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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a conventional
loudspeaker, FIG. 2 is a top view of a plate of the loudspeaker, FIG. 3 is a mechanical equivalent
circuit diagram of the loudspeaker, and FIG. Sound pressure frequency characteristics, FIG. 5, FIG.
6, and FIG. 7 are front views of the plate in the embodiment of the present invention. 4 · · · · · · · · ·
· · · · plate · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Figure 3-Figure 4-
DETAILED DESCRIPTION OF THE INVENTION The present invention provides a speaker & quot;
'capable of expanding the bass range reproduction area. FIG. 1 shows a cross section of a
conventional loudspeaker. In FIG. 1, 1 is a cylindrical yoke having an expanded surface, 2 is a
magnet fixed to the bottom of the yoke 1, 3 is a center pole fixed to the upper surface of the
magnet 2, 4 is an upper surface opening of the yoke 1 An annular magnetic gap is formed
between the inner peripheral surface of the plate 4 and the outer peripheral surface of the center
pole 3. As shown in FIG. 2, four through holes 6 are formed on the same circumference of the
plate 4 as shown in FIG. An annular frame 6 is fixed on the plate 4 and a flat diaphragm 7 is
supported by the frame 6 through an edge member 8. The reference numeral 9 denotes a coil
coil fixed to the lower surface of the flat diaphragm 7, and the voice coil 10 is wound around the
coil bobbin 9. The voice coil 10 is disposed in the magnetic gap portion. The mechanical
equivalent circuit of the conventional speaker shown in FIG. 1 is shown in FIG. Fvはボイスコイ
ル10による。 Driving force, RME: electromagnetic damping resistance by voice coil 10 '), MD:
mass of diaphragm 7, RD' 2) 7 '31: resistance of vibration system, CD: vibration of edge member
8) System compliance, lViM ^ Is the radiation mass, RM ^ is the radioactive substance 'A, MB + is
the acoustic mass of the through hole 6 in the plate 4, CB + is the back compliance by the air
chamber a at the top of the plate 4 ICB 2 is the air chamber at the bottom of the plate 4 Indicates
back compliance by. Normally, the air chamber a is smaller than the air chamber, and CBI <CB2.
The sound pressure characteristic of the speaker shown in FIG. 1 is a stepped characteristic as
shown by the characteristic B in FIG. Since the size of the through hole 6 is small, the mass of the
through hole 6 enters in series in the low frequency range, and the efficiency is reduced. far
represents the anti-resonance frequency generated by mB1, CB1 and CB2, above which the
efficiency is highly reproduced. Further, the characteristic in the case where the through hole 6 is
closed to the metal becomes A in FIG. In this case, the compliance on the rear surface of the
diaphragm is only the air chamber a, and the low range characteristic is degraded. Conversely, if
the through hole 6 is enlarged, the characteristics of C in FIG. 4 become like 1 \, but the yoke
width of the plate 4 is narrow at four places where the through hole 5 of the magnetic circuit is
provided. Since the magnetic flux density is increased, the magnetic saturation occurs, the
magnetic flux density of the magnetic gap decreases, and the sound pressure of the speaker
decreases, so the through hole 5 can not be enlarged.
The present invention is intended to eliminate the above-mentioned conventional drawbacks, and
to provide a speaker capable of expanding the low range reproduction region without causing
magnetic saturation. In the following, one embodiment of the present invention will be described
with reference to FIG. FIG. 6 shows a plate 4 used for the speaker of the present invention. The
plate 4 has a central hole 11 of radius a, and four fan-shaped through holes 12 are formed
concentrically of radius r. The fan-shaped through hole 12 is formed such that the width of the
through hole 12 becomes smaller toward the central portion of the plate 4 and the length 11 of
the yoke portion other than the through hole 12 on the concentric circle of radius r = l + 1, AI +
A2 + I13 + A4. It is formed to be 2πa. As described above, when the fan-shaped through holes
12 are formed in the plate 4, the magnetic saturation of the plate 4 does not occur, and the
reproduction region of the bass region can be expanded. FIG. 6 shows another embodiment of
the present invention, which has a radius r1. r2. 16 holes, 8 holes and 4 holes of diameter d are
formed on concentric circles of r3 respectively, satisfying 2yrr-nd (n = number of through holes
formed on concentric circles) in 2πa It is. FIG. 7 shows still another embodiment of the present
invention. In this embodiment, a V-shaped recess 14 is formed from the outer peripheral surface
side of the plate 4, and this recess 14 is shown in FIG. Is equivalent to the fan-shaped through
hole 12 in FIG. In the present invention, as described above, the maximum value of the crosssectional area on the concentric circle on which the through holes of the plate are formed is
made substantially the same as the area of the inner peripheral surface of the plate, so that
magnetic saturation does not occur. Has the advantage of being able to
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