JPS58131896A - Diaphragm for loudspeaker - Google Patents

Abstract

PURPOSE:To obtain a reproducing sound of high fidelity, by using cross-liking polypropyrene foams which have independent bubbles of a specified bubble fraction, and have specified specific gravity and a specified Young's modulus, for a diaphragm material. CONSTITUTION:A diaphragm is manufactured by using a material consisting of cross-linking polypropyrene foams having independent bubbles, and forming it in the shape of a dome. A bubble fraction of these independent bubbles is set to <=100%, specific gravity of the polypropyrene foams is set to 0.03-0.05, and also its Youngs's modulus is set within a range of 4.30-14.80kg/cm<2>. This diaphragm becomes light since it has independent bubbles in its inside in this way, also since it has moderate rigidity, generation of peak dip in high frequency range can be prevented completely, and it is possible to obtain a tone quality which is excellent in force, softness, brightness and delicacy, and also is well-balanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diaphragm for a speaker, and particularly to a diaphragm for a dome-shaped speaker used in a lighter or a squawker.

(1) In general, the characteristics of the diaphragm used in high-fidelity speakers require that the material be relatively highly elastic, have an appropriate internal loss, and be lightweight. ing.

However, the materials that have been used or proposed in the above-mentioned speakers include cloth materials impregnated with rubber resin such as latex, polyester films, and metal materials such as aluminum titanium. etc.

However, cloth materials impregnated with resin generally have a low limit frequency for high-frequency reproduction (hereinafter referred to as high-frequency limit frequency), and as mentioned above, since they are impregnated with resin, the specific gravity is large, and therefore Conversion efficiency tends to decrease.

There is a diaphragm made of polyester film that eliminates the above-mentioned drawbacks.This material has a high limit frequency that is generally higher than that of the above-mentioned materials, and also has a lower specific gravity. The disadvantage is that the peak depth is particularly noticeable in the high frequency range, so it has the disadvantage that it is difficult to obtain faithful (2) reproduced sound.

In addition, metal materials that have been proposed in recent years have a higher limit frequency in the high range than that of polyester films, but on the other hand, they have a higher limit frequency in the low range (that is, it is difficult to produce bass sounds), and the peak depth described above is higher. It also has different drawbacks, which are most noticeable in the treble range.

On the other hand, as for problems in processing, the above-mentioned metal materials have poor processability due to their nature, while polyester resins have the disadvantage of being easily deformed after molding. In addition, a cloth material impregnated with resin requires an extra step of applying resin on top of it after molding and attaching it to the speaker.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a novel diaphragm for a dome-shaped speaker that eliminates the various drawbacks of the above-mentioned materials.

The diaphragm for a dome-shaped speaker according to the present invention (hereinafter referred to as the product of the present invention) will be described below.

The product of the present invention is a diaphragm formed into a so-called dome shape using a material made of cross-linked polypropylene (3) foam having closed cells, and its closed cell ratio is 100%.
These are as follows. And its specific gravity is 0.03-0.0
The range shall be 5. As the crosslinked polypropylene foam, for example, Torepef PP (registered trademark) manufactured by Toshi Co., Ltd. can be used.

The product of this invention has closed cells inside, so it is extremely lightweight (
It has a specific gravity of 0.05 or less), which increases the conversion efficiency, and also has moderate rigidity due to the above-mentioned crosslinking effect (Young's modulus is 4.30 to 14.80 kg/m2), so it has a high conversion efficiency. As will be described later in the sound range, the occurrence of peaks and dips is almost completely prevented.

Regarding processability, it does not require resin coating unlike cloth materials, and there is no risk of shape deformation after molding as with polyester resins. Furthermore, it does not have the difficulty of processing that occurs with metal materials, and therefore has the advantage that it can be easily processed in a very uniform molded state.

Furthermore, it also exhibits appropriate values for properties related to so-called weather resistance, such as water resistance, heat resistance, cold resistance, and water absorption, which are required for speaker diaphragms (4).

In other words, the heat-resistant temperature and cold-resistant temperature are each 120″c.

The temperature is -20℃, and the tree maturity rate is JIS K6.
767 The above-mentioned Toray Pef l) P by the prescribed measurement method
About 9 cm/mi. It has a value of , and is suitable as a diaphragm for speakers.

The frequency characteristics of a speaker fabricated as a tweeter by processing the above-mentioned material into a dome shape are shown in FIG.

In the same figure, as mentioned above, the frequency characteristic is 1,500H.
It can be seen that it is approximately flat in the range of 2 to 30,000 Hz, the peak and depth are not noticeable in the high frequency range, and the high frequency limit frequency is also higher than that of the cloth material.

Figure 2 (independent) Figure 4 shows the frequency characteristics of speakers made of cloth, polyester resin, and metal, in order, and the ones made of cloth have a noticeable off-peak depth in the high frequency range. High frequency limit (5) The frequency is lower, and the overall output sound pressure level is also lower than in the case of the product of the present invention.

Further, in the case of polyester-based materials, even larger peaks and depths than those described above are observed in the case of metals (titanium-based gold in FIG. 4), and are particularly large in the case of metal materials.

The above is the frequency characteristic in the case of a tweeter, but even when a dome-shaped squawker according to the present invention is created, the result is similar to that in the case of the tweeter, except that the frequency characteristic as a whole shifts from the left (lower side). I was able to confirm that it was.

In addition, speakers using the product of the present invention have a well-balanced sound quality that is rich in power, softness, brightness, and delicacy.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the frequency characteristics of a dome-shaped tweeter using a product of the present invention, FIG. 2 using a cloth material, FIG. 3 using a polyester resin, and FIG. 4 using a titanium-based metal material. (6)

Claims (3)

[Claims] (1) A diaphragm for a dome-shaped speaker used in a tweeter or a squawker, which is made of a cross-linked polypropylene foam having closed cells. (2) The diaphragm for a dome-shaped speaker according to claim 1, wherein the closed cell ratio of the closed cells is 100% or less. (3) The specific gravity of the crosslinked polypropylene foam is 01.
03 to 0.05, and the Young's modulus is 4.30 to 1.
4. The diaphragm for a dome-shaped speaker according to claim 1, wherein the diaphragm is in the range of 4.80 Kg/.2.