JPS631000B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diaphragm for an electroacoustic transmission device.
It also relates in particular to a transmission device in which the diaphragm is coupled to an electromechanical transmission device, for example a moving coil loudspeaker. The quality of reproduction of a program by a loudspeaker is a function of its axial response/frequency characteristics and directional characteristics, and among other things, a factor known as coloration. For the best reproduction to be obtained, it is necessary to correct each of these factors, which are not necessarily completely independent. It is thus possible to some extent to reduce the effect of coloration by changing the axial response/frequency characteristics. It is also possible to reduce defects in directional characteristics by changing the axial response/frequency characteristics. In either case, the modification of the axial response/frequency characteristic must not be so extreme that this characteristic itself becomes unsatisfactory. Furthermore, the proper balance of the above characteristics for one type of program is not necessarily optimal for another type of program. For these reasons, in the highest quality loudspeakers, the frequency band is divided into two or three parts, using different units for each different band and with a suitable frequency division network spanning each unit. be done. Thus, a morning glory-shaped loudspeaker diaphragm with a low frequency unit is used. The shapes include conical to hyperbolic cross-sectional shapes. These are commonly called "cones". For high frequency bands, so-called tweeter domes are used. In this way, each unit can operate over its optimum band range, resulting in a corresponding improvement in overall sound quality. Such designs, however, involve considerable cost and manufacturing effort. This is because, in addition to the cost of two or more loudspeaker units, the cost of the necessary frequency division network and the work involved in ensuring that the sensitivity of each of these units is commensurate with the particular design geometry. This is because it is necessary to add For these reasons it is generally preferred to use a single unit that covers the entire frequency band. This, of course, comes with the relatively large risk that the sound will be altered, that the loudspeaker will be too directional, and that the axial response/frequency response will be too limited. Historically, diaphragms for electroacoustic transmission devices have been made from a wide variety of materials with varying physical properties. Thus, for example, in British patent specification no. It is being British Patent Specification No. 1,271,539 discloses a diaphragm for a loudspeaker consisting of a cloth fused to a foamed synthetic resin. British Patent Specification No. 1186722 discloses a flat plate type loudspeaker, the diaphragm of which is made of foamed resin such as polystyrene, polyvinyl chloride, polyethylene, etc. as in the case of British Patent Specification No. 1384716. polyamide, polyurethane,
Formed from acrylonitrile-butadiene-styrene resin. Furthermore, British Patent Specification No. 1174911
No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, 2003, discloses a loudspeaker diaphragm formed from metal, particularly titanium. However, the plastic and metal materials mentioned above do not provide the desired quality of playback, especially of programs over the entire frequency band. An object of the present invention is to provide a diaphragm for an electroacoustic transmission device that can be used satisfactorily over the entire frequency band. Another object of the present invention is to provide a synthetic resin material for use in the structure, diaphragm and other parts of a moving coil loudspeaker in order to ensure that the loudspeaker can be satisfactorily used over the entire frequency range. Our goal is to provide the following. According to one aspect of the invention, the diaphragm-forming material has a mechanical quality factor of 7 to 12 and a mechanical quality factor of 8.5 to 15.5.
Young's modulus of ×10 ⁵ KN/M ² and 0.85 to 1.05 g/cc
A diaphragm for an electroacoustic transmission device is provided, characterized in that it is made of polypropylene or a copolymer of propylene and a small amount of ethylene, and has a density of up to 100 ml. Here, the mechanical "Q" value is expressed by the following relational expression and indicates a factor of any vibration system. Q=2π×Energy/Energy loss during one cycle The thickness of the diaphragm is within the normal range for diaphragms for electroacoustic transmission devices, and the physical properties of the material for forming the diaphragm are It has no impact whatsoever. According to a second aspect of the invention, there is provided a moving coil loudspeaker having a diaphragm formed from a material having the properties described above. As for the mechanical Q factor, which is the most important parameter among the three parameters mentioned above, if it is less than 7 it will cause a large loss of sound waves as they travel outward from the voice coil. It also causes excessive dispersion. This dispersion is a change in the group delay of the sound waves as they travel through the diaphragm. This excessive absorption of sound waves reduces the high acoustic sensitivity, which is an important property to maintain in electroacoustic transmission devices. On the other hand, a mechanical Q factor greater than 12 provides a diaphragm that begins to vibrate with the excitation from the voice coil and then continues to vibrate to produce an acoustic output even after the initial excitation is removed. . This leads to poor coloration of the sound output and therefore poor quality sound output. For Young's modulus, this is 8.5×10 ⁵ KN/M ²
If less, the diaphragm has no piston action, resulting in a loss of acoustic output. That is, when the center of the diaphragm is driven forward by the voice coil, the outer periphery of the diaphragm is not simultaneously driven forward because the stiffness of the diaphragm is insufficient to simultaneously support the piston movement. On the other hand, if the Young's modulus exceeds 15.5×10 ⁵ KN/M ² , it is very difficult to terminate the sound waves at the outer periphery of the diaphragm. This means, in other words, that high speed waves traveling outward from the voice coil are reflected at its outer periphery, resulting in acoustic coloration. Also, regarding density, if it is less than 0.85 g/cc, it will give the material insufficient impact strength and tensile modulus and therefore damage due to high accelerations generated from voice coil forces. The other density is 1.05
If it exceeds g/cc, it results in a decrease in the acoustic sensitivity of the electroacoustic transmission device for a given electrical input. Therefore, the material for forming the diaphragm was prepared from 7 as described above.
Mechanical Q value up to 12 and 8.5 to 15.5×10 ⁵ KN/
If it is made of polypropylene or a copolymer of propylene and a small amount of ethylene with a Young's modulus of ^M2 and a density of 0.85 to 1.05 g/cc, good sound quality can be achieved without coloration over the entire frequency range. can be played. Heretofore, the materials used in the construction of loudspeaker diaphragms have not been able to meet these requirements. A particularly preferred material that provides the above-mentioned physical properties suitable for use in the manufacture of diaphragms for electroacoustic transmission devices is polypropylene. Propylene can be used by itself or in copolymers with small proportions of ethylene, but in such copolymers that the physical properties of the copolymers do not fall outside the ranges mentioned above. In addition to forming a diaphragm of such plastic material, the plastic material may be coated on one or both sides with a certain plastic, metal or ceramic material, as long as the physical properties mentioned above remain within the specified ranges therefor. may be formed. In this way, a change in the quality of program playback is achieved. Thus, polypropylene copolymers can be provided with thin coatings (e.g., 38 microns) of low density polyethylene or high attact polypropylene and are suitable for use in loudspeakers. Propylene homopolymer and copolymer diaphragms may also be made of light metals such as aluminum, titanium or beryllium, or of other plastic materials such as polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene terpolymers, polyethylene, etc. It is also possible to construct sandwich fillers between thin coatings of even ceramic materials, such as ceramics of the barium titanate group. There is no obvious reason why, for example, polypropylene provides a diaphragm with the required acoustic properties while other plastic materials with similar physical properties are not satisfactory. The microcrystals in polypropylene are randomly oriented, but polyethylene, for example, has a structure that causes the molecules to slide against each other in response to the stress applied under the high acceleration generated by the voice coil, thereby causing acoustic distortion. It is probably not likely that this will occur. Coated and sandwich-shaped cones can be manufactured by various techniques depending on the materials involved. Thus, when manufacturing a metallized cone, metal can be applied to the filler as a preformed foil or by vapor deposition. In the former case, adhesives such as polyvinyl acetate-based adhesives are used to provide the necessary bonding. When the plastic materials are bonded together, hot welding can be used. With the various mechanical Q values listed in the table below,
We prepared samples of diaphragms for electroacoustic transmission devices made of various plastic materials with different Young's moduli and densities, and compared the sound quality of loudspeakers using these samples.

[Table] Among the above samples, it was confirmed that Samples E, F, G, and J could reproduce good sound quality without causing any color difference over the entire frequency band. However, samples A, C, D1, D2, D3, and H were not able to reproduce sound quality as good as samples E, F, G, and J. The present invention may be applied to electroacoustic transmission devices of various shapes already discussed above. In particular it can be applied to cone-shaped and dome-shaped diaphragms. The directivity and axial response/frequency characteristics of the loudspeaker unit are
The shape or contour of the cone is a function, or the material from which the cone is made is also a function. When a single unit is used to cover the entire frequency band, it is preferable to use a diaphragm according to the invention that is configured in a hyperbolic shape. Under these conditions the wave motion from the voice coil along the cone expands at such a rate that the effective dimensions of the source seem to become considerably smaller as the frequency rises even as the entire cone participates in the radiation. The combination of mechanical damping of the material and its surroundings ensures a low standing wave ratio. Therefore, the effective mechanical impedance sensed by the voice coil is also smaller as the frequency rises, so that the axial response/frequency characteristics are maintained up to high frequencies. Although a loudspeaker unit with a single loudspeaker unit including a diaphragm according to the invention works particularly well for the best acoustic properties to be achieved, it is nevertheless possible to use loudspeakers with different frequencies according to the invention. Preferably, it consists of two or three units covering the band. This is obviously a more expensive operation, but the quality of reproduction then obtained is greater than that obtained with a multi-unit loudspeaker consisting of a diaphragm made of a material not in accordance with the diaphragm specified for use in the present invention. It was recognized that it was better than what was available. The quality of reproduction that can be obtained with the diaphragm according to the invention is particularly important when the diaphragms are used in one loudspeaker, although the diaphragm is negligible compared to the coloration resulting from the use of materials other than the inventive materials of which it is constructed;
It is also relatively important and noticeable to the experienced ear. Plastics are also commonly used in loudspeaker unit construction for the so-called outer cone support ring (cone only) and for the so-called spider or centering member (cone and dome). According to another aspect of the invention, where relevant, these components are formed from a plastic material having the physical properties described above. For a better understanding of the invention, embodiments of the invention will be described with reference to the accompanying drawings. In the drawing, the loudspeaker is of a low frequency type and is shown in cutaway view as a simple conical shape, but in reality it consists of a hyperbolic frusto-conical diaphragm 1, which is also coated with a thin layer of adhesive. It has a cylindrical portion 2 which terminates in a voice coil forming body 3 attached to four sides. The diaphragm 1 is made of polypropylene having the above-mentioned physical properties according to the invention. The voice coil formation 3 has a voice coil 5 formed of a number of windings and located in the air gap between two pole pieces 6 and 7 made of, for example, mild steel.
A magnet 8 made of ferrite is provided apart from the pole piece. In the configuration shown, the magnet 8 is set on the cylindrical pole piece 6 and the pole piece 7
It is a thick type that is coated on its top surface. The voice coil 5 is approximately 0.0254 cm for each of these pole pieces.
It is set within the cylindrical cavity 9 to provide a gap. The voice coil forming body 3 and the diaphragm 1
In use, a spider 10, also made of polypropylene having the physical properties mentioned above, is used to connect the voice coil formation 3 to the pole piece 6 so as to cause it to vibrate strictly vertically. It will be done. At its upper end, the diaphragm 1 is connected to a support basket 11 by an outer cone support ring 12. The support ring 12, like the diaphragm 1, is made of polypropylene having the physical properties described above. The support ring 12 is adhesively fixed to the diaphragm 1 and the basket 11. The support basket 11 with a metal frame structure at its lower end supports the pole piece 6
is fixed to. In order to prevent dirt from entering the cavity 9, a dust cap 1 preferably made of polypropylene having the above-mentioned physical properties is provided.
3 is installed on the inner surface of the diaphragm in its lower region, straddling the center. A second spider 14, preferably made of polypropylene having the physical properties described above, connects the diaphragm 1 to the circumferential surface of the support basket 11 and connects the spider 10.
It is also used to provide a parallelogram force that aids in the stability of the diaphragm 1 and the voice coil formation 3. In FIG. 2, a tweeter-type loudspeaker is shown. The loudspeaker consists of a dome-shaped diaphragm 19 made of polypropylene having the physical properties described above and having a cylindrical portion 20 bonded to a voice coil formation 21. The voice coil formation 21 and the portion 20 of the diaphragm 19 are positioned within the air gap 22 between the two pole pieces 23 and 24;
A ring magnet 25 is placed between these pole pieces. Alternatively, the magnetic circuit can take the form shown in the first diagram. The voice coil formation 21 extends downwardly into an annular chamber 26 and is connected to a ring magnet 25 by a spider 27 formed from polypropylene having the physical properties described above. At its upper end, the voice coil forming body 21
is connected to the pole piece 23 by another spider 28 made of polypropylene having the physical properties described above. In the accompanying drawings, it will be appreciated that many features are shown in cross-section and are shown somewhat off-scale for ease of illustrative size. This applies in particular to the size of the air gap and the size of the air gap between the diaphragm and the voice coil formation. The embodiments of the present invention are as follows. Aspect 1: The diaphragm for an electroacoustic transmission device according to claim 2, wherein the plastic material is low or medium density polyethylene or atactic propylene. Aspect 2: The diaphragm for an electroacoustic transmission device according to claim 3, wherein the metal is aluminum, titanium, or beryllium. Aspect 3 The diaphragm for an electroacoustic transmission device according to claim 3, wherein the plastic is polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene terpolymer, or polyethylene. Aspect 4 Claims 1 to 3 and Aspect 1
In any of the descriptions of 3 to 3, the diaphragm for an electroacoustic transmission device is a hyperbolic cone. Aspect 5 Claims 1 to 3 and Aspect 1
In any of the descriptions of 3 to 3, the diaphragm for an electroacoustic transmission device is a tweeter dome. Aspect 6 Any claim is a loudspeaker including the diaphragm according to any of the above aspects.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a moving coil loudspeaker according to an embodiment of the present invention, and FIG. 2 is a sectional view of a modified example. 1...Polypropylene diaphragm, 5...Voice coil, 6...Magnetic pole piece, 7...Magnetic pole piece, 8...Magnet, 10...Polypropylene spider, 12
...polypropylene outer cone support ring.

Claims (1)

[Claims] 1. The material for forming the diaphragm has a mechanical Q value of 7 to 12, a Young's modulus of 8.5 to 15.5×10 ⁵ KN/M ² ,
A diaphragm for an electroacoustic transmission device, characterized in that it is made of polypropylene or a copolymer of propylene and a small amount of ethylene, and has a density of from 0.85 to 1.05 g/cc. 2. The material for forming the diaphragm has a mechanical Q value of 7 to 12, a Young's modulus of 8.5 to 15.5×10 ⁵ KN/M ² ,
A diaphragm for an electroacoustic transmission device, characterized in that it is made of polypropylene or a copolymer of propylene and a small amount of ethylene and has a density of 0.85 to 1.05 g/cc, and is coated with a plastic material. 3. The material for forming the diaphragm has a mechanical Q value of 7 to 12, a Young's modulus of 8.5 to 15.5×10 ⁵ KN/M ² ,
A polypropylene or a copolymer of propylene and a small amount of ethylene with a density of 0.85 to 1.05 g/cc, coated on both sides with metal, plastic or ceramic layers to form a sandwich construction. A diaphragm for electroacoustic transmission devices with special features. 4. The material for forming the diaphragm has a mechanical Q value of 7 to 12, a Young's modulus of 8.5 to 15.5×10 ⁵ KN/M ² ,
polypropylene or a copolymer of propylene and a small amount of ethylene having a density of from 0.85 to 1.05 g/cc, comprising a spider and a support ring, at least Either one has a mechanical Q value of 7 to 12 and 8.5 to 15.5 for the diaphragm.
Young's modulus of ×10 ⁵ KN/M ² and 0.85 to 1.05 g/cc
Loudspeaker made of a material that is polypropylene or a copolymer of propylene and a small amount of ethylene, having a density of .