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JP2010278590

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DESCRIPTION JP2010278590
The present invention provides a speaker unit capable of creating a large sound field space even
in a high frequency range with high sound quality with little noise. A speaker unit is configured
to drive a diaphragm (5) through a voice coil (3) by a magnetic circuit (2) including a pole piece
(24), and the diaphragm (5) faces an upper end face of the pole piece (24). A center cap 8 is
provided at the center of the diaphragm 5 opposite to the upper end face of the pole piece 24.
On the upper end surface of the pole piece 24 is fixed an acoustic anisotropic member 6 having
anisotropy in the propagation velocity of sound waves and having an internal loss larger than
that of the pole piece 24. The acoustic anisotropy member 6 is a wood piece such as a hippo, and
its fiber direction is crossed to the axis of the pole piece 24. [Selected figure] Figure 1
スピーカユニット
[0001]
The present invention relates to a dynamic type speaker unit provided with a magnetic circuit
including a magnetic circuit including a pole piece that generates a direct current magnetic field
acting on a voice coil, and can reproduce high quality sound with particularly low noise and
create a large sound field space even in a high sound range. The present invention relates to a
speaker unit that can be
[0002]
The speaker unit is roughly classified into a dynamic type (electrodynamic type) and a capacitor
type (electrostatic type) according to a method of converting an alternating current electric
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signal into mechanical vibration, and the main stream is a dynamic type.
A dynamic speaker unit has a voice coil placed in a direct current magnetic field formed by a
magnetic circuit including a pole piece, and is configured to drive a diaphragm by Lorentz force
generated there (for example, Patent Document 1).
[0003]
The magnetic circuit is of an inner magnet type or an outer magnet type, and in each of the voice
coils, a pole piece constituting a magnetic circuit is inserted. In addition, the diaphragms joined to
the voice coil include a dome type, a flat type, a cone type, etc., and the whole of the dome type
diaphragm is bonded to the voice coil facing the upper end face of the pole piece and the planar
type diaphragm Is partially joined to the voice coil so as to face the upper end face of the pole
piece, and in the case of a cone type diaphragm, a center cap opposite to the upper end face of
the pole piece is mounted at the center thereof. The upper end surface of the pole piece refers to
the surface on the diaphragm side in a state in which the speaker unit is placed with the
diaphragm on the upper side.
[0004]
JP 2003-333688 A
[0005]
In the speaker unit as described above, when the center cap or diaphragm opposed to the upper
end face of the pole piece vibrates, the sound radiated to the back side of them vibrates on the
pole piece to generate echo sound, or the pole piece It resonates to generate resonance sound.
The echo sound and resonance sound are mixed with the sound directly radiated forward from
the diaphragm and are heard as offensive noise.
[0006]
Therefore, it is also practiced to fill a sound absorbing material such as glass wool between the
pole cap and the center cap or the back side of the diaphragm, but according to this, it is
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necessary to suppress the generation of echo and resonance noise by the pole piece. Even if it is
possible, the reproduced sound is aurally turbid and the high-range sound does not spread, so
the directivity in the high range is sharp and a large sound field space can not be created.
[0007]
The present invention has been made in view of the above-described circumstances, and an
object thereof is to provide a speaker unit capable of creating a large sound field space with high
sound quality with little noise and high pitch.
[0008]
In order to achieve the above object, a speaker unit according to the present invention comprises:
a voice coil 3 formed by winding a conductive wire around a coil bobbin 31; a magnetic circuit 2
including a pole piece 24 inserted inside the voice coil 3; The diaphragm 5 joined to the tip of the
voice coil 3 has an anisotropy in the propagation velocity of the sound wave and an internal loss
larger than that of the pole piece 24 so as to face the diaphragm 5 of the pole piece 24 And an
acoustic anisotropic member 6 fixed to the opposite surface.
[0009]
The diaphragm 5 is characterized by being a dome-shaped diaphragm.
The diaphragm 5 is a cone-shaped diaphragm having a central hole 5a communicating with the
voice coil 3, and further includes a center cap 8 covering the central hole 5a.
[0010]
In addition, the acoustic anisotropic member 6 is characterized in that it is a wood piece arranged
so that the fiber direction intersects the direction orthogonal to the opposing surface of the pole
piece 24.
Furthermore, the wood piece includes a first wood piece 6a and a second wood piece 6b
arranged so that the fiber directions are orthogonal to each other in the plane of the opposing
surface of the pole piece 24 or in a plane parallel to the opposing surface. It features.
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[0011]
According to the speaker unit according to the present invention, the acoustic anisotropic
member having anisotropy in the propagation velocity of the sound wave and the internal loss
larger than that of the pole piece is fixed to the opposing surface of the pole piece facing the
diaphragm. Thus, the sound radiated from the diaphragm or center cap opposite to the opposing
surface of the pole piece to the back side is attenuated to suppress the generation of resonance
noise or echo due to the pole piece, and by the acoustic anisotropic member. The sound field can
be expanded by spreading the sound in the direction in which the propagation speed of the
sound wave is high.
[0012]
In particular, since wood chips are used as the acoustic anisotropic member, the product cost can
be suppressed, and the propagation speed of the sound wave is high in the fiber direction of the
wood pieces, and the fiber direction intersects the direction orthogonal to the facing surface of
the pole piece As such, the reproduction sound can be spread in the fiber direction intersecting
the direction orthogonal to the facing surface.
[0013]
In addition, a wood piece as the acoustically anisotropic member includes a first wood piece and
a second wood piece arranged so that the fiber directions are orthogonal to each other in the
plane of the facing surface of the pole piece or in the plane parallel to the facing surface. In this
case, the reproduced sound can be spread in two directions (upper, lower, left, and right
directions) corresponding to the fiber directions of both pieces of wood.
[0014]
Sectional drawing which shows the speaker unit which concerns on one embodiment of this
invention Schematic which shows the front end surface of the pole piece which fixed the acoustic
anisotropic member, Explanatory drawing which shows the fiber direction of the wood piece
which comprises an acoustic anisotropic member acoustic difference Explanatory drawing which
shows the example of a change of a directional member, sectional drawing which shows the
example of a change of the speaker unit concerning one embodiment of the present invention
[0015]
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Hereinafter, an embodiment of the present invention will be described in detail based on the
drawings.
First, referring to FIG. 1, an embodiment of a speaker unit according to the present invention will
be described. The speaker unit is an electrodynamic (dynamic) tweeter (for high sound).
Reference numeral 1 denotes a frame of the speaker unit, and a magnetic circuit 2 (external
magnet type in the illustrated example) is attached to the frame 1.
[0016]
The magnetic circuit 2 is mounted on a ring-shaped magnet 21 magnetized in the thickness
direction, a ring-shaped top plate 22 mounted on one of the magnetic poles of the magnet 21,
and the other magnetic pole of the magnet 21. And a pole piece 24 provided at the center of the
back plate 23. A magnetic gap G in which the magnetic flux of the magnet 21 acts is formed
between the pole piece 24 and the top plate 22. It is done.
[0017]
The top plate 22, the back plate 23, and the pole piece 24 become a yoke for collecting the
magnetic flux of the magnet 21 in the magnetic gap G, and the voice coil 3 is inserted in the
magnetic gap G.
The back plate 23 and the pole piece 24 may be integrally formed.
[0018]
The voice coil 3 is formed by winding a conductive wire such as copper or aluminum coated with
an insulating film around the outer periphery of a non-conductive (a conductive nonmagnetic
material such as aluminum may be used) made of paper or the like. The upper end portion of the
pole piece 24 is inserted into the inner periphery of the wire portion 32, and the inner peripheral
surface of the top plate 22 faces the winding portion 32 of the outer periphery.
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The voice coil 3 is attached to the frame 1 via the damper 4 and supported movably in the frontrear direction (the direction of the axis passing through the center of the voice coil 3 and in the
vertical direction in FIG. 1) by the damper 4 Its tip is joined to the dome-shaped diaphragm 5.
[0019]
The diaphragm 5 is a dome-shaped radiator formed of paper, wood, or a synthetic resin such as
polypropylene or polyester, aluminum or other metal, or chemical fiber, as is apparent from FIG.
Of the voice coil 3 so as to face the upper end surface of the voice coil 3.
The upper end surface of the pole piece 24 is an opposing surface opposed to the back surface of
the diaphragm 5.
[0020]
Then, according to the speaker unit configured as described above, it is known that the voice
current flows in the voice coil 3 (precisely, the winding portion 32) orthogonal to the magnetic
lines of the direct current magnetic field generated in the magnetic gap G. Thus, the voice coil 3
vibrates by obtaining an oscillating force in the axial direction, and the vibration is converted to
air vibration through the diaphragm 5 so that sound can be reproduced.
[0021]
When the diaphragm 5 vibrates in the front-rear direction (vertical direction in FIG. 1), the sound
radiated to the back side (the rear side where the pole piece 24 is located) is reflected to the pole
piece 24 to generate echo sound. The pole piece 24 resonates to generate a resonant sound.
Therefore, according to the present embodiment, the acoustic anisotropic member 6 instead of
the conventional sound absorbing material is fixed (fixed) to the upper end surface of the pole
piece 24 with an adhesive or the like.
[0022]
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The acoustic anisotropic member 6 has anisotropy in the propagation speed of sound waves
(hereinafter referred to as the speed of sound) and has an internal loss larger than that of the
pole piece 24.
The pole piece 24 is made of magnetic metal and its internal loss varies depending on the
material, but is about 0.001 to 0.01. Those having a larger internal loss than the pole piece 24 of
that kind and having anisotropy in the speed of sound include pieces of wood in which fibers
such as hippopotamus, china or beech extend along one direction. Their internal loss is 0.02 to
0.03, and the speed of sound is 4.5 to 6 km / s in the fiber direction (longitudinal direction), and
2 to 2.5 km / s in the direction orthogonal to the fiber direction (lateral direction) It is. In
particular, as the above-mentioned wood chip, a grained grain material in which grain appears
parallel is suitably used, and for this purpose, it is also possible to use plate grain wood or
bamboo which is plate-shaped by hot pressing. In the wood grain, the grain by the annual rings
appears in a non-parallel state, but the fiber direction is constant although slightly inclined with
respect to the board surface. Moreover, it is preferable that a wood piece as the acoustic
anisotropic member 6 has a plate shape having a predetermined thickness (about 5 mm in this
example), and even if it is a sheet shape having a thickness of 0.1 to 1 mm. Good.
[0023]
FIG. 2 shows the upper end surface of the pole piece 24 to which the acoustic anisotropic
member 6 made of wood pieces as described above is fixed. The arrows in the figure indicate the
fiber direction of the wood piece as the acoustic anisotropic member 6. As apparent from FIG. 2,
the acoustically anisotropic member 6 made of wood pieces is a rectangular plate having a size
that fits within the upper end face of the pole piece 24, and the fiber direction is perpendicular to
the axis of the pole piece 24 (upper face It is arranged to intersect (orthogonal to) the direction.
[0024]
The acoustic anisotropic member 6 as described above attenuates the sound radiated to the back
side of the diaphragm 5 because the internal loss thereof is larger than that of the pole piece 24,
and the resonance sound or echo sound by the pole piece 24 Can be suppressed.
[0025]
In particular, FIG. 2A shows a state in which the acoustic anisotropic member 6 is fixed so that
the fiber direction is in the vertical direction (vertical direction) in the usage mode of the speaker
unit. The radiated sound spreads in the fiber direction, and the sound field expansion in the same
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direction (vertical direction) becomes remarkable.
[0026]
Further, FIG. 2 (b) is a state in which the acoustic anisotropic member 6 is fixed so that the fiber
direction becomes the horizontal direction (horizontal direction) in the usage mode of the
speaker unit. The radiated sound spreads in the fiber direction, and the sound field expansion in
the same direction (left and right direction) becomes remarkable.
[0027]
In addition, when the acoustic performance of the speaker unit of the present embodiment
provided with the acoustic anisotropy member 6 as described above and the conventional
loudspeaker unit without the acoustic anisotropy member 6 is compared, the directivity pattern
in the horizontal direction is obtained. Although the speaker unit of the present embodiment has
less noise and high sound quality compared to the conventional speaker unit, and a good sense
of sound field in the high frequency range, the auditory sense is good. The superiority was clear.
[0028]
Although the preferred embodiment of the present invention has been described above, the
acoustic anisotropic member 6 is not limited to a rectangular shape, and may be a circular plate
having the same shape and size as the upper end surface of the pole piece 24.
Also, the wood piece as the acoustic anisotropic member 6 is not limited to the fiber direction
being directed vertically and horizontally.
[0029]
For example, as shown in FIG. 3, regarding the left and right speaker units L and R used for
stereo reproduction, the acoustic anisotropic member 6 is fixed so that the fiber direction is
inclined in a plane parallel to the upper end face of the pole piece 24 The fiber direction of the
acoustic anisotropic member 6 in both speaker units L and R may cross in a V shape.
According to this, it is possible to expand the sound field space in the up, down, left, and right
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directions as indicated by the one-dot chain line in FIG.
[0030]
Further, as shown in FIG. 4A, the acoustic anisotropic member 6 is constituted by the first wood
piece 6a and the two second wood pieces 6b arranged so that the fiber directions are orthogonal
to each other in the same plane, The two pieces of wood 6a and 6b may be arranged and fixed in
the same plane with the upper end face of the pole piece 24 so that the respective fiber
directions are orthogonal to each other in the plane of the upper end face of the pole piece 24
Even in such a mode, the sound field space can be expanded in the vertical and horizontal
directions.
FIG. 4 (b) shows that each fiber direction is orthogonal in a plane parallel to the upper end face
of the pole piece 24 by overlapping the first wood piece 6a on the second wood piece 6b.
Also in the mode shown in FIG. 4B, the sound field space can be expanded in the vertical and
horizontal directions.
[0031]
Furthermore, although the speaker unit according to the present embodiment has been described
as a dome-shaped speaker in the above example, in the present invention, the flat panel speaker
in which a part of the diaphragm faces the upper end surface of the pole piece or the upper end
surface of the pole piece It can apply also to a cone type speaker etc. which have a center cap
which counters.
[0032]
FIG. 5 shows an example applied to a cone type speaker.
In FIG. 5, the parts having the same structure and function as the dome-shaped speaker shown in
FIG. 1 are assigned the same reference numerals and detailed explanations thereof will be
omitted.
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[0033]
Here, the cone type speaker shown in FIG. 5 is a full range type or woofer, and its diaphragm 5 is
made of paper, wood, or a synthetic resin such as polypropylene or polyester, aluminum or other
metal, or chemical fiber, etc. A circular central hole 5a communicating with the voice coil 3 is
formed in an inner central portion which is of a cone shape and joined to the voice coil 3.
Further, the outer periphery of the cone-shaped diaphragm 5 on the large diameter side is
supported by the frame 1 via an edge 7 which allows the movement of the diaphragm 5 in the
front-rear direction.
[0034]
Further, at the center of the diaphragm 5, a center cap 8 covering the center hole 5a is mounted
facing the upper end surface of the pole piece 24. The center cap 8 is a dome-shaped member
larger than the center hole 5a of the diaphragm 5, and is formed of paper, wood, metal, or a
synthetic resin such as propylene or polyester like the diaphragm 5, and the outer periphery is
While being fixed to the diaphragm 5 with an adhesive, the tip of the voice coil 3 is also bonded
to the center cap 8. In the configuration of FIG. 5, the upper end surface of the pole piece 24 is
an opposing surface opposed to the back surface of the diaphragm 5 and the center cap 8.
[0035]
The center cap 8 has a dustproof function to prevent dust from invading the magnetic circuit 2,
and the center cap 8 itself also vibrates along with the diaphragm 5 to affect the acoustic
characteristics. In particular, when the center cap 8 vibrates in the back and forth direction, the
sound radiated to the back side (the rear where the pole piece 24 is located) is reflected to the
pole piece 24 to generate echo sound, or the pole piece 24 resonates. It generates resonance
noise. For this reason, also in such a speaker unit, the acoustic anisotropic member 6 as
described above is fixed to the upper end surface of the pole piece 24 in the same manner as in
the above example, using an adhesive or the like.
[0036]
Therefore, it is possible to spread the sound in the fiber direction of the wood piece as the
acoustic anisotropic member 6 and to expand the sound field in the same direction while
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suppressing the resonance sound and echo sound by the pole piece 24 even with the cone type
speaker concerned. .
[0037]
DESCRIPTION OF SYMBOLS 2 Magnetic circuit 24 pole piece 3 voice coil 31 coil bobbin 32
winding part 5 diaphragm 5a center hole 6 acoustic anisotropy member 6a 1st wood piece 6b
2nd wood piece 8 center cap
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