JPH0235520B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to open-air headphones, and aims to provide a headphone that can reproduce rich bass, firm midrange, and extended high range while reducing the size of the headphones. Traditionally, headphones have tended to become smaller,
When miniaturized in this way, the resonant frequency f ₀ becomes high, resulting in a disadvantage that the bass range is insufficient. For example, caliber 23
In headphones called mm, a resin sheet with a thickness of about 12μ to 20μ is normally used as a diaphragm, but in such headphones, the resonant frequency f ₀ is 200Hz to 220Hz, which is low. I can't reach my full vocal range. In such a case, if the thickness of the sheet or diaphragm is made thinner, the resonant frequency f ₀ will be lowered and the above objective can be satisfied, but in this case, the high frequency range will not be produced and the overall sound will be weaker. This results in the disadvantage that the so-called sound tension is lost. That is, when the thickness of the diaphragm is t, the Young's modulus is E, and the stiffness is S, the stiffness S is given by S=kEt ³ , and as t becomes smaller, S becomes extremely small.
Sound resolution deteriorates. Note that k is a proportionality constant. In view of these points, the present invention has been developed to make the entire speaker smaller, that is, even if the headphone in this example is manufactured with a small diameter, it can satisfy the low frequency range and produce a strong signal even in the high frequency range. The aim was to create a compact dynamic headphone that could play music. The inventors of the present invention repeatedly conducted various experiments for this purpose, and found a certain relationship between the structure of the diaphragm itself, the diameter of the movable part of the diaphragm, its thickness, etc. First, the unit of this type of headphone will be explained with reference to the drawings. Reference numeral 1 denotes a frame made of a magnetic material, that is, it also serves as a magnetic circuit. 2 is a magnet, which in this case is magnetized in the thickness direction. 3 is a top plate, which is also made of magnetic material, and its outer peripheral surface and frame 1
A magnetic gap 4 is formed between a portion (a portion forming an inner circumferential surface) of. Reference numeral 5 denotes a diaphragm, the outer periphery of which is bonded in advance to an edge ring 6, and by installing this edge ring 6 within the outer periphery edge 1a of the frame 1, the diaphragm 5 is placed at a predetermined position on the frame 1. The coil bobbin 7 is placed in the magnetic gap 4 described above. 8 is a voice coil. In such a configuration, in the present invention,
The diaphragm 5 is formed from a single sheet made of polyethylene terephthalate resin (product name: Mylar, Lumirror, etc.), which is one of the polyester resins, and the diameter of the vibrating portion of the diaphragm 5 In the example, when the inner diameter of the edge ring 6) is φ, and the thickness of the diaphragm 5 is t, the ratio t/φ=D should be D=4×10 ^-4 to 5×10 ^-4. It was selected as follows. Next, data will be shown for each example. Table 1 shows φ=27mm, Table 2 shows φ
= 20 mm, Table 3 shows the resonance frequency when the thickness t of the diaphragm is changed at φ = 14.4 mm.
It shows the value of D when f ₀ and .
Note that φ ₀ is the diameter of the driver unit, and φ ₁ is the diameter of the coil bobbin 7.

【table】

【table】

[Table] φ ₁ /φ of the unit in each table is 0.52. FIGS. 2 and 3 show the characteristics of Tables 1 and 2, respectively, using the above-mentioned D as a parameter, with frequency on the horizontal axis and level on the vertical axis. However, ×10 ^-4 is omitted. In the case of the units shown in Table 1, D=3.3 (however ×
10 ^-4 is omitted; the same applies hereafter), the f ₀ is sufficiently low, but in this case, there is no so-called tension in the midrange and treble range, and the sound is unsatisfactory in terms of hearing. Also, for the unit with D = 5.9, f ₀ is 210
It was found that the frequency became quite high, such as Hz, and that the extension of the so-called bass range was insufficient. On the other hand, the one with D=4.4 has a sufficiently low f ₀ , that is, it has a rich bass range and a sufficiently smooth and firm tone in the midrange and high range, which is extremely good for hearing. This was recognized. In the case of the units shown in Table 2, D=
It was recognized that the one with 4.5 has a rich bass range and very smooth midrange and high range, and D=
With the 3.0 unit, there is no so-called tension in the sound, and the D
I felt that the midrange range was lacking with the one with =6. In the case of the units shown in Table 3, D=
It was found that 4.2 was the most preferable in terms of hearing, while D=2.8 lacked tension, and D=6.5 lacked bass. As a result of various other experiments, we found that the diaphragm 5 was
Although the dynamic headphone is made smaller by forming it from a sheet of polyethylene terephthalate resin and by selecting the ratio D of t/φ between 4×10 ^-4 and 5×10 ^-4 , In this case, it has been confirmed that it is possible to obtain a unit that can reproduce sound with good extension in the bass range, firmness, and good audibility, almost regardless of the size.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a dynamic headphone to which the present invention can be applied;
3 and 3 are characteristic curve diagrams thereof, respectively. 1 is a frame, 2 is a magnet, and 5 is a diaphragm.

Claims (1)

[Claims] 1. A diaphragm to which a bobbin of a voice coil arranged in a magnetic circuit is attached is made of a single sheet made of polyethylene terephthalate resin material, and the vibrating diameter of the sheet is φ. , where the thickness is t, the ratio t/φ is selected from t/φ=4×10 ^-4 to 5×10 ^-4 .