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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
improvement of a bass reflex cabinet for enhancing the bass output of a speaker.
2. Description of the Related Art In order to enhance the bass output of a speaker, it is generally
practiced to invert the sound output emitted from the back of the speaker and to guide it to the
front side. FIG. 3 shows a conventional speaker system in which a speaker 20 for sound emission
is disposed on the front side of a housing 10, and a phase inversion baffle is configured by an
acoustic duct 30. As shown in FIG.
Although this phase-reversal baffle system is known to further enhance the output of the bass by
increasing the length of the acoustic duct 30, the length of the acoustic duct 30 corresponds to
the wavelength of the acoustic wave output. As shown by the thick line in FIG. 4, a sharp dip p
occurs in the sound pressure frequency characteristic of the speaker system at 1/2 point, and
when the drop of this frequency fa reaches 300 to 500 cycles, the sound emission characteristic
significantly deteriorates. Have the problem of
Therefore, a bass reflex type speaker system as shown in FIG. 5 is known in place of the acoustic
duct 30.
In this speaker system, the diaphragm 50 is attached to the bass reflex opening 40 by the edge
60, and the mass of the diaphragm 50 and the air capacity in the housing 10 resonate to make a
passive radiator system that enhances the sound output of bass. It is a thing.
In the equalizing circuit of this bass reflex type speaker system, as shown in FIG. 6, the drive
signal source V is converted to sound pressure by the electroacoustic transducer transformer TS
via the inductances r and l of the voice coil, and the noise is emitted. At the same time as the
output PS, a phase inversion output PR is obtained through a low pass circuit consisting of an
equivalent impedance L of compliance in the housing and an impedance C indicating the mass of
the diaphragm 50, and the bass frequency is enhanced. (Note that this equivalent circuit is shown
by speed-voltage conversion. Note that D indicates the vibration characteristics of the speaker as
mechanical impedances r1, C1 and L1, E indicates equivalently the mechanical impedances r2
and L2 of the ridge 60 of the diaphragm 50.
By the way, as understood from this circuit configuration, in order to obtain a bass output, the
capacity of the housing is increased to increase the compliance, or the vibration serving as a
passive radiator is obtained. Although it is necessary to increase the mass of the plate 50, since
the capacity can not be increased in a small speaker system, the mass (C) of the diaphragm
serving as a passive radiator is increased to further enhance the bass output. Is required.
However, if the mass of the passive radiator is increased, the edge 60 made of a visco-elastic
material is supported so as to support the passive radiator, and if it is stiffened to suppress the
deflection, the compliance of the edge can not be ignored. Good low frequency characteristics
can not be obtained.
That is, there is a problem that the mechanical impedance (r2, L2) degrades the characteristics of
the phase inversion output PR. Also, at this time, noise may be generated from the edge.
SUMMARY OF THE INVENTION The present invention has been made to solve the above
problems, and by constituting the passive radiator with a suspended diaphragm, the mechanical
of its holding mechanism is realized. By making the impedance a non-influential value, the mass
of the passive radiator is increased at that time.
[Function] The mass of the diaphragm is increased by making it suspended, and resonating with
the space of the cabinet by pendulum movement at a low frequency when it is vibrated by the
back pressure of the speaker Can.
In addition, since the mechanical impedance due to suspension has little influence on vibration
characteristics, it easily enhances high-quality bass acoustic vibration waves.
speaker system according to the present invention, and FIG. 2 is an enlarged perspective view of
a portion of a closing plate which becomes a passive radiator. In this figure, reference numeral
10 denotes a closed casing, and on the front side thereof, a speaker 20 for sound emission is
attached. A bass reflex opening 40 is provided on the front side of the housing 10 in the same
manner as in FIG. 5, and a closing plate 80 suspended by a hinge 70 is disposed in the bass
reflex opening 40.
The periphery of the bass reflex opening 40 is a frame 90 slightly larger than the closing plate
80, and the closing plate 12 is fixed for pendulum movement by a hanging hinge 70 at the upper
end of the frame 90. The bottom 90a of the frame 90 is formed in an arc shape as shown in FIG.
2 and is always constant between the bottom end face of the closing plate 80 and the bottom
90a of the frame when the closing plate 80 is pendulous In such a way that a narrow gap of
The speaker system according to the present invention having the above-described structure
allows vibration pressure to be generated in the space inside the housing by the sound pressure
emitted from the back surface of the speaker 20, and the closing plate is made according to the
vibration pressure. The 80 oscillates and the mechanical resonance frequency determined by the
air compliance in the housing and the mass of the closing plate enhances the bass of the acoustic
output. Then, the bass acoustic wave is emitted from the bass reflex opening 40 in a phaseinverted state to increase the bass output of the speaker.
The bass resonance frequency can be lowered as the mass of the closing plate is increased. In the
case of the present invention, since the closing plate 80 is only suspended by the hanging hinge
70, the hinge 70 does not inhibit its movement even when the closing plate's mass increases. Can
be made and the vibration characteristic of the bass part can be made sufficient.
The hanging hinge 70 may be made of a flexible material and high in tensile strength. For
example, a skin, a thread or the like can be used. In addition, the closing plate 80 itself is made of
a material that hardly causes divided vibration, and can be, for example, wood, a diaphragm
material, or a metal product. In the case of a metal product, it is preferable that a standing wave
is not generated by appropriately providing an uneven groove.
As described above, the loudspeaker system according to the present invention uses the closing
plate suspended in the bass reflex opening as the diaphragm which becomes a conventional
passive radiator. Increasing the mass of the closure plate makes the hinge holding the closure
plate stiffer so that its mechanical properties do not affect the vibration characteristics. In
addition, since the resonance frequency of the bass portion can be lowered by increasing the
mass, there is an effect that a sufficient bass acoustic wave can be obtained with a small cabinet.
Brief description of the drawings
1 is a schematic diagram showing the speaker system of the present invention FIG. 2 is a
perspective view of the bass reflex opening of FIG. 2 is an explanatory view of a conventional
example of the bass reflex speaker system of FIG.
4 is a sound emission characteristic diagram of the speaker.
5 is a schematic diagram of a passive radiator type speaker system.
6 is an equivalent circuit diagram of a passive radiator system.
Explanation of sign
DESCRIPTION OF SYMBOLS 10 Speaker housing 20 Speaker 30 Sound duct 40 Bass reflex
opening 70 Hanging type hinge 80 is a closing plate
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description, jph04309096
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