Speaker sound pressure inversion wave diaphragm

Abstract

Increasing the radiating surface area of ​​the wave diaphragm increases the reaction force as an air spring within the cabinet, raising the lowest resonant frequency. Therefore, the challenge is to improve the low-frequency radiation efficiency by increasing the radiating surface area without raising the lowest resonant frequency. [Solution] The crescent-shaped gap between the upper and lower parts, formed by the doubling of the wave diaphragm, is penetrated by an intermediate interlocking support plate, providing ventilation holes. This design effectively utilizes the force generated in the crescent-shaped gap, the Bernoulli force caused by the upward and downward velocity, in addition to the force that causes the wave diaphragm to move mechanically due to the sound pressure behind the speaker, to counteract the load acting as an air spring.

Description

Technical Field

[0001] The present invention relates to a passive radiator with a wavy diaphragm that has the characteristics of a sealed cabinet in a speaker system while improving the bass radiation efficiency and high-fidelity reproduction.

Background Art

[0002] A passive radiator in a general phase-inverting speaker tends to be effective for the way of producing bass at a small size.

[0003] In addition, the phase-inverting mechanism diaphragm of a speaker by the present inventor (see Patent Document 1) has the characteristics of a sealed cabinet by the immediate response operation of the radiation surface linked to the vibration that vertically fixes and supports and intermediate swing supports a wavy paper diaphragm to a cabinet, and achieves simultaneous inversion independent of periodic elements, and also copes with enlargement.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When setting the phase-inverting mechanism diaphragm of a speaker (Patent Document 1) in a cabinet, since the enlargement of the radiation surface is a factor that raises the lowest resonance frequency, it is an issue to enable the enlargement of the radiation surface without raising the lowest resonance frequency, and to improve the bass radiation efficiency and the sound quality with high sensitivity and clarity.

Means for Solving the Problems

[0006] Conventionally (Patent Document 1), the mechanism used a wave diaphragm with fixed upper and lower supports and an intermediate swing support as the passive surface, and branched the radiating surface to the lower side to create a double structure. However, this invention enhances the effectiveness of the pressure action and Bernoulli force caused by the flow velocity generated in the crescent-shaped gap, and also provides a means to improve low-frequency characteristics by assisting (supporting) vibration through the expansion of the radiating surface.

[0007] To enhance such assistive force, in a wave diaphragm with a double upper section, an intermediate connecting plate with ventilation holes maintains an intermediate gap, forming an upper and lower crescent shape that penetrates through the middle, thereby further enhancing the assistive force through the upper gap.

[0008] In such an action, the negative and positive pressure changes behind the speaker cone during its forward and backward movement cause the wave diaphragm to move in the same direction as the cone. The upper gap expands with forward movement (negative pressure) and contracts with backward movement (positive pressure), while the lower gap moves in the opposite direction. As a result, the intermediate flow velocity, which is moving in volume vertically, synchronizes with the period when the air spring force on the rear surface of the diaphragm is at its maximum, raising the lowest resonant frequency. The intermediate flow velocity (inertia) and the Bernoulli force act as a counterforce to this.

[0009] In the swing support and the interlocking of the lower radiating surface and its overlapping rear surface via a connecting plate, gap expansion causes the rear concave surface to extend and the front convex surface to extend, resulting in a retraction motion. Conversely, gap contraction causes the radiating surface to protrude, which coincides with the speaker's movement and the wave diaphragm's movement direction.

[0010] Based on the above, even with an enlarged radiating surface, the force of the air spring inside the cabinet counteracts the rise in the lowest resonant frequency, thus suppressing the increase in volume below the lowest resonant frequency. [Effects of the Invention]

[0011] By doubling the wave diaphragm, the pressure action and flow velocity kinetic force caused by the alternating expansion and contraction of the upper and lower gaps assist the mechanism's operation. This also counteracts the reaction force of the air spring within the cabinet even with an enlarged radiating surface, making it possible to improve low-frequency radiation efficiency without increasing the lowest resonant frequency.

[0012] Furthermore, the acoustic output from the rear of the speaker precedes the movement of the wave diaphragm, and the speed at which sound is emitted from the radiating surface is faster than the speed of sound in air. As a result, the acoustic output from the radiating surface precedes the speed at which reflected waves and standing waves are generated inside the cabinet. Therefore, even with an enlarged radiating surface, the usefulness of sound-absorbing materials can be avoided, and the subtle nuances of the original sound can be reproduced with high sensitivity. [Brief explanation of the drawing]

[0013] [Figure 1] Front partial cross-sectional view A and side cross-sectional view B show embodiments and examples. [Figure 2] Impedance characteristics C and sound pressure frequency characteristics D in the example [Modes for carrying out the invention]

[0014] In both small and large speaker systems, a common embodiment is shown in Figure 1, where the four curves, consisting of double wave diaphragms 3 and 4, are set to a central angle of 45° from the perspective of vibration damping, and the vertical lengths are standardized in an alternating 1:1 relationship from the perspective of suppressing higher-order vibrations, thereby making it easier to achieve a sound quality without distortion.

[0015] By setting the chord length of the passive surface 4r behind the radiating surface 4 to be longer than the curved chord length of the radiating surface 4, the crescent-shaped displacement force is increased. Furthermore, the setting of the intermediate gap G is also related to the displacement force and affects the volume below the lowest resonant frequency.

[0016] Even ordinary kraft paper or gray recycled paper can function well as a material for wave diaphragms if the grain of the paper fibers is used vertically. In the lateral direction of the grain, if the width is large (200 mm or more), there is a risk of deformation due to expansion in humid conditions, so vertical slit grooves 11 for stress absorption are provided.

[0017] The gap 12 between the cabinet side and the diaphragm is set to be about 0.4 mm in low humidity and 0.25 mm in high humidity. However, since the cabinet wood is also affected by humidity, it is polished until the t0.25 mm sandpaper loosens, resulting in an even gap. There is no specific change in the characteristics and sound quality due to the gap being below this value.

[0018] The joint of the upper and lower fixed support parts 5 and the middle swing support part uses the steel material 9 as an anti-vibration reinforcement material because vibration concentrates linearly.

[0019] The front and rear swing support 6 also has the grain direction in the front and rear direction, and the bending part 8 of the joint surface is the main movable part, ensuring a swing operation that is difficult to bend. There is no fiber fatigue in the bending part.

[0020] The cardboard flat part of the intermediate connecting plate 7 with ventilation holes also requires reinforcement that is difficult to bend. However, in the vicinity of the joint (1 - 2 mm), a joint that is not hardened with reinforcement or adhesive is preferred for a somewhat flexible movement.

[0021] By providing small holes 14 and 13 at the upper and lower ends of the diaphragm 3, it is effective for characteristic and sound quality adjustment.

[0022] For the vibrations in the same front and rear direction on the upper and lower rear surfaces of the wave diaphragm, the reflected waves in the vertical direction of the cabinet are likely to give loads with different phases, which is a factor in the generation of higher-order waves. Therefore, a partition plate 10 is provided in the middle. The determined position is set in a state where the change in the peak f (lowest resonance frequency) of the impedance characteristic shown in Figure 2, C is small.

Example

[0023] An example of a wave diaphragm for obtaining good sound quality in a 30 cm diameter full-range speaker system will be described based on Figure 1. The wave diaphragm set to the internal dimensions of the cabinet (H760×W420×D370) used gray recycled paper with a paper thickness of 0.64 mm. The lowest resonant frequency of the speaker used varies depending on the temperature, ranging from 80Hz to 95Hz (nominal value 90Hz).

[0024] The intermediate connecting plate 7 (H60 x W419 x t0.64) and the front and rear swing supports 6 were used to set the maximum intermediate gap G to 15 mm.

[0025] To compensate for the reduced strength caused by the numerous ventilation holes covering approximately 30% of the area of ​​the intermediate connecting plate 7, a t0.65mm layer was overlapped and bonded.

[0026] The swing support 6 is made of kraft paper with a thickness of 0.35 mm, and the swing section 6 is 20 mm in length.

[0027] Small holes 14 consist of 4 x φ10mm holes, and small holes 13 consist of 10 x φ10mm holes. While half of these is the minimum required, doubling them does not worsen the sound quality and remains within an effective range for sound adjustment.

[0028] To prevent deformation of the large-area diaphragm due to high humidity, a vertical slit groove (3 mm wide) 11 is provided, which is a flexible groove (0.1 mm thick paper tape, front and back), thus avoiding expansion deformation due to high humidity.

[0029] In the sound pressure frequency response shown in Figure 2, D, for the sound pressure a in front of the speaker below 50Hz, the sound pressure b in front of the radiating surface also shows a smooth increase in bass level. The impedance characteristic C requires the characteristics of a sealed cabinet even with an enlarged radiating surface, enabling highly faithful bass reproduction. [Explanation of symbols]

[0030] 1 Cabinet 2 speakers 3-Wave Diaphragm 4. Wave diaphragm (radiating surface) 4r Rear radiation surface 5 Upper and lower fixed support parts 6. Swing support, swing section 7. Intermediate connecting plate (with numerous ventilation holes) 8. Bending points on the swing support joint surface 9. Reinforcement steel 10 partition plates 12 Gap 13 Ventilation holes 14 Ventilation holes 15 Reinforcement material G intermediate gap

Claims

1. A speaker sound pressure inversion wave diaphragm is formed by a double woof diaphragm 3, 4 held by upper and lower support parts 5 and intermediate front and rear swing supports 6, and an intermediate connecting plate 7 with ventilation holes, which penetrates the upper and lower crescent-shaped gap.

2. The sound pressure inversion wave diaphragm for a speaker according to claim 1, wherein small holes 13 and 14 for sound quality adjustment are provided at the upper and lower ends of the wave diaphragm 3 on the speaker side.

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