JPH11331976A - Speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve tones of a piezoelectric speaker by placing an acoustic diaphragm in the front area of a baffle and attaching a piezoelectric vibrator to the acoustic diaphragm. SOLUTION: A piezoelectric speaker 40 contains an acoustic diaphragm 42 and a piezoelectric vibrator 44. The diaphragm 42 consists of a thin plate- shaped circular member having a diameter smaller than that of a woofer cone 24, and the vibrator 44 includes the piezoelectric element layers or moving layers which are formed almost on the entire surfaces of both sides of a circular metallic plate. A pair of rubber dampers 46 are attached to one of both sides of the vibrator 44 which is attached onto the back of the diaphragm 42 via a vibration transmission member 48 made of a columnar or disk-shaped member. The speaker 40 of such a constitution is attached at a joint part set between the cone 24 and an edge 26 via plural thin plate attachment members 50, and plural arc-shaped sound transmission holes are formed between the diaphragm 42 and the cone 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a speaker.

[0002]

2. Description of the Related Art Hitherto, it has been known to use a piezoelectric vibrating plate, for example, a bimorph, as a sound source of an acoustic device such as a speaker. Has been devised and put into practical use.

[0003]

However, it is known that a piezoelectric vibrating plate is particularly excellent in high sound characteristics, but that resonance occurs within the piezoelectric vibrating plate at a specific frequency and that it has a peak frequency. It is considered that this peak frequency deteriorates the so-called "tone color" of the speaker using the piezoelectric vibrator (hereinafter, piezoelectric speaker).

[0004] In addition, a piezoelectric speaker is described as "cold" or "metallic" when heard by a human ear, even if the generated sound is flat and good in sound pressure characteristics. It is said that the timbre characteristics are not good.

An object of the present invention is to solve such problems of the prior art, and an object of the present invention is to improve the tone of a speaker provided with a piezoelectric speaker.

[0006]

According to the present invention, there is provided a loudspeaker in which an acoustic diaphragm is provided in a front region of a baffle, and a piezoelectric vibrator is attached to the acoustic diaphragm.

Further, the present invention is characterized in that a bottomed recess is formed in the baffle, an acoustic diaphragm is disposed in a region in front of the recess, and a piezoelectric vibrator is attached to the acoustic diaphragm. Of the speaker.

According to another feature of the present invention, a dynamic speaker is mounted on a baffle, an acoustic diaphragm is disposed in a front region of the dynamic speaker, and a piezoelectric vibrator is mounted on the acoustic diaphragm. A speaker is provided.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, referring to FIGS. 1 to 4, a speaker 10 according to a first embodiment of the present invention includes a front surface or a baffle 12 a of an enclosure or housing 12.
The woofer 20 includes a woofer 20 as a low-frequency sound reproduction speaker attached to the woofer 20, and a high-frequency sound reproduction piezoelectric speaker 40 disposed in a front region of the woofer 20. The woofer 20 includes a frame 22 fixed to the front surface 12a of the housing 12 by bolts 22a, and a woofer cone 24 is formed on the frame 22 via a semicircular arc-shaped edge 26 made of a flexible material such as foamed urethane. Are linked.
The woofer cone 24 is driven by the interaction between the fluctuating magnetic field formed by the voice coil 30 disposed on the back surface thereof and the magnetic field formed by the permanent magnet 28, the pole 28a, and the yoke 28. That is, the woofer 20 constitutes a dynamic speaker. In FIG. 1, the enclosure or case 12 is a bus-flex type case having a duct 12b on a front surface 12a, but various types such as an open type, a closed type, and a backload type can be used.

The piezoelectric speaker 40 includes a circular acoustic diaphragm 42 and a piezoelectric vibrator 44 for vibrating and driving the acoustic diaphragm 42. The acoustic diaphragm 42 is a thin circular member having a diameter smaller than the diameter of the woofer cone 24. The acoustic diaphragm 42 is formed of a composite material such as a fiber-reinforced plastic in which carbon fibers are attached to both sides of a honeycomb body made of aramid fibers. Can be. The piezoelectric vibrator 44 is formed by providing a piezoelectric element layer or a bimorph layer 44b over substantially the entire surface of both sides of a circular metal plate 44a. The piezoelectric vibrator 44 is attached to the back surface of the acoustic diaphragm 42 via a vibration transmitting member 48 formed of a columnar or disk-shaped member. Preferably, the piezoelectric vibrator 4
4. The vibration transmitting member 48 and the acoustic diaphragm 42 are relatively positioned so that their respective centers match.

A pair of dampers 46 made of a rubber material are attached to one side of the piezoelectric vibrating body 44. Although not shown in detail, the damper 46 has a trapezoidal or substantially triangular shape, and is preferably disposed symmetrically with respect to the center of the piezoelectric vibrator 44. By providing the damper 46 in this manner, the exciting force of the piezoelectric vibrating body 44 is efficiently transmitted to the acoustic diaphragm 42 via the vibration transmitting member 48.

The piezoelectric speaker 40 constructed as described above
Are attached to the joint between the woofer cone 24 and the edge 26 via a plurality of thin plate-like attachment members 50. Since the acoustic diaphragm 42 has a smaller diameter than the woofer cone 24, the acoustic diaphragm 42 and the woofer cone 24
A plurality of arc-shaped sound emission holes 52 separated by the mounting member 50 are formed therebetween. However, the number of the attachment members 50 is not limited to four as shown in the figure, and a larger number of attachment members, for example, six or eight or more attachment members may be provided. Furthermore, not an even number but an odd number of attachment members such as 5, 7, 9 may be provided.

Next, the operation of the speaker 10 according to the present embodiment will be described. When an audio signal is applied from the amplifier 60 to the voice coil 30 and the piezoelectric vibrating body 44 of the woofer 20, each of the woofer cone 24 and the piezoelectric starting body 44 vibrates in response to the audio signal. At this time, the woofer 20 which is a dynamic speaker is
, An L circuit is formed with respect to the amplifier 60, and the piezoelectric speaker 40 is formed with a C circuit with respect to the amplifier 60 since the piezoelectric speaker 40 has a piezoelectric element. Therefore, a relatively low frequency signal of the audio signal is mainly supplied to the woofer 20, and a high frequency signal is mainly supplied to the piezoelectric speaker 40, and the audio signal is naturally transmitted to the woofer 20 without providing a bridge circuit or the like. It is distributed to the piezoelectric speaker 40. According to the experiment, a crossover point is formed at about 2000 Hz.

The low frequency vibration from the woofer cone 24 is propagated to the air between the woofer cone 24 and the acoustic diaphragm 42 and is directly emitted from the sound emission hole 52 to the surrounding air, and is also transmitted through the mounting member 50. The sound is transmitted from the peripheral area of the acoustic vibrator 42 toward the center thereof, and is transmitted from the acoustic diaphragm 42 to the surrounding air. At this time, the sound wave transmitted from the woofer cone 24 to the acoustic diaphragm 42 and emitted again from the acoustic diaphragm 42 is further emitted from the front portion of the acoustic diaphragm 42 and from the back surface of the acoustic diaphragm 42. And the part to be done. Vibration from the front of the acoustic diaphragm 42 is propagated to the surrounding air. Acoustic diaphragm 4
Vibration from the back of 2 is propagated to the air between the acoustic diaphragm 42 and the woofer cone 24 and from the sound output holes 52 to the surrounding air.

The vibration from the piezoelectric vibrating body 44 is transmitted to the center of the acoustic diaphragm 42 via a vibration transmitting member 48, and propagates to the entire acoustic diaphragm 42 and to the surrounding air. More specifically, as described above with respect to the vibration from the woofer 20, the sound wave radiated from the front surface of the acoustic diaphragm 42 is directly propagated to the surrounding air, and the sound wave radiated from the rear surface of the acoustic diaphragm 42 is The light is transmitted to the air between the diaphragm 42 and the woofer cone 24, is reflected by the woofer cone 24, and is emitted forward from the sound output hole 52.

As in the present embodiment, the piezoelectric speaker 40 is combined with the front area of the woofer 20, that is, the woofer 20 as a bass dynamic speaker is attached to the housing 12, and the acoustic vibration is provided in the front area of the woofer 20. By arranging the plate 42 and attaching the piezoelectric vibrating body 44 to the acoustic diaphragm 42 and attaching the acoustic diaphragm 42 to the edge portion of the woofer 20 via the attaching member 50, the following phenomenon occurs. Can be considered. (1) Sound waves emitted from the back of the acoustic diaphragm 42 of the piezoelectric speaker 40 are reflected by the woofer cone 24 and propagate forward. Therefore, the sound pressure mainly in the high-tone region increases. (2) Vibration from the woofer 20 is directly propagated from the sound output hole 52 to the surrounding air, from the acoustic diaphragm 42 to the air in front, and from the acoustic diaphragm 42 to the woofer from the acoustic diaphragm 42. Sound transmission hole 5 propagated to cone 24
2 and a portion propagating forward, and each is transmitted to the surrounding air with a slight time difference. Similarly, the vibration from the piezoelectric speaker 40 is also divided into a portion which is propagated from the acoustic diaphragm 42 to the woofer cone 24 from the acoustic diaphragm 42 and which propagates forward from the sound output hole 52, and each of them has a slight time difference or phase difference. To be propagated to the surrounding air. Therefore, the sound reproduced from the speaker 10 according to the present embodiment includes components having a time difference slightly in the entire region from the bass region to the treble region, and the reproduced sound has a so-called “deepness” or “warmth”. Expressions relating to the timbre are given. (3) The periphery of the acoustic diaphragm 42 of the piezoelectric speaker 40 is supported by a plurality of attachment members 50, and the peripheral portion thereof can be said to be substantially free-end supported. for that reason,
The reflection of the vibration transmitted from the piezoelectric diaphragm 44 to the center of the acoustic diaphragm 42 and propagated in the outer peripheral direction of the acoustic diaphragm 42 does not occur at the peripheral edge of the acoustic diaphragm 42. Conventionally, it has been considered that the reflected wave of the vibration at the peripheral portion of the acoustic diaphragm 42 has a bad influence on the vibration mode of the acoustic diaphragm 42, but in the present embodiment, this is removed. In the embodiment shown in FIG. 4, in order to enhance the effect of the reflection removal,
The peripheral portion of the acoustic diaphragm 42 is formed so as to be tapered and thin. (4) According to the present embodiment, as shown in FIG. 5, in the acoustic diaphragm 42, the high frequency component from the piezoelectric diaphragm 44 propagates from the center of the acoustic diaphragm 42 toward the outer periphery, and the low frequency component Will propagate from the woofer 20 toward the center of the acoustic diaphragm 20 via the mounting member 50. These
It can be considered that the symmetrical superposition of the high frequency component and the low frequency component in the facing direction forms a favorable vibration mode in the acoustic diaphragm 20.

Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, four mounting members 50 are provided around the acoustic diaphragm 42.
As shown in FIG. 7, the diameter of the acoustic diaphragm 62 is equal to the outer diameter of the woofer cone 24 or the inner diameter of the edge 26, and a plurality of slots 64 corresponding to sound output holes are arranged along the peripheral edge of the acoustic diaphragm 62. May be.

Further, in the first embodiment, the piezoelectric speaker 40 is disposed substantially in the plane formed by the edge 26 of the woofer 20, but the present invention is not limited to this. For example, in the third embodiment of the present invention shown in FIG.
The piezoelectric speaker 70 may be disposed in a front area separated from the woofer 20 by a plurality of mounting members 72 protruding forward from the front surface 12a of the housing. Also in this embodiment, the phenomena (1) to (4) described above are considered to occur, and the same operation and effect as those of the first embodiment can be obtained. However, in this case, the low frequency component from the woofer 20 is not transmitted directly from the woofer 20 as in the first embodiment, but is
The signal is transmitted to the acoustic diaphragm 20 via 2a.

Further, in the above-described embodiment, the piezoelectric speaker is mounted on the front surface of the woofer.
As shown in FIG. 9, a piezoelectric speaker may be provided in a region in front of a recess formed on the front surface of the housing. The loudspeaker 80 according to the fourth embodiment of the present invention shown in FIGS. 8 and 9 has the woofer 20 attached to the front surface 82a of the housing 82,
A bottomed recess 84 is formed in the front surface 82a. A piezoelectric speaker 90 is attached to the housing 82 in a region in front of the recess 84 via a plurality of, in this embodiment, four attachment members 92.

It is considered that the above-described phenomena (1) to (4) have occurred in such a configuration, and the same operation and effect as those of the first embodiment can be obtained. That is, the woofer 20 in the first embodiment also serves as the bottomed concave portion 84 in the fourth embodiment. 8 and 9
In the configuration shown in FIG. 7, low-frequency vibration from the woofer 20 is also transmitted to the piezoelectric speaker 9 via the housing 82 and the mounting member 92.
0 is transmitted to the peripheral portion of the acoustic diaphragm 94 and the acoustic diaphragm 9
The light is propagated toward the center from the peripheral portion of No. 4. However, in the embodiment shown in FIGS. 8 and 9, the vibration directly propagating from the woofer 20 to the air does not propagate with a time difference or a phase difference as in the first embodiment. It can be considered that the embodiment can obtain a better sound effect.

Furthermore, the piezoelectric speaker is simply disposed in the front region of the recess provided in the woofer or the housing without mounting the piezoelectric speaker to the woofer or the housing via the mounting members 50, 72, 92. By doing so, at least the effect (1) described above can be obtained. Further, even if the bottomed recess 84 is not particularly provided as in the fourth embodiment, the piezoelectric speaker may be provided on the front surface of the housing or on the front region of the baffle. The effect of can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of a speaker according to a first embodiment.

FIG. 2 is an overall front view of the speaker of FIG.

FIG. 3 is an enlarged plan view of a portion of a piezoelectric speaker of the speaker of FIG. 1;

FIG. 4 is a sectional view of a piezoelectric speaker.

FIG. 5 is a diagram schematically illustrating the propagation of vibration on an acoustic diaphragm of a piezoelectric speaker to a enemy.

FIG. 6 is a plan view of an acoustic diaphragm according to a second embodiment.

FIG. 7 is a partially enlarged cross-sectional view of a speaker according to a third embodiment.

FIG. 8 is a front view of a speaker according to a fourth embodiment.

FIG. 9 is a sectional view of the speaker of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Speaker 12 ... Case or enclosure 12a ... Front or baffle of case 20 ... Woofer 40 ... Piezoelectric speaker 42 ... Acoustic diaphragm 44 ... Piezoelectric diaphragm 84 ... Bottom-shaped recess formed in the front of case.

Claims (3)

[Claims] 1. A loudspeaker wherein an acoustic diaphragm is disposed in a front region of a baffle, and a piezoelectric vibrator is attached to the acoustic diaphragm. 2. A loudspeaker wherein a bottomed recess is formed in a baffle, an acoustic diaphragm is disposed in a front region of the recess, and a piezoelectric vibrator is attached to the acoustic diaphragm. 3. A loudspeaker wherein a dynamic speaker is mounted on a baffle, an acoustic diaphragm is disposed in a front region of the dynamic speaker, and a piezoelectric vibrator is mounted on the acoustic diaphragm.