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FIELD OF THE INVENTION This invention relates to loudspeakers used in acoustic products, such
as radio cassettes, etc. (I-F1 stereo). 2. Prior Art Conventionally, the speaker is as shown in FIG. 3
in the case of an external magnet type speaker of a conically shaped diaphragm as an example.
That is, the magnet 2 is joined to the pole piece attached plate l, and the top plate 3 is joined to
the face on the opposite side to the joined face of the magnet with the pole piece attached plate.
Then, in the magnetic gap G formed by the top plate 3 and the pole piece 1, the wire ring 5 of the
voice coil 5 joined to the damper 4 fixed to the frame 7 is not touched around the gap. Distribute.
The diaphragm 6 is joined to the voice coil 5, and the outer periphery is joined to the frame 7 via
the edge 8. Further, in the middle of the diaphragm 6, a dust gap 9 is joined in order to prevent
dust from entering the magnetic gap. Next, in operation, when a source current flows through the
voice coil wire ring 5, the wire ring 5 receives force from the magnetic flux of the magnetic gap
and reciprocates in the direction of the arrow (@) in the figure. The diaphragm 6 joined to the
voice coil 5 moves along with it, and vibrates the air in front of the diaphragm to generate a
sound. Originally, a speaker ideally has a constant sound pressure-frequency characteristic and a
constant sound power characteristic from the low band to the high band, but the limit frequency
of the high band that can be reproduced by the conventional speaker is that of the diaphragm. It
is known that the reproduction acoustic power is determined by the apex angle “α”, and is
reduced by −6 dBloCT from the frequency of “Ka> 1” (the length of the outer periphery of the
diaphragm is larger than the wavelength) to the high frequency range. The problem to be solved
by the invention In the conventional speaker, a feeder. When designing a speaker that
reproduces a high range, such as a full range speaker, the limitation to the high range
reproduction described above appears notably, and the speaker performance is determined. If
this phenomenon is represented by a sound pressure frequency characteristic, FIG. It will be.
Here, the high frequency range reproduction limit frequency I is determined by the apex angle of
the diaphragm. Also, the frequency f where the sound pressure drop in the directional
characteristics (here defined as the sound pressure-frequency characteristics at a position at an
angle from the front of the speaker) is determined by the diameter of the diaphragm, and the
larger the speaker, the higher the sound area This indicates that the reproduction capability is
lowered, and the reason why the sound pressure of the directional characteristics is lowered is
because the sound power is lowered, even if the sound pressure at the front of the speaker is not
lowered (FIG. A). The sound pressure is lowered due to the directivity characteristics and the
sound power is lowered as a whole (FIG. B), where B is an angle from the front of the speaker at
the listening point when the front of the speaker is 06. It is a thing.
Then, in order to improve these characteristics conventionally, FIG. 5 (a), Tb1. (The method of cl
etc. is adopted. In the same figure (al: the cross section of the diaphragm is curved in order to
make the apex angle B of the diaphragm small and the high frequency range reproduction limit
frequency f high), the frequency fd starting to have directivity, and In order to increase jh, the
area of the vibrating plate is smaller and the weight of the vibrating plate is smaller as the treble
range becomes smaller, and a corrugation 6a having compliance is provided in the middle of the
vibrating plate, as shown in FIG. A speaker having a dome-shaped diaphragm 6, which is mainly
used for tweeters, has a small diaphragm diameter, a low vibration weight, and a high fd = jh.
However, each of these has drawbacks, and Ta1. (Bl can increase fh, but the point of reducing the
diameter of vibration of the diaphragm according to the frequency is not sufficiently realized, and
split resonance of the diaphragm occurs around the diaphragm, so the directivity characteristics
In the example of (C), f, j, can be made to have a sufficiently high frequency, but the area of the
diaphragm decreases accordingly, and a cone diaphragm designed with the same magnetic
circuit The present invention has a drawback that the sound pressure at a constant input voltage
and distance is lower than that of a speaker having a lower efficiency, that is, the present
invention aims to provide a speaker capable of solving this problem. Means for Solving the
Problems The loudspeaker of the present invention has a diaphragm with a conical shape.
Operation With this structure, the sound of each point of the diaphragm can be diffused in the
form of radiation, and the reduction of efficiency can be prevented. EXAMPLE To explain the
mechanism of directivity of the conventional speaker in the example of the space combined type
speaker system in FIG. 6, the sound pressure at a distance sufficiently larger than the system
dimension in the direction of a constant angle θ from the system center The sum of the sound
pressure of the speakers, and at θ−0, the sounds of the respective speakers 81 to S 4 are in
phase at the listening point and do not interfere, but as θ increases, the distance to the listening
point between the speakers This causes a difference in phase at the listening point of the sound
of each speaker, causing interference and a drop in sound pressure. That is, there is no difference
in the distance to the listening point of S1 to S4 with R1′′TR2 # R3I = IR, when θ−0 @, but R,
′ − R2 ° + rsin θ when θ> 0. R2 ′ ′ qRa ′ + rsin θ, R8 °! As R4 '+ rsin?, A difference
occurs in the distance R "to the listening point of each speaker. This interference is higher in
That is, the wavelength is increased. That is, the shorter the wavelength, the more noticeable it
becomes. With such a mechanism, the spatial combination type speaker produces directivity, but
this can be applied to the speaker unit alone. That is, the sound at each point of the diaphragm
interferes at a listening point having an angle from the front of the speaker, and the sound
pressure here is lower than that of the front of the speaker. Therefore, directivity can be
improved by arranging the speakers 81 to S5 radially on a curve as shown in FIG. It is the
present invention that this method is applied to a speaker unit. That is, it suffices to realize a
structure in which the sound of each point of the diaphragm is diffused radially, which can be
obtained by making the shape of the diaphragm reverse to the conventional one. FIG. 1 is a crosssectional view of an essential part of a speaker according to an embodiment of the present
invention. In the figure, the same reference numerals as in FIG. 3 denote the same parts. Note
that 6 'is a diaphragm whose shape is smaller than the apex angle .alpha. Of the straight line
connecting the voice coil 5 and the outer periphery of the diaphragm. I am trying to be Fig. 2 (al
is the loudspeaker of this embodiment, Fig. 2 (bl is the measured value of the directivity
characteristic of the conventional loudspeaker, but the characteristics of the loudspeaker of this
embodiment with θ-45 with respect to θ-00) It can be seen that the difference is significantly
improved compared to that of conventional speakers. On the other hand, it can also be seen that
the sound pressure level is lowered by an amount corresponding to the improvement of the
directivity characteristic in the θ−0 ° characteristic. Effect of the Invention The present
invention does not cause deterioration of directivity characteristics, which is a drawback of the
conventional high-frequency reproduction speaker (it is possible to reproduce up to the highfrequency range, and causes differences in sound quality due to differences in listening position
to the acoustic system. It is possible to realize a difficult acoustic system.
Brief description of the drawings
Name of Agent Attorney Nakao Toshio Nakao 1 /--Onl Heath 'L-) z--Mabnet 6'-1 1 謙 第 Figure 3
Figure 4 f District jh 錬 5 Fig. 6
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