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JP2004112283

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DESCRIPTION JP2004112283
A distributed loudspeaker system suitable for sound image localization is provided. A plurality of
downward speakers 21 are dispersedly arranged on a ceiling 5 above a sound surface Ph, and a
diaphragm 22 of the speakers 21 has a hyperbolic paraboloid shape. The outer diameter W of
the diaphragm 22 is set to a size that makes it possible to easily obtain the required sound
pressure level on the sound receiving surface Ph according to the distance to the sound receiving
surface Ph (ceiling height H-sound receiving surface height h) The ratio of the diameter B of the
voice coil coupled to the inner end along the diaphragm shape to the outer diameter W is
determined so that the directivity characteristic is flat in the low / mid range and gradually
decreases in the high range. Preferably, the voice coil diameter B is 28 to 69% of the diaphragm
outer diameter W. The diaphragm 22 is desirably made of a material having a low density and a
high Young's modulus. More preferably, the horn 25 having an opening angle corresponding to
the distance between the sound receiving surface Ph and the ceiling 5 is attached to the speaker
21, and the diaphragm 22 is used as a horn driver. [Selected figure] Figure 1
Distributed loudspeaker system
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
distributed loudspeaker system, and more particularly, to a loudspeaker system for providing
loudspeakers having a uniform timbre on the receiving surface of the large space by means of
loudspeakers distributed on the ceiling of the large space. About. The present invention can be
effectively applied to a loudspeaker system that uses a distributed speaker to localize a sound
image. [0002] When designing a loudspeaker system in a large space such as a public facility, a
sports facility, a hall, etc. used by an unspecified number of people, the direction of the speaker
using the hearth effect (preceding sound effect) It is important to localize the sound image so
that the sound can be heard from the speaker and to enhance it to create a sense of unity
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between the speaker and the listener and to improve the clarity of the sound. The hearth effect is,
for example, as shown in FIG. 13B, when a sound from the direction of the speaker A (preceding
sound) is heard at the sound receiving point, the time delay and sound pressure of a certain
range from the speaker B in another direction It is a psychoacoustic effect which localizes
another sound (reinforcement sound) which arrives with a level difference in the direction of the
speaker A (direction of preceding sound). FIG. 13A shows the arrival time difference between the
preceding sound and the reinforced sound at which the hearth effect is obtained at the sound
receiving point (delay time, Tb-Ta = the sound receiving point arrival time of the reinforced
sound-received the preceding sound) The relationship between the point arrival time) and the
arrival sound pressure level difference (Lb−La = the sound reception point arrival sound
pressure level of the reinforcement sound−the sound reception point arrival sound pressure
level of the preceding sound) is shown. The shaded area in the figure is the area where the
hearth effect is obtained, that is, the sound image localization area. Conventionally, a semidispersed loudspeaker system is known as a loudspeaker system using the hearth effect. In the
semi-dispersed loudspeaker system, the main speaker is arranged near the speaker, and the
sound is also emitted from the distributed speaker arranged on the ceiling, and the sound of the
main speaker is dispersed about 10 ms seconds after reaching the receiving point. The sound
image is localized to the speaker by controlling the time of sound generation of each speaker so
that the sound from the speaker reaches the sound receiving point. However, the semi-dispersed
loudspeaker system is sometimes referred to as a loudspeaker target space (hereinafter referred
to as a sound field). Is applicable if the distance is relatively narrow (for example, R2 / R1 = 3 to
5 where R2 is the distance from the speaker to the rearmost seat and R1 is the ceiling height),
but if the sound field becomes wider It is difficult to obtain sound image localization at all sound
receiving points, and there is a problem that it is difficult to cope with changes in the position of
the sound source. On the other hand, the present inventor does not use a main speaker different
from a distributed speaker like the semi-distributed speaker system, but uses a distributed
speaker system using only the distributed speakers having substantially the same acoustic
characteristics. Sound image localization and loud sound that can obtain sound image localization
at all sound receiving points even in a field (for example, the sound field of R2 / R1> 5) and can
adjust the direction of sound image localization to the sound source according to the change of
the position of the sound source There is also a system (hereinafter, referred to as a distributed
sound system for sound image localization.
Was developed and disclosed in Patent Document 1. An example of the sound image localization
system disclosed in Patent Document 1 is shown in FIG. In the illustrated example, a plurality of
speakers Sj (1 ≦ j ≦ n) having substantially the same acoustic characteristics used for the
amplification of the sound of the sound source O at a predetermined position above the sound
receiving surface Ph %) And dispersed downward, and the portions on the sound receiving
surface Ph below the speakers Sj in the vertical direction are regarded as the sound receiving
points Pi (1.ltoreq.i.ltoreq.n). The sound receiving surface Ph is, for example, a virtual surface
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assumed at the height h of the ear of the listener 2 on the floor surface 6. A microphone 3 is
placed in the vicinity of a sound source O such as a speaker or a performer in a sound field, and
an acoustic signal from the sound source O is input to each speaker Sj distributed by the signal
transmission device 10. The signal adjustment device (effector) 20 for adjusting the acoustic
delay and the sound pressure level of each speaker Sj is inserted between the signal transmission
device 10 and each speaker Sj, and each signal adjustment is performed by the computer 30
connected to each signal adjustment device 20 The control of the acoustic delay and the input
power of the device 20 is collectively controlled. The code ¦ symbol 11 in a figure shows a mixer
and the code ¦ symbol 12 shows an amplifier. FIG. 15 shows a flow chart of a control method of
the signal conditioning device 20 by the computer 30 to obtain sound image localization. First, of
the speakers Sj, the speaker closest to the sound source O (for example, S1) is selected as the
main speaker So by the speaker selection means 31 of the computer 30, and the remaining
speakers are ascending order of distance from the main speaker So by the speaker ranking
means 32. The peripheral speakers Sgx (x = 1, 2,..., (N-1)) are ranked (steps S001 to S003). From
the main speaker So, the main speaker sound instruction means 33 of the computer 30 produces
the loud sound of the sound of the sound source O at the time zero without time delay with the
required input power (step S 004). In steps S 005 to S 008 in FIG. 15, according to the ascending
order of the order of the peripheral speakers Sgx, the sound generation time of each peripheral
speaker Sgx is determined by the peripheral speaker sound instructing means 34 of the
computer 30. That is, for each of the peripheral speakers Sgx, the loud sound arrival time Txx
from the peripheral speaker Sgx is the loud sound arrival time Tox from the main speaker So at
the sound reception point Pgx (for example Pg15) below the peripheral speaker Sgx (for example
Sg15). On the other hand, the tone generation time of the peripheral speaker Sgx (for example,
Sg15) is calculated so as to be delayed by the delay time Δtx for giving the hearth effect (Txx =
Tox + Δtx).
Further, in steps S 009 to S 012 in FIG. 15, according to the ascending order of the order of the
peripheral speakers Sgx, the peripheral speaker sound instructing unit 34 determines the input
power of each of the peripheral speakers Sgx. That is, for each of the peripheral speakers Sgx, the
lower ranks reached prior to the loud sound arrival time Txx from the peripheral speaker Sgx (for
example Sg15) at the sound reception point Pgx (for example Pg15) below the peripheral
speaker Sgx (for example Sg15) The sum total (ΣLkx + Lox) of the reaching sound pressure
levels of the peripheral speakers Sgk (k = 1, 2,..., (X−1)) of the speaker and the loud sound from
the main speaker So is determined Loud sound arrival sound pressure level Lxx (= ΣLkx + Lox +
ΔLx) from the peripheral speaker Sgx (for example, Sg15) is determined to be higher by the
sound pressure level difference ΔLx to be supplied, and peripheral speaker Sgx (for example,
corresponding to the determined arrival sound pressure level Lxx) Calculate the input power of
Sg15). The arrival sound pressure levels Lkx and Lox from the peripheral speakers Sgk and the
main speakers So at the sound receiving point Pgx are the distances from the respective speakers
Sgk and So to the sound receiving point Pgx and the input power and acoustic characteristics of
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the speakers Sgk and So. It can be determined as a function. The tone generation time and input
power of each of the peripheral speakers Sgx can be determined by repeating steps S005 to
S012 in FIG. 15 in ascending order of rank for all the peripheral speakers Sgx. By generating the
loud sound of the sound of the sound source O from each of the peripheral speakers Sgx at the
calculated sounding time by the signal adjustment device 20 at the calculated sounding time, the
sound source is generated at every sound receiving point Pi on the sound receiving surface Ph.
The sound image can be localized in the direction toward O. In addition, localization of the sound
image to the moving sound source O (for example, a questioner appearing at an unspecified
position) by reselecting the main speakers and ranking the peripheral speakers according to the
movement of the position of the sound source O Can. A conventional distributed loudspeaker
system uses a frequency band that includes most of the audio power (eg, a frequency band
ranging from 125 Hz to 8 kHz). Hereinafter, it is called a voice band. Generally, it is common to
use a full-range type cone speaker for reproducing one by one, or a composite speaker in which a
low range reproduction speaker (woofer part) and a high range reproduction speaker (tweeter
part) are combined. For example, when the ceiling of the sound field is not very high, a system is
constructed by distributively arranging full-range cone speakers having a nominal aperture of
about 10 to 16 cm on the ceiling.
When the ceiling is high, for example, a woofer unit in which the horn is attached to a largediameter cone speaker with a nominal aperture of about 250 to 300 mm and a tweeter unit in
which the horn is attached in order to obtain sufficient sound pressure on the sound receiving
surface Ph. The two-way type composite speaker to be used is used. [Patent Document 1]
Japanese Patent No. 3273561 [Patent Document 2] Japanese Patent Application Laid-Open No.
10-229595 [Non-Patent Document 1] Hirataro Nakajima "Hi-Fi Speaker" "Japanese Broadcasting
and Publishing Association", Japan Broadcasting and Publishing Association, January 20, 1943
First edition, p52 to p55 [Non-Patent Document 2] JAS journal, MARCH 2000 No. 1 3. Japan
Audio Society, March 2000 [0012] However, when actually constructing the above-described
sound image localization system using a conventional full-range type cone speaker or composite
speaker system The following points are problems. (1) The directivity characteristics are not
secured in the vicinity of the crossover frequency of the woofer part and the tweeter part in the
conventional composite type speaker, and both timbres are different due to the difference in the
diaphragm material of the woofer part and the tweeter part. Because of the difference, the clarity
may be reduced or the reproduced sound may be unnatural. It is known that the Haas effect
shown in FIG. 13 is likely to occur when the sounds from the two speakers A and B have the
same frequency characteristics for both ears. However, in the composite type speaker, the
directivity characteristics of the woofer and the tweeter become discontinuous at frequencies
near the crossover, and dips are generated due to phase interference between the woofer and the
tweeter, so that the hearth effect hardly occurs. . In order to construct a sound image localization
system, it is desirable to use a full range speaker rather than a composite speaker so that uniform
sound pressure frequency characteristics can be obtained over the entire voice band. (2) On the
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other hand, in the conventional full-range type cone speaker, peaks and valleys occur in the
output sound pressure level in the high range of the voice band, and the directivity characteristic
is rapidly degraded although the sound pressure on the front axis is relatively high There is a
problem. In general, the directivity of a cone speaker is determined by the ratio k (= a / λ)
between the effective vibration radius of the cone (ie, the outer diameter of the cone) a and the
wavelength λ of the sound wave, and the higher the frequency, the more effective the vibration
radius a of the cone. It is known that the larger the directivity and the farther it is from the front
axis of the speaker, the more the directivity deteriorates (Non-Patent Document 1). Therefore,
when a sound image localization system is constructed using a conventional full-range cone
speaker, for example, the timbre of the high range from the speaker S5 and the height from the
speaker S4 between the sound reception point P5 and the sound reception point P4 in FIG. A
situation may occur where the tone color of the range is different, and there may be a sound
receiving point where the Hearth effect is less likely to occur.
In order to improve the generation of peaks and valleys in the high range of the cone speaker, a
curved cone speaker having a morning cone cone as a diaphragm is known (Non-Patent
Document 1). However, even with the use of a curved cone, it is difficult to sufficiently improve
the directivity. Fig. 9 shows the frequency characteristics of the sound pressure level on the front
axis of a speaker with a nominal aperture of 16 cm using a curved cone (solid line graph) and the
frequency characteristics of the sound pressure level on an axis inclined 45 degrees from the
front axis (dotted line) Graph). As can be seen from the figure, even when a curved cone is used,
large peaks and valleys occur in the sound pressure level on the front axis at a relatively low
frequency of about 5 kHz or more, and the sound pressure level on the 45 degree inclination axis
is rapid. Have deteriorated. In order to put a sound image localization system into practical use,
development of a full range type speaker in which directivity characteristics do not rapidly
deteriorate in a high range is desired. (3) Further, the conventional full-range type cone speaker
has a problem that the peak becomes large when the cone is thickened in order to obtain the
strength to withstand the horn load when the horn is attached. In order to improve the directivity
of the high-frequency range of the cone speaker, it is considered necessary to reduce the mass of
the cone, and if the cone is thickened to increase the mass, the directivity of the high-frequency
range is lowered. I will. That is, conventional cones are not suitable for horn drivers. For practical
use of the sound image localization system, it is necessary to develop a full-range type speaker
whose directivity characteristics do not deteriorate even when the horn is attached. Therefore, an
object of the present invention is to provide a distributed loudspeaker system suitable for sound
image localization. [Means for Solving the Problems] The inventor of the present invention
sometimes refers to a cone speaker (hereinafter referred to as an HP-type speaker) in which a
diaphragm has a hyperbolic paraboloid shape. I focused on). A hyperbolic parabolic diaphragm
(hereinafter referred to as an HP-type diaphragm). ) Is formed by a curved surface formed by
moving a straight line (or line segment) connecting two points on two line segments at the
position of twist along the two straight lines, or a combination of the curved surfaces It is a
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vibrating plate. Heretofore, an HP-type speaker using a hyperbolic parabolic diaphragm has been
proposed for the purpose of suppressing split vibration and obtaining high-quality sound (see
Patent Document 2 and Non-patent Document 2). An example of the HP-type speaker disclosed
in Patent Document 2 is shown in FIG.
The figure (A) shows the preparation method of an example of the HP type ¦ mold diaphragm 22,
code ¦ symbol C in a figure represents the central axis of the HP type diaphragm 22, and Q
represents the central point of the HP type diaphragm 22. FIG. Let F1 and F3 and F2 be both
ends and the middle point of arc E1 obtained by dividing the outer end peripheral edge 23 of the
cone 22 into four equal points, and let G1 and G2 be points displaced in the same direction from
the central point Q on the central axis C . For example, by moving both ends G1 and F2 of a line
connecting G1 and F2 along a straight line G1-G2 and a curve F2-F3, a hyperbolic paraboloid is
formed in a region surrounded by F2, G1, G2, and F3. Form Similarly, by moving both ends G1
and F2 of a line connecting G1 and F2 along a straight line G1-G2 and a curve F2-F1, a
hyperbolic paraboloid is formed in a region surrounded by F2, G1, G2, and F1. Form An HP-type
diaphragm is constituted by eight hyperbolic paraboloids formed in two planes of four arcs E1,
E2, E3 and E4, respectively. In the HP-type diaphragm 22 in the same figure, a hyperbolic
paraboloid surface has circumferentially a peak (for example, a region connecting F2-G1) and a
valley (for example, a region connecting F3-G2 and F1-G2). It is alternately formed. Also, as
shown in FIG. 6B, each hyperbolic paraboloid is composed of four cross sections of straight lines
in two directions, hyperbolic (Hyperbolic), and parabola (Paraboloid). It is known that the
hyperbolic paraboloid created in this manner has a lightweight but strong structure because only
shear force (shift stress) acts on the straight line of each element and bending does not occur.
The same figure (C) shows a sectional view of an example of the HP type speaker 21
incorporating the HP type diaphragm 22. The HP-type speaker 21 of the illustrated example is
characterized in the structure of the HP-type diaphragm 22, and the conventional configuration
is applied to the other parts. Conventionally, it has been reported that the HP-type speaker 21
can be used in a wide frequency band and can be manufactured inexpensively because the
degree of freedom in selecting materials is wide (paragraph 0022 of Patent Document 2).
However, the directivity characteristics of the HP-type speaker 21 have not been studied in
detail. The inventor made a prototype of the HP-type speaker 21 having the diaphragm structure
shown in FIGS. 3 to 5 and conducted a simulation experiment to confirm the directivity
characteristic of the HP-type speaker 21. The HP-type diaphragm 22 shown in FIG. 5A has a
structure in which a 16 cm circle is divided into five equal sectors, and peaks (point A) are
defined on the radius of each sector and valleys at the center of the sector. A hyperbolic
paraboloid is formed by a straight line (dotted line in the figure) connecting the ridges of the
peaks and valleys and the arcs of the fan-shaped portions.
As shown in the cross-sectional view of FIG. 5B, the outer diameter W of the HP-type diaphragm
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22 is 110 mm. FIG. 3 shows a cross-sectional view of an HP-type speaker 21 (speaker nominal
aperture 160 mm) incorporating the HP-type diaphragm 22 of FIG. As shown in the figure, the
outer peripheral edge of the HP diaphragm 22 is locked to the tip of the frame 55 by an edge 56,
and the voice coil 27 of a predetermined diameter is joined to the inward end of the HP
diaphragm 22. Unlike the conventional cone-type, the HP-type diaphragm 22 has a flat and
complex shape at the junction with the voice coil 27. Therefore, the coupling adapter 28 along
the diaphragm shape as shown in FIG. The HP type diaphragm 22 and the voice coil 27 were
joined using this. The joining position of the HP diaphragm 22 and the voice coil 27 (the drive
position of the HP diaphragm 22) is polygonal as shown in FIG. 5A. The diameter B of the voice
coil 27 is slightly smaller than the diameter of the adapter 28 because it is joined along the inner
peripheral edge of the adapter 28. A magnet 51, a center pole 52 and a yoke 53 are provided at
a portion facing the voice coil 27, and a magnetic field is formed between the center pole 52 and
the yoke 53 by the magnet 51. When the current of the voice coil 27 flows according to the voice
signal, a force is applied to the voice coil 27, and the HP diaphragm 22 joined to the voice coil 27
vibrates back and forth (up and down in the figure) to open the outer edge. Emits sound waves
from The code ¦ symbol 54 in a figure shows a damper, 54a shows a damper ring, 58 shows a
terminal board. FIG. 4 shows a perspective view of the HP diaphragm 22 including the edge 56
and the damper 54. With the diameter B of the voice coil 27 of FIG. 3 set to 20 mm, 35 mm and
50 mm, the directivity characteristic of the HP speaker 21 at each voice coil diameter B was
simulated. The simulation results are shown in the graphs of FIGS. The graph in FIG. 6 shows the
frequency characteristics on the front axis of the speaker (solid line graph) and the frequency
characteristics on the 45-degree inclination axis (dotted line graph) when the voice coil diameter
B is 20 mm. It shows that peaks and dips (peaks and valleys) occur around 1 kHz of the tone
range. It is considered that the generation of the peaks and valleys in the middle range is due to
the drive position of the voice coil 27 being too close to the center point Q of the HP diaphragm
22 (see FIG. 5B) and lack of drive power. . The graph in FIG. 8 shows the frequency characteristic
on the front axis of the speaker (solid line graph) and the frequency characteristic on the 45degree inclination axis (dotted line graph) when the voice coil diameter B is 50 mm, Indicates
that the pressure decreases.
From this graph, it is considered that the voice coil diameter B which is too large is not suitable
for a full range speaker. On the other hand, when the voice coil diameter B shown in FIG. 7 is 35
mm, the frequency characteristics on the front axis of the speaker (solid line graph) and the
frequency characteristics on the 45 degree inclination axis (dotted line graph) are shown in FIG.
There is neither a large valley on the front axis nor a sharp deterioration of the sound pressure
level on the 45-degree inclined axis, and both the on-axis characteristics and directivity
characteristics are flat in the low and middle ranges and gradually decrease in the high range
doing. If the HP type diaphragm 22 of the characteristic of FIG. 7 is used, it can be set as a full
range type speaker in which a directivity characteristic does not deteriorate rapidly in a high
sound range. FIG. 10 shows the sound pressure level on the 45 ° inclined axis of the HP
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diaphragm 22 shown in FIG. 7 and the sound pressure level on the 45 ° inclined axis of the
curved cone diaphragm shown in FIG. The comparison results are shown. In order to investigate
the cause of the difference between both graphs shown in FIG. 10, the inventor conducted a
modal analysis of the divided vibration state near 5 kHz of both diaphragms. The analysis results
are shown in FIG. 11 and FIG. In the figure, the white part corresponds to the part in the divided
vibration state. FIG. 12 shows the divided vibration state of the curved cone type diaphragm, and
shows that the resonance portion is concentrated on the outer peripheral portion of the
diaphragm. The rapid deterioration of the directivity characteristic of the curved cone type
diaphragm in the high range is considered to be the result of the phase interference becoming
stronger at a position where the angle deviates from the center due to the divided vibration
concentrated on the diaphragm outer peripheral portion. On the other hand, FIG. 11 shows the
divided vibration state of the HP-type diaphragm 22, and shows that the resonance portion is
dispersed in the whole diaphragm. In the HP-type diaphragm 22, it is considered that rapid
deterioration of the directivity characteristic does not occur because the resonance portions are
dispersed as described above. Furthermore, the inventor repeats the above simulation
experiment also for the HP diaphragm 22 other than the outer diameter W = 110 mm, and the
ratio of the diameter B of the voice coil 27 to the outer diameter W of the diaphragm 22 is 28 to
69%. It has been found that the on-axis characteristics and directivity characteristics similar to
those of FIG. 7 can be obtained by selecting within the range. That is, in the HP diaphragm 22,
the directivity characteristic is improved by adjusting the ratio of the voice coil diameter B to the
diaphragm outer diameter W, and the directivity characteristic is flat in the low / mid range and
gradually decreases in the high range. Can. The present invention has been completed as a result
of further research and development based on this finding. Referring to the embodiment of FIG.
1, the distributed loudspeaker system according to the present invention is a distributed
loudspeaker system in which the sound of the sound source O is amplified by a plurality of
downward speakers 21 distributed in the ceiling 5 above the sound receiving surface Ph. In the
speaker system, the diaphragm 22 of the speaker 21 has a hyperbolic paraboloid shape, and the
outer diameter W (see FIGS. 3 and 5) of the diaphragm 22 is the distance to the receiving surface
Ph (ceiling height H in the illustrated example) -A diameter B of the voice coil 27 coupled to the
inward end of the diaphragm 22 along the diaphragm shape so that the required sound pressure
level can be easily obtained on the sound reception surface Ph according to the sound reception
surface height h) The ratio to the outer diameter W of 3) and 5) is determined so that the
directivity characteristic is flat in the low and middle range and gradually decreases in the high
range.
Preferably, the voice coil diameter B is in the range of 28 to 69% of the diaphragm outer
diameter W. More preferably, the diaphragm 22 is made of a material having a low density and a
high Young's modulus. For example, the material of the diaphragm 22 is preferably in the range
of a density of 0.60 to 1.15 g / cm <3> and a Young's modulus of 6 to 15 GPa. DETAILED
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the
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speaker system of the present invention is applied to a sound field in which ceilings different in
height H1 and H2 are adjacent to each other. In the illustrated example, on the ceiling 5 above
the sound receiving surface Ph, for example, a plurality of HP-type speakers 21 in which HP-type
diaphragms 22 shown in FIGS. However, the shape of the HP diaphragm 22 is not limited to the
illustrated example, and there are various possibilities. For example, the number and height of
the peaks and valleys of the HP-type diaphragm 22 shown in FIG. 5 and the overall depth are
also optimum by repeating modal analysis (FEM modal analysis) by the finite element method
and in-kind simulation. It can be determined experimentally to obtain on-axis characteristics and
directional characteristics. The outer diameter W of the diaphragm 22 of each HP speaker 21 is
the required sound on the sound receiving surface Ph when an appropriate input power is
applied according to the distance between the ceiling 5 and the sound receiving surface Ph. The
pressure level can be adjusted to be easily obtained. If necessary, the horn 25 may be attached as
described later. Even when there is a step in the height (ceiling height) H from the floor 6 to the
ceiling 5 in the sound field as in the illustrated example, the external diameter W of the
diaphragm 22 for each HP speaker 21 and the dimensions of the horn are received If adjustment
is made so that a uniform sound pressure level can be easily obtained on the surface Ph, the
sound receiving surface Ph in the sound field can be concentrated on an event by adjusting the
loudness volume by the signal adjustment device 20 of each speaker 21 It can be a level. For
example, the appropriate voice level of speech in a quiet space is about 55 to 65 dB. On the other
hand, in a typical high-rise building, the distance between slabs is about 3.0, 4.5, 6.0 or 9.0m,
and the height of the ceiling of the sound field is due to this slab distance and the space under
the ceiling and under the floor. H is determined. As an example of the outer diameter W of the
diaphragm 22 where a sound pressure level of about 55 to 65 dB can be easily obtained on the
sound receiving surface Ph in the sound field, its ceiling height H is 2.2 to 4.0 m around 3.0 m
When 34-69 mm, ceiling height H is 3.8-5.2 m around 4.5 m, 69-89 mm, ceiling height H is 5.07.5 m around 6.0 m When it is 89-138 mm and ceiling height H is 7.0-11.0 m centering on 9.0
m, it is 138-280 mm.
However, in the present invention, the outer diameter W of the diaphragm 22 can be
appropriately selected according to the purpose of the sound field, the type of the event to be
held, and the like, and is not limited to this example. The mutual distance D of the HP-type
speakers 21 can be adjusted in accordance with the directivity angle of the speakers 21 so that
the sound is not interrupted at the time of sound image localization on the sound receiving
surface Ph. The directivity angle is an opening angle at which the sound pressure level is
attenuated by 6 dB with respect to the front axis direction of the speaker. In general, the
directivity angle is wider in the lower range and narrower in the higher range. Human voices
range approximately from 125 Hz to 8 kHz, but the main force is four octaves wide, from 250 Hz
to 2 kHz. For example, the mutual intervals D of the speakers 21 can be designed such that the
directivity angles of 2 kHz of the respective speakers 21 partially overlap each other (for
example, about 10 to 25%) in the sound receiving surface Ph. Further, in the present invention,
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the ratio of the voice coil diameter B to the outer diameter W of the HP diaphragm 22 is
adjusted, and as described above with reference to FIG. A wide directivity angle can be secured in
the tone range. Therefore, by designing the mutual spacing D of the loudspeakers 21 so that the
directivity angles of the treble range higher than 2 kHz of each loudspeaker 21 overlap,
substantially uniform sound pressure frequency characteristics over the entire voice band at all
points on the sound receiving surface Ph. It is possible to create a clear, near-natural sound
image localization. According to the outer diameter W of the diaphragm 22 of the HP-type
speaker 21, the voice coil diameter B in each HP-type speaker 21 has an optimum directivity in
the range of 28 to 69% of the outer diameter W Can be adjusted to An example of the voice coil
diameter B that provides the optimum directivity characteristics is 10 to 40 mm when the
diaphragm outer diameter W is less than 34 to 69 mm, and 20 to 50 mm when the diaphragm
outer diameter W is less than 69 to 89 mm, vibration When the plate outer diameter W is less
than 89 to 138 mm, it is 25 to 100 mm, and when the diaphragm outer diameter W is 138 to
280 mm, it is 40 to 160 mm. The size of the voice coil aperture B with respect to the specific
diaphragm outer diameter W can be determined by the above-described simulation experiment
within the range of 28 to 69%. Generally, the outer diameter W of the diaphragm 22 is often
described as the nominal diameter of the speaker 21. Strictly speaking, however, the diaphragm
21 is provided around the diaphragm even if the nominal diameter of the speaker 21 is the same.
The outer diameter W of the diaphragm 22 differs depending on the width of the edge 56.
For example, the diaphragm 22 used for the speaker 21 with a nominal aperture of 160 mm
shown in FIG. 3 may have an outer diameter of about 120 mm as well as the outer diameter of
110 mm. The nominal diameter of the speaker 21 is substantially determined by the pitch of the
mounting holes 59, and the outer diameter W of the diaphragm 22 is determined by the nominal
diameter and the width of the edge 56. The width of the edge 56 is appropriately selected
according to the required specification (amplitude characteristics, shape, etc.) of the speaker 21.
However, in the normal case, the HP diaphragm 22 used in the present invention can be about
69% of the nominal diameter of the speaker 21. Therefore, in the normal case, the diaphragm
outer diameter W = 34 to 69 mm corresponds to the speaker nominal aperture = 50 to 100 mm,
and the diaphragm outer diameter W = 69 to 89 mm corresponds to the speaker nominal
aperture = 100 to 130 mm, and the diaphragm The outer diameter W = 89 to 138 mm
corresponds to the speaker nominal aperture = 130 to 200 mm, and the diaphragm outer
diameter W = 138 to 280 mm corresponds to the speaker nominal aperture = 200 to 400 mm.
The present invention uses a full-range type speaker incorporating an HP-type diaphragm with
an outer diameter W according to the ceiling height, so that sound in the vicinity of a crossover
between a low range and a high range like a composite type speaker A pressure level
discontinuity and the like can be avoided, and uniform sound pressure frequency characteristics
can be obtained over the entire voice band. Also, by adjusting the ratio of the voice coil diameter
B to the outer diameter W of the HP-type diaphragm, a wide pointing angle can be secured in the
high range, so by appropriately designing the speaker spacing, any point on the sound receiving
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surface Substantially uniform sound pressure frequency characteristics can be obtained.
Therefore, the occurrence of the sound receiving point where the Hearth effect hardly occurs is
avoided. Moreover, since a wide directivity angle of each speaker can be secured in the high
sound range, the intervals (the intervals D1 to D3 in FIG. 1) of the distributed speakers can be
expanded compared to the conventional cone speaker system, and the number of speakers is
saved. It is possible to make an economical speaker system. Thus, it is possible to achieve the
provision of the "distributed loudspeaker system suitable for sound image localization", which is
the object of the present invention. Preferably, the HP diaphragm 22 is made of a material having
a high Young's modulus and a relatively low density. In a conventional cone speaker, it is known
that a resonance frequency (high sound limit frequency) f of a high sound range where peaks and
valleys are generated due to divided vibration as shown in FIG. 12 is expressed by equation (1).
In equation (1), t represents the thickness of the diaphragm, E represents the Young's modulus,
and ρ represents the density. Equation (1) indicates that the resonance frequency in the high
range can be increased by decreasing the density ρ of the diaphragm 22 and increasing the
Young's modulus E.
By making the HP diaphragm 22 of a material having a low density and a high Young's modulus,
it is possible to expect further improvement of the directivity characteristic of the high tone
range in the present invention. F∝ {E · (t <2> / ρ)} <1/2> = t (E / ρ) <1/2>. Further, by making
the HP-type diaphragm 22 of a material having a low density and a high Young's modulus, it is
possible to make the diaphragm 22 thicker and to improve its bending rigidity. As will be
described later, the HP diaphragm 22 does not generate a large peak at a specific frequency even
if it is thick to obtain strength to withstand the horn load when the horn 25 is attached. By doing
this, it is possible to prevent the deterioration of the directivity characteristics of the high range
to a minimum. Therefore, the HP diaphragm 22 is suitable for the driver of the horn, and the
loudspeaker system of the present invention can be a full range loudspeaker system in which the
directivity characteristic does not deteriorate even when the horn 25 is attached. For example,
the material of the HP diaphragm 22 can be made to have a density of 0.60 to 1.15 g / cm <3>
and a Young's modulus of 6 to 15 GPa. An example of such a material is a composite material in
which biocellulose (manufactured by Ajinomoto Co., Ltd.) is used as a matrix material and high
elastic carbon fibers, fibers such as wood pulp, mica powder and the like are used as a
reinforcing material. In the embodiment of FIG. 1, a horn 25 having an opening angle
corresponding to the distance between the sound receiving surface Ph and the ceiling 5 is
mounted on the HP-type speaker 21, and the HP-type diaphragm 22 is used as a horn driver. I
use it. An example of the HP-type speaker 21 equipped with the horn 25 is shown in FIG. By
mounting the horn 25 on the HP-type speaker 21, even when the ceiling 5 of the sound field is
high, it is possible to easily set the sound pressure level on the sound receiving surface Ph to a
necessary and sufficient level. The HP-type speaker 21 with a horn 25 shown in FIG. 2 has the
HP-type speaker 21 and the horn 25 housed in a support frame 42 provided in a space on the
ceiling. In the conventional cone speaker, it is advantageous for the outer diameter of the
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diaphragm to be small in order to avoid the rapid deterioration of directivity in the high
frequency range, and when the ceiling 5 is high, the required sound pressure level on the sound
receiving surface Ph is small. It was necessary to lengthen the horn 25 so that it could be
obtained. On the other hand, since the HP diaphragm 22 has a good directivity in the high
frequency range, the diaphragm can be made relatively large, and the horn 25 can be shortened
even when the horn 25 is mounted.
The HP-type speaker 21 with the horn 25 shown in FIG. 2 can be made compact by shortening
the horn 25 and has the advantage that the restriction on the installation on the ceiling 5 is
small. Further, for example, since the speaker 21 and the horn 25 can be hidden on the ceiling,
design restrictions can also be reduced. The opening angle of the horn 25 mounted on the HPtype speaker 21 limits the spread of the low / mid range, and the sound pressure frequency
characteristic substantially uniform over the entire voice band at each point on the sound
receiving surface Ph The size can be obtained. Since the HP type speaker 21 can secure a wide
directivity angle of about 90 degrees even in the high sound range, the directivity is controlled
over the entire voice band by adjusting the directivity characteristics of the low / mid range by
the opening angle of the horn 25 It is possible. For example, when constructing the sound image
localization system of FIGS. 14 and 15, the directivity in the entire band is controlled by using the
HP-type speaker 21 equipped with the horn 25, and the low and mid-range reach of each HPtype speaker 21 is reached. By limiting the range, it is possible to avoid the problem that the low
/ mid range affects far, and to avoid the arrival of the loud sound having different timbre on the
sound receiving surface Ph, so that clear sound image localization can be expected. In order to
adjust the spread of the low / mid range and make the sound pressure frequency characteristics
substantially uniform at each point on the sound receiving surface Ph, for example, the ceiling
height H is centered at 3.0 m. It is not necessary to attach the horn 25 when it is 2 to 4.0 m, but
when the ceiling height H is 3.8 to 5.2 m around 4.5 m, the opening angle is within the range of
90 ± 20 degrees, the ceiling When the height H is 5.0 to 7.5 m around 6.0 m, the opening angle
is within the range of 60 ± 20 degrees, and the ceiling height H is 7.0 to 1 1.0 m around 9.0 m
It is desirable to mount the horn 25 within the range of the opening angle 45 ± 15. In this case,
the opening angle for attenuating the mutual distance D of the HP-type speakers 21 by 3 dB of
the sound pressure level in the front axial direction of the horn 25 is a part of each other (for
example, about 10 to 20%) ) It is desirable to design to overlap. Generally, when the horn 25 is
used, the output from the horn opening surface is enhanced on the front axis, but the output
sound pressure level in the high range is reduced in the direction away from the front axis. By
partially overlapping each other by the opening angle at which the sound pressure level is
attenuated by 3 dB with respect to the front axial direction of the horn 25, the influence of the
reduction of the high sound area sound pressure level on the sound receiving surface Ph is
minimized and the sound receiving surface Ph At each of the above points, it becomes possible to
obtain a substantially uniform sound pressure frequency characteristic over the entire voice
band.
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For example, when the mutual distance D of the HP-type speakers 21 in FIG. 1 is 2.2 to 4.0 m
with a ceiling height H of 3.0 m as a center, the ceiling When the height H is 3.8 to 5.2 m around
4.5 m, the ceiling height H is 5.0 to 7.5 m around 6.0 m within the range of 4.5 ± 1.0 m When
the sound height is within the range of 6.0 ± 1.5m, the ceiling height H is within the range of
9.0 ± 2.0m when it is 7.0 to 11.0m around the center of 9.0m. It is possible to partially overlap
each other with an opening angle that attenuates the pressure level by 3 dB. As described above,
according to the loudspeaker system of the present invention, the hyperbolic parabola of the
outside diameter can easily be obtained on the sound receiving surface with the ceiling above the
sound receiving surface. The loudspeakers of the diaphragm with a plane structure are
distributed, and the ratio of the diameter of the voice coil of the diaphragm to the outside
diameter is flat in the low / mid range and flat in the high range so that directional
characteristics are obtained. As you adjust, it produces the following remarkable effects. (A) Since
a full-range type loudspeaker with a diaphragm outer diameter corresponding to the ceiling
height is used, uniform sound pressure frequency characteristics can be obtained over the entire
sound band on the sound receiving surface. (B) Since a wide pointing angle can be secured in the
high tone range, by designing the mutual spacing of the speakers appropriately, it is possible to
make virtually all points on the sound receiving surface a sound pressure frequency
characteristic that is substantially uniform. (C) It is possible to construct a system capable of
sound image localization by the hearth effect at any point on the sound reception surface,
avoiding the occurrence of the sound reception point where the hearth effect hardly occurs. (D)
Since the directivity angle of the high range is wide, the distance between the distributed
speakers can be increased, and the number of speakers can be saved to provide an economical
system. (E) By making the diaphragm of a material having a low density and a high Young's
modulus, it is possible to expect further improvement of the directivity characteristics in the high
sound range. (F) Further, by making the diaphragm made of a material having a low density and
a high Young's modulus, it is possible to obtain a system in which the directivity characteristics
do not deteriorate even if the horn is attached. (G) By mounting the horn to limit the spread of
the low / mid range, it is possible to control the directivity over the entire voice band. (H) Even if
the diaphragm is enlarged, good directivity characteristics in the high sound range can be
obtained. Therefore, even when the horn is attached, the horn can be shortened to provide a
system with few restrictions on installation. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an
explanatory view of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an embodiment of an HP-type speaker equipped with a horn.
FIG. 3 is an explanatory diagram of an embodiment of an HP-type speaker. FIG. 4 is an
explanatory view of an HP diaphragm used for the speaker of FIG. 3; 5 is a top view and a
sectional view of the HP-type diaphragm of FIG. 4 and an explanatory view of an adapter for
connecting a voice coil. 6 is an example of a graph showing directivity characteristics when the
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voice coil diameter of the HP type speaker of FIG. 3 is 20 mm. 7 is an example of a graph
showing directivity characteristics when the voice coil diameter of the HP type speaker of FIG. 3
is 35 mm. 8 is an example of a graph showing directivity characteristics when the voice coil
diameter of the HP speaker of FIG. 3 is 50 mm. FIG. 9 is an example of a graph showing
directivity characteristics of a conventional curved-cone diaphragm. 10 is a diagram comparing
the directivity characteristic graph of FIG. 7 with the directivity characteristic graph of FIG. 9; 11
is a view showing a modal analysis result of a divided vibration state in the vicinity of 5 kHz of
the HP diaphragm of FIG. 4; FIG. 12 is a view showing a modal analysis result of a divided
vibration state in the vicinity of 5 kHz of a conventional cone diaphragm. FIG. 13 is an
explanatory view of the Haas effect. FIG. 14 is an explanatory view of a conventional dispersive
sound system of sound localization; FIG. 15 is an example of a flowchart of the speaker control
method of FIG. 14; FIG. 16 is an explanatory diagram of an example of a conventional HP-type
speaker. Explanation of mark 1 ... speaker 2 ... listener 3 ... microphone 5 ... ceiling 5 a ... ceiling
material 6 ... floor 10 ... signal transmission device 11 ... mixer 12 ... amplifier 20 ... signal
conditioning device 21 ... HP type speaker 22 ... HP type Diaphragm 23: Outer edge 24: Inner
edge 27: Voice coil 28: Adapter 30: Computer 31: Speaker selection means 32: Speaker ranking
means 33: Main speaker sound instruction means 34: Peripheral speaker sound instruction
means 37 ... Microphone position detection device 40 ... Speaker device 41 ... Horn 42 ... Support
frame 43 ... Vibration proof rubber 44 ... Front protective frame 50 ... Cylindrical body 51 ...
Magnet 52 ... Center pole 53 ... Yoke 54: Damper 54a: Damper ring 55: Frame 56: Edge 57: Plate
58: Terminal plate 59: Mounting hole B: Voice coil diameter C: Loudspeaker central axis D:
Loudspeaker mutual spacing H: Ceiling height h: Receiving surface Height L: Sound pressure
level O: Sound source Pi: Sound receiving point Ph: Sound receiving surface Q: Diaphragm center
point R: Distance S, Sj: Speaker So: Main speaker Sgx: Peripheral speaker T: Time Δt: Delay time
W ... diaphragm outer diameter
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