JPH0371797A - Speaker unit - Google Patents

Abstract

PURPOSE:To improve acoustic characteristic by forming an equalizer with a porous structure having a porous material whose specific gravity is varied continuously in the layer broadwise direction or in the facial direction. CONSTITUTION:An equalizer 8 is made of a porous structure 9 having a porous material whose specific gravity is varied continuously in the layer broadwise direction or in the facial direction. The porous structure 9 consists of a solid layer having a large specific gravity and comprises an impermeable melting layer 10 formed by melting a thermoplastic resin granular material and a normally permeable material 11 whose porosity is varied continuously in the broadwise direction. Thus, since the sound absorbing characteristic of the equalizer 8 is large and no reflection sound or resonance sound is caused therefrom and the equalizer 8 is formed into a complicated shape with high accuracy, the uniform desired characteristic is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the performance of a speaker unit.

[Prior Art] As a conventional example similar to the above claim 4, there is an equalizer (5) in FIG. 2 in which the metal acid such as aluminum is formed of a synthetic resin such as ABS. As a conventional example similar to the above, as shown in FIG. 3, the equalizer (5) is made of a synthetic resin such as PBT or a fiber system such as felt or glass wool.

As a conventional example similar to the above-mentioned claim 6, there is one in which the equalizer (5) is made of foamed urethane or the like, as shown in FIG.

As a conventional example similar to claim 7, as shown in FIG. 5, there is an equalizer (5) made of metal such as aluminum, felt, fibers such as glass wool, etc. In the system shown in FIG. 2, the reproduction frequency characteristics of the speaker are improved by changing the shape of the equalizer and the distance between the diaphragm and the equalizer, and the effect shown in FIG. 6 is obtained. In the figure, the solid line shows the characteristics when an equalizer is installed, and the broken line shows the characteristics when no equalizer is installed.

In the system shown in FIG. 4, the shape of the equalizer improves the influence of standing waves inside the voice coil bobbin and the influence of the cone concave effect, resulting in the effects shown in FIG. 7.

In addition, the systems shown in Figures 3 and 5 prevent disturbance of the characteristics due to standing waves in the upper part of the pole piece or the cavity inside the magnetic circuit, and prevent reflection of sound from the pole piece, magnet, etc. Obtain the same effect as above.

[Problems to be Solved by the Invention] The equalizer in the speaker unit has a greater effect than the conventional one, but the one shown in Fig. 2 does not.

Since it is located just in front of the sound emitting surface of the diaphragm, there is a problem in that unnecessary sounds such as reflections and resonance from the equalizer are added to the sound reproduced by the speaker unit, degrading the sound quality performance.

In the case shown in FIGS. 3 and 4, dimensional accuracy can be easily achieved using a resin-based material, but there are problems such as reflected sound and resonance sound as described above. When fiber-based materials are used, sound absorption performance is effective, but when using glass wool or felt,
There was a problem in obtaining a uniform effect because the shape and installation accuracy were inconsistent. Furthermore, in the case of urethane-based materials, there were problems with weather resistance when used in exposed areas.

In the case shown in Fig. 5, for example, if an aluminum ring is used, shape accuracy can be obtained, but the problem of reflected sound and resonance sound as mentioned above remains, and if fiber-based materials are used, the shape and installation Problems remained in obtaining uniformity. As described above, conventional equalizers have a problem in that it is difficult to obtain an equalizer that has an optimal shape and good sound absorption characteristics.

This invention was made to solve the above-mentioned problems, and by having a porous layer with varying specific gravity, it has a porous layer that has good sound absorption properties and can be used with complex materials. The purpose is to improve the performance of speaker units by using a structure to create an equalizer.

[Means for Solving the Problems] A porous structure forming an equalizer according to the present invention includes:
It has a porous layer in which the specific gravity is continuously changed in the thickness direction or in the plane direction of the layer.

Further, in the porous structure forming the equalizer according to the present invention, the granular material constituting the porous layer with varying specific gravity is made into a sphere or an ellipsoid, and furthermore, the major axis is 0.2 ~3.0 (mm).

Further, the porous structure forming the equalizer according to the present invention is a layered structure including a porous layer having a different specific gravity and a solid layer having a smaller porosity than the porous layer, and further is one in which the solid layer is fused to the porous layer in the fusion layer, and furthermore.

This fusion layer is made non-air permeable.

[Function] In the present invention, the porous layer, which forms the equalizer and has a changed specific gravity, that is, porosity, improves various properties. For example, the degree of change in porosity may be changed depending on the thickness or the like to control the frequency characteristics of the sound absorption characteristics.

Furthermore, when a spherical material is used, the layer condition during molding becomes stable. Note that there is a granular shape that optimizes the sound absorption characteristics based on the penetration depth of sound waves and the wall-to-wall viscosity effect of acoustic energy.

In addition, the porous layer and the solid layer or skin layer are fused together, and especially when the non-breathable solid layer is layered, the sound insulation properties are improved.
Furthermore, the fused skin layer minimizes the acoustic impedance of the porous body at low frequencies, improving sound absorption characteristics in the low frequency range.

A multilayer material with arbitrary layers exhibits functions synergistically and also has an added function as a structure.

Furthermore, if a granular material that contributes to sound insulation, shielding, or strength improvement is included in addition to the resin particles, this function is added.

By using an equalizer formed of a porous structure having a porous layer as described above, the characteristics of the speaker can be improved due to its shape.

Furthermore, sound absorption characteristics can be improved.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 8 is a sectional view showing an example in which a porous structure is adopted as an equalizer in contrast to the conventional example shown in FIG. 2. In the same figure, (5) is an equalizer, (6) is a diaphragm, and (7)
is the voice coil, and (8) is the pole piece. - The equalizer is located in front of the diaphragm that is the sound source, with the porous 7ft (3) on the diaphragm side and the fusion layer (2) on the outside.

With the above configuration, the shape of the equalizer improves the reproduction frequency characteristics of the speaker, and prevents the sound radiated from the diaphragm from reflecting and resonating between the diaphragm and the equalizer, thereby suppressing the generation of unnecessary sound.

FIGS. 9 and 10 are cross-sectional views showing an example in which a porous structure is adopted as an equalizer in contrast to the conventional examples shown in FIGS. 3 and 4, respectively. The equalizer is attached to the top of the pole piece, and has a porous layer on the diaphragm side and the side facing the voice coil. With this configuration, the shape of the equalizer prevents disturbances in characteristics due to standing waves in the space above the pole piece and the cone concave effect, and its sound-absorbing effect suppresses unnecessary sound from inside the speaker.

FIG. 11 is a sectional view showing an example in which a porous structure is used as an equalizer in contrast to the conventional example shown in FIG. The equalizer is attached to the inner circumference of the magnet. With this configuration, the internal volume of the magnetic circuit can be adjusted arbitrarily, and the frequency characteristics of the speaker can be controlled, and the sound absorption effect suppresses the generation of unnecessary sounds from inside the speaker.

FIGS. 1A and 1B are diagrams each schematically showing a cross section taken in the thickness direction of the multilayer material (1) constituting the equalizer of the present invention. (2) is a layer with a high specific gravity, such as a fusion layer, and may be either air permeable or non-air permeable. (3
) is a porous layer with low specific gravity, usually breathable, and the porosity changes continuously in the thickness direction. (4) is a skin layer whose specific gravity is usually between layer (2) and layer (3),
For example, a fused layer with a thickness of 100 microns or less. The multilayer material (1) is made up of an integrated fused layer (2) and porous M (3). Similarly, the fusion layer (2), porous layer (3), and skin layer (4) are integrated.

When using the multilayer material (1) as a sound absorbing material, the porous layer (3) is placed facing the sound source side to absorb and attenuate sound energy and prevent the sound waves from passing through the fusion layer (2). .

The raw material for the porous structure forming the equalizer according to the present invention may be a thermoplastic resin or a thermosetting resin, and can be selected depending on the intended use.

Note that typical examples of the granular material raw material for the thermoplastic resin include PP (polypropylene), AS (acrylic styrene), and styrene. Also, when methyl ethyl ketone (MEK) cellulose, varnish, or acetone is sprayed or mixed as a binder into the thermoplastic resin granular material, the adhesion of each granular material in the multilayer material increases and the mechanical strength improves. , the handling is improved.

Examples of granular raw materials for thermosetting resins include phenol, PBT (polybutylene terephthalate), and PET.
Particles of a granular material such as polyethylene terephthalate (polyethylene terephthalate) with a diameter of about 0.2 to 3 are mixed with a binder such as cellulose, varnish, various adhesives, etc., and heated and pressed.

FIG. 12 is a diagram showing an example of the porosity (specific gravity) distribution in the thickness direction of a porous structure with a thickness of 10 mm (mostly the entire area is a porous layer).

In the figure, curves A and C exhibit characteristics in which the porosity is approximately -like in the thickness direction, and is about 25(1) and about 10(%), respectively. Curve B has a porosity distribution in the thickness direction, and 1
It changes continuously in the range of 0 to 25 (%).

When using this type of porous structure as a sound absorbing material, its sound absorbing properties become an issue. FIG. 13 shows the results of measuring the normal incidence sound absorption coefficients of samples having the three types of porosity distributions shown in FIG. In addition, in the sample having a porosity distribution in the thickness direction of curve B, the side with a porosity of 10 (%) was set as the surface on which the sound waves were incident.

As can be seen from the figure, it was confirmed that the sample with porosity distribution (curve B) had the best sound absorption characteristics.6 Next, by changing the porosity (specific gravity) in the plane direction of the porous body, The effect of improving sound absorption characteristics will be explained. Figure 14 shows
The change in porosity of three types of samples is shown, and the curve A→B→
The porosity decreases in the order of C. The sound absorption characteristics at this time are shown in FIG. From this figure, especially if the porosity on the sound wave incident surface side is made smaller (corresponding to curve C), the sound absorption coefficient in the low frequency range is improved. Therefore, by providing a distribution in the porosity in the planar direction of the porous body, good sound absorption characteristics can be obtained in a wide frequency band.

It has been confirmed that there is a range in the shape and major axis of the granular material that has better properties as a porous body, especially in terms of sound absorption properties. This will be explained below.

FIG. 16 is a diagram showing the variation in the characteristics of the normal incidence sound absorption coefficient when the shape of the granular material is changed (the variation in the characteristics for five samples). Curve A has a granular material with a diameter of 0.8
(+nn+), a cylindrical one with a length of 1 (mm), and curve B a spherical one with a diameter of 1 (au++). In each case, the thickness of the porous layer was 10 (mm), and the frequency at which the sound absorption coefficient was measured was 2 KHz. From the same figure, it can be seen that the one-spherical one (curve B) has little difference in characteristics due to differences in samples and is extremely stable. The reason for this is that in the case of a spherical shape, there is only one point of contact between the granular materials, so that the molding, especially the layer state of the granular materials, becomes stable and uniform.

In this way, it is better to use a spherical shape (sphere or ellipsoid), especially when stability of properties is required between samples.
A more preferable porous structure can be obtained.

It was also confirmed that the sound absorption properties differ depending on the length of the granular material. FIG. 17 shows the relationship between the long axis of the granular material and the sound absorption coefficient. The thickness of the sample was 10 (mm), and the measurement frequency was 2 (KHz). If the diameter of the granular material is made too small or too large, it will be difficult for sound waves to penetrate into the porous body, and the specific acoustic impedance of the porous body will not match the specific acoustic impedance of the air side, resulting in poor sound absorption. rate decreases. From the same figure, the long axis of the granular material can be set in the practical range of 0.2 to 3.0 (+nm), preferably in the range of 1.0 to 2.0 (am), to improve sound absorption properties. I confirmed that it can be done.

Although the embodiment shown in FIG. 11 uses an outer magnetic circuit, this equalizer may be used around the magnet of the inner magnetic circuit to obtain the same effect.

[Effects of the Invention] As explained above, the present invention has an equalizer formed in a porous structure having porosity in which the specific gravity is continuously changed in the thickness direction of the layer or in the surface direction of the layer. It is possible to obtain a speaker unit that is excellent and generates less unnecessary sound.

Further, according to the present invention, a porous layer with a changed specific gravity;
This porous layer is layered with a solid layer that has a smaller porosity than the porous layer, and furthermore, the solid layer is fused to the porous layer in a fused layer, and this fused layer is made non-porous, so it is possible to create an equalizer. It can improve the sound absorption properties of. Furthermore, since the layers are fused together, it is possible to obtain an equalizer that can accommodate complex shapes.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are schematic cross-sectional views of a multilayer material (porous structure) according to the present invention, FIGS. 2 to 5 are cross-sectional views showing conventional examples, and FIG. 6 is a schematic cross-sectional view of a multilayer material (porous structure) according to the present invention. FIG. 7 is a characteristic diagram showing the effect of the equalizer in FIG. 4, FIGS. 8 to 11 are cross-sectional views showing the speaker unit in this invention, and FIG. 1st
FIG. 13 is a curve diagram showing the porosity versus thickness of the porous structure of Example 1, and FIG. Figure I4 is a curve diagram showing the porosity versus thickness of the porous structure according to the second embodiment of the present invention, and Figure 15 is a vertical diagram of the porous structure whose porosity curve is shown in Figure 14. Characteristic curve diagram of incident sound absorption coefficient,
Figure 16 is a diagram showing the variation in the characteristics of normal incidence sound absorption coefficient when the shape of the granular material forming the porous layer is changed.
FIG. 7 is a characteristic diagram showing the relationship between the diameter of the granular material and the sound absorption coefficient. In the figure, (1) is a multilayer material (porous structure), (2) is a fused layer (layer with high specific gravity, solid layer), (3) is a porous layer, (
4) is the skin layer, (5) is the equalizer, (6) is the diaphragm, (7) is the voice coil, (8) is the pole piece, (
9) is a magnet, and (10) is a plate. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (7)

[Claims] (1) A speaker unit having an equalizer formed of a porous structure having a porous layer whose specific gravity is continuously changed in the thickness direction or the surface direction of the layer. (2) A patent claim having an equalizer formed of a porous structure characterized by layering the porous layer according to claim 1 and a solid layer having a smaller porosity than the porous layer. The speaker unit according to item 1. (3) The speaker unit according to claim 2, having an equalizer formed of a porous structure, wherein the solid layer is a fused layer and is fused to the porous layer. (4) The speaker unit according to claim 1, 2, or 3, wherein the equalizer is located in front of the diaphragm and has a circular, donut-shaped, or rectangular shape. (5) The speaker unit according to claim 1, 2, or 3, characterized in that the equalizer is attached to the tip of the pole piece and positioned between the pole piece and the diaphragm. (6) A speaker according to claim 1, 2, or 3, characterized in that the equalizer is attached to the tip of the pole piece, and further has a shape that projects from the voice coil bobbin and the diaphragm neck. unit. (7) A speaker unit according to claim 1, 2 or 3, characterized in that the equalizer is attached inside the magnetic circuit so as to be located on the inner or outer surface of the magnet.