JP2000115872A - Loudspeaker cabinet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve sound absorption effect in terms of the quantity and low-frequency characteristics, unlike the conventional raw materials, by mounting a porous sound absorber made of a synthetic resin hollow yarn in the loudspeaker cabinet including the reverse surface of a baffle plate. SOLUTION: A porous sound absorber 5 made of synthetic resin yarn is mounted inside the loudspeaker cabinet 1 which is equipped with a loudspeaker 3 and includes the reverse surface of the baffle plate 2. The porous sound absorber 5 is made of polypropylene-made hollow yarn which is produced by fusing. threading, and extending a polypropylene raw material in an extending direction and has many indefinite-shape holes of 0.1 to 1 μm in width and about 0.5 to 0.3 μm in length distributed on the hollow yarn surface. Consequently, the phenomenon in which the response waves undulate is reduced from 100 Hz to 1 Hz frequency characteristic, and low-frequency characteristic whose response decrease is suppressed so as to be -6dB or less at about 50 Hz are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker cabinet using a sound-absorbing material, and more particularly to a cabinet in which a low-frequency characteristic of a speaker is improved by using a non-conventional hollow-fiber-based sound absorbing material. .

[0002]

2. Description of the Related Art Conventionally, a sound absorbing material has been used in a cabinet body for a body and a baffle plate on a front surface. This is because the resonance frequency of the baffle plate is considerably reduced by adding a sound absorbing material in order to reduce the size of the main body of AR Corporation in the United States, and thus it has been used for a long time. Conventionally, as a sound absorbing material, glass wool, rock wool, sound absorbing felt, urethane foam, and the like are known. These sound absorbing materials are a measure for absorbing standing waves generated in the main body.

As a method, for example, these sound absorbing materials 15, 16, 1 are layered on the inner wall surface of a rectangular parallelepiped main body 1 shown in FIG.
7, 18 were pasted. The vibration of the speaker 3 is generated on the front side and the back side, and reaches the human ear together with the sound on the front side as vibration in the speaker cabinet. For this reason, especially the characteristics in the low frequency range depend on the material and structure of the sound absorbing material used for the main body.

The main reasons for using a sound absorbing material are as follows. In the bass reflex type, the output of the low frequency range is increased by Helmholtz resonance. In this case, the sound absorbing material acts as acoustic resistance, lowering the Q of the system, and reducing the phenomenon of infinite resonance. This is an attempt to exhibit ideal low-frequency characteristics. Next is the standing wave. This is a baffle board 2
This can be achieved by placing the sound absorbing material 5 on the back surface of the speaker 3 in order to quickly absorb the generation of the standing wave accompanying the reflection from the back side of the speaker 3. The standing waves generated above and below the main body 1 have been solved by disposing sound absorbing materials 5 and 6 above and below the main body. Furthermore, it was used for the absorption effect of preventing echo in the high frequency range. This is a phenomenon in which the reflected sound leaks from the baffle plate 4 and the port 4 to the outside. Therefore, these sound absorbing effects are significantly improved as compared with the case where no sound absorbing material is inserted in the main body.

[0005] However, these conventional sound-absorbing materials cannot achieve the effect unless a considerable amount is used. For this reason, another problem arises. If the sound absorbing material is made larger as a whole, Helmholtz resonance will be weakened, and the bass will be lowered. For this reason, the sound is clear, but the extension in the low range is insufficient, and characteristics such as a sense of reality are insufficient. If the number is reduced to avoid this, the problem remains. Further, for example, in the case of the glass wool described above as a sound absorbing material, there is a high risk of sticking to the eyes and limbs of an operator due to the fine glass fibers in handling, and it is necessary to consider extremely safety. The same applies to the case of replacing the speaker on the user side. Rock wool and sound-absorbing felt have problems in terms of performance, such as generation of dust, water absorption due to moisture during use, and dirt, and safety.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and aims to solve the sound absorbing effect of a speaker cabinet using a hollow fiber sound absorbing material in terms of both volume and low frequency characteristics which are not available in conventional materials. Things. In particular, the present invention aims to provide a lightweight, simple structure, and low cost together with the above effects by focusing on hollow fibers. Also, the present invention relates to a speaker cabinet improved in safety and manufacturing.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a speaker cabinet having a speaker mounted on a front baffle plate, and comprising a synthetic fiber made of synthetic fiber hollow fibers inside a cabinet including the back surface of the front baffle plate of the cabinet. The speaker cabinet is provided with a porous sound absorbing material made of fiber.

Further, when the cabinet is a rectangular parallelepiped cabinet, when the hollow fiber is made of an olefin-based material, or when the attenuation rate of a standing wave by the sound absorbing material is 0.3 or more, Is provided by the speaker cabinet described above, wherein is made of polypropylene.

Furthermore, the present invention is more effectively provided when the hollow fiber is attached to at least the upper, lower, front and rear sides of the opposing surface on the inner surface of the cabinet, and is adhered to all opposing surfaces. Further, when the insertion amount of the hollow fiber per cabinet volume is set at 0.1 kg / cubic m to 10 kg / cubic m, the speaker cabinet is further provided with the polypropylene having a hole diameter of 100 to 500 μm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be specifically described below in each example. Embodiment 1 Embodiment 1 will be described with reference to the drawings. FIG. 1 is an example of a speaker cabinet of the present invention, which is generally formed in a rectangular parallelepiped. In addition, cabinet shapes such as a front surface having a substantially circular shape, an elliptical shape, or a spherical shape or an elliptical shape as a whole can be used in the present invention. The speaker 3 is attached to a front baffle plate 2 of a speaker cabinet (hereinafter, referred to as a cabinet) 1. A port 4 is formed in the baffle plate 2. The other surface of the cabinet 1 is closed. A hollow fiber (hollow fiber) made of polypropylene fiber is attached to each inner surface of the cabinet 1.

It is generally known that when a speaker is used in the cabinet 1, particularly the bass characteristics and sound quality depend on the material of the cabinet 1 used. That is, when the diaphragm of the speaker vibrates, sound waves are transmitted from the front and rear surfaces as air density. A baffle plate is needed to radiate this effectively.

Ideally, the baffle plate must have an infinite extent, but in reality, a finite baffle plate must be used. For this reason, the characteristic decreases in proportion to the frequency below the resonance frequency depending on the size of the baffle plate. It is shown as a value inversely proportional to the size of the baffle plate. Also, there is known a phenomenon in which the response undulates above and below the resonance frequency, which is said to be a ridge and valley so-called frequency characteristic.

Therefore, the characteristics of the speaker 3 are improved, the material, thickness and shape of the cabinet 1 are set.
Improvements have been made to the arrangement of ports 4 and the like. In recent years, as for speaker cabinets, further miniaturization has been desired, and as a countermeasure, improvements have been made to the speakers to achieve the purpose, but the situation has reached the limit. In addition, a large speaker size is required to reduce lowering of the bass by the baffle plate, and as a result, the size of the cabinet is increased.

Next, it is necessary to seal the cabinet as a countermeasure against the sound emitted from the back of the cabinet. However, volume expansion is essential, not just sealing. In conclusion, there is a frequency limit for cabinet volume that depends on the size of the cabinet. While the cabinet volume is large, it is affected by the bass resonance of the speaker. Conversely, if the volume is less than a certain level, the volume dependency increases. For this reason, it is impossible to further extend the bass reproduction limit only by improving the speakers.

The port 4 of the phase inversion baffle type cabinet 1 is touched. Conventionally, the port 4 is disposed on the same baffle plate 2 as the speaker 3. This is for inverting the phase of the sound emitted from the rear surface of the diaphragm and radiating it from the front port 4. As an effect, it is possible to radiate sound with low distortion in a low frequency range. However, the conditions for selecting a speaker become strict. There is also a drawback such as deterioration of the so-called transient characteristics in the low frequency range, and these improvements are also required.

From the above points, the speaker cabinet in which the port 4 is provided and the speaker 3 is provided has many disadvantages, and various sound absorbing materials have been conventionally used as an improvement. However, a sufficient sound absorbing effect was not always obtained, and improvement was called for.

FIG. 3 is an explanatory view of the shape of the cross-sectional structure drawn from an electron micrograph of the cross section of the polypropylene hollow fiber used in the present invention. As a whole, it is white and almost opaque. The outer diameter is about 300μm and the thickness is about 30μm
It is in the form of a hollow fiber. The side surface is almost a uniform thread shape, and the surface has voids in a discontinuous arrangement so that air can enter and exit inside and outside the hollow fiber.

These hollow fibers are formed by melting polypropylene pellets and spinning. At the time of this yarn production, the yarn is drawn in a certain drawing direction while lowering the temperature from a certain molten state, and is drawn to form an orientation. Fine holes are formed with this stretching orientation. The pore size used was an irregular pore having a diameter of about 1 to 10 μm, which did not allow hemoglobin in blood to pass through an artificial lung or the like. The shape of this hole is JEOL scanning electron microscope JSMT-
Photographs were taken at 220A. As a result of photographing at an accelerating voltage of 15 kV and a magnification of 10000 times, a large number of irregularly shaped holes having a slightly longer length, a width of 0.1 to 1 μm, and various distributions, and a length of about 0.5 to 3 μm were distributed.

A method for inserting a hollow fiber into a cabinet will be specifically described. The cabinet 1 used a box having a height of about 55 cm, a depth of 25 cm, and a width of 35 cm by the internal method. Port 4 has an inner diameter of 95 mm and a depth of 1 inside the port.
The cylindrical shape was 10 mm.

The used hollow fiber is cut into a length of 60 cm.
They were randomly stacked and placed in the cabinet 1 almost on average. It was placed so as to have a volume ratio of about 50%, but in practice, it should be experimentally set depending on the size, material, and speaker used, such as the thickness of the cabinet. Regarding the necessary amount of the hollow fiber, it is essential to use the minimum amount in any case such as weight or volume per speaker cabinet volume.

In the present invention, 0.27 kg was used as the weight of the cabinet 1. The back of the speaker 3 in direct contact was avoided, and the inside of the port 4 cylinder was not mounted. Care should be taken that the hollow fibers are desirably placed on each inner surface on average. When the hollow fiber itself is polypropylene, a method of forming the hollow fiber into a plate shape utilizing the properties of polypropylene itself is suitable.

Other materials are possible as well. As another method, a method of sticking to the inner surface of a cabinet by a sandwich method using a mesh net is suitable. In any case, it is desirable to place the hollow fiber so that the hollow fiber adheres to the inner surface.

FIG. 1 shows a state in which hollow fiber sound absorbing members 5, 6, 7, and 8 made of polypropylene are attached to the entire inner surface of the cabinet 1. The hollow fiber sound absorbing material (sound absorbing material) 5 is on the back of the cabinet 1, the sound absorbing material 6 is on the ceiling, the sound absorbing material 7 is on the floor, and the sound absorbing material 8 is on both left and right sides. However, speaker 3,
It was also attached to a part of the front baffle 2 excluding the port 4 part. FIG. 2 shows a state in which the sound absorbing members 5 and 7 made of polypropylene are attached to a part of the inner surface of the cabinet 1.
The sound absorbing material 5 was stuck to the back of the cabinet 1 and the sound absorbing material 7 was stuck to the front baffle 2.

FIGS. 4 to 6 show the results of the sound pressure frequency characteristics. FIG. 4 shows the measurement method. The port 4 was measured with a cloth packed in the open part and sealed to see the characteristics of only the sound absorbing material. Cabinet 1 is about 55c high by internal method
m, depth 25 cm, width 35 cm, plate thickness 24 mm, and a material used was a Yonematsu laminated board. The measurement was performed in the direction perpendicular to the speaker vibration plane on the front of the speaker cabinet 1.
The microphone 9 was placed at a position of cm, and the measurement was performed.

The speaker has an outer diameter of 165 manufactured by DAITO.
mm-sized ones were used. The acoustic characteristic measuring device used was Accuphase DG-28. This measuring instrument was a digital type of 1/6 octave, 64 bands, 0.5 dB step, and used a graphic equalizer in an acoustic characteristic measuring instrument mode (the display was shown as an oscillator). FIGS. 5 and 6 show these outputs as drawings. Oscillator 10
Was connected to the speaker 3 by a cable 11. Microphone 9 output from cable 14 to sound pressure gauge 13
Was connected and measured. Reference sound pressure measurement is made by Nippon Audio S
Using an L-1 type sound pressure meter, a reference sound pressure of 70 dB (1 kHz)
z). Sound pressure frequency characteristic is 40Hz to 16kHz
The test was performed in the audible range of z.

FIG. 5 shows the acoustic characteristics of a conventional example using micron glass wool which has been considered to be excellent as a sound absorbing material. FIG. 6 shows the acoustic characteristics using the hollow fiber of the sound absorbing material of the present invention in Example 1. All weight 27
At 0 g, it was placed on almost the entire speaker cabinet 1 and measured. In addition, although not specifically shown in the figure as other hollow fibers, similar results were obtained. This is considered to be the effect of the hollow fiber as the form.

In the figure, the vertical axis represents sound pressure sensitivity, and the horizontal axis represents frequency. 1 kHz is represented as a reference 0 dB. The results are as shown in the figure, but the features are as follows. The results showed that the sound absorbing material of the present invention was excellent in function as a hollow fiber.

A reduction in the so-called flare phenomenon is observed.
From 1 kHz to 100 Hz, an improvement in the phenomenon that the response is wavy up and down, which is said to be the so-called frequency characteristic of peaks and valleys in the present invention, is recognized.

An improvement in low-frequency characteristics of 1 kHz or less is recognized. In particular, in the conventional example, a decrease to -3 dB or more is observed by about 100 Hz. In the present invention, it was flat up to almost 63 Hz. Further, when the sound pressure is 6 dB, that is, when the sound is compared at a half pitch, the conventional example has a sound pressure of about 63 dB.
By about Hz, a decrease to -6 dB is observed. In the present invention, the drop was -6 dB at about 50 Hz. In the conventional example, a sharp down was observed even below that, and 40 Hz
, It is recognized that the sound pressure becomes -15 dB or more. In the present invention, the sound pressure was about -13 dB.

An improvement in high frequency characteristics is also observed. Almost 12.
About 5 kHz, about -6 to -10 dB in the conventional example
The decrease is observed until. In the present invention, the decrease was only about -6 dB at about 16 kHz. As a result, clear significance was recognized. Next, an actual viewing confirmation test was performed. A significant difference was confirmed between the presence and absence of the hollow fiber sound-absorbing material, such as the elimination of cabinet box noise and the reduction of sound and reverberation.

In addition, it was confirmed that the listener actually listened to the music as having a natural feeling, and that the crisp feeling in the high frequency range was not unnatural. These are considered to be because the adverse effects of standing waves could be avoided. As a measurement result of this point, a result that the attenuation rate with respect to the standing wave was 0.3 or more was obtained by the quantitative control of the sound absorbing material. One of the features is that the selection of the listening position in the room and the countermeasures against the reflection of the surroundings are considerably reduced by this. As a result, the effect of the hollow fiber sound absorbing material is a standing wave effect due to the presence of the porous material on the surface of the hollow fiber. This was a relative measure of muffled crispness and oppression, but was corrected and rated as a significant difference for listeners. It is thought that the reason is that acoustic energy accompanying harmonics is replaced by frictional heat, but elucidation is considered as a further research topic. From the above results, in the present invention, it is the first that the so-called low-end in the low frequency range is largely extended, and further, the improvement effect in the high frequency range and the entire frequency range is recognized.

Embodiment 2 Embodiment 2 will be described with reference to the drawings. FIG. 2 specifically illustrates a method of inserting a hollow fiber into a cabinet in another embodiment of the present invention. Cabinet 1 main body is external dimensions, height about 49cm, depth 21cm, width 29cm,
A box having a total thickness of 2 cm was used. Port 4 is 60m
The inner diameter of the port was 70 mm and the inside diameter of the port was 70 mm. In this cabinet, the sound-absorbing material is placed at the minimum necessary position as a whole, and the effect in terms of manufacturing and material is confirmed. As a result, characteristics similar to those in FIG. 6 were obtained. The amount of the sound absorbing material used was about 270 g.

FIG. 7 shows the acoustic characteristics when no sound absorbing material is used in the conventional example. FIG. 8 shows the acoustic characteristics using the hollow fiber of the present invention as a sound absorbing material in Example 2. With a weight of 270 g, it was placed on the cabinet 1 according to FIG. 2 and measured. The results are as shown in the figure. In the case where no sound absorbing material is used, comprehensive acoustic characteristics are exhibited from the cabinet, the speaker and the measurement environment. As a change to this, the effect of inserting the sound absorbing material was confirmed. As a result, an excellent result was obtained in which the sound absorbing material effect was caused by the material.

More specifically, the frequency is increased by about 3 dB at 100 Hz, and is reduced by about 3 to about 63 to 40 Hz.
Or up to 6 dB. From these, the resonance frequency was extended to a lower range as compared with the case without the sound absorbing material, and the low-frequency characteristics were improved by appropriately suppressing the diaphragm. About 2 sound absorbing materials
By setting the weight to 70 g, a moderate response was evaluated. Too much sound absorbing material will produce low frequencies, but the response will be negative and the amount should be determined experimentally based on cabinet material, shape, and speaker characteristics. As a result, it was evaluated as a crisp cabinet sound-absorbing material that eliminated the resonance phenomenon.

In the range of 100 Hz to 1 kHz, the power was increased by about 2 to 3 dB. As a result, it was possible to obtain a flat and improved acoustic characteristic. An improvement in the phenomenon that the response undulates above and below the so-called frequency characteristics of the above-mentioned peaks and valleys is recognized.

Next, an actual viewing confirmation test was performed.
A significant difference was confirmed between the presence and absence of the hollow fiber sound-absorbing material, such as the elimination of cabinet box noise and the reduction of sound and reverberation. In addition, although not specifically shown in the figure as other hollow fibers, similar results were obtained. This is considered to be the effect of the hollow fiber as the form.

Similarly, other hollow fibers were confirmed.
In the present invention, as the hollow fiber made of a synthetic fiber, a cellulose fiber, an olefin fiber, a polymethyl methacrylate fiber or the like which can be used as a material for artificial lungs and artificial kidneys at present can be used. The workability of the material, in particular, it has a disadvantage that it is easily broken due to its small outer diameter of 200 to 1000 μm, and among them, polypropylene hollow fiber is the best in terms of strength. However, this does not deny other materials. At the same time, as mentioned above, advantages in terms of handling safety compared to conventional glass wool are pointed out. This is similar to other conventional sound absorbing materials.

The effects of the present invention described above are not limited to this. In addition, attention should be paid to the sound absorbing material that has recently been pointed out particularly in terms of health. In particular, safety for lungs and eyes due to fine droplets scattered in the air generated from glass wool and worsted felt has been called for. In the hollow fiber of the present invention,
There are no fine droplets scattered in the air, and on the contrary, safety is improved because they are used in artificial lungs and the like.

Further, it is effective to use it for a cabinet because it has a moisture absorbing surface and is hardly contaminated. Furthermore, since the weight ratio per volume was greatly reduced as compared with the conventional one, the weight of the cabinet was reduced.

[0040]

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a speaker cabinet on which a sound absorbing material of the present invention is mounted.

FIG. 2 is a side view of a main part of a speaker cabinet in which a position of a sound absorbing material according to the present invention is limited.

FIG. 3 is an explanatory view of a main part showing a cut surface of a hollow fiber.

FIG. 4 is a device for measuring characteristics of a speaker cabinet.

FIG. 5 shows a frequency characteristic of a speaker cabinet on which conventional sound absorbing material micron glass wool is mounted.

FIG. 6 shows a frequency characteristic of the speaker cabinet of the first embodiment on which the sound absorbing material of the present invention is mounted.

FIG. 7 shows a frequency characteristic of a speaker cabinet without a conventional sound absorbing material.

FIG. 8 shows a frequency characteristic of the speaker cabinet of Embodiment 2 on which the sound absorbing material of the present invention is mounted.

FIG. 9 is a side view of a main part of a speaker cabinet on which a conventional sound absorbing material is placed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Speaker cabinet 2 Baffle board 3 Speaker 4 Port 5 Hollow fiber sound absorbing material 9 Microphone 10 Oscillator 13 Sound pressure gauge

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[Procedure amendment]

[Submission Date] September 6, 1999 (September 9, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Wherein said attenuation factor for the standing wave due to sound absorbing material is 0.3 or more claims 1 and speaker cabinet according to claim 3.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

The present invention relates to a speaker cabinet having a speaker mounted on a front baffle plate, wherein a porous sound absorbing material made of synthetic fiber hollow fibers is placed inside a cabinet including the back surface of the baffle plate. A width of 0.1 to 1 μm is applied to the surface of the hollow fiber which is oriented by stretching the synthetic fiber hollow fiber by melting and spinning a polypropylene material and stretching in the stretching direction.
m, a porous sound-absorbing material consisting of a hollow fiber made of polypropylene in which a large number of fine irregular holes having a length of about 0.5 to 3 μm are distributed, and 100 Hz at 1 kHz or less.
Of the frequency response up and down, which is said to be the highest in the frequency characteristics up to
It is provided by a speaker cabinet having an improved low-frequency characteristic within the response reduction range of 6 dB.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

When the cabinet is a rectangular parallelepiped cabinet, and when a port is provided on the front surface of the cabinet, the cabinet size has an outer height 49c.
m, depth 21cm, width 29cm, overall thickness 2cm
When the inner diameter of the port is 6 cm, the depth is 7 cm, and the amount of the porous sound absorbing material used is 270 g and the amount used is minimized, the attenuation rate of the standing wave by the sound absorbing material is 0.3 or more. Advantageously provided by certain of the foregoing speaker cabinets.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

Further, the hollow fibers are stuck on at least the upper, lower, front and rear sides of the facing surface on the inner surface of the cabinet, and the polypropylene has a pore diameter of 100 to 5 mm.
When it is 00 μm, it is stuck on all opposing surfaces, and the pore size of the polypropylene is 100 to 500.
It is effectively provided by the aforementioned speaker cabinet which is μm. Further, when the insertion amount of the hollow fiber per cabinet volume is 0.1 kg / cubic m to 10 kg / cubic m, the polypropylene has a pore diameter of 100 kg / cubic m.
.About.500 .mu.m, and when the porous sound-absorbing material is placed in a sandwich manner by a mesh-like net, the above-mentioned speaker cabinet provides the same effect.

Claims (9)

[Claims] 1. A speaker cabinet having a speaker mounted on a front baffle plate, wherein a speaker including a porous sound absorbing material made of synthetic fiber hollow fiber is placed inside a cabinet including a back surface of the front baffle plate of the cabinet. cabinet. 2. The speaker cabinet according to claim 1, wherein the cabinet is a rectangular parallelepiped cabinet. 3. The speaker cabinet according to claim 1, wherein said hollow fiber is made of an olefin-based material. 4. The speaker cabinet according to claim 1, wherein an attenuation rate of the standing wave by the sound absorbing material is 0.3 or more. 5. The speaker cabinet according to claim 1, wherein said hollow fiber is made of polypropylene. 6. The speaker cabinet according to claim 1, wherein the hollow fibers are attached to at least upper, lower, front and rear sides of the facing surface on the inner surface of the cabinet. 7. The speaker cabinet according to claim 1, wherein the hollow fibers are attached to all opposing surfaces on the inner surface of the cabinet. 8. The speaker cabinet according to claim 1, wherein an insertion amount of the hollow fiber per cabinet volume is 0.1 kg / cubic m to 10 kg / cubic m. 9. The polypropylene having a pore size of 100 to 5
The speaker cabinet according to claim 1, wherein the speaker cabinet has a thickness of 00 μm.