JP2737936B2 - Electric / electronic musical instruments - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric musical instrument or an electric / electronic musical instrument such as an electric musical instrument for producing musical sounds via an electric acoustic device, and particularly to an entire musical range that can be pronounced, In particular, the present invention relates to an electric / electronic musical instrument capable of generating a musical sound of good sound quality in a low temperature range.

[Related Art] Conventionally, electronic musical instruments and electric musical instruments have been known as musical instruments provided with an electric acoustic device. An electric musical instrument is provided with a sound generating device that generates sound by mechanical vibration similar to a guitar, a drum, a whistle, or the like, and temporarily converts the mechanical vibration or sound into an electric signal to electrically amplify the electric signal. The sound is re-converted into sound and is pronounced, and the musical sound can be sounded with a loud sound or processed with a special effect, etc., as compared to the case where the sound is generated directly. .

On the other hand, an electronic musical instrument electrically generates a sound signal by an electronic circuit using an oscillator, a memory, or the like in accordance with an instruction from a sound instruction unit such as a keyboard, a drum pad, and a respiratory input device, and converts the sound signal into an acoustic device. It is pronounced through.

[Problems to be Solved by the Invention] By the way, in such an electric / electronic musical instrument, the frequency characteristic of an acoustic device is conventionally fixed, and in the case of an electronic keyboard musical instrument having a wide sound range, not all electric / electronic musical instruments are necessarily used. Good sound quality was not obtained in the sound range.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electronic musical instrument capable of obtaining good sound quality over a wide range of sounds, in view of the problems in the conventional example.

Means for Solving the Problems In order to achieve the above object, according to the present invention, sound generation control means for generating a musical sound waveform electric signal according to a performance operation, and an audio device which converts the electric signal into sound and emits sound Wherein the acoustic device comprises a resonator comprising a closed cavity, a duct for acoustically connecting the cavity to an external region, and a part of a box forming the cavity. And a vibrator having a vibrator for driving the resonator on one surface, and vibrator driving means for driving the vibrator,
Detecting means for detecting the pitch or range of the musical tone to be pronounced;
Control means is provided for variably controlling the frequency characteristics of the acoustic device by controlling at least one of the cavity and the duct in accordance with a pitch or a sound range detected by the detection means. In a preferred embodiment of the present invention, the vibrator driving means is configured to perform a positive feedback of a voltage signal corresponding to a driving current of the vibrator to an input side of the vibrator driving means, so that an output impedance of the vibrator driving means is controlled. A negative impedance generating circuit for driving the vibrator so as to generate a negative impedance component equivalently therein and equivalently reduce or invalidate an internal impedance inherent to the vibrator; Reducing or eliminating the interdependence condition of the characteristics of the resonance system of the resonator and the characteristics of the vibration system of the vibrator with respect to the reproduction characteristics of the sound due to the resonance from the resonator, and setting the resonance frequency of the resonator to the vibrator driving means. Generates an equivalently zero or more resistance component in the output impedance of the vibrator driving means and drives the vibrator. The lower frequency can be set lower than the lowest frequency at which the low-temperature resonance radiating ability is ensured, and the magnitude of the negative impedance component generated by the vibrator driving means is changed by the Q value of the resonance system of the vibrator. The internal impedance is equivalently reduced so as not to exceed the magnitude of the internal impedance specific to the vibrator so that the combined reproduction characteristic with the resonator becomes smaller than the Q value when the uniform low-frequency reproduction characteristic is obtained. Is set to a value that is reduced or invalidated.

[Operation] In the present invention, the frequency characteristic of the acoustic device is variably controlled. For this reason, by setting a frequency characteristic according to the content of the performance in advance before the performance, or by automatically setting the frequency characteristic according to the pitch or sound quality specified at the time of the performance, It is possible to produce high-quality musical tones and realize musical effects that have never been achieved before. Especially when the frequency characteristic of the acoustic device is variably controlled by controlling the shape of the cavity or duct of the resonator, the vibrator and the cavity or duct can be shared by a plurality of pitches or sound ranges. Therefore, the size of the acoustic device can be greatly reduced as compared with the case where the vibrator and the resonator are arranged for each of a plurality of famous pitches or sound ranges (for example, see Japanese Utility Model Application Laid-Open No. 58-31598).

In a conventional acoustic device, the vibrator is driven by so-called constant voltage using vibrator driving means having an output impedance of substantially zero. In such an acoustic device, the low-frequency side reproduction limit of the output sound pressure of the sound directly radiated from the vibrator (for example, a speaker unit) is determined by the characteristic value (f _O , Q _O ) of the vibrator and the mounting of the vibrator It was determined by the volume of the box (for example, speaker cabinet). Therefore, in order to arbitrarily change the frequency characteristics, a large-sized vibrator and a box capable of reproducing the lowest frequency in the variable range are required. Further, in order to reduce the size of the vibrator and the box, the minimum reproduction limit frequency as a speaker system is set high, and the shortage of the low-frequency reproduction level is compensated by boosting the input signal level of the vibrator driving means. It is also possible. However, in the conventional audio apparatus, since the output sound pressure below the low-frequency side reproduction limit is reduced by 12 dB / oct, it is difficult or impossible to significantly compensate for the low-frequency characteristic. Also, in an acoustic device using a speaker system having a resonator such as a phase inversion type (bass reflex type) speaker system, the direct radiation characteristic of the vibrator and the resonance radiation characteristic of the resonator depend on each other. In order to make the characteristics flat, relatively strict settings are required,
If you change the resonance frequency, especially when it is set extremely low,
The swell of 12 dB / oct occurred in the low frequency characteristics, and it was difficult to compensate for the flatness.

In the present invention, the vibrator driving means preferably drives the vibrator so as to cancel the action of the vibrator on the vibrating body from the resonator (cavity) side. That is, the vibrator is driven in a so-called dead state that is not affected by the action from the resonator side and is sufficiently braked. For this reason, the frequency characteristics of the direct radiated sound from the vibrator vibrator are not affected by the volume of the space behind the direct radiation surface of the diaphragm, and the volume of this space is used as a cavity of the resonator and as a container of the vibrator. As long as there is no inconvenience, you can make it smaller,
At this time, the decrease in the output sound pressure of the direct radiated sound in a range lower than the lowest resonance frequency f _O of the vibrator is 6 dB / oct. From the resonator side, driving the vibrator to cancel the action from the resonator side when driving the resonator means that the diaphragm of the vibrator cannot be driven from the resonator side. It is turned into a wall. Therefore,
The Q value of the resonator is not affected by the characteristic values (f _O , Q _O ) of the vibrator, and a sufficiently high Q value can be ensured even if the resonance frequency is lowered. As a result, even if the cavity, that is, the box is made smaller, a sufficient level of heavy bass (resonance) from the resonator is obtained.
Can occur. Further, the resonance frequency of the resonator can be changed independently of the direct radiation characteristic,
At this time, even if the swell of the frequency characteristic occurs, it can be flattened with 6 dB / out of the same level of compensation as the normal tone control. The resonance frequency of the resonator can be changed by changing the cavity volume and the acoustic mass. Further, the frequency characteristics, particularly the low-frequency characteristics, can also be varied by varying the degree of cancellation of the action from the resonator side in the vibrator driving means.

[Effects] As described above, according to the present invention, the frequency characteristics of the sound device can be changed as needed, so that a high-quality musical tone can be produced by matching the pitch of the performance musical sound with the frequency characteristics of the sound device. be able to. Further, by combining the pitch of the musical performance tone with the frequency characteristic of the acoustic device, or changing this combination during the performance, it is possible to obtain a musical tone effect which cannot be obtained conventionally.

Also, by controlling the shape of the cavity or duct of the resonator to vary the frequency characteristics of the acoustic device, the vibrator, duct or cavity can be commonly used for each pitch or range, and It can be reduced in size. Further, by driving the vibrator by vibrator driving means for canceling the action of the air in the resonator on the vibrating body, the cavity, that is, the box can be downsized, and the acoustic device itself can be further downsized. can do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an electric musical instrument according to one embodiment of the present invention.

In the electric musical instrument shown in FIG. 1, a box (speaker box) 1 has a hollow piston 3 having a hollow portion (duct) 2 at one end and a vibrator (electrodynamic speaker unit) 4 at the other end.
This uses a cylinder 5 closed by a cylinder. The electric musical instrument further includes a sound generating device 7 that generates a musical sound by mechanically or acoustically vibrating itself by playing, such as a drum membrane, a string or a lead of a guitar or the like, and a mechanical or acoustic vibration of the sound generating device 7. And a vibrator driving circuit 9 for driving the vibrator 4 based on a tone signal supplied from the sound generating circuit 8.

In this electric musical instrument, a Helmholtz resonator is constituted by a cavity 6 in a box 1 and a duct 2 of a hollow piston 3. In this Helmholtz resonator, an air spring in a closed cavity 6 and a duct in a duct 2 are provided. An air resonance phenomenon occurs due to the air mass. And this resonance frequency f _OP
Is Can be obtained as Here, V ₁ is the volume of the cavity 6, S ₁ is the cross-sectional area of the duct 2, l ₁ is the duct 2 length, c is the speed of sound. The hollow piston 3 can move back and forth (left and right in the figure) in the cylinder 5. By moving the hollow piston 3, the volume V ₁ of the box 1, that is, the cavity 6 can be changed, and the resonance frequency f _OP can be changed.

When driving the Helmholtz resonator, the vibrator driving circuit 8 operates the Helmholtz resonator, that is, a closed box (cavity).
The vibrator 4 is driven so as to cancel an atmospheric reaction to the action of the vibrator 4 from the side 5. As such a driving device, a negative impedance generating circuit that generates a negative impedance component (−Z _O ) equivalently in an output impedance or a motional signal corresponding to the movement of a vibrating body is detected by some method and input. A known circuit such as a motional feedback (MFB) circuit that performs negative feedback on the side can be applied.

 Next, the operation of the electric musical instrument of FIG. 1 will be described.

When the sounding device 7 is operated during the performance of the electric musical instrument,
A sound generation circuit 8 converts the electric or acoustic vibration in the sound generation device 7 into an electric signal. The vibrator driving circuit 9 generates the vibrator 4 based on the electric signal supplied from the sound generating circuit 8.
Drive.

When a drive signal is given to the vibrator 4 from the vibrator drive circuit 9, the vibrator 4 performs electromechanical conversion of the drive signal and reciprocates the diaphragm 41 back and forth (left and right in the figure). The diaphragm 41 converts this reciprocating motion into mechanical sound. Here, the front side (the left side in the figure) of the diaphragm 41 forms a direct radiating portion for directly radiating the sound to the outside, and the rear side (the right side in the figure) of the diaphragm 41 is the cavity. 6 and a duct 2 for driving a Helmholtz resonator. Atmospheric reaction from the air in the cavity 6 is applied to the rear side of the vibration plate 41, and the vibrator driving circuit 9 drives the vibrator 4 to cancel the atmospheric reaction.

As described above, when the vibrator 4 is driven so as to cancel the atmospheric reaction from the resonator when the Helmholtz resonator is driven, the diaphragm 41 cannot be driven from the side of the resonator. Acts as a rigid body or wall. Therefore, the resonance frequency and Q of the Helmholtz resonator are independent of the resonance frequency and Q of the diaphragm 41 and the vibrator 4 as a direct radiator, and the resonator driving energy from the vibrator 4 is also directly radiated. Will be given independently of the department. Further, the vibrator 4 is not affected by the atmospheric reaction from the resonator, that is, the cavity 6 side,
Since it is driven in a so-called dead state, the frequency characteristics of the direct radiation sound are not affected by the volume of the cavity 6. Therefore, according to the configuration of this embodiment, the volume of the cavity 6, which is the cavity of the Helmholtz resonator, can be varied widely without directly affecting the frequency characteristics of the radiated sound. Further, even when the volume of the cavity 6 is made smaller than that of the conventional musical instrument and the resonance frequency f _OP is set lower than that of the conventional musical instrument, the Q value of the resonator can be set to a sufficient value. Furthermore, according to the acoustic device for an electric musical instrument of this embodiment, even if the cavity 6 is made much smaller than a conventional musical instrument,
It is possible to reproduce even lower sounds.

In FIG. 1, a vibrator 4 drives a diaphragm 41 in response to a driving signal from a vibrator driving circuit 9, and independently drives a Helmholtz resonator composed of a cavity 6 and a duct 2. give. As a result, sound is directly radiated from the diaphragm 41 as shown by an arrow a in FIG. 1, and the air in the cavity 6 is resonated, as shown by an arrow b in FIG. Sound having a sufficient sound pressure is radiated by resonance from the radiating portion (the opening of the duct 2). FIG. 2 shows the first
3 shows a frequency characteristic of an output sound pressure of the electric musical instrument of FIG. In FIG. 2, a shows the frequency characteristic of the acoustic sound pressure radiated directly from the vibrator 4 and b shows the frequency characteristic of the acoustic sound pressure radiated from the opening of the duct 2. The frequency c obtained by combining the frequency characteristics a and b becomes the output sound pressure characteristic of the speaker system including the box 1 (cavity 6), the duct 2 and the vibrator 4, and is used as the input signal of the vibrator drive circuit 9. The value d corrected by increasing or decreasing the level becomes the overall frequency characteristic of the electric musical instrument shown in FIG. Here, the hollow piston 3 acts as frequency characteristic variable control means. If the hollow piston 3 is slid left and right in the figure like a trombone to change the resonance frequency f _OP of the Helmholtz resonator, direct radiation is achieved. The lower limit of the frequency characteristic can be changed without adversely affecting the phase characteristic of the sound. At this time, if the frequency characteristic has undulation, the overall frequency characteristic can be flattened by increasing or decreasing the level of the input signal of the vibrator driving circuit 9 as described above.

FIG. 3 shows a configuration of an electric musical instrument according to another embodiment of the present invention. In this embodiment, the volume V _{1 of the} box 1 is fixed, a plurality of pipes having different cross-sectional areas S and lengths 1 are arranged as ducts 2, and a valve 21 is provided at a connection portion of each pipe 2 with the box 1. It is provided. Here, the valve 21 acts as a frequency characteristic variable control means, and these valves 21 are opened and closed to
By connecting one or more ducts 2 to the cavity 6 of the box 1, the resonance frequency f _OP of the Helmholtz resonator constituted by the duct 2 and the cavity 6 can be varied. A valve that is "open" when the performer starts playing.
By setting 21 in advance, the sound quality and frequency characteristics can be matched to the music to be played or the taste of the player. The pipe 2 may be used as it is as a musical instrument stand, or may be stored in a side plate or a back plate of the musical instrument.

FIG. 4 shows still another embodiment of the present invention. In this embodiment, a small speaker unit 4 (4a to 4d) is directly attached to a closed box 1 (1a to 1d) having a double pipe structure.
A plurality of speaker systems 11 (11a to 11d) having different volumes V and different cross-sectional areas S and lengths 1 of the ducts 2 (2a to 2d) and thus different Helmholtz resonance frequencies f _OP are arranged, and speakers driven by the drive circuit 9 are arranged. A drive speaker selection control circuit 12 for selecting the unit 4 according to the setting of the frequency characteristic is provided.

In the electric musical instrument shown in FIG. 4, the drive speaker selection control circuit 10 acts as frequency characteristic variable control means, and one or more speaker systems 11 are selected and driven by the drive circuit 9 to obtain sound quality and sound quality. The frequency characteristics can be matched to the music to be played or the preference of the player.

In the embodiments shown in FIGS. 1, 3 and 4, the sound pitch (range) detecting means for detecting the performance pitch or performance range, and the frequency characteristics of the acoustic device are varied according to the detection result. It is also possible to provide a control means for controlling the frequency characteristic of the acoustic device variably according to the calculated pitch or the performance range. Specifically, for example, in the case of the electric musical instrument shown in FIG. 1, a piston driving means is provided as the control means, and the piston 3 is controlled according to the detected pitch (or sound range).
Is driven to change the frequency characteristic by changing the volume V of the cavity 6, it is possible to obtain a musical instrument having an unprecedented musical tone effect corresponding to the musical instrument performance in real time. In this case, when a plurality of pitches or tone ranges are detected at the same time, it is preferable to perform control in accordance with the lowest tone or the lowest tone range for the purpose of improving bass characteristics.

Next, the operation of the acoustic device that drives a speaker system using a Helmholtz resonator with a negative impedance generating circuit will be described.

FIG. 5 is an electrical equivalent diagram of the vibrator drive circuit 9 shown in FIGS. 1, 3 and 4 and a speaker system with a resonance port composed of the vibrator 4, the cavity 6, and the duct 2. 1 shows a circuit. Here, E _O indicates a voltage source that is a drive signal source. Further, the parallel resonance circuit Z ₁ is by the equivalent motional impedance of the vibrator 4, r _O vibration system equivalent resistance, S _O is the oscillation system of equivalent stiffness, m _O is an equivalent mass of the vibration system I have. Series resonance circuit Z ₂ is duct 2
This is due to the equivalent motional impedance of the Helmholtz resonator composed of the cavity 6 and the cavity 6, where r _C is the equivalent resistance of the cavity 6, S _C is the equivalent stiffness of the cavity 6, r _P is the equivalent resistance of the duct 2, m _P Indicates the equivalent mass of the duct 2. A is a force coefficient. When the vibrator 4 is an electrodynamic direct radiating speaker, B is a magnetic flux density in a magnetic gap,
The l _V comes to a conductor the entire length of the voice coil and A = Bl _V. Further, Z _V in the figure is the internal impedance of the vibrator 4 (non-motional impedance), when the vibrator 4 is dynamic conductivity type direct radiation speaker unit, primarily voice coil resistance R _V, and the slightly inductance Contains.

FIG. 6 is an electrical equivalent circuit when Z _V −Z _O = 0 in FIG. 5, that is, when the internal impedance (non-motional impedance) of the vibrator 4 is equivalently and completely invalidated. Here, the coefficient added to the value of each element is omitted.

 The following is clear from this equivalent circuit.

First, oscillator equivalent motional parallel resonance circuit Z ₁ due to impedance of 4, both ends are short-circuited in an AC manner zero impedance. Therefore, this parallel resonant circuit
Z ₁ has a Q value of 0, and is substantially no longer a resonant circuit. That is, in the vibrator 4, the concept of the lowest resonance frequency, which is simply provided when the vibrator 4 is attached to the Helmholtz resonator, is no longer present. Hereinafter, when referring to the amount corresponding to the lowest resonance frequency f _O of the vibrator 4, the above concept, which has been substantially invalidated, is merely referred to. Thus, the unit resonance system (parallel resonance circuit) results Z ₁ is not substantially the resonant circuit, the resonance system in this acoustic apparatus Helmholtz resonance system become only only one (series resonant circuit) Z _2.

Also, the vibrator 4 has a vibration system that is substantially no longer a resonance circuit. As a result, the vibrator 4 makes a linear response in real time to the drive signal input, and does not make any transient response. The signal E _O ) is faithfully electromechanically converted, and the diaphragm 41 is displaced. That is, it is in a complete braking state (so-called speaker dead state). The lowest resonance frequency of this speaker unit in this state
The direct emission output sound pressure frequency characteristic near f _O equivalent value is 6 dB / oc
t. On the other hand, the characteristic in the normal voltage drive state is 1
2dB / oct.

On the other hand, the series resonance circuit Z ₂ by equivalent motional impedance of the Helmholtz resonator, since it is connected with a zero impedance to the drive signal source E _O, not interdependent relationship between the longer and the parallel resonance circuit Z ₁ , it will coexist independently independently of the parallel resonance circuit Z ₁ and series resonance circuit Z _2. Therefore, the volume of the cavity 6 (in inverse proportion to S _C ) and the shape and size of the duct 2 (in proportion to m _P ) do not affect the direct radiation characteristics of the vibrator 4, and the resonance frequency f of the Helmholtz resonator _{The CP} and the Q value Q _CP are not affected by the equivalent motional impedance of the vibrator 4. That is, the characteristic value of the Helmholtz resonator and the characteristic value of the vibrator 4 can be set independently. Further, the series resistance of the series resonance circuit Z ₂ is only r _C + r _P , which is usually a sufficiently small value. Therefore, the Q value of the series resonance circuit Z ₂ , that is, the Q value of the Helmholtz resonator is set sufficiently high. can do.

Viewed another way, since the unit vibration system to effectively gone by resonance system, displaced in response to the driving signal input, an external force, in particular substantially the atmospheric reaction by equivalent stiffness S _C of the cavity 6 Not affected. Therefore, the diaphragm 41 of the vibrator 4 is equivalent to a wall when viewed from the cavity 6 side, and the existence of the vibrator 4 when viewed from the Helmholtz resonator is invalidated. Therefore, the resonance frequency and the Q value of the Helmholtz resonator do not depend on the non-motional impedance of the vibrator 4, and the resonance frequency is set to a frequency at which the resonance Q value becomes very small in the conventional constant voltage driving method. Can be maintained at a sufficiently large value. Further, the Helmholtz resonance system has become a virtual speaker that emits acoustic radiation completely independently of the unit vibration system. Although this virtual speaker is realized with a small aperture corresponding to the port diameter, it is equivalent to an extremely large aperture as a real speaker unit in view of its low sound reproduction capability.

Comparing the above to a conventional system in which a bass reflex type or resonator-equipped loudspeaker system as used in the electric musical instrument is driven at a constant voltage by a conventional power amplifier, the conventional system, as is well known, has a unit vibration system. Z ₁ and there are a plurality of the resonance system of the Helmholtz resonance system Z _2, moreover resonant frequency and Q values of each resonance system were closely interdependent.
For example, longer or the duct 2 in order to reduce the resonance frequency of the Helmholtz resonance system Z _2, to (m _P increases) thinner and, Q value in the unit vibration system Z ₁ is increased and the Helmholtz resonance system Z ₂ it is lower, to reduce the volume of the cavity 6 and (S _C increases), or a longer duct 2, even if kept constant resonance frequency of the Helmholtz resonance system Z ₂ and thin, the unit vibration system Z Q value and the resonance frequency in the ₁ becomes high, the Q value in the Helmholtz resonance system Z ₂ had become even lower. That is, since the output sound pressure frequency characteristics of the speaker system are closely related to the characteristics of the speaker unit 4, the volume of the cavity 6, and the dimensions of the duct 2,
In order to match these, advanced design techniques were required. Also, even if they are perfectly matched,
The lower limit of the uniform reproduction is at most the resonance frequency f _OC with the speaker unit 4 attached to the cavity 6. After matching, once, the sound reproduction band of the existing system can be easily reduced without reducing the size of the cavity 6 without deteriorating the output sound pressure characteristics, particularly the low-frequency characteristics, and without deteriorating the characteristics such as sound quality. Expanding was generally considered impossible. In addition, the Helmholtz resonance system Z ₂
The relationship between the frequency in a band lower than the resonance frequency f _OP and the direct radiating ability is, when viewed from the sound pressure level, decreases at a rate of about 12 dB / oct with respect to the decrease in the frequency. If the basic concept of a speaker system with a resonator is set extremely low, it is extremely difficult to correct the input signal level by increasing or decreasing the input signal level.

As described above, the driving device of this embodiment drives the speaker system using Helmholtz resonance in negative impedance, so that the characteristics and dimensions of the unit vibration system and the Helmholtz resonance system of the system can be set independently. Also, even if the resonance frequency of the Helmholm resonance system is set to a low value, the Q value and bass reproduction performance can be maintained high, and the direct radiation capability of the unit vibration system also becomes strong (6 dB / oct). It is possible to obtain such a characteristic that the undulation of the frequency characteristic can be corrected by increasing or decreasing the input signal level, for example, by increasing or decreasing the normal sound quality adjustment. Further, as a result of the unit vibration system being substantially no longer a resonance system, there is no rapid phase change near the frequency f _OC , and the phase characteristics are improved. For this reason, the cavity 6 can be miniaturized without deteriorating the frequency characteristics and sound quality, and the speaker system can be miniaturized. In addition, the resonance frequency f _OP can be varied without adversely affecting the direct radiation capability of the unit vibration system. Can be. As a result, the sound quality of the existing speaker system can be improved as compared with the case of the conventional constant voltage drive, or the sound reproduction band, particularly the bass side, can be easily expanded and driven. In addition, even if the resonance frequency is variably set, the swell of the frequency characteristic can be easily corrected, and sound quality suitable for the performance contents and music can be set in a wide frequency range.

In the above description, only the case where Z _V −Z _O = 0 has been described. However, when Z _V −Z _O > 0, the characteristic values and the like of the unit drive system and the Helmholtz resonance system are equal to the impedance Z _V −Z depending on the value of _O to fall between the case of the Z _V -Z _O = 0 if the conventional constant voltage drive system. Therefore, by actively utilizing this property, for example, instead of adjusting the Q value of the Helmholtz resonance system by adjusting the port diameter or inserting a mechanical Q damper such as glass wool or felt into the cavity 6, The adjustment can be performed by adjusting the negative impedance −Z _O.

FIG. 7 shows a basic configuration of a negative impedance generating circuit 8 for driving the vibrator (speaker unit) 4 with negative impedance.

Circuit in the figure, giving an output of the gain A of the amplifier 81 to a load Z _L by the vibrator 4. Then, the current flowing through the load Z _L
Detects I _L and amplifies it through the feedback circuit 83 with transmission gain β
Positive feedback to 81. In this way, the output impedance Z _{O of the} circuit is obtained as Z _O = Z _S (1−Aβ) (2). From the equation (2), if Aβ> 1,
Z _O is an open stable negative impedance. here,
Z _S is the impedance of the sensor that detects the current.

Thus, in the circuit of Figure 5, by appropriately selecting the type of impedance Z _S, it may be included a desired negative impedance component in an output impedance. For example, in the case of detecting the current I _L by the voltage across the impedance Z _S is the impedance Z _S is the resistance
In the case of R _S , the negative impedance component becomes a negative resistance component, in the case of the inductance L _S , it becomes a negative inductance component, and in the case of the capacitance C _S , it becomes a negative capacitance. Further, the integrator used in the feedback circuit 83, the impedance Z _S negative impedance component by detecting and integrating the voltage across the inductance L _S of the can is referred to as negative resistance component, further in the feedback circuit 83 using differentiator, negative impedance component be detected by differentiating the voltage across the capacitance C _S as the impedance Z _S becomes a negative resistance component. As the current detection sensor, in addition to these impedance elements R _S , L _S , and C _S , a current probe such as a CT or a Hall element can be used.

A specific example corresponding to such a circuit is described in, for example,
No. 51771.

It is also possible to perform the current detection on the non-ground side of the vibrator. A specific example of such a circuit is described in, for example,
No. -83704. FIG. 8 shows an example of the BTL connection, but it is easy to apply to the circuit of FIG. Reference numeral 84 in FIG. 8 denotes an inverting circuit.

FIG. 9 shows a specific circuit example of an amplifier including a negative resistance component in the output impedance.

The output impedance Z _O in the amplifier of FIG. 9 is as follows: Z _O = R _S (1−R _b / R _a ) = 0.22 (1−30 / 1.6) = − 3.9 (Ω)

[Modifications of Embodiments] The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications. For example, in the above-described embodiment, a duct having an open port is used as an acoustic mass means for forming a resonator,
This may be a passive vibrator such as a mere opening or a drone cone.

Further, in the above-described embodiment, the case where the negative impedance generating circuit is mainly used as the driving unit is described. However, this driving unit drives the vibrator of the vibrator so as to cancel the reaction from the surroundings. If it is something,
For example, the so-called M disclosed in Japanese Patent Publication No. 58-81156
It may be an FB circuit.

Further, in the above-described embodiment, an example in which the present invention is applied to an electric musical instrument has been described. However, the present invention can also be applied to an electronic musical instrument. This electronic musical instrument is replaced with, for example, a sound generation control unit including a sound generation device 7 and a sound generation circuit 8 shown in FIG.
It is provided with sounding instruction means such as a keyboard, a drum pad or a respiratory input device, and musical sound forming means for electrically forming a musical tone signal specified by the sounding instruction means. This electronic musical instrument is similar to the musical instrument of FIG. 1 except that the musical sound signal at the time of performance is not a mechanical or acoustic vibration converted into an electric signal, but is formed in an electric circuit such as a memory or an oscillator. Operate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electric musical instrument according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of an output sound pressure frequency characteristic of an acoustic device of the musical instrument of FIG. 1, and FIG. FIG. 4 is a block diagram of an electric musical instrument according to another embodiment, FIG. 4 is a block diagram of an electric musical instrument according to still another embodiment of the present invention, and FIG. 5 is a diagram of FIG. 1, FIG. 3 and FIG. FIG. 6 is an equivalent circuit diagram when Z _V −Z _O = 0 in FIG. 4, and FIG. 7 is a basic diagram of a circuit that generates a negative impedance. FIG. 8 is a circuit diagram showing a modification of the circuit of FIG. 7, and FIG. 9 is a circuit diagram showing a specific example of the circuit of FIG. 1: Box (speaker box) 2: Duct (hollow piston, pipe) 3: Piston 4: Vibrator (speaker unit) 5: Cylinder 6: Cavity 7: Sound generator 8: Sound generator 9: Vibrator drive

Claims (5)

(57) [Claims] 1. An electric / electronic musical instrument comprising: sound generation control means for generating a musical sound waveform electric signal according to a performance operation; and a sound device for converting the electric signal into sound and generating sound. A resonator comprising a closed cavity and a duct for acoustically connecting the cavity to an external region; and a vibrator which forms a part of a box forming the cavity and drives the resonator on one surface. A vibrator driving means for driving the vibrator, a detecting means for detecting a pitch or a tone range of a musical tone to be pronounced, and the vibrator according to a pitch or a tone range detected by the detecting means. Control means for variably controlling the frequency characteristics of the acoustic device by controlling the shape of at least one of the cavity and the duct. 2. A pitch information generating means for generating pitch information indicating a pitch, a generating means for generating, based on the pitch, a musical tone waveform electric signal having a pitch indicated by the pitch information; A vibrating body driven based on the signal, a box partially formed by the vibrating body, and a duct for acoustically connecting a cavity formed in the box to an external region, and converting the electric signal to sound. An electric / electronic musical instrument comprising: an acoustic device that converts and produces sound; and control means that controls a shape of a cavity or a duct of the acoustic device based on the pitch information. 3. The resonator comprises a single cavity and a plurality of ducts having different shapes connected to the cavity through respective valves, and the control means controls opening and closing of each of the valves. The electric / electronic musical instrument according to claim 1, wherein the shape of the duct is controlled by the control. 4. The cavity is formed by a cylinder, a diaphragm of a vibrator for closing one end of the cylinder, and a piston movable in the cylinder at the other end of the cylinder. 3. The electric / electronic musical instrument according to claim 1, wherein the shape of the cavity is controlled by controlling the position of the musical instrument. 5. The vibrator driving means is configured to provide a voltage signal corresponding to a driving current of the vibrator to the input side of the vibrator driving means by positive feedback, thereby providing an equivalent in the output impedance of the vibrator driving means. And a negative impedance generating circuit that drives the vibrator so as to reduce or invalidate the internal impedance inherent to the vibrator equivalently. Reducing or eliminating the interdependency condition of the characteristics of the resonance system of the resonator and the characteristics of the vibration system of the vibrator with respect to the sound reproduction characteristics of the vibrator. When the vibrator is driven by generating a resistance component equal to or greater than zero in the output impedance of the resonator driving means, the bass resonance radiation capability of the resonator becomes It can be set lower than the minimum frequency to be secured, and the magnitude of the negative impedance component generated by the vibrator driving means is determined by the Q value of the resonance system of the vibrator and the combination of the vibrator and the resonator. The internal impedance is equivalently reduced or invalidated so as not to exceed the magnitude of the internal impedance inherent in the vibrator so that the reproduction characteristic becomes smaller than the Q value when the uniform low-frequency reproduction characteristic is obtained. 2. The electric / electronic musical instrument according to claim 1, wherein the electric / electronic musical instrument is set to a value.