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JPS5531379

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DESCRIPTION JPS5531379
-Specification 1, title of the invention
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3. Detailed Description of the Invention The present invention relates to a loudspeaker using a
flat diaphragm, and provides a loudspeaker having a wide reproduction band and excellent
directivity. First, a speaker using a conventional flat diaphragm will be described with reference
to FIG. In FIG. 1, 1 is a yoke, 2 is a magnet fixed in the yoke 1, 3 is a plate fixed to the upper
surface of the magnet 2, and the outer peripheral surface of the plate 3 and the upper inner
peripheral surface of the yoke 1 A frame 6 is fixed to the upper surface of 1 between them, 6 is a
flat diaphragm, and an outer peripheral portion of the flat diaphragm 6 is supported by the
frame 5. A coil bobbin 7 is fixed to the lower surface of the flat diaphragm 6, and a voice coil 8 is
wound around the coil bobbin 7. The voice coil 8 is located in the magnetic gap 4. A damper 9
supports the coil bobbin 7. In this type of speaker, when a signal current is supplied to the voice
coil 8, the flat diaphragm 6 vibrates, but split resonance occurs at a certain frequency, and a
nodal circle with a diameter of about 68% of the diameter of the flat diaphragm 6 occurs. , The
inside and the outside of this nodal circle vibrate in opposite phase. Therefore, as shown in FIG.
1, when the coil bobbin 7 having a diameter of about 68 inches of the diameter of the flat
diaphragm 6 is provided and the joint circle of the flat diaphragm 6 is driven, the split resonance
mode is suppressed and the sound pressure frequency characteristic is The upper limit of the
parallel band is expanded to the second order split resonance layer mantissa. However, in the
conventional speaker described above, the voice coil EndPage: 1-1 of a diameter of about 68
inches of the diameter of the flat plate diaphragm 6 is used, and the magnetic circuit becomes
large and the cost of the magnetic circuit increases significantly. is there. Further, in the abovedescribed conventional example, the upper limit of the reproduction band can be extended only
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to the second divided resonance frequency. The present invention eliminates the abovementioned conventional drawbacks, and one embodiment of the present invention will be
described below with reference to FIG. In FIG. 2, the same parts as in FIG. 1 are given the same
reference numerals. In FIG. 2, reference numeral 10 denotes an annular flat diaphragm, and an
outer peripheral portion of the flat diaphragm 1o is supported by the frame 5 via an edge
member 11, and 012 is a link-like suspension such as a bellows. The lower surface of the ringshaped suspension 12 is fixed to the upper surface of the annular flat diaphragm. The reference
numeral 13 denotes a disk-shaped flat diaphragm, and the flat diaphragm 13 is mounted on the
upper surface of the ring-shaped suspension 12. The reference numeral 7 designates the
attachment of the flat plate vibration plate 12 to the flat plate vibration plate 10 at the joint
circle portion due to the division resonance of the flat plate vibration plate 1o, and the
attachment point of the coil bobbin 7 to the flat plate vibration plate 13 It is the inside of the part
by plate 130 division resonance.
The split resonance frequency of the flat plate diaphragm ?lO? is equal to the divided
resonance frequency of the flat plate diaphragm 13 in consideration of the plate thickness and
outer diameter of the annular flat plate diaphragm 1 o and the disk flat plate diaphragm 13. Is
also low. Next, the operation of the speaker of the present invention will be described. In FIG. 2,
when a signal is applied to the voice coil 8, the coil bobbin 7 vibrates, the flat plate diaphragm 13
vibrates, and this vibration is transmitted to the flat plate diaphragm 1o via the ring-shaped
suspension 12; The plate 10 vibrates. At such low frequencies, both flat diaphragms 13.10
vibrate. In this case, although the ring-shaped diaphragm 10 should produce split resonance at
the frequency f1 shown in FIG. 3, the inside of the plate diaphragm 10 is driven by the ringshaped superstrate 12. Also, the flat + 4r pressure frequency characteristic 1-1 is obtained up to
the frequency f2 at which the second order split resonance occurs. When the frequency is further
increased, the stiffness of the link-like suspension 12 operates as a noise filter at a frequency of
13 or more, no vibration is transmitted to the flat plate diaphragm 10, and only the flat plate
diaphragm 13 vibrates, Sound is emitted only by this flat diaphragm 13. The split resonance
should occur at the frequency 14 where the frequency is higher, but since the coil bobbin 7 is
attached to the inside of the flat plate 14, the split resonance mode at the frequency f 4 is
suppressed and the higher frequency The characteristics are flat up to the band. In the flat
diaphragm, the following relationship exists between the sound pressure P and the diaphragm
area S, and the mass m of the vibration system. P-?. , SF / 2?r?m... Density of air, F: driving
force, r + distance to measurement point on speaker axis, S 2 ? a ? (a + diaphragm radius) or 1
m 2 M 1 + 10 M 3 ииииииииии ...? ) M2: mass of diaphragm 13 M8: mass of diaphragm 10 In the
speaker of the above embodiment, the diaphragm 13 is integrally vibrated up to f3 but when it is
more than that, only the diaphragm 13 vibrates and As a result, the apparent diaphragm radius a
decreases. If you look at the mass of the vibration system in the 18 or more band, is the stiffness
of the suspension 12? Since the mass M3 of the diaphragm 10 in the equation (1) can be
ignored, the mass of the vibration system becomes Dini M ++ M2, and the vibration system mass
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m in the formula (1) also decreases. Considering the above, while the sound pressure decreases
with the decrease of the diaphragm area S at 13 or more, the decrease of the vibration system
mass m contributes to the increase of the sound pressure.
Here, assuming that the area of the diaphragm 13 is 81, and the area of the disk-shaped
diaphragm having the same outer diameter as that of the diaphragm 1Q is St, the diameter and
mass of each diaphragm for achieving sound pressure spreading over the entire town area. Find
the relationship between The sound pressure P1 at f3 or less is p, =: p6S2F / 2yrr (M, + Mt + Ma)
? ? (3) The sound pressure P2 at 13 or more is EndPage: 2 ?, JP2 = p6SIF / 2?r (M, ?1) -M,)=-(s) Therefore, it is sufficient for P2 to be in the condition P of sound compression. For example,
if the radius of the diaphragm 13 is three and the radius of the diaphragm 1o is six degrees, then
?? /B,=0.25 and the vibration maintenance mass Mt + k + Ms = 6f, in order to satisfy the fourth
formula. In addition, M ? + M2: 1.25, 7 and M3 = 3.75 y? are connected to enable flat
reproduction of sound pressure over the entire region. 3a shows the characteristics of the band
in which the flat diaphragm 13.10 vibrates integrally, and FIG. 3 shows the characteristics of the
band in which only the flat diaphragm 13 vibrates. As described above, according to the present
invention, it is sufficient to drive the node circle of the flat plate diaphragm having an outer
diameter which is sufficiently smaller than the outer diameter of the conventional flat plate
vibration / moving plate. It is possible to reduce the size to about half, which leads to the
miniaturization of the magnetic circuit and the advantage of cost reduction. Further, according to
the present invention, the reproduction band is wide: 0. Since the signal is reproduced by only
one diaphragm having a small diameter in the high region, the directivity is not sharpened in the
high region.
4. Brief Description of the Drawings FIG. 1 is a cross-sectional view of a conventional speaker,
FIG. 2 is a cross-sectional view of the speaker in an embodiment of the present invention, and
FIG. 3 is a sound pressure frequency characteristic diagram of the same speaker. Reference Signs
List 1 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и 8 иии Voice coil, 9 и и и и Damper, 10-и и и Flat diaphragm, 11 ░ ░ work flange member, 12 и и и и и и и
и ring-shaped suspension, 13 и "и и и -Flat plate diaphragm. Name of agent Attorney Nakao Toshio
and others 1 person Figure 1 Figure 2 Figure 3 ?
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