GB1599546A

GB1599546A - Loudspeaker

Info

Publication number: GB1599546A
Application number: GB2732880A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-07-13
Filing date: 1978-03-08
Publication date: 1981-10-07
Also published as: JPS5419733A

Description

(54) LOUDSPEAKER (71) I, KENKIOHI TSUKAMOTO, of Japanese nationality, of 47, Koyamashimofura-Cho, Kita-Ku, Kyoto Shi, Kyoto-Fu, Japan, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to loudspeakers, and more particularly to the diaphragm of a loudspeaker and to the selection of material forming the supporting means of the diaphragm and the construction of the supporting means.

In a loudspeaker such as for instance a direct radiation type loudspeaker as shown in FIG. 1, the peripheral Portion of the diaphragm 10 in particular form is, in general, supported by a supporting means 11 called an edge, and the diaphragm 10 is vibrated by a voice coil 12 fixedly secured to the central opening of the diaphragm 10. In this case, the vibration of the diaphragm 10 and accordingly the voice coil 12 is suppressed by a damper 13. Furthermore, a cap 14 is provided at the center of the diaphragm 10 so as to prevent the passage of the air through the diaphragm.

Since both of the edge 11 and the damper 13 serve to support the diaphragm 10, they will be hereinafter referred to as "a supporting means" when applicable.

Heretofore, in the loudspeaker of this type, the diaphragm is made of paper.

Recently, a diaphragm made of carbon fibers has been proposed in the art. However, since the weight is an important factor affecting the characteristics of such a loudspeaker, a method of intentionally coating the diaphragm with a damping agent thereby to increase the internal loss has not been employed. Furthermore, as the damping agent is applied to the edge of the loudspeaker, the response characteristic thereof to a small signal applied thereto is very low.

However, in the loudspeaker, it is desirable that the vibrating part thereof can operate as one unit without deformation and that the supporting means can respond to any small signal.

According to the invention there is provided a loudspeaker in which a supporting means and an airtight means for a diaphragm are separately provided, said supporting means is made of material which is elastic, and said airtight means is made of a material which has a low mechanical hysteresis coefficient relative to the diaphragm.

An example of the invention will now be described with reference to the accompanying drawing in which: Fig. 1 is a schematic sectional view showing a conventional direct radiation type loudspeaker; Fig. 2 is a sectional view showing an embodiment of the invention; Fig. 3 is a plan view showing a supporting means employed in the embodiment shown in Fig. 2; and Fig. 4 is a sectional view showing a modification of the embodiment shown in Fig. 2.

Figure 2 shows an embodiment of this invention, which is a direct radiation type loudspeaker, in which the edge member is of a double construction.

A coil bobbin 141 is fixedly provided at the center of a diaphragm, and a coil 141a is wound on the coil bobbin 141. One end of the coil bobbin is covered with a cap 142 to prevent the passage of the air, while the center pole 144 of a magnetic circuit is inserted into the coil bobbin 141 through the other end thereof. Both sides of the coil 141a of the coil bobbin 141 are supported through supporting means 145 according to this invention on the yoke 143 of the magnetic circuit.

he peripheral portion 140a of the diaphragm 140 is fixedly fastened through the supporting means 146 according to the invention and through an airtight means 147 to the peripheral edge 148a of a frame 148 which is extended in conical form from the yoke 143. Accordingly, the coil bobbin 141 and the diaphragm 140 will vibrate in the direction A with the aid of the means 145, 146 and 147.

The above-described various means 145, 146 and 147 are similar to those described with reference to Figs. 5 and 6 of the copending application 9243/78 Serial No.

1599545 from which this application is divided, and are like that shown in Fig. 3.

Shown in FIG. 3 is the supporting means 146 provided for the peripheral portion 140a of the diaphragm 140. The supporting means 146 has an inner ring 120 and an outer ring 121 which are arranged coaxially with a space of several millimeters therebetween. The inner ring 120 is connected to the outer ring 121 through arms 122 which extend in tangential directions from points on the inner ring 120. Similarly as in the above-described case, it is preferable that the number of connection points between the inner ring 120 and the outer ring 121 is a prime number in view of vibration.

Such a supporting means 146 is obtained by subjecting a supportable material which is not viscoelastic but elastic to photoetching or pressing. Such a material is beryllium copper or carbon fiber for instance.

The peripheral portion 140a of the diaphragm 140 may be connected to the peripheral edge 148a of the frame 148 through metal wires which satisfy the above-described conditions.

The airtight means 147 is to prevent the passage of the air due to the supporting means 146, and is made of a material which is low in viscoelasticity and extremely low in elasticity. Such a material is a deerskin leather or a polyester film for instance.

Because of these properties of the airtight means 147, airtightness is positively maintained without disturbing the motion of the supporting means; that is, the vibration of the diaphragm 140 will not be absorbed unintentionally. In other words, the diaphragm can respond to any small signal applied to the loudspeaker.

The construction of the supporting means 154 may be similar to that of the supporting means 146. The supporting means 145 can be obtained by connecting an inner ring whose diameter is equal to the outside diameter of the voice coil 141 to an outer ring whose diameter is equal to the diameter of the yoke 143 with a prime number of arms. The material of the supporting means 145 may be so selected that the supporting means 145 itself performs damping; however, the damping may be effected by other means such as an oil damper or an aircolumn damper.

The construction of the loudspeaker in which the supporting means of the diaphragm is separated from the airtight means, can be applied not only to a direct radiation type loudspeaker but also to the diaphragm 130 of a dome radiator loudspeaker and a horn speaker as shown in FIG. 4. In the loudspeaker shown in FIG. 4, the diaphragm 130 is fixedly secured to a coil bobbin 131, and the coil bobbin 131 is supported on the yoke 135 of a magnetic circuit through a supporting means 136 and an airtight means 137 which are similar to those described above. The magnetic circuit is made up of a magnet 132, a disk 133 adapted as a bottom plate and having a central hole 133a, a center pole 134 having a through-hole 134a, and the yoke 135.

In the loudspeaker described above, the supporting means and the airtight means are arranged in the stated order as viewed from the rear of the loudspeaker; however, it is obvious that the order of arrangement may be reversed.

As is apparent from the above descrip tion, according to the invention, the sup porting means of the loudspeaker diaphragm is separated from the airtight means.

As a result, it is possible to provide an excellent loudspeaker which can sufficiently respond to even a small signal without absorbing it and which can be suitably damped.

In addition, in order to increase the internal loss, intentionally a damping agent of a viscoelastic material such as semi-plastic epoxy resin, viscolloid, acrylic resin, urethane resin, nitrile or rubber may be applied to the diaphragm.

WHAT I CLAIM IS: 1. A loudspeaker in which a supporting means and an airtight means for a diaphragm are separately provided, said supporting means is made of material which is elastic, and said airtight means is made of a material which has a low mechanical hysteresis coefficient relative to the diaphragm.

2. A loudspeaker substantially as herein described with reference to and as illustrated in Figures 2 and 3 or Figure 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

with reference to Figs. 5 and 6 of the copending application 9243/78 Serial No.

1599545 from which this application is divided, and are like that shown in Fig. 3.

Shown in FIG. 3 is the supporting means

146 provided for the peripheral portion 140a of the diaphragm 140. The supporting means 146 has an inner ring 120 and an outer ring 121 which are arranged coaxially with a space of several millimeters therebetween. The inner ring 120 is connected to the outer ring 121 through arms 122 which extend in tangential directions from points on the inner ring 120. Similarly as in the above-described case, it is preferable that the number of connection points between the inner ring 120 and the outer ring 121 is a prime number in view of vibration.

Such a supporting means 146 is obtained by subjecting a supportable material which is not viscoelastic but elastic to photoetching or pressing. Such a material is beryllium copper or carbon fiber for instance.

The peripheral portion 140a of the diaphragm 140 may be connected to the peripheral edge 148a of the frame 148 through metal wires which satisfy the above-described conditions.

The airtight means 147 is to prevent the passage of the air due to the supporting means 146, and is made of a material which is low in viscoelasticity and extremely low in elasticity. Such a material is a deerskin leather or a polyester film for instance.

Because of these properties of the airtight means 147, airtightness is positively maintained without disturbing the motion of the supporting means; that is, the vibration of the diaphragm 140 will not be absorbed unintentionally. In other words, the diaphragm can respond to any small signal applied to the loudspeaker.

The construction of the supporting means 154 may be similar to that of the supporting means 146. The supporting means 145 can be obtained by connecting an inner ring whose diameter is equal to the outside diameter of the voice coil 141 to an outer ring whose diameter is equal to the diameter of the yoke 143 with a prime number of arms. The material of the supporting means 145 may be so selected that the supporting means 145 itself performs damping; however, the damping may be effected by other means such as an oil damper or an aircolumn damper.

The construction of the loudspeaker in which the supporting means of the diaphragm is separated from the airtight means, can be applied not only to a direct radiation type loudspeaker but also to the diaphragm 130 of a dome radiator loudspeaker and a horn speaker as shown in FIG. 4. In the loudspeaker shown in FIG. 4, the diaphragm 130 is fixedly secured to a coil bobbin 131, and the coil bobbin 131 is supported on the yoke 135 of a magnetic circuit through a supporting means 136 and an airtight means 137 which are similar to those described above. The magnetic circuit is made up of a magnet 132, a disk 133 adapted as a bottom plate and having a central hole 133a, a center pole 134 having a through-hole 134a, and the yoke 135.

In the loudspeaker described above, the supporting means and the airtight means are arranged in the stated order as viewed from the rear of the loudspeaker; however, it is obvious that the order of arrangement may be reversed.

As is apparent from the above descrip tion, according to the invention, the sup porting means of the loudspeaker diaphragm is separated from the airtight means.

As a result, it is possible to provide an excellent loudspeaker which can sufficiently respond to even a small signal without absorbing it and which can be suitably damped.

In addition, in order to increase the internal loss, intentionally a damping agent of a viscoelastic material such as semi-plastic epoxy resin, viscolloid, acrylic resin, urethane resin, nitrile or rubber may be applied to the diaphragm.

WHAT I CLAIM IS: 1. A loudspeaker in which a supporting means and an airtight means for a diaphragm are separately provided, said supporting means is made of material which is elastic, and said airtight means is made of a material which has a low mechanical hysteresis coefficient relative to the diaphragm.
2. A loudspeaker substantially as herein described with reference to and as illustrated in Figures 2 and 3 or Figure 4 of the accompanying drawings.