JPH01272297A - Driving device - Google Patents

Abstract

PURPOSE:To attain the improvement of the performance of a system by disposing an oscillator in a cabinet having a resonance opening, defining one of the impedance to be a negative impedance and providing mutually output impedance values. CONSTITUTION:At the time of driving the oscillator of an acoustic device for disposing the oscillator in the cabinet having the resonance opening, in a first resonance frequency f1 determined by a substantial oscillator and the cabinet and a second resonance frequency f2 determined substantially by the oscillator and the cabinet and the resonance opening, driving impedances Z1, Z2 are defined to be both negative values or Z1 Z2 or define one of Z1, Z2 to be zero or a positive value and the other to be a negative. Accordingly, the resonance frequency can be independently set. Namely, for instance, the speaker system can be designed irrespective of the restriction of an ordinary bus reflecting type. Thereby, system performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive device for driving a vibrator disposed in a cabinet having a resonant opening.

[Prior Art] Conventionally, a phase inversion type (bass reflex type) speaker system is known as an acoustic device in which a vibrator is arranged in a cabinet having a resonance opening (resonance boat). FIGS. 21(a) and 21(b) are a perspective view and a sectional view showing an example of the configuration of such a bass reflex type speaker system. In the speaker system shown in the figure, a hole is made in the front of a cabinet 1, a vibrator (speaker unit) 4 consisting of a diaphragm 2 and an electrodynamic electroacoustic transducer 3 is attached, and an opening 6 and a sound path are installed below the vibrator (speaker unit) 4. A resonant boat 8 having a resonant boat 7 is provided. The cabinet 1 and the resonance boat 8 constitute a Helmholtz type resonator.

As a driving device for driving the speaker unit 4 of such a speaker system, a power amplifier with an output impedance of substantially O has generally been used.

FIG. 22 shows an electrical equivalent circuit when the bass reflex type speaker system of FIGS. 21(a) and 21(b) is driven at a constant voltage by a power amplifier with an output impedance of 0. In the figure, Ev is the output pressure of a constant voltage source that is a power amplifier, Rv is the voice coil resistance of the speaker unit 4, and L is the voice coil resistance of the speaker unit 4.

and C8 are the equivalent capacitance (or equivalent mass) and equivalent inductance (or the reciprocal of the equivalent stiffness) of the impedance generated by the movement of the voice coil of the speaker unit 4, and Lc is the equivalent inductance (or the reciprocal of the equivalent stiffness) of the cabinet 1. , and C indicate the equivalent capacity (or equivalent mass) of the boat 8.

FIG. 23 shows the electrical impedance frequency characteristics of the circuit of FIG. 22. In the figure, fl is the resonant frequency (hereinafter referred to as unit-side resonant system) of the first resonant system (hereinafter referred to as unit-side resonant system) that is substantially formed by the active impedance LO, co of the speaker unit 4 and the equivalent stiffness 1/bc of the cabinet 1. first resonance frequency), f2 is the equivalent mass CP of the boat 8
The resonant frequency (first resonant frequency) of the second resonant system (hereinafter referred to as the resonant side resonant system) formed by is substantially the impedance L of the speaker unit 4. , Co and the equivalent mass CP of the boat 8.

Among these resonant frequencies, the resonant frequencies f, and f2
directly affects the sound pressure, and the Q value Q1 of the unit side resonance system at the resonance frequency f1 and the Q value Q2 of the resonance side resonance system at the resonance frequency f2 greatly affect the frequency characteristics and sound quality of the output sound pressure.

By the way, such a bass reflex speaker system is
When driving at a constant voltage, for example, if the resonant frequency f2 on the resonance side is lowered, the Q value Q+ on the unit side increases and the Q value on the resonance side increases.
Since the resonant frequency and Q value depend on each other as the value Q2 decreases, in order to flatten the frequency characteristics of the output sound pressure, for example, the Q value Q1 on the unit side is changed to Ql =, f'r,
It is necessary to highly match the unit side and the resonance side, such as setting the resonant frequency f2 on the resonance side to f2=f, 15, which is disadvantageous in that there are many design restrictions.

Further, when the cabinet is made smaller, the equivalent stiffness 1/Lc of the cabinet becomes larger, and the equivalent inductance LC becomes smaller. As a result, Q1 becomes larger and Q becomes smaller. For this reason, it is difficult to operate normally as a bass reflex speaker system using the conventional constant voltage drive method, so it is necessary to downsize the cabinet of the bass reflex speaker system without sacrificing the frequency characteristics of the output sound pressure and the sound quality. That was difficult.

Figure 24 shows the patent application filed earlier by the applicant in 1986-33.
4262 shows the negative impedance generation circuit shown in No. 4262. If such a negative impedance generating circuit is used as a drive device in the equivalent circuit of FIG. 22 and a negative resistance -Ro is included in the output impedance, the voice coil resistance RV is reduced or nullified, and the output impedance O Q can be made smaller and Q2 larger than when driving at a constant voltage with a power amplifier,
This is effective in downsizing bass reflex speaker systems.

However, even in this case, if the negative resistance -R8 is constant, it is not possible to set Ql and Q2 independently, so in order to set each of Ql and Q2 to the desired values, it is necessary to The disadvantage is that some restrictions remain.

[Problems to be Solved by the Invention] In view of the problems with the conventional type described above, the present invention provides a drive device for driving a vibrator of an acoustic device in which a vibrator is disposed in a cabinet having one opening. In this method, it is possible to independently set the respective Q values at the first resonant frequency based on the stiffness of the vibrator and the cabinet and the second resonant frequency based on the stiffness of the cabinet and the resonant aperture, thereby reducing the size of the acoustic device and reducing the damping force. It is an object of the present invention to improve the performance of a system including the acoustic device and the drive device of the present invention.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a drive device for driving a vibrator of an acoustic device in which a vibrator is disposed in a cabinet having a resonant opening. and the stiffness of the cabinet, and the second resonance frequency according to the stiffness of the cabinet and the resonant aperture.
The present invention is characterized in that at least one of the output impedances at the resonance frequency is a negative impedance, and the output impedance values are different from each other.

[Function] The output impedance of the drive device becomes negative impedance -
Zo and the impedance ZV specific to the vibrator
(e.g. RV in FIG. 22), i.e. zv-Z.

= 0 (Rv −Ro = O in FIG. 22), the equivalent circuit in FIG. system) is short-circuited via a constant voltage #iEV, which is a driving device, so that Q becomes 0 and there is no substantial resonance. In other words, this unit side resonant circuit is the driving device Eν
The vehicle will be driven in a fully braked state. In addition, the series resonance circuit on the resonance side (resonance side resonance system) consisting of the equivalent stiffness 1/Lc of the cabinet and the equivalent trade amount C of the resonance aperture is also short-circuited via the drive device Ev, but this is a series resonance circuit. Therefore, if the acoustic equivalent resistance of the cabinet and resonant aperture is ignored, the calculated Ql
becomes ■. In addition, in this case, the unit-side resonant circuit and the resonance-side resonant circuit are each driven independently from the drive device EV, and the interdependence between the unit-side resonant circuit and the resonance-side resonant circuit described above is eliminated. Therefore, the resonance frequencies f, , f2 and Q values Ql, Ql can be set independently. In addition, in the case of Rv-RO>O, or when the acoustic equivalent resistance of the cabinet and the resonant opening cannot be ignored, the above Q+ and Ql are 0 and (1) above, and the output impedance of the drive device is 0. This value is between the Q value in the case of a conventional general driving method. Furthermore, when the output impedance of the drive device is a positive value, Ql increases and Ql decreases as the value of the output impedance increases.

If we consider a bass reflex speaker system that uses a small cabinet and sets the resonant frequency between the cabinet and the boat (resonance aperture) low, this has a large Ql compared to a bass reflex speaker system with a standard design.
and a small Ql. And this is negative resistance -
When driven with Ro (Rv-R0≧0), as mentioned above, the larger the absolute value of negative resistance -R8, the smaller Ql becomes, and Q,
becomes larger. FIG. 1 shows the relationship between such negative resistance -Ro and Ql.

In the same figure, when Ro"O is a conventional general constant voltage driving state.Here, -Ro is made smaller than 0,
As it approaches −Rv, Ql decreases almost linearly toward 0, and conversely Ql increases, but does not become ■.
The value approaches the value determined by the acoustic resistance of the cabinet or boat.

Therefore, at a certain -R0, Ql and Ql may have desired values, but as shown in FIG. 1, the value of -R6 (-R8=-
RA) and the value of -R8 (-Ro = -Ra) at which the desired Ql (=B) is obtained are often different.

According to the invention, in such a case, the drive impedance -Z at frequency f1. (=2+) to -RA, drive impedance -Zo (
=22) to −RB, the desired Ql
, Ql can be obtained.

Also, depending on the cabinet design, Q.

There are cases where both Q2 and Q2 become large and it is desired to lower the Q value of both. In such a case, according to the present invention, as shown in FIG. 2, the drive impedance ZI at the frequency f1 may be set to negative (-RA), and the drive impedance Z2 at the frequency f2 may be set to be positive (RB). Furthermore, if, on the contrary, both Ql and Q2 are desired to have large values, according to the present invention, the frequency f.

The drive impedance Z1 at frequency f2 is set to positive (RA), and the drive impedance Z2 at frequency f2 is set to negative (-Ra).
).

Note that for another resonance point f, there is no particular restriction because it is not related to the output sound pressure, but in order to suppress unnecessary operation, the impedance Z3 at this frequency f3
It is desirable to set Zs to zero.

[Effect] As described above, according to the present invention, when driving a vibrator of an acoustic device in which a vibrator is disposed in a cabinet having a resonant opening, the effect is substantially determined by the vibrator and the cabinet. The driving impedance (output impedance of the driving device) Zl and Z at each of the first resonant frequency f+ and the second resonant frequency f2 determined by the cabinet and the resonant aperture are both negative values, and Zl ≠22 Alternatively, by setting one of zl and z2 to be positive or 0 and setting the other to be negative, Ql.

Q2 can be set independently. This makes it possible to design an acoustic device having a resonant aperture, such as a speaker system, without being bound by the constraints of a normal bass reflex type. For example, it is possible to downsize the system by making the cabinet smaller without sacrificing sound pressure and quality. In addition, since an appropriate Q value can be obtained at each resonance frequency f, f2, the degree of freedom in design is further improved than when the output impedance is negative (-Z.) and constant. Performance can be expected to improve over a fixed value. Further, by setting the drive impedance Z1 at the first resonance frequency f to a negative value and lowering Ql, it is possible to drive the unit side in a braked state.

[Example code] Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows the basic circuit configuration of a drive device according to an embodiment of the present invention. In the drive device shown in the figure, the output of an amplifier circuit 31 with a gain of A is applied to a load zL formed by a speaker 32. Then, the current IL flowing through this load ZL is detected and positively fed back to the amplifier circuit 31 via a feedback circuit 33 with a transfer gain β.

In this way, the output impedance z0 of the drive device
is the impedance of the sensor that detects the current ■, 23
Then, Zo = Zs (1-Aβ). From this equation, if Aβ>1, Zo becomes an open stable negative impedance.

Here, if A, β, or Zs has a frequency characteristic, the output impedance Zo can have a frequency characteristic.

FIG. 4 shows a circuit example in which the output impedances Z1 and Z2 at frequencies f1 and f2 are both negative impedances and may have values close to each other.

The circuit shown in the figure uses a current detection resistor R3 as a sensor for detecting current 5, and also includes a capacitor C1 and resistors R+ and R2 as a negative feedback circuit 33, and has frequency characteristics (the frequency characteristics within the required band are flat). not) CR
The transfer gain β of the negative feedback circuit 33 is made to have a frequency characteristic by using the circuit 33a and the amplifier 33b which does not have a frequency characteristic (the frequency characteristic is flat within the required band).

Note that this circuit can also be considered to provide the sensor Zg with frequency characteristics by including the CR circuit 33a in the current detection sensor ZS. FIG. 5 shows the frequency characteristics of the circuit of FIG. 4. In FIG. 5, Z2 = Rs (1-Aβ0). Also, when the output impedance curve is approximated by a polygonal line according to the Nyquist method, the output impedance is Z,
The frequency fP of the turning point P falling from Zl toward Zl is approximately 1/2πClR2.

FIG. 6 shows an example of the circuit when Z 1 < 22 < O, and FIG. 7 shows the frequency characteristics of the circuit shown in FIG.

In Figure 6, Z+=Ri(1-Aβ.) , and the corner frequency fP is approximately 1/2πC,J.

Figure 8 shows 2. An example of a circuit where Zl is greatly changed with respect to Zl with <22 is shown. In the circuit shown in the same figure,
A signal with a dip at frequency f2 is sent to the amplifier circuit 3 by the twin T circuit 35 whose dip frequency is set to f2.
Returned to 1. Therefore, as shown in FIG. 9, the output impedance can be increased only around the frequency f2. In the circuit of FIG. 8, the output impedance at frequencies f+ and f3 is 2.
．． 23 is Zl = 13 = Rs (1-Ar1), and can be set to any value by selecting β0. moreover,
The shape of the curve in FIG. 9 can be varied as shown in FIG. 10 by the variable resistor VR in the circuit of FIG. 8, and it can be varied as shown in FIG. 11 by the variable resistor VR. be able to.

In the circuit shown in FIG. 8, if the dip frequency of the twin T circuit 35 is set to fl, it is possible to make Zl >22 and Za as shown in FIG.

The resonance at frequency f is not related to sound pressure, but in the circuits shown in Figures 4, 6, and 8, the output impedance Z3 at frequency f is set as a negative impedance. The Q value Q at frequency f3 is lowered to sufficiently damp the speaker 32 so that it does not move unnecessarily.

FIG. 13 shows a circuit in which an LC resonant circuit 36 is used instead of the twin T circuit 35 in the circuit shown in FIG. By using the LC resonant circuit 36 in this manner, the same operation as the circuit shown in FIG. 8 is possible.

FIG. 14 shows an LC resonant circuit 37 connected in series to the feedback system. In the circuit shown in the figure, the amount of feedback (transfer gain β) is maximum at the resonant frequency of the LC resonant circuit 37, so it is possible to minimize the output impedance at that frequency f, as shown in Fig. 15. can.

Therefore, by setting this frequency f to fl or f2, it is possible to make the output impedances ZI and 22 significantly different, as shown in FIG. 16 or FIG. 17.

FIG. 18 shows a circuit in which a second LC resonant circuit 38 that resonates at frequency f3 is added to the circuit in FIG.
As shown in FIG. 9, the Q value Q3 is lowered by lowering the output impedance at the frequency f3. This is effective in preventing unnecessary movement of the speaker 32. In FIG. 19, .

In the above embodiment, the output impedance Zo is
Zo = Rs (I Aβ), and when β≧0, the maximum value of Zo is Rs, but by using the feedback circuit 33 for both positive feedback and negative feedback, 2. ．． 2. One of them can be a negative value while the other can be a positive value of R8 or more.

FIG. 20 shows that the transfer gain β is β=βo (F (X) − F (Y) ),
An example of a circuit with both positive and negative components is shown.

As shown in the figure, the feedback circuit 33 has a certain transfer characteristic F.
(X) and −F (Y), in the band where the gain of F (X) exceeds F (Y), β>O, and ZO
= R8(1-Aβ), the output impedance is less than R3, and negative impedance can be realized when Aβ>1, and conversely, the gain of F (Y) is F (X
) in a band exceeding 0, the output impedance becomes a positive impedance of FtS or more.

In this way, a speaker system having a bass reflex type structure is driven with a negative impedance at least one of the resonance points f1 and f2 related to the sound pressure, and each resonance point f
The output impedance values Zl, Z2 at l, f2 are Z
By setting 1≠Z2, Q at each resonance point f+, f*
Value Q1. Q2 can be set independently, braking force,
Performance and sound quality can be improved.

[Modified Example of Embodiment] In the above-mentioned embodiment, an example was shown in which the resistor R3 was used as a sensor for current detection, but this sensor may also be a current transformer (C, T, ), a Hall element, etc. A current probe may also be used.

Further, a reactance element such as a capacitor or an inductance may be used as the sensor, and in this case, the sensor itself can have frequency characteristics. moreover,
By differentiating or integrating the outputs of these sensors, it is possible to give them frequency characteristics or make them flat.

For example, if the current I is detected by the terminal voltage of the resistor Rs, and this is differentiated or integrated in the feedback circuit 33, the transfer gain β can have a frequency characteristic, and the current IL is detected by the terminal voltage of the capacitor, and the feedback If this is differentiated in the circuit 33, the frequency characteristic of the transfer gain β becomes flat.

In addition, in order to give the feedback circuit 33 a frequency characteristic,
The feedback amplifier (for example, 33b in FIG. 4) itself may have frequency characteristics by performing current or voltage feedback internally.

[Brief explanation of the drawing]

1 and 2 are characteristic diagrams showing the relationship between output impedance and Q value for explaining the basic concept of this invention, and FIG. 3 shows the basic configuration of an audio device according to an embodiment of this invention. FIG. 4 is a circuit diagram showing the first embodiment of the invention, FIG. 5 is a frequency characteristic diagram of the output impedance of the circuit of FIG. 4, and FIG. 6 is a diagram showing the second embodiment of the invention. 7 is a frequency characteristic diagram of the output impedance of the circuit of FIG. 6, FIG. 8 is a circuit diagram showing a third embodiment of the present invention, and FIGS. 9 to 12 are: FIG. 13 is a circuit diagram showing a fourth embodiment of the present invention which operates in the same manner as the circuit shown in FIG. 8; Fig. 14 is a circuit diagram showing the fifth embodiment of the present invention, Figs. 15 to 17 are frequency characteristic diagrams of output impedance according to the settings of each constant in the circuit of Fig. A circuit diagram showing a sixth embodiment of the invention; FIG. 19 is a frequency characteristic diagram of the output impedance of the circuit in FIG. 18; FIG. 20 is a circuit diagram showing a seventh embodiment of the invention; Figures (a) and (b) are cross-sectional views showing the configuration of a conventional bass reflex speaker system. Figure 22 is an electrical equivalent circuit diagram when the bass reflex speaker system of Figure 21 is driven at a constant voltage. Figure 23 is the electrical impedance frequency characteristic diagram of the equivalent circuit in Fig. 22,
FIG. 24 is a basic configuration diagram of the negative impedance generating circuit according to the prior application. 1: Cabinet 4; Vibrator (speaker unit) 8; Resonance boat (resonance aperture) 31: Amplification circuit 32: Speaker 33: Feedback circuit f,: First resonant frequency f2; Second resonant frequency

Claims (1)

[Claims] (1) Driving a vibrator that is disposed in a cabinet having a resonant opening and directly radiates sound, and also drives a Helmholtz resonator constituted by the resonant opening and the cabinet to radiate resonant sound from the resonant opening. In the driving device, the driving device has a first resonant frequency substantially determined by the dynamic impedance of the vibrator and an equivalent stiffness of the cabinet, and a second resonant frequency that is the resonant frequency of the Helmholtz resonator. A drive device characterized in that each of the impedances has at least one negative impedance and is configured to have different output impedance values.