close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JPH01319791

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH01319791
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electronic musical instrument having a built-in sound system for generating musical tones, and
more particularly, to an electronic instrument having a miniaturized sound system and improved
frequency characteristics, particularly low frequency reproduction characteristics. About the
instrument. 2. Description of the Related Art In electronic musical instruments, design, frequency
characteristics, operability, etc. are both important factors. As for the frequency characteristics,
for example, the lowest sound (Ao) of the 88-key piano is 27.5 Hz, and the number of cycles eL
of the fundamental wave of the bass drum in the automatic rhythm performance is about 30 Hz.
These ultra low tones are only for the harmonics to be reproduced, even if the fundamental wave
itself is not reproduced. ! As the feeling level is corrected, there is no problem in monitoring a
normal performance. However, for example, in the case of a lotus drum, if only about 30 Hz of
the fundamental wave is emitted slightly and 50 to 60 Hz of overtones are emitted sufficiently,
the lowest reproduction frequency is felt as a heavy bass that shakes the body. There is a big
difference in sound quality, such as using a sound system of about 70 Hz or more will result in a
light sound like "bon, bon". Many recent electronic musical instruments use PCM sound sources
as sound sources, and the sound quality is extremely high if the human power signal to the
sound system is reproduced as it is. In order to reproduce high-quality musical tones, it is
desirable to improve the fidelity of a sound system incorporated in an electronic musical
instrument. The reproduction characteristics of the sound system are determined by the
reproduction characteristics of the loudspeaker system. Conventionally, a sound system
incorporated in an electronic musical instrument is constituted of a closed or phase-reversal
(bass reflex) speaker system and a power amplifier substantially having an output impedance O
for driving the so-called constant voltage. It was In this case, the minimum reproduction
frequency of the speaker system is mainly determined by the volume of the box (cabinet) and the
16-04-2019
1
characteristics (fo, Qo, etc.) of the speaker unit being used. That is, in the case of conventional
electronic musical instruments, if it is intended to reproduce lower frequency sounds, a box with
a larger volume is required, freedom in design is limited, and depending on the arrangement, it
becomes an obstacle to playing, etc. There is a disadvantage that an operation problem occurs.
FIG. 14 shows the appearance of an electronic musical instrument of a design in which the back
wall 21 and the box 7 are integrated. In the figure, 9a and 9b are bass reflex ports (resonance
ports). SUMMARY OF THE INVENTION The present invention has been made in view of the
problems in the conventional electronic musical instrument described above, and a sound
system, particularly a box constituting a speaker system, has frequency characteristics,
particularly low frequency reproduction characteristics. It is an object of the present invention to
provide an electronic musical instrument which can be downsized to improve the freedom of
design and operability, or improve the low-frequency reproduction characteristics without
upsizing the box.
[Means for Solving the Problems] The electronic musical instrument of the present invention has
an electroacoustic transducer disposed on the outer wall surface of a box with a resonant port
that constitutes a Helmholtz resonator as a sound system. A speaker system with a resonance
port, which drives the Helmholtz resonator on the inner side of the vibrating body and radiates
the sound directly on the outer side, and the transducer from the Helmholtz resonator; A sound
system including: driving means for driving so as to cancel atmospheric reaction to the vibrator
is incorporated, and at least a part of the inner wall of the box body is formed of a buffer material
for preventing pipe resonance. And In the present invention, the loudspeaker system is of the
type having a Helmholtz resonator, similar to a bass reflex loudspeaker system. Therefore, the
sound is emitted directly from the vibrating body of the electroacoustic transducer and also
emitted from the Helmholtz resonator driven by the vibrating body, and the frequency
characteristic of the output sound pressure of the speaker system corresponds to those of the
electroacoustic transducer. Radiation sound from the oscillator of the resonator and the
resonance sound from the resonator are combined and lower by a certain amount of the
resonance sound than those emitting only the direct radiation sound as in a closed speaker
system Area characteristics can be extended. In the present invention, the drive means of the
electroacoustic transducer drives the transducer so as to cancel the atmospheric reaction from
the resonator side when the Helmholtz resonator is driven. As such a driving means, a negative
impedance generation circuit which generates the negative impedance component (-20)
isometrically in the output impedance or a motional signal corresponding to the movement of the
vibrating body is detected by some method and inputted. A known circuit such as a motional
feedback (MFB) circuit which negatively feeds back to the end can be applied. Thus, if the
converter is driven to cancel the reaction to the vibrator of the electric sound transducer, for
example, if the atmospheric reaction is completely canceled, the converter is converted to the
atmosphere from the resonator side, that is, the box side. It is to be driven in a so-called "steady"
state, which is not influenced by the reaction, but is sufficiently damped. For this reason, the
16-04-2019
2
frequency characteristics of the direct radiation acoustics are not influenced by the volume of the
space on the rear face of the transducer, and the volume of the box is reduced as long as the
Helmholtz resonator cavity and the container of the transducer do not occur. be able to. Also,
when viewed from the Helmholtz resonator side, driving the converter so as to cancel the
atmospheric reaction from the resonator side when driving the resonator means that the vibrator
of the converter can not be driven from the resonator side, etc. It has become a part of the
measuring wall, that is, the inner wall of the resonator.
Therefore, the Q value as the Helmholtz resonator is not affected by the characteristics of the
converter, and a sufficiently high Q value can be secured even if the resonant frequency between
the resonant port and the box is lowered. As a result, even if the cabinet is miniaturized, it is
possible to generate a deep level (resonance) of a sufficient level from the Helmholtz resonator.
That is, according to a sound system combining the speaker system with a resonance port of the
present invention and driving means for driving the transducer of the speaker system so as to
cancel the atmospheric reaction from the resonator side when the Helmholtz resonator is driven,
The volume of the box can be reduced as compared with the case where the conventional bass
reflex type speaker system is driven at a constant voltage, and the resonance port can be
elongated to set the resonance frequency of the resonator low, thereby further reducing the bass
range. Reproduction is possible. Thus, according to the present invention, the volume of the box
can be reduced and the thickness can be reduced. However, as the box becomes thinner and the
ratio of the maximum dimension to the minimum dimension in the vertical, horizontal, and depth
dimensions increases, the properties as a tube become stronger, and as a result, 1/2, 1. of the
maximum dimension. The level and frequency of the tube resonance sound with... One
wavelength can not be ignored as noise or distortion components. In the present invention, by
forming at least a part of the inner wall of the box body with the buffer material for preventing
the tube well 1, the generation of noise or distortion component due to tube resonance is
prevented. [Effects] As described above, according to the present invention, the box of the
speaker unit can be miniaturized without impairing the reproduction low-frequency
characteristics to improve the operability and the design freedom of the electronic musical
instrument, or the box It is possible to improve the reproduction low frequency characteristics
without increasing the In addition, since at least a part of the inner wall of the box is formed of a
buffer material for preventing tube resonance, even if the box is thinned due to the relationship
of the arrangement and design of the box, noise is generated by tube resonance. Or distortion
can be prevented from increasing. Hereinafter, the present invention will be described in detail
with reference to the drawings. FIG. 1 shows the appearance of an electronic musical instrument
according to an embodiment of the present invention. This electronic musical instrument uses a
speaker system with a resonance port having a Helmholtz resonator as well as the conventional
bass reflex type loudspeaker system as a speaker system constituting a sound system, and is also
similar in shape to this bass reflex type. It is a thing. However, the volume of the cavity of the
Helmholtz resonator is extremely reduced to a few ° C compared to 2.30 fl of the conventional
16-04-2019
3
bass reflex type, and the resonant port is elongated to make the resonant frequency of the
resonator equal to that of the bass reflex type, or The lower setting is 50 to 60 Hz.
FIG. 2 is a cross-sectional view taken along the line A-A of FIG. 1, and FIG. In FIGS. 1 to 3, the
shelf board 1 is held at a predetermined height by two legs 2a and 2b provided vertically, and
the keyboard 3 and the speaker units 4a and 4b are placed on the shelf board 1. The speaker
mounts 5a and 5b for right and left two channels to which 1 is attached and a single circuit (not
shown) including a sound source and a speaker driving amplifier for each channel are mounted.
Further, the shelf board 1 is provided with openings 6a and 6b, and a box body 7 forming a
cavity and a resonance port section between the shelf board 1 and the lower side of the shelf
board 1 is disposed. ing. In the box 7, as shown in FIGS. 4 (a) and 4 (b), the bottom plate 8 is
provided with the opening port portions 9a and 9b, and the inside is further divided by the
intermediate plate 10 and the partition plates 11a to lid. . The opening port portions 9a and 9b
and the portions separated by the partition plates 11a to lid communicating with the opening
port portions 9a and 9b are attached to the shelf plate 1 to close the upper portion by the box
body 7 and thereby the resonance port portion of the Helmholtz resonator Form In addition, the
space of the portion excluding the resonance port portion is a portion that forms a cavity when
the box 7 is attached to the shelf plate 1 to close the upper portion, and for each of the left and
right speaker systems It is divided into two at the end. These spaces communicate with spaces
formed on the rear side of the speaker units of the left and right speaker mounts 5a and 5b
through the openings 6a and 6b, respectively, when the electronic musical instrument is
completed. The space of the body 7 and the space of the speaker mounts 5a and 5b form a cavity
of the Helmholtz resonator. Here, by attaching the middle plate 8 slightly to the right in the
figure, the cavity volume for the left channel speaker system is approximately 5.5 sentences, and
the cavity volume for the right channel speaker system is approximately 4.52. It is distributed.
The resonance frequencies of the left and right Helmholtz resonators are set to 50 Hz and 60 Hz,
which are different from each other. Resonant frequency f of such a Helmholtz resonator. Let P
be the speed of sound C, the cross section of the C1 resonance port S, the length of the resonance
port ° C, and the volume of the cavity V. fop = C (s, 'l1v) "2/2 yr ··· (1) Is required. Felts 12a and
12b are attached to the bottom plate 8 of the box 7. In this embodiment, since the box 7 is thin
at a thickness of 1/1 o or less of the width, the space portion strongly appears as a pipe, and the
entire wall surrounding the space is made of wood, plastic or metal. If it is a rigid body, the width
dimension of the space portion is 1⁄2, 1.
・ ・ ・ ・ ・ ・ The tube resonance which makes it a wavelength is produced. Here, the tube
resonance is prevented by attaching the felts 12a and 12b. Instead of the felts 12a and 12b,
other materials having breathability and acoustic resistance, such as sponges, non-woven fabrics
and woven fabrics, can be used as the tube resonance preventing means. Furthermore, a material
having flexibility and viscoelasticity, for example, one formed of rubber may be used. Such a
16-04-2019
4
flexible and visco-elastic material exhibits a pressure relaxation function substantially equivalent
to the breathability of the felt or the like due to its flexibility, and acts as a resistance that
consumes energy at the time of bending due to the visco-elasticity. . This box 7 is reinforced by
attaching reinforcing members 13a to 13f of triangular prism shape at several places. Referring
to FIGS. 1 to 3, in this electronic musical instrument, the front panel 14 is provided with slit-like
aperture groups 15a and 15b, and the direct radiation sound of the speaker units 4a and 4b
disposed obliquely inside is the same. It is released to the outside through the openings 15a and
15b, respectively. As a result, it is not necessary to provide the top plate 16 with the opening for
direct radiation sound emission, and it is possible to place an object such as a musical score or an
ornament on the top plate 16 without worrying about the sound quality or the like. Between the
legs 2a and 2b, on the lower side of the box 7, a hook 21 is extended to reinforce the structure
including the shelf 1 and the legs 2a and 2b. FIG. 5 is a figure for demonstrating the basic
composition of the acoustic apparatus (sound system) incorporated in the electronic musical
instrument of FIG. The acoustic device includes the speaker system with the resonance port and
an amplifier for driving the speaker system. The configuration in the mounting state of the
speaker system is shown in FIGS. In the speaker system 40 of FIG. 5, a dynamic electroacoustic
transducer (speaker unit) 4 (4a, 4b) having a diaphragm 41 is formed by making a hole in the
front face of a cabinet (box) 7, and A resonance port 18 having a sound path 17 opened to the
outside of the cabinet 7 through the opening port 9 (9a, 9b) is provided below, and a Helmholtz
resonator is formed by the resonance port 18 and the cabinet 7. In this Helmholtz resonator, the
air resonance phenomenon occurs due to the air spring of the cabinet 7 which is a closed cavity
and the air mass in the sound path 17 of the resonance port 18. The resonance frequency fOP is
obtained by the equation (1) as fo, = C (S /, QV) '/' / 2yr.
In FIG. 5, the drive circuit 50 comprises an f characteristic correction circuit 51, a negative
impedance circuit 52 and the like. The negative impedance circuit 52 is composed of an
amplification circuit 53, a resistor R3 and a feedback circuit 54. In this negative impedance
circuit 52, the output of the amplification circuit 53 of gain A is applied to the speaker unit 4 of
the speaker system as a load. Then, the load current detection resistor R3 detects the current I
flowing in the speaker unit 4 and positively feeds back to the amplification circuit 52 via the
feedback circuit 54 of the transmission gain β. In this way, the output impedance Z0 of the drive
circuit 50 can be obtained as RO = R, (1-A.beta.) (2). From this equation, if Aβ> 1, then Ro is an
open stable negative resistance. FIG. 6 shows the speaker system of FIG. 5 replaced with an
electrical equivalent circuit. The parallel resonance circuit Z1 in FIG. 6 is due to the equivalent
motional impedance generated by the movement of a unit S consisting of the diaphragm 41 of
the speaker unit 4 and the like, r)) is the equivalent resistance of the vibration system, So is The
equivalent stiffness of the vibration system, mo indicates the equivalent mass of the vibration
system. Further, the series resonant circuit Z2 is based on the equivalent motional impedance of
the Helmholtz resonator composed of the resonance port and the air, rc is the equivalent
resistance of the cavity, SC is the equivalent stiffness of the cavity, r is the resonance The
16-04-2019
5
equivalent resistance of the port, mp, indicates the equivalent mass of the resonant port. In
addition, A in the figure is a force coefficient, and when the speaker unit 4 is an electrodynamic
direct radiation speaker, A = BfLV, where B is the magnetic flux density in the magnetic gap and
XV is the total length of the conductor of the voice coil . Furthermore, Zv in the figure is the
internal impedance (non-motional impedance) of the speaker unit 4, and the speaker unit 4 is a
static type it! When the speaker is a radiation speaker, it is mainly the resistance Rv of the voice
coil and contains a small amount of inductance. Next, the operation of the acoustic device having
the configuration shown in FIGS. 5 and 6 will be described. When a drive signal having a negative
impedance drive function is supplied to the speaker unit 4 from the drive circuit 50, the unit 4
electromechanically converts it to drive the diaphragm 41 back and forth (left and right in FIG.
5). The diaphragm 41 mechanically acoustically converts this reciprocating motion. Here, since
the drive circuit 50 has a negative impedance drive function, the internal impedance of the unit 4
is isometrically low fA (ideally disabled).
Therefore, the unit 4 drives the diaphragm 41 faithfully in response to the drive signal manually
input to the drive circuit 50, and is independent of the Helmholtz resonator composed of the
resonance port 18 and the cabinet 7 described above. Drive energy. At this time, the front side
(right side in FIG. 5) of the diaphragm 41 constitutes a direct radiation portion for radiating the
sound directly to the outside, and the rear side (left side in FIG. 5) of the diaphragm 41. )
Constitute a resonator drive unit for driving a Helmholtz resonator consisting of a cabinet 7 and
a resonance port 18. For this reason, as shown by arrow a in FIG. 5, the sound is directly radiated
from the diaphragm 41 and the air in the cabinet 7 is resonated, and as shown by the arrow in
FIG. Sound of sufficient sound pressure is resonantly emitted from the portion (the opening port
portion 9 of the resonance port 18). And this resonance frequency f by adjusting the air
equivalent mass in the resonance port 18 in the Hermholtz single mouth unit. Helmholtz
resonance frequency f which is a standard setting value for P as a conventional bass reflex
speaker system. P = fQC /, / 7 (where fOc is lower than the resonance frequency of the unit 4
when the speaker unit 4 is attached to the bass reflex type key vinet), and the Q value by
adjusting the equivalent resistance of the resonance port 18 By setting the level to the
appropriate level, the sound pressure of the appropriate level can be obtained from the opening,
and by appropriately increasing or decreasing the level of the human power signal, for example,
the sound pressure as shown by the solid line in FIG. Frequency characteristics can be obtained.
In FIG. 7, the two-dot chain line shows the impedance characteristic of the conventional closedtype speaker system and the output sound pressure frequency characteristic when this is driven
at a constant voltage, and the broken line shows the impedance characteristic and output sound
pressure of the conventional bass reflex type speaker system Indicates frequency characteristics.
Hereinafter, the operation in the case of negative impedance driving of a speaker system using a
Helmholtz resonator will be described in more detail. FIG. 8 shows that in FIG. 6, ZV-ZO = Q, that
is, the electric part of the negative impedance circuit 52 and thereafter when the internal
impedance (non-motional impedance) of the speaker unit 4 is completely nullified. Equivalent
16-04-2019
6
circuit. Here, the equivalent resistance rC + rp of the resonance port 18 and the cavity is
converted into a series resistance and the coefficient attached to the value of each element is
omitted. The following is apparent from this equivalent circuit. First, both ends of the parallel
resonant circuit Z1 based on the equivalent motional impedance of the speaker unit 4 are
shorted with zero impedance in an alternating manner.
Therefore, this parallel resonant circuit z1 has a Q value of 0 and is substantially no longer a
resonant circuit. That is, in the speaker unit 4, the concept of the lowest resonance frequency,
which has been provided in a state where the speaker unit 4 is attached to the Helmholtz
resonator in a car, is no longer present. Hereinafter, in the case where the minimum resonance
frequency f0 equivalent of the speaker unit 4 is referred to, the above concept which has been
substantially nullified is only provisionally called. Thus, as a result of the unit resonant system
(parallel resonant circuit) 2+ not being substantially a resonant circuit, the resonant system in
this acoustic device is only the port resonant system (series resonant circuit) Z2 by the
equivalent motional impedance of the Helmholtz resonator. It will be connected. In addition, the
speaker unit 4 responds linearly in real time to the drive signal input as a result of the vibration
system being substantially non-resonant, and does not make a transient response at all. And the
diaphragm 41 is displaced. That is, it is a complete braking state (a so-called speaker dead state).
The lowest resonance frequency f of this speaker in this state. The output sound pressure
frequency characteristic near the equivalent value is 6 d B / o c t. On the other hand, the
characteristic of the normal voltage drive state is 12 d B / o c t. On the other hand, since the
series resonant circuit Z2 based on the equivalent motional impedance of the Helmholtz
resonator is connected to the drive signal source E0 with zero impedance, there is no mutual
dependence relationship with the parallel resonant circuit Z1, The circuit Zl and the series
resonant circuit Z2 independently coexist independently. Therefore, the volume of the cabinet 7
(which is inversely proportional to SC) and the shape and size of the resonant port 18 (which is
proportional to mp) do not affect the direct radiation characteristics of the speaker unit 4 and
also the resonant frequency of the Helmholtz resonator and The Q value is also not affected by
the equivalent motional impedance of the speaker unit 4. That is, the characteristic value (f or, Q
op) of the Helmholtz resonator and the characteristic value (f OC + Q oc) of the speaker unit 4
can be set independently. Furthermore, since the series resistance of the series resonant circuit
Z2 is only rc + rp, and these are usually sufficiently small values, the Q value of this series
resonant circuit Z2, that is, the Helmholtz's first device may be set sufficiently high. it can. From
another point of view, since the unit vibration system is not effectively a resonant system, the
drive signal is displaced according to the human force, and the external force, particularly the
equivalent stiffness S of the cabinet 7.
It is not substantially affected by the atmospheric reaction caused by Therefore, the diaphragm
41 of the speaker unit 4 is an isometric wall as seen from the cabinet side, and the presence of
16-04-2019
7
the speaker unit 4 when viewed from the Helmholtz resonator is invalidated. Therefore, the
resonance frequency (hereinafter referred to as a port resonance frequency) for and Helmholtz
resonator does not depend on the non-motional impedance of the speaker unit 4, and the
resonance frequency is determined by the normal constant voltage drive method. Even when the
frequency is set to a very small value, the Q value can be maintained at a sufficiently large value.
In addition, the port resonance system Z2 is to be said to be a virtual speaker that performs
acoustic radiation completely independently of the unit vibration system Z1. And although this
virtual speaker is realized with a small aperture equivalent to the port diameter, it is equivalent to
an extremely large aperture as a real loudspeaker from the viewpoint of its bass reproduction
capability. Comparing the above with the conventional system in which the conventional bass
reflex type speaker system is driven with a constant voltage by a normal power amplifier, in the
conventional system, as is well known, a plurality of resonances of the unit pregnancy w J system
Z and the port resonance system z 2 There was a system, and the resonant frequency and Q
value of each resonant system were closely dependent on each other. For example, if the port is
lengthened or narrowed (m p increases) to lower the resonance frequency of the port resonance
system Z2, the Q value becomes high in the unit vibration system Z1, and becomes low in the
port resonance system Z2, Even if the volume of the cabinet is reduced (when SC increases, 9),
even if the port is lengthened or narrowed to keep the resonance frequency of port resonance
system Z2 constant, the unit vibration system Z1 has a Q value and a resonance frequency of The
Q value became further lower in the port resonance system Z2. That is, since the output sound
pressure frequency characteristics of the speaker system are closely related to the characteristics
of the speaker unit, the volume of the cabinet and the dimensions of the port, a high level design
technique is required to match them, and the output It was generally considered impossible to
miniaturize the cabinet (system) without impairing the sound pressure frequency characteristics,
particularly the low frequency characteristics. Also, the resonance frequency f in the port
resonance system Z. The relationship between the frequency in the band lower than P and the
resonant acoustic radiation ability is, in terms of sound pressure level, a rate of about 126 B 10
ct relative to the drop in frequency, and the resonant frequency is against the basic idea of the
bass reflex speaker system If it is set extremely low, correction due to increase or decrease of the
manual signal level becomes extremely difficult.
In addition, the increase in Q value near the resonance point and the deterioration of the sound
quality based on the phase characteristics were not corrected. Since the drive circuit of this
embodiment drives the speaker system using Helmholtz resonance as described above in
negative impedance, the characteristics, dimensions, etc. of the unit vibration system and port
resonance system of the system can be set independently, and Also, even if the resonance
frequency of the port resonance system is set low, the Q value and bass reproduction ability can
be kept high, and the resonator drive ability of the unit vibration system is also strong (6 d B / o
c t) Therefore, it is possible to obtain an advantage that the frequency characteristic waviness can
be corrected by increasing or decreasing the input signal level by the f characteristic correction
16-04-2019
8
circuit 51, for example, by increasing or decreasing the usual sound quality adjustment. Instead,
it is possible to miniaturize the cabinet and configure the speaker system to be compact. Further,
according to the drive circuit of this embodiment, since the resonance frequency and Q value of
each resonance system can be set relatively freely, the sound quality can be improved compared
to the case where the existing speaker system is driven by the conventional constant voltage. .
Alternatively, it is possible to easily expand and drive the sound reproduction band, in particular,
the bass side. In the above, only the case of Zv Zo = O has been described, but in this
embodiment, -Z. If Z0, then ZvZo> O, and in this case, the characteristic values of the unit
vibration system and the port resonance system, etc. are Zv-Zo = O according to the value of the
impedance ZV-Zo. It is a value between the case and the case of the conventional constant
voltage drive system. Therefore, instead of actively using this property, for example, adjusting the
Q value of the port resonance system, adjusting the port diameter or inserting a range Q damper
such as glass wool or felt in the cabinet It can be done by adjusting the negative impedance -Zo.
9 (a) (b) (c) are diagrams simulating the electrical characteristics of the acoustic device of FIG. 5
using the speaker system with the resonance port and the drive circuit 50. FIG. Here, the nominal
impedance of the speaker unit 4 is 8Ω, the AC input voltage e of the negative impedance
generation circuit 52 of the drive circuit 5o is IV, and the output impedance -ZO is 17Ω. In FIG. 9
(a), the solid line a is the impedance ZL of the speaker system with the resonance port, the
broken line is the impedance by the equivalent inductance A '/ So of the speaker unit 4, and the
broken line C is the equivalent capacitance mo / A2 of the speaker unit 4. The impedance, the
broken line d shows the impedance of the cabinet 7 by the equivalent inductance A2 / Sc, the
broken line e shows the impedance of the equivalent capacitance mP / A2 of the cabinet 7, the
dotted line f, and the impedance of the Hall unit resonance system Z1. .
In the figure, the resonance frequency of the unit resonance system is about 35 Hz, which is the
intersection of the broken line C and the broken line C, and the resonance frequency of the port
resonance system is about 40 Hz, the intersection of the broken line d and the broken line e. In
FIG. 9 (b), the solid line g is the output voltage of the negative impedance generating circuit 52,
the broken line is the output sound pressure characteristic of the resonance radiation sound from
the port resonance system, and the broken line i is the direct emission from the unit resonance
system. The sound output sound pressure characteristic, and the solid line j is a combination of a
broken line and a broken line i, and shows a total output sound pressure characteristic as a
speaker system. The output terminal voltage V is obtained by (1) = ZLe / (ZL + -20) (3). したがっ
て、20. Assuming that ZL is respectively pure resistance -RO (= -7 Ω) and RL, voltage V
changes as V = 8 V at RL = 8 Ω, V = 4.5 V at RL = 9 Ω, ..... . In FIG. 9 (c), the input voltage e of the
negative impedance generation circuit 52 is increased or decreased according to the frequency
by the f characteristic correction circuit 51 of the drive circuit 50, and the output voltage of the
circuit 52 is corrected as shown by solid line g °. This indicates that a flat output sound
pressure characteristic can be obtained at 50 Hz or higher as indicated by the solid line j °. In
the figure, the broken line indicates the output power (W) characteristic of the amplifier 53 (that
16-04-2019
9
is, the negative impedance generation circuit 52) when the output sound pressure characteristic
is made flat. In the electronic musical instrument of FIG. 1, the port resonance frequencies of the
speaker system in the two-channel sound speaker apparatus are set to 50 Hz and 60 Hz which
are different from each other. In this way, the overall frequency characteristic of the left and
right speaker systems is the sound pressure characteristic having a peak at 50 Hz from the
resonance port of the left speaker with respect to the flat output sound pressure characteristic of
60 Hz or more from the right speaker system. Can be extended to the lower side. Of course, by
appropriately setting the characteristics of the f-characteristic correction circuit 51, it is possible
to extend the low frequency side of the uniform reproduction band to 50 Hz only with the right
channel, but in this case the broken line in FIG. As indicated by k, it is necessary to increase the
output power of the amplifier 53 near the port resonance frequency. As shown in the figure, in
order to extend the low frequency side of the -like reproduction frequency by 10 Hz, an amplifier
53 having a large output power of 6 dB (four times) is required. In particular, in the case of an
electronic musical instrument, the size of the amplifier 53 needs to be considered at a continuous
rating, taking into account the case where the key is kept depressed, and the intermittent or
instantaneous maximum output should be considered if the normal output is the same. It
requires a power amplifier several times more power than a sufficient audio amplifier.
It is extremely burdensome in circuit design to further increase the output to flatten the
frequency characteristics. Therefore, in this embodiment, the port resonance frequency on the
left side is set to 50 Hz which is a frequency lower by 10 Hz than the right side, and the output
sound pressure of the frequency near 50 Hz is mainly radiated from the resonance port of the
left speaker system. The burden on the drive circuit 50 is reduced. Similarly, the sound in the
vicinity of 60 Hz reduces the burden on the left drive circuit 50 by mainly radiating it from the
resonance port of the right speaker system. In a low frequency region of several tens Hz or less,
the directivity of the sound is weak because the wavelength is several meters or more, and which
of the left and right channels is emitted hardly matters. That is, in the low frequency region,
problems such as localization of a sound image do not occur even if sounds with different sound
pressures are emitted from the left and right as described above. In this example, as a result of
extending the output sound pressure characteristic of the sound device to a lower frequency, the
piano sound on the bass side is different from the actual timbre which is rather dark. Therefore,
the sound quality is adjusted here by reducing or removing the fundamental wave component in
the sound source. FIG. 10 shows the basic configuration of a negative impedance generating
circuit 52 for driving the imaging device in negative impedance. The circuit of the figure gives
the output of the amplifier 53 of gain A to the load ZL by the speaker system. And, the current 1
flowing to this load ZL. Is detected and is positively fed back to the amplification circuit 53 via
the feedback circuit 54 of the transmission gain β. In this way, the output impedance Z0 of the
circuit can be obtained as zo = zs (1−Aβ) (4). From the equation (4), if Aβ> 1, then Zo is an
open stable negative impedance. Here, Z8 is the impedance of the sensor that detects the current.
Therefore, in the circuit of FIG. 10, a desired negative impedance component can be included in
16-04-2019
10
the output impedance by appropriately selecting the type of impedance ZS. For example, current
1. をインピーダンス2. If the impedance ZS is a resistor R3, the negative impedance component
is a negative resistance component, if it is an inductance L5, it is a negative inductance
component, and if it is a capacitance C5, it is a negative capacitance. . In addition, by using an
integrator for the feedback circuit 54 and integrating and detecting the voltage across the
inductance LS as the impedance zs, the negative impedance component can be made a negative
resistance component. The negative impedance component is a negative resistance component
even when the voltage across the capacitance C5 as impedance Z is differentiated and detected
using a differentiator.
As the current detection sensor, in addition to the impedance elements R8, Ls, Cs, etc., it is also
possible to use a current probe such as C, T or a Hall element. A specific example corresponding
to such a circuit is shown, for example, in Japanese Patent Publication No. 59-51771. It is also
possible to perform current detection on the non-grounded side of the speaker unit 4. An
example of such a circuit is shown, for example, in Japanese Patent Publication No. 54-33704.
Although FIG. 11 is an example of BTL connection, it is easy to apply to the circuit of FIG. 56 in
FIG. 11 is an inverting circuit. FIG. 12 shows a specific circuit example of an amplifier including a
negative resistance component in the output impedance. The output impedance z0 in the
amplifier of FIG. 12 is Zo = Rs (IRb / Ra) = 0.22 (1-30 / 1.6) =-3, 9 (.OMEGA.). [Modification of the
embodiment] The present invention can be appropriately modified and implemented without
being limited to the above embodiment. For example, the drive circuit may be any one as long as
it drives the vibrator to cancel the reaction from the surroundings when driving the resonator,
and as disclosed in Japanese Patent Publication No. 58-31156 besides the negative impedance
generation circuit. Using a so-called MFB circuit. Also, by giving frequency characteristics to the
output impedance, the degree of freedom in setting Qoc, Qop, etc. can be improved, or
characteristics, in particular, resonance frequency f. Cおよびf。 It is also possible to adjust the
output sound pressure characteristic in the vicinity of P, or to suppress an increase in distortion
factor due to non-linearity of the voice coil inductance component in the high region.
Furthermore, the tube resonance may be eliminated by outputting the output of the resonance
port through the mechanical acoustic filter, in which case one filter is used for the left and right
channels as shown in FIG. 13 (a). May be shared to configure a so-called 3D (three dimensional)
system. Further, in this case, it is also possible to make the frequency of port resonance different
from each other by making the lengths of the left and right resonance ports 18a and 18b
different. As a mechanical filter, any type of band pass, band elimination and low pass may be
used as long as they pass port resonance sound and block tube resonance sound, regardless of
the structure, for example, FIG. 13 (b) Alternatively, one as shown in (C) can be used. FIG. 13 (b)
shows that the box 7c is provided with an opening 91 and acts as a low pass filter which passes
only frequencies lower than the tube resonance.
16-04-2019
11
FIG. 13 (b) shows a box 7C provided with a passive vibrator 92 such as a drone cone, which acts
as a band pass filter that passes only the band including port resonance. The resonance ports
18a and 18b may be housed inside the box 7a, 7b or 7C in the case shown in FIG. 4 or FIG. 5, in
which case the whole system can be made more compact. Take.
[0002]
Brief description of the drawings
[0003]
1 is a perspective view showing the appearance of an electronic musical instrument according to
an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A of FIG.
1, and FIG. 3 is an exterior of the electronic musical instrument of FIG. 4 (a) and 4 (b) are a top
view and a right side view of the box in FIG. 1, and FIG. 5 is an explanatory view showing the
basic configuration of the electronic musical instrument of FIG. 6 is an electric equivalent circuit
diagram of the acoustic device of FIGS. 1 and 5. FIG. 7 is a frequency characteristic diagram of
the sound pressure of the sound radiated from the acoustic device of FIGS. 1 and 5. Fig. 8 is an
equivalent circuit diagram when Zv Zo "O in Fig. 5, Fig. 9 (a) (b) (c) is an explanatory view of the
frequency characteristics of the acoustic device of Fig. 5, Fig. 10 Fig. 11 and Fig. 11 are basic
circuit diagrams of circuits generating negative impedance respectively, Fig. 12 is a specific
circuit diagram of negative resistance driving, Fig. 13 (a) (b) (C) is a block diagram of a 3D
system according to another embodiment of the present invention, and FIG. 14 is a perspective
view showing the appearance of an electronic musical instrument incorporating an acoustic
device for constant-voltage driving a conventional bass reflex speaker system. It is.
1 ° fence plate, 3 keyboards, 4a, 4b nissbee caninants, 5a, 5b: speaker mounts, 7, cabinets
(boxes), 12a, 12b: felts, 18 resonant ports, 41: diaphragms, 5o: Drive circuit, 52: negative
impedance generation circuit.
16-04-2019
12
Документ
Категория
Без категории
Просмотров
0
Размер файла
31 Кб
Теги
description, jph01319791
1/--страниц
Пожаловаться на содержимое документа