FIG. 12 is a cross-sectional view showing a configuration of a conventional passive radiator described in Patent Document 2. In FIG.

In FIG. 12, an edge 101 and a damper 104 are attached to a frame 103, and the diaphragm 102 is supported at its outer periphery by the edge 101, and is supported at its inner periphery by a damper 104 via a bobbin 105. . The weight 106 is disposed at the tip of the bobbin 105 and near the center of gravity of the vibration system. With this configuration, since the weight balance of the vibration system can be achieved, rolling can be prevented.
Japanese Utility Model Publication No.59-25892 Japanese Utility Model Publication No.57-4888

  However, in the conventional passive radiator as shown in FIG. 11 described above, since the mass of the diaphragm back plate 92d is dominant, the center of gravity position of the entire vibration system including the mass of the diaphragm 92 and the effective vibration mass of the edge 91 is obtained. Since G and the amplitude center position 91c of the support portion with respect to the diaphragm of the edge 91 are separated from each other and the mass distribution density of the diaphragm 92 is uniform, the secondary resonance inertia moment of the vibration system is large, and the diaphragm is rolling. There was a problem that stable sound pressure reproduction was not possible. This will be described in detail in the first embodiment of the present invention.

  Further, in the conventional passive radiator as shown in FIG. 12 described above, since the diaphragm 102 is supported by both the edge 101 and the damper 104, the stiffness of the damper 104 is added to the stiffness of the edge 101, and the vibration system becomes difficult to move. The bass reproduction efficiency decreases. In other words, there is a problem that the reproduction limit frequency of the bass is higher than that of the port, and if the mass of the vibration system is increased to prevent this, the bass becomes boomy and the efficiency is lowered. In addition, since the number of parts is large, there is a problem that the cost increases and the depth space increases.

  The present invention solves such a conventional problem, the vibration system is easy to move, the bass reproduction efficiency is high, the diaphragm does not generate rolling, can stably reproduce the high sound pressure bass, and the cost is low. An object is to provide a passive radiator with a small depth space.

  The passive radiator of the present invention supports the outer peripheral portion of the diaphragm with only a roll-shaped edge without using a damper, and the center of gravity position of the entire vibration system including the mass of the diaphragm and the effective vibration mass of the edge Is provided in the vicinity of the amplitude center position of the support portion of the edge with respect to the diaphragm, and the mass distribution density of the inner peripheral portion of the diaphragm is increased.

  With this configuration, the secondary resonance moment of inertia of the vibration system can be reduced, so that rolling can be prevented from occurring even if the diaphragm is supported only by the edge without using a damper.

  According to the passive radiator of the present invention, since no damper is used, the stiffness of the support system can be reduced, and the bass reproduction efficiency can be increased. A center of gravity position of the entire vibration system including the mass of the diaphragm and the effective vibration mass of the edge is provided in the vicinity of the amplitude center position of the support portion with respect to the diaphragm of the edge, and the mass distribution density of the inner peripheral portion of the diaphragm is determined. Since it is increased, the secondary resonance moment of inertia of the vibration system is reduced, and stable high sound pressure bass reproduction can be achieved without causing rolling even when the diaphragm has a large amplitude. Further, since the number of parts is small, the cost can be reduced and the depth space can be reduced.

  In addition, when the minimum resonance frequency of the vibration system is f0 and the secondary resonance mode frequency is fr, the second resonance moment of inertia of the vibration system can be further reduced by configuring so that fr / f0 ≧ 1.4. For this reason, even when the amplitude is large, it is possible to perform a more stable amplitude operation without rolling, and it is possible to reproduce a higher sound pressure bass sound.

  Further, by arranging a material having a specific gravity larger than that of the diaphragm material on the inner peripheral portion of the diaphragm, the secondary resonance moment of inertia of the vibration system can be further reduced, so that a more stable large-amplitude operation without rolling is performed. It is possible to reproduce a higher sound pressure bass sound. Further, the passive radiator can be further reduced in thickness.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
First, the configuration of the passive radiator in the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a configuration of a passive radiator according to Embodiment 1 of the present invention.

  In FIG. 1, an edge 1 is attached to a frame 3, and an edge support portion 1 a for the diaphragm is attached to the outer peripheral portion of the diaphragm 2. That is, the outer peripheral part of the diaphragm 2 is supported only by the roll-shaped edge 1 and no damper is used. The reason why the edge 1 is formed in a roll shape is that yielding deformation is likely to occur in other edge shapes due to the fact that a large amplitude can be generated and the difference in atmospheric pressure inside and outside the cabinet due to the sound pressure inside the cabinet during reproduction of high sound pressure and low sound.

  The center-of-gravity position G of the entire vibration system including the mass of the diaphragm 2 and the effective vibration mass of the edge 1 is substantially aligned with the amplitude center position 1c of the edge support portion with respect to the diaphragm. The effective vibration mass of the edge 1 is the sum of the mass of the edge support portion 1a with respect to the diaphragm and the effective vibration mass portion 1b of the edge movable portion. It is known that the effective vibration mass of a movable part of a support system such as an edge or a damper corresponds to a mass corresponding to an area of about 1/3 from the inner peripheral side of the entire movable part. Further, the inner peripheral portion 2a of the diaphragm is thick to increase the mass distribution density. In other words, the mass distribution density of the outer peripheral portion of the diaphragm 2 is lowered.

Next, specific dimensions and materials of the components of the passive radiator according to the first embodiment will be described. The nominal diameter of this passive radiator is 25 cm, which indicates the outer diameter of the frame 3. The roll outer diameter of the edge 1 is 216 mm, the roll inner diameter is 172 mm, the roll radius is 11 mm, the effective vibration radius is 97 mm, the edge thickness is 1.5 mm, and the material is NBR rubber. Its specific gravity is 1.2 g / m ³ . The inner diameter of the edge support portion 1a with respect to the diaphragm is 160 mm.

The diameter of the diaphragm 2 is 168 mm, and the material is ABS resin. Its specific gravity is 1.06 g / m ³ . The thickness of the diaphragm 2 is 1.8 mm at the outer periphery. The inner peripheral portion 2a that is thick, that is, has a high mass distribution density, has a diameter of 56 mm and a thickness of 17 mm. The inner peripheral portion 2a is offset 3.6 mm backward with respect to the front-rear direction of the diaphragm 2, and the protrusion of the inner peripheral portion 2a from the outer peripheral portion of the diaphragm 2 to the front surface side is 4 mm, and the protrusion to the rear surface side. Is 11.2 mm.

  The mass of the diaphragm 2 is 82 g, the mass of the edge support portion 1 a with respect to the diaphragm is 7 g, and the mass of the effective vibration mass equivalent portion 1 b of the edge movable portion is 6 g. That is, the effective vibration mass of the vibration system not including the additional mass of air is 95 g in total. The equivalent added mass of air is about 3 g, and when this is added, the effective vibration mass is about 98 g. However, since the equivalent added mass of air is added to both the front and back surfaces of the diaphragm 2 and the mass is also small, the vibration system It can be ignored when considering the center of gravity.

  By configuring with the above dimensions and materials, the center of gravity position G of the entire vibration system including the mass of the diaphragm 2 and the effective vibration mass of the edge 1 is about 2.8 mm behind the surface of the diaphragm 2, It is located 6.8 mm rearward from the surface of the inner periphery 2a. The amplitude center position 1c of the edge support portion with respect to the diaphragm corresponds to the center position of the edge thickness because the edge material is uniform in the thickness direction, and is about 2.55 mm behind the surface of the diaphragm 2. That is, the center-of-gravity position G of the entire vibration system including the mass of the diaphragm 2 and the effective vibration mass of the edge 1 is only 0.25 mm away from the amplitude center position 1c of the edge support portion with respect to the diaphragm. Almost complete.

  In other words, in the first embodiment, the amplitude center position 1c of the support portion of the edge with respect to the diaphragm is behind the rear surface of the diaphragm 2, but the inner peripheral portion 2a of the diaphragm having a higher mass distribution density is placed rearward. By offsetting, the center of gravity position G of the entire vibration system including the mass of the diaphragm 2 and the effective vibration mass of the edge 1 is moved backward, and is substantially aligned with the amplitude center position 1c of the edge support portion with respect to the diaphragm. It is.

  The operation and effect of the passive radiator according to the first embodiment configured as described above will be described below. First, referring to FIG. 7, FIG. 8, FIG. 9, and FIG. 10, regarding the problems of the conventional passive radiator. While explaining in detail.

  7 and 8 are cross-sectional views showing the configuration of a more general conventional passive radiator, and are the same in operation as the conventional passive radiator of FIG. 11 described in Patent Document 1. The diameter of this conventional passive radiator is 25 cm, similar to the passive radiator of the first embodiment. 7 and 8, the dimensions and materials of the edges 61 and 71, respectively, and the dimensions of the edge support portions 61a and 71a with respect to the diaphragm are the same as those of the passive radiator of the first embodiment.

In FIG. 7, the edge support portion 61 a for the diaphragm is attached to the surface side of the diaphragm 62. The diaphragm 62 has a diameter of 172 mm, a thickness of 6 mm, and a uniform mass distribution density. The material of the diaphragm 62 is cardboard, and the specific gravity is 0.59 g / m ³ . The mass of diaphragm 62 is 82 g, the mass of edge support portion 61 a with respect to the diaphragm is 7 g, and the mass of effective vibration mass equivalent portion 61 b of the edge movable portion is 6 g, which is the same as that of the passive radiator of the first embodiment.

  The center of gravity G of the entire vibration system including the mass of the diaphragm 62 of this conventional passive radiator and the effective vibration mass of the edge 61 is located about 2.5 mm behind the surface of the diaphragm 62. The amplitude center position 61c of the edge support portion 61a with respect to the diaphragm is about 0.75 mm forward from the surface of the diaphragm 2. That is, the center of gravity G of the entire vibration system including the mass of the diaphragm 62 and the effective vibration mass of the edge 61 is shifted backward by 3.25 mm from the amplitude center position 61c of the edge support portion with respect to the diaphragm.

In FIG. 8, the edge support portion 71 a for the diaphragm is attached to the back side of the diaphragm 72. The diaphragm 72 has a diameter of 168 mm, a thickness of 6.3 mm, and a uniform mass distribution density. The material of the diaphragm 72 is cardboard, and the specific gravity is 0.59 g / m ³ . The mass of the diaphragm 72 is 82 g, the mass of the edge support portion 71 a with respect to the diaphragm is 7 g, and the mass of the effective vibration mass equivalent portion 71 b of the edge movable portion is 6 g, which is the same as that of the passive radiator of the first embodiment.

  The center of gravity G of the entire vibration system including the mass of the diaphragm 72 of the conventional passive radiator and the effective vibration mass of the edge 71 is located about 2.8 mm forward from the back surface of the diaphragm 72. The amplitude center position 71 c of the edge support portion with respect to the diaphragm is about 0.75 mm behind the rear surface of the diaphragm 72. That is, the center-of-gravity position G of the entire vibration system including the mass of the diaphragm 72 and the effective vibration mass of the edge 71 is shifted forward by about 3.55 mm from the amplitude center position 71c of the edge support portion with respect to the diaphragm.

  10A and 10B show vibration modes of the diaphragm of the conventional passive radiator shown in FIG. 8, where FIG. 10A is a diagram illustrating the primary resonance mode, and FIG. 10C is a diagram illustrating the secondary resonance mode. (A) The primary resonance mode in the figure is at the lowest resonance frequency of the vibration system and represents normal amplitude operation without rolling. (B) The secondary resonance mode in the figure corresponds to the rolling resonance mode, and the diaphragm 82 rolls and the edge 81 is twisted.

  Next, if the position of the center of gravity and the position of the center of amplitude of the vibration system are deviated as in the case of conventional passive radiators, and if the mass distribution density of the diaphragm is uniform, the secondary resonance moment of inertia increases and rolling is likely to occur. It becomes clear quantitatively.

  FIG. 9 is an explanatory diagram showing a calculation concept of the secondary resonance moment of inertia of the vibration system of the passive radiator. In FIG. 9, 81a is an edge support portion for the diaphragm, 81b is an effective vibration mass equivalent portion of the edge movable portion, 81c is the amplitude center position of the edge support portion for the diaphragm, 82 is the diaphragm, and AA 'is 2 This is the central axis of the next resonance mode.

  P is an arbitrary small mass point in the vibration system including the mass of the diaphragm and the effective vibration mass of the edge. That is, P is an arbitrary minute point in the diaphragm 82, the edge support portion 81a for the diaphragm, and the effective vibration mass equivalent portion 81b of the edge movable portion. r is the vertical distance from the secondary resonance mode central axis A-A 'to P. It is known in physics that the secondary resonance moment of inertia is I and the mass of the minute mass point P is dm.

On the other hand, the present inventors have found that the ease of rolling is dependent on the secondary resonance sharpness. Since it is known in physics that an object with a larger moment of inertia is less likely to move, it is generally thought that rolling is less likely to occur, but the opposite is explained below.

  The secondary resonance mode frequency (corresponding to the rolling resonance frequency) of the vibration system is fr, the secondary resonance sharpness of the vibration system is Qr, the secondary resonance moment of inertia is I, the torsional stiffness of the edge at the secondary resonance frequency is Kr, When the torsion mechanical resistance of the edge at the secondary resonance frequency is Rr, the following equations 2 and 3 are obtained. Accordingly, as the secondary resonance inertia moment I increases, the secondary resonance frequency fr decreases and the secondary resonance sharpness Qr increases.

  If the sound pressure of the bass in the cabinet becomes uneven depending on the location, or if the thickness and material of the diaphragm and edges vary and the axial symmetry balance of the vibration system decreases, it will try to generate rolling resonance in the diaphragm. Excitation force works. However, if the secondary resonance sharpness Qr is low, the secondary resonance mode is braked and rolling does not occur. On the other hand, when the secondary resonance sharpness Qr is high, the secondary resonance mode grows while receiving the excitation force, and finally rolling occurs.

  As a result of the experiment, it was found that the growth rate of the secondary resonance mode is almost inversely proportional to the secondary resonance sharpness Qr, and that the growth is faster as the secondary resonance sharpness Qr is higher.

  In order to prevent the occurrence of rolling, it is necessary to lower the secondary resonance sharpness Qr, that is, to reduce the secondary resonance inertia moment I.

  As can be seen from FIGS. 9 and 1, if the position of the center of gravity of the vibration system is shifted from the position of the amplitude center, and if the mass distribution density of the diaphragm is uniform, it is far from the center axis AA ′ of the secondary resonance mode. The integral value of the small mass point P becomes larger and the secondary resonance inertia moment I becomes larger. Therefore, in the conventional passive radiator as shown in FIGS. 7, 8, and 11, the secondary resonance inertia moment I is large. For this reason, in the conventional passive radiator, since the secondary resonance sharpness Qr is increased, the occurrence of rolling cannot be prevented.

  In FIG. 9, if the integral value of the minute mass point P far from the center axis AA ′ of the secondary resonance mode is reduced, that is, the center of gravity position and the amplitude center position of the vibration system are aligned, and the mass of the outer peripheral portion of the diaphragm If the distribution density is reduced, the secondary resonance inertia moment I can be reduced. Since the first embodiment is configured so as to satisfy the above, the secondary resonance inertia moment I becomes small, and the occurrence of rolling can be prevented even during reproduction of high sound pressure bass.

  This time, I was able to find a parameter that represents the ease of rolling. It is a frequency ratio: fr / f0 between the lowest resonance frequency f0 of the vibration system of the passive radiator and the secondary resonance mode frequency (that is, rolling resonance frequency) fr.

  The minimum resonance frequency f0 is given by Equation 4, where m0 is the effective vibration mass of the vibration system and K0 is the amplitude direction stiffness of the edge. On the other hand, Qr = Kr / (2πfr × Rr) is derived from Equations 2 and 3 above, and it can be seen that the resonance sharpness Qr increases as the secondary resonance mode frequency fr decreases.

  If the edge is fixed to the roll shape, the amplitude direction stiffness K0 and the torsional stiffness Kr of the edge at the secondary resonance mode frequency are Kr <K0, but the ratio between them: Kr / K0 has a certain value α. . If the mechanical resistance of the edge in the amplitude direction is Rm, the torsional mechanical resistance of the edge at the secondary resonance mode vibration frequency is Rr where Rr <Rm, but the ratio between the two: Rr / Rm has a certain value β. Have. Therefore, Kr = αK0 and Rr = βRm are set.

Then, Qr = Kr / (2πfr × Rr) = αK0 / (2πfr × βRm). Since K0 = m0 (2πf0) ^{2 from} Equation 4, Qr = αm0 (2πf0) ² / (2πfr × βRm) = (2παf0m0 / βRm) ) / (Fr / f0). Since (2παf0m0 / βRm) is a constant value unless the mass and edge of the vibration system are changed, the secondary resonance sharpness Qr is inversely proportional to the frequency ratio fr / f0. Therefore, rolling is less likely to occur as the frequency ratio fr / f0 is larger.

  As a result of experiments and computer vibration analysis, f0 = 20 Hz, fr = 26 Hz, and fr / f0 = 1.3 in the conventional passive radiator shown in FIGS. In contrast, in the passive radiator of the first embodiment shown in FIG. 1, f0 = 20 Hz, fr = 34 Hz, and fr / f0 = 1.7.

  When the conventional passive radiator is used for a bass reproduction kelton speaker having an internal volume of 11 liters, a driver unit diameter of 16 cm, and a flat reproduction frequency band of 50 Hz to 100 Hz (-3 dB), the diaphragm amplitude is about 8 mm (peak). to peak) rolling occurred. However, in the passive radiator according to the first embodiment, even when the diaphragm amplitude reaches about 15 mm (peak to peak), which is the maximum amplitude limit, no rolling is generated, and extremely stable high sound pressure bass reproduction can be realized.

  This time, various diaphragm shapes were examined, and the frequency ratio: fr / f0 and the rolling condition were examined, which will be described below. Based on the passive radiator according to the first embodiment described with reference to FIG. 1, experiments and computer vibration analysis were performed while changing the mass distribution density of the inner peripheral portion of the diaphragm. That is, the edge is made of the same NBR rubber material as in the first embodiment, the same size and thickness, the same ABS material is used for the diaphragm material, and the thickness of the outer peripheral portion of the diaphragm is constant at 1.8 mm. The shape of the inner peripheral portion of the diaphragm was changed while the diaphragm mass was also kept constant at 82 g. In both cases, the center of gravity of the vibration system of the entire vibration system including the mass of the diaphragm and the effective vibration mass of the edge and the position of the amplitude center are substantially aligned.

  The dimensional specifications of the inner periphery of the diaphragm examined below are shown below. Specification 1: Diameter 126 mm, Thickness 4.8 mm Specification 2: Diameter 100 mm, Thickness 6.6 mm Specification 3: Diameter 84 mm, Thickness 8.6 mm Specification 4: Diameter 63 mm, Thickness 14 mm Specification 5 (corresponding to the first embodiment): Diameter 56 mm, thickness 17 mm Specification 6: Diameter 42 mm, thickness 29 mm Specification 7: Diameter 31 mm, thickness 52 mm

Further, as a reference specification 1, a diaphragm having a diameter of 168 mm and a uniform thickness of 3.5 mm, a passive radiator shown in FIG. 4 as a reference specification 2 and a passive radiator shown in FIG. In FIG. 4, the dimension of the inner peripheral portion 32a of the diaphragm is 21 mm in diameter,
Thickness (depth length) is 110 mm. The thickness of the diaphragm 32 is 1.8 mm. The passive radiator shown in FIG. 5 is provided with a thick portion 42b on the outer peripheral portion of the diaphragm, and its dimensions are an outer diameter of 168 mm, an inner diameter of 160 mm, and a thickness of 10.2 mm. The inner peripheral portion 42a has a diameter of 56 mm and a thickness of 10 mm. The thickness of the diaphragm 42 is 1.8 mm.

  The above specifications 1 to 7 and reference specifications 1 to 3 are all f0 = 20 Hz, fr and frequency ratio: fr / f0, and the rolling situation when used in the above-described bass reproduction kelton speaker is as follows. It became so.

  Reference specification 1 was fr = 26.8 Hz, fr / f0 = 1.33, and rolling occurred when the diaphragm amplitude was about 12 mm (peak to peak). Specification 1 had fr = 27.6 Hz and fr / f0 = 1.38, and the diaphragm generated rolling near the maximum amplitude limit of 15 mm (peak to peak). Specification 2 was fr = 28 Hz and fr / f0 = 1.4, and no rolling occurred. Specification 3 had fr = 32 Hz and fr / f0 = 1.6, and no rolling occurred. Specification 4 was fr = 33.4 Hz and fr / f0 = 1.67, and no rolling occurred. Specification 5 (corresponding to the first embodiment) is fr = 34 Hz and fr / f0 = 1.7, and no rolling occurred. Specification 6 had fr = 35 Hz and fr / f0 = 1.75, and no rolling occurred. Specification 7 had fr = 35 Hz and fr / f0 = 1.75, and no rolling occurred. Reference specification 2 was fr = 32 Hz and fr / f0 = 1.6, and no rolling occurred. Reference specification 3 was fr = 26.2 Hz, fr / f0 = 1.31, and rolling occurred when the diaphragm amplitude was about 10 mm (peak to peak).

  The above is the result of an experiment with a passive radiator with a caliber of 25 cm. Similar frequency ratio and rolling results were obtained. From the above results, it was found that if the frequency ratio fr / f0 is configured to be 1.4 or more, the occurrence of rolling can be prevented even during reproduction of high sound pressure and low sound.

  In addition, from the above results, when the mass distribution density of the inner peripheral portion of the diaphragm is increased, the frequency ratio: fr / f0 does not increase even if the thickness (depth length) of the inner peripheral portion is extremely increased. It turns out that it falls. This is because the moment of inertia in the longitudinal direction of the diaphragm becomes large. Further, even if the mass distribution density in the inner peripheral portion is increased, if the mass distribution density in the outer peripheral portion is increased, the frequency ratio fr / f0 is significantly reduced, and rolling occurs.

  Therefore, as described above, according to the configuration of the first embodiment, since the damper is not used, the stiffness of the support system can be reduced and the bass reproduction efficiency can be increased. The center of gravity G of the entire vibration system including the mass of the diaphragm 2 and the effective vibration mass of the edge 1 is provided in the vicinity of the amplitude center position 1b of the support portion with respect to the diaphragm of the edge, and the mass of the inner peripheral portion 2a of the diaphragm. Since the distribution density is increased, the secondary resonance moment of inertia of the vibration system is reduced, and stable high sound pressure bass reproduction can be achieved without causing rolling even when the diaphragm has a large amplitude. Further, since the number of parts is small, the cost can be reduced and the depth space can be reduced.

  Further, since the frequency ratio of the lowest resonance frequency f0 of the vibration system of the passive radiator to the secondary resonance mode frequency fr: fr / f0 is set to 1.4 or more, the secondary resonance moment of inertia of the vibration system is further increased. Since the secondary resonance sharpness can be reduced by reducing the size, it is possible to perform a more stable operation without rolling even at a large amplitude, and a very stable high sound pressure bass reproduction can be performed.

  By the way, in order to exert the above effect of the present invention, if the mass of the edge support portion with respect to the diaphragm is large, the secondary resonance inertia moment becomes large at the outer peripheral portion of the diaphragm. It is desirable not to be too large. If the frequency ratio fr / f0 is finally set to 1.4 or more, there is no problem.

  In the first embodiment, the shape of the diaphragm 2 is a flat shape, but the diaphragm shape can be a shallow cone type or dome type. With such a configuration, the natural resonance frequency of the diaphragm itself is increased, and it is easy to prevent so-called diaphragm noise.

  In the first embodiment, the material of the edge 1 is NBR rubber, but it goes without saying that it may be urethane foam, a cloth coated with rubber, or the like. If the physical properties of the edge in the thickness direction are not uniform, the amplitude center position of the support portion with respect to the diaphragm of the edge may be considered as the stress center position of the edge. For example, when one side surface of the edge is coated and only one side surface of the edge is hardened, the amplitude center position of the support portion with respect to the diaphragm of the edge is closer to the coating surface than the center of the edge thickness.

  In the first embodiment, the diaphragm inner peripheral part 2a is a thick disk to increase the mass distribution density of the inner peripheral part of the diaphragm. However, this has various shapes such as a ring shape and a quadrangle with a large thickness. It can be. Of course, the mass distribution density of the inner peripheral portion may be increased by making the cross-sectional shape of the diaphragm such that the thickness gradually decreases from the central portion to the outer peripheral portion.

In addition, it goes without saying that the present invention is not limited to the examples described above.
(Embodiment 2)
Next, a passive radiator according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view showing the configuration of the passive radiator according to the second embodiment of the present invention. The edge 11, the edge support portion 11a for the diaphragm, the effective vibration mass portion 11b of the edge movable portion, and the frame 13 are shown in the embodiment. Since it is the same as 1, description is abbreviate | omitted. Moreover, the thickness of the outer peripheral part of the diaphragm 12 is 1.8 mm, which is the same as that of the first embodiment, and the diaphragm is made of the same ABS resin and has the same mass of 82 g.

  Also in the second embodiment, the center-of-gravity position G of the entire vibration system including the mass of the diaphragm 12 and the effective vibration mass of the edge 11 is substantially aligned with the amplitude center position 11c of the edge support portion with respect to the diaphragm.

  In the second embodiment, the diaphragm 12 has a diameter of 170 mm, and the inner peripheral portion 12a, which is thick and has a high mass distribution density, has a diameter of 56 mm and a thickness of 16.7 mm. The inner peripheral part 12a is offset 3.8 mm forward with respect to the front-rear direction of the diaphragm 12, and the protrusion of the inner peripheral part 12a from the outer peripheral part of the diaphragm 12 to the front side is 11.2 mm, toward the rear side. The pop-up of 3.7 mm is 3.7 mm.

  With this configuration, the center-of-gravity position G of the entire vibration system including the mass of the diaphragm 12 and the effective vibration mass of the edge 11 is about 1 mm forward from the surface of the diaphragm 12 and 10 .mu.m from the surface of the inner peripheral portion 12a of the diaphragm. It is located about 2 mm behind. The amplitude center position 11 c of the edge support portion with respect to the diaphragm is about 0.75 mm forward from the surface of the diaphragm 12. That is, the center-of-gravity position G of the entire vibration system including the mass of the diaphragm 12 and the effective vibration mass of the edge 11 is only 0.25 mm away from the amplitude center position 11c of the edge support portion with respect to the diaphragm. Almost complete.

  In other words, in the second embodiment, the amplitude center position 11c of the edge support portion with respect to the diaphragm is ahead of the surface of the diaphragm 2, but the inner peripheral portion 12a of the diaphragm having a higher mass distribution density is placed forward. By offsetting, the center of gravity G of the entire vibration system including the mass of the diaphragm 12 and the effective vibration mass of the edge 11 is moved forward, and is substantially aligned with the amplitude center position 11c of the edge support portion with respect to the diaphragm. It is.

With the above configuration, the passive radiator of the second embodiment also has f0 = 20 Hz, fr = 34 Hz, and fr / f0 = 1.7. As in the first embodiment, no rolling occurs even when the diaphragm has a large amplitude, and extremely stable high sound pressure bass reproduction can be achieved.
(Embodiment 3)
Next, a passive radiator according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the configuration of the passive radiator according to the third embodiment of the present invention. The edge 21, the edge support portion 21a for the diaphragm, the effective vibration mass portion 21b of the edge movable portion, and the frame 23 are shown in the embodiment. Since it is the same as 1, description is abbreviate | omitted. Moreover, the thickness of the outer peripheral part of the diaphragm 12 is 1.8 mm, which is the same as that of the first embodiment, and the diaphragm is made of the same ABS resin and has the same mass of 82 g.

  Also in the third embodiment, the center of gravity G of the entire vibration system including the mass of the diaphragm 22 and the effective vibration mass of the edge 21 is aligned with the amplitude center position 21c of the edge support portion with respect to the diaphragm.

  In the third embodiment, the diaphragm 12 has a diameter of 168 mm, a shallow cone shape, and a thickness of 1.8 mm. The outer diameter of the cone-shaped portion is 158 mm, the inner diameter is 65 mm, and the depth of the cone shape is 7.6 mm. The inner peripheral portion 22a, which is thick and has a high mass distribution density, has a surface-side diameter of 61 mm, a bottom diameter of 65 mm, and a thickness of 13.6 mm.

  The inner peripheral portion 22a is positioned at the center without being offset with respect to the amplitude center position 21c of the edge support portion with respect to the diaphragm. The outer peripheral portion of the diaphragm 22 is a shallow cone, and is configured such that the same amount of diaphragm mass is distributed forward and backward as viewed from the amplitude center position 21c of the edge support portion with respect to the diaphragm. .

  With this configuration, the center of gravity G of the entire vibration system including the mass of the diaphragm 22 and the effective vibration mass of the edge 21 is located 6.8 mm behind the surface of the inner peripheral portion 22a of the diaphragm. The amplitude center position 21c of the edge support portion with respect to the diaphragm is also about 6.8 mm forward from the surface of the inner peripheral portion 22a of the diaphragm. That is, the center-of-gravity position G of the entire vibration system including the mass of the diaphragm 12 and the effective vibration mass of the edge 11 coincides with the amplitude center position 11c of the edge support portion with respect to the diaphragm.

With the above configuration, the passive radiator of the third embodiment has f0 = 20 Hz, fr = 33 Hz, and fr / f0 = 1.65. As in the first embodiment, no rolling occurs even when the diaphragm has a large amplitude, and extremely stable high sound pressure bass reproduction can be achieved. In the third embodiment, the diaphragm 22 is a shallow cone type, so that the natural resonance of the diaphragm is less likely to occur, and the reproduction band can be expanded to the high frequency side. In addition, the degree of freedom in appearance design can be increased.
(Embodiment 4)
Next, a passive radiator according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view showing the configuration of the passive radiator according to the fourth embodiment of the present invention. The edge 51, the edge support portion 51a for the diaphragm, the effective vibration mass portion 51b of the edge movable portion, and the frame 53 are shown in the embodiment. Since it is the same as 1, description is abbreviate | omitted.

  In the third embodiment, the diaphragm 52 has a diameter of 168 mm, a thickness of 1.8 mm, and is made of ABS resin. A weight 52a made of an iron plate is attached to the center of the inner periphery. Its diameter is 47 mm and its thickness is 3 mm. The total mass of the diaphragm 52 and the weight 52a is 82 g.

  With this configuration, the center of gravity G of the entire vibration system including the masses of the diaphragm 52 and the weight 52a and the effective vibration mass of the edge 51 is located about 2.1 mm behind the surface of the diaphragm 52. The amplitude center position 51 c of the edge support portion with respect to the diaphragm is about 2.55 mm forward from the surface of the diaphragm 52. That is, the center of gravity G of the entire vibration system including the mass of the diaphragm 12 and the effective vibration mass of the edge 11 is only 0.45 mm away from the amplitude center position 51c of the edge support portion with respect to the diaphragm, and both are close to each other. In position.

  With the above configuration, the passive radiator of the fourth embodiment has f0 = 20 Hz, fr = 36.6 Hz, and fr / f0 = 1.83. As in the first embodiment, no rolling occurs even when the diaphragm has a large amplitude, and extremely stable reproduction of high sound pressure and low sound can be achieved. In the fourth embodiment, since a material having a specific gravity larger than that of the diaphragm is disposed on the inner peripheral portion of the diaphragm, the space for increasing the mass distribution density of the inner peripheral portion of the diaphragm can be reduced. Further, the passive radiator can be further reduced in thickness.

  According to the passive radiator of the present invention, low sound reproduction efficiency can be increased, and stable high sound pressure low sound reproduction can be performed without causing rolling even when the diaphragm has a large amplitude. Further, the cost can be reduced and the depth space can be reduced. Therefore, it is useful not only for low-frequency sound reproduction speakers such as home theaters but also for various sound reproduction devices such as television speakers and vehicle-mounted speakers. As described above, the passive radiator of the present invention has extremely high practical value.

Sectional drawing which shows the structure of the passive radiator in Embodiment 1 of this invention Sectional drawing which shows the structure of the passive radiator in Embodiment 2 of this invention Sectional drawing which shows the structure of the passive radiator in Embodiment 3 of this invention Sectional drawing which shows the structure of the reference passive radiator of this invention Sectional drawing which shows the structure of the reference passive radiator of this invention Sectional drawing which shows the structure of the passive radiator in Embodiment 4 of this invention Sectional drawing which shows the structure of the conventional passive radiator Sectional drawing which shows the structure of the conventional passive radiator Explanatory drawing which shows the calculation concept of the secondary resonance moment of inertia of the vibration system of the passive radiator Explanatory drawing which shows the vibration mode of the diaphragm of the conventional passive radiator Sectional drawing which shows the structure of the conventional passive radiator Sectional drawing which shows the structure of the conventional passive radiator Sectional drawing showing the configuration of a bass reflex type speaker using a conventional passive radiator Sectional drawing which shows the structure of the Kelton type speaker by the conventional passive radiator

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Edge 1a Edge support part with respect to diaphragm 1b Effective vibration mass equivalent part of edge movable part 1c Amplitude center position of edge support part with respect to diaphragm 2 Vibration plate 2a Inner peripheral part of diaphragm 3 Frame G Center of gravity position of vibration system

Claims (3)

A passive radiator that supports the outer periphery of the diaphragm with only a roll-shaped edge without using a damper, and the center of gravity position of the entire vibration system including the mass of the diaphragm and the effective vibration mass of the edge The passive radiator is provided near the amplitude center position of the support portion with respect to the diaphragm, and the mass distribution density of the inner peripheral portion of the diaphragm is increased. 2. The passive radiator according to claim 1, wherein fr / f 0 ≧ 1.4 when the lowest resonance frequency of the vibration system is f 0 and the secondary resonance mode frequency is fr. 3. The passive radiator according to claim 1, wherein a material having a specific gravity greater than that of the material of the outer peripheral portion of the diaphragm is disposed on the inner peripheral portion of the diaphragm. 4.

Images