JPH01265700A - Driver - Google Patents

Abstract

PURPOSE:To increase the degree of freedom of design by providing a specific equivalent impedance in an output impedance of a driver. CONSTITUTION:The driver is so constituted that the output impedance includes the negative impedance component (-RA) reducing or invalidating the internal impedance specific to the vibrator to be driven, the reactance component (CX or LX) connected in series with the component (-RA) and a resistive component (RX) connected in parallel with the reactance component as required thereby increasing the degree of freedom of design. Moreover, it is possible to develop a speaker system having a characteristic or size disabled at present by the combination with various cabinets.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drive device for driving a vibrator such as a speaker, and particularly relates to a drive device that drives a vibrator such as a speaker, and in particular, the characteristics of the vibrator and the structure and size of a casing that houses the vibrator. The present invention relates to a drive device that can be driven by electrically and equivalently adjusting the characteristics determined by the above.

[Prior Art] Conventionally, a power amplifier for driving a speaker system has generally driven a speaker unit at a constant voltage.

FIG. 19 shows an equivalent circuit of a mechanical system when an electrodynamic speaker unit is attached to an infinite baffle and driven at a constant voltage. In the figure, ro represents the equivalent resistance of the vibration system, So represents the equivalent stiffness of the vibration system, and mo represents the equivalent stiffness of the vibration system. Further, A is a force coefficient, and when the speaker unit is an electrodynamic direct radiation speaker, A=Bρ, where B is the magnetic flux density in the magnetic gap and l is the total length of the voice coil conductor. Furthermore, RV in the figure indicates the conductor resistance of the voice coil, and EV indicates the voice coil drive voltage. The current in this circuit becomes the speed V of the vibration system.

FIG. 20 shows the current in the circuit of FIG. 19, ie, the speed V of the vibration system. Furthermore, since the output sound pressure is approximately proportional to the acceleration, it becomes as shown in FIG. 21.

here, It is.

As shown in FIG. 21, the low frequency characteristics of the speaker range from f to f. Above that, the sound pressure becomes constant and below f0, it decreases.

Therefore, f becomes difficult to reproduce flatly below f.
In many cases, o is expressed as the bass limit frequency. Also, the shape of the characteristic at fo is determined by the value of Qo. +: 1 gives the flattest characteristics.

For this reason, when designing speakers, f
The settings of o and Qo are important factors.

As shown in equation (1), fo for a single unit is determined by mo and So specific to the unit.

The same <Qo is as shown in equation (2).

re here is mechanical braking resistance, A 2 /R
V is an electromagnetic braking resistance when driven at a constant voltage.

Generally, A2/Rv>ro, so Qo is mostly determined by the electromagnetic braking resistance.

Up to this point, we have described the operation of the unit when it is attached to an infinite baffle, but in reality, the speaker unit is used by being attached to a cabinet with a finite capacity, such as a closed type or bass reflex type.

The mechanical equivalent circuit of a unit installed in a closed cabinet is shown in FIG. 22, in which the acoustic stiffness Sc of the cabinet and the braking resistance re of the cabinet are added. Again, generally A2/RV)ro.

Therefore, foo of the unit when placed in the cabinet
becomes, and the addition of Sc increases the resonant frequency. Similarly, the Qo' of a unit placed in the cabinet is generally r r) + r c (A 2/Rv, so the Qo decrease due to the addition of rc is small, and f
0' is f. Q due to higher price. The increase in temperature becomes dominant, and Qo'>Qo.

This effect is particularly large when installed in a small cabinet where 1/S c < 1/S o, and both fo' and Qoo become extremely large, making it difficult to reproduce low frequencies, and qoo becomes This causes a large peak in foo, resulting in reproduced sound with poor transient response.

To obtain a low value of fol in a small cabinet, use (3
) As is clear from the equation, the only options are to reduce S0+Sc or to increase mo. Even if the unit 80 is made smaller, the limit is determined by the cabinet SC, so it is necessary to increase mo. Increasing mo will reduce the efficiency of the speaker. Also, as shown in equation (4), if mo is increased, Q. ° will also rise. Therefore, in order to lower foo and Qo' in a small cabinet, m should be used to lower foo. is large, Qo
In order to lower o, it is necessary to use a large unit for A”/Rv. To increase A2/RV, a large magnetic circuit can be used, but this results in an expensive unit and m
Since o is large, efficiency also decreases. However, this method is actually used in designing small cabinets to produce bass sounds.

In addition, in order to supplement the bass reproduction ability in a small cabinet,
As shown in FIG. 23, there is an example in which the bass is boosted by a tone control, a Graphco, a dedicated equalizer, etc. on the drive amplifier side.

This is a method of increasing the sound pressure by increasing the input voltage for the band below fo°, which is difficult to reproduce.

Although it is possible to raise the sound pressure below fo' with this method, the transient response at f.° may deteriorate due to the increased Qo' caused by placing it in a small cabinet, and the same <fO' due to the high Qoo. Since the negative effects of increased Qo', such as sudden phase changes in You cannot get the same sound quality as other speaker systems.

Additionally, although rare, there have been cases where units have been installed in cabinets with too large a capacity.

In this case, both sfo' + Qo' have small values, and since fol is low, it is possible to reproduce bass sounds, but Qo' is too small, resulting in a sloping characteristic.
On the contrary, the i-feel of the bass is lost.

However, in this case, the value of Qo' is small and the transient response characteristics are good, so if you compensate for the drop in the low frequency range (overdamping) due to the small QO' by boosting the bass on the drive side, you can achieve high quality playback. can be expected.

However, configuring a speaker system for this purpose requires a large-capacity cabinet, which is not efficient.

Additionally, a cabinet system called a bass reflex type is also commonly used. FIG. 24 shows a mechanical equivalent circuit of a speaker system (bass reflex speaker system) using such a bass reflex cabinet.

In the figure, vc is the speed inside the cabinet, Vu is the speed of the unit, Vp is the speed of the boat in %, rp is the braking resistance of the boat, and mp is the equivalent mass of the boat.

The bass reflex type is advantageous for low frequency reproduction because the bass is emitted from the boat, but in Fig. 24, in this case as well, generally A2/Rv > ro, re, and A'/R
Since v becomes a series braking resistance for the resonance of the unit, it becomes a parallel braking resistance for the resonance of the boat (parallel resonance of mp and 17Sc), and serves as both braking resistances. Therefore, in order to set the resonance Q of both the unit and the boat to an appropriate value, it is more difficult to determine the cabinet volume than the closed type, and there are more design constraints than the closed type.

When designing early speaker systems, the approach was to first design a complete speaker unit as a single unit, and then complete the speaker system using a cabinet that fully demonstrated its performance. For this reason, it was thought that the smaller the effect the cabinet had on the speaker unit, the better, and large cabinets were mainly used.

However, if the same characteristics can be obtained, it is natural that a smaller cabinet will take up less space and be easier to handle, and many ideas have been developed to make it smaller (A
R type, etc.). These methods do not treat the speaker unit and the cabinet as separate entities, but instead design the unit by considering its total performance when placed in the cabinet.

The size of a speaker system is determined by the cabinet, not the unit, so recently, contrary to the initial method, the size of the cabinet is determined first, and a unit that takes full advantage of that cabinet volume is later designed to obtain the overall characteristics. This design is more common.

Therefore, many demands are placed on the speaker unit. Furthermore, since low frequency reproduction is most affected by the cabinet volume, the requirements placed on the speaker unit are also largely related to low frequency reproduction.

As mentioned above, in order to reproduce sufficient bass with a small sealed cabinet, it is sufficient to prevent fo'+Qo' from becoming large, so in order to improve these with a speaker unit, mo should be increased and S.

It is sufficient to make A2/RV small and A2/RV large. 5 of these
It is relatively easy to reduce 0 by making the damper and edges that support the vibration system softer, but even if the value is reduced beyond a certain point, SC becomes dominant, so this is a limitation. However, increasing mo causes a decrease in sound pressure,
Increasing A2/Rv requires the use of a large magnetic circuit, which increases the size of the unit, and there is a limit to its ability to fit into a small cabinet. In fact, the miniaturization of cabinets is
The limits have been set by the problem of reducing the sound pressure and increasing the size of the magnetic circuit.

If we look at the individual characteristics of a unit that satisfies these conditions, from equation (1), if mo is large, fo will be low, and from equation (2), if A2/Rv is large, Qo will be low. I understand that there is something. however,
As mentioned above, even if 50 is decreased, fo will decrease, but Sc
In consideration of this, S.

Even if FOO is lowered beyond a certain level, foo will not fall.

Therefore, the cabinet can be made smaller if there is a unit with an extremely large mo and, as a result, an extremely low f and an extremely low Qo.

It's basically the same for the bass reflex type, with no being larger than f. It is possible to miniaturize by using a unit with a small +Qo value, but as mentioned above, in the case of a bass reflex, there are appropriate values for the cabinet, and appropriate no and fo can be achieved without miniaturization.

Creating a unit with Qo is itself difficult.

This is because a speaker unit cannot produce high-quality reproduced sound without considering not only bass characteristics but also midrange and treble characteristics, so it is possible to design a speaker unit by focusing only on fa and Qo, which are the factors of bass characteristics. Because it's not even a thing.

FIG. 25 is a diagram in which the mechanical equivalent circuit in FIG. 19 is replaced with an electrical equivalent circuit. By replacing the mechanical system with the electrical system, inductance and capacitance C
Then, the capacitance C is replaced by an inductance, and the resonant circuit is expressed in parallel form. This circuit has the same electrical impedance characteristics as the unit, but the difference is that in the unit, the glue in the circuit, C, is not electrical, but it is created using the impedance generated by the vibration system capturing the image. . However, since there is no problem in considering this as electrical or C, this circuit is generally often used as an electrical equivalent circuit. even here,
The mechanical braking element A'/r6 is A'/r
Since o > Ry, the damping of the resonant circuit is almost R
Determined by v.

[Problems to be Solved by the Invention] As described above, the characteristics of conventional speaker systems were set on the premise that they would be driven at a constant voltage, so they were subject to various constraints in the design of speaker units and cabinets. , foo.

It has been difficult to downsize the system without sacrificing overall characteristics related to Qo'.

This invention was made in view of the above-mentioned problems, and it is possible to improve the f, ' and, if necessary, the Q of a speaker system. An object of the present invention is to provide a drive device that can drive a speaker unit by adjusting the angle.

[Means and operations for solving the problems] Hereinafter, the present invention will be explained in detail with reference to the drawings. As shown in FIG. 1 or 2, the drive device of the present invention has a negative impedance component (-RA) in the output impedance that reduces or nullifies the inherent internal impedance (RV) of the vibrator to be driven. ) and a reactance component (CX or Lx
) and, if necessary, a resistance component connected in parallel to this reactance component.

Figure 3 shows the inherent internal impedance (RV) of the vibrator.
An example of a negative impedance generating circuit that reduces or nullifies the impedance is shown below.

The output impedance of the circuit shown in the figure can be expressed as Rs(1-Aβ) (6). Here, if Aβ>l, the drive impedance to the load becomes negative, and the circuit becomes an open stable negative impedance drive circuit. This equivalent circuit can be expressed as shown in FIG. In the same figure, -RA=Rs (1-
Aβ), and this -RA is negative resistance.

-RA in FIG. 4 becomes as shown in FIG. 5 when the speaker unit is used as a load, and the operation at this time is the same as that in FIG. 6. -RA has the effect of reducing RV or making it O in this way.

In Figure 6, when RV=RA, RV-RA=0
As shown in FIG. 7, when viewed from the Ev side, it is directly connected to the C resonant circuit (actually, it is a dynamic impedance) without passing through the RV.

Now, let's consider the electrical equivalent circuit of Subikaninit.

As shown in FIG. 8, the equivalent circuit of the speaker unit is considered to be an RV part and parallel resonant circuit parts of Co, Lo, and Ro connected in series.

As mentioned above, Co and Lo are actually dynamic impedances, but they can be thought of as electrical C and L, so
If an electric capacitor CX can be further connected in parallel to the resonant circuit made of Co, Lo, and Ro, the total capacitance of the resonant system will be Co + Cx, f. can be lowered.

However, since actual speaker units do not have terminals like the dotted lines in Figure 8, such a CX is
Connections can only be made through the . For this reason,
Connecting an electrical capacitor to the speaker terminal like CY in Figure 9 has little effect on lowering fo, because in a parallel resonant circuit, co + t and o are directly connected, so at the resonant frequency This is because a large current flows and causes a resonance phenomenon, but since CY is connected to the resonance circuit through RV, Rv becomes a current limiting element and cannot positively influence the resonance system.

In FIG. 9, Ro>Rv, and since Ro is generally very high, the impedance of the resonant current loop at the resonant frequency is small (Ro is completely O at ω), and a large resonant current flows. Since the current loop including CY has RV, the resonant frequency becomes i, (i), and the effect of lowering f0 due to the addition of CY cannot be expected much.

Here, if only Rv can be reduced or made O by some means, CY and the resonance system will have a close relationship, and fo can be reduced.

It is possible to reduce only the value of RV in a car by reducing the number of turns in the voice coil of the speaker, but since Rv is the resistance of the coil itself that generates dynamic impedance, this also reduces the dynamic impedance itself. There is no point in decreasing, and if the unit itself actually improves,
Isometrically, RV
There are methods such as using a large magnetic circuit to reduce the value of (increase dynamic impedance), but it is impossible to change it significantly.

However, this is possible using the negative resistance shown in FIG. When the circuit of FIG. 4 and the speaker unit are connected with a capacitor having a value of Cx, the result is as shown in FIG. 10.

Since the series elements remain the same even if their positions are changed, FIG. 10 can be rewritten as shown in FIG. 11. Here, if Rce RA=O is set, the result will be as shown in FIG. 12. Ev is a voltage source, so when considering a resonance system, short it (
The equivalent circuit of the resonant system is as shown in Figure 13, and as with Cx in Figure 8, it has the same effect as connecting CX directly in parallel to the resonant system, and fo decreases. .

However, as it is, the only braking resistance that determines the Q of the resonance system is the mechanical Ro, and since this is actually a large value, the Qo of the system becomes extremely large. Therefore, as shown in FIG. 14, by connecting RX in parallel with CX, this is used as a braking resistor. Here, CX and R
Since x can be set regardless of the unit, using this method, the fo of the unit can be lowered to an arbitrary value by CX,
By using RX, it becomes possible to set the Qo of the resonance system to an arbitrary value (although it cannot be made larger than the Q determined by Ro't').

Here, CX and RX are the original fa and Qo formulas (1
) and (2), when replacing it with a mechanical element, Cx = m, /A2 ----・- (7) (where mx is the isometric additional mass), and mx = A2C, ... (8) Therefore, adding the mass of A2CX to the actual vibration system,
It has the same effect as above, and if the new resonant frequency is fx, it becomes , which is a lower value than the original fo.

However, in this case, the speaker unit is electrically m
Although the operation is equivalent to adding the mass of X = A2Cx, since no mass is actually added to the diaphragm, the acoustic conversion efficiency of the unit itself does not change, and the above-mentioned m. The effect is that there is no decrease in efficiency, especially in the middle and high ranges, due to the increase in .

As for Q, the original electromagnetic braking resistance RV changes to RX, and the new Q becomes Qx.

Here, if the RX and drive section are included, it will be as shown in FIG. 15. Further, if RV RA = 0, the result will be as shown in FIG. 16.

Here, electrical equivalent mass co+CX and electromagnetic braking resistance R
Considering a normal speaker unit with X, this should be as shown in FIG. 17, and the position of CX is different from that in FIG. 16. Therefore, the speaker in FIG. 16 and the speaker in FIG. 17 have the same resonance frequency f and the same Q of the resonance system, but
The output sound pressure constant wavenumber characteristics when the driving voltage Ev is constant are different.

However, this difference is only a difference in the frequency characteristics of the sound pressure in the car, and does not mean that the resonance frequency and its Q value, which are important in the bass range mentioned above, are different, so if necessary, as shown in Figure 18, By simply correcting only the frequency characteristics on the drive side, the same sound pressure characteristics as in FIG. 17 can be obtained with the one in FIG. 16.

However, here, the frequency correction circuit not only approaches the one shown in Figure 17 (whether or not the one shown in Figure 17 has the optimal frequency characteristic is another matter), but also actively compensates for the shortcomings of the unit. Of course, it does not matter if the correction is made as follows.

Also, the explanation so far has been made assuming RV-RA=O, but as mentioned in Fig. 9, the impedance of the resonant current loop (1+ loop) is not completely O due to the presence of R6, so Rv is also The above-mentioned effect can be obtained even if the setting is not completely O, and this does not mean that it cannot be operated unless Rv-RA=O.

FIG. 26 shows an example of an amplifier having an output impedance as shown in FIG. The output impedance Z0 in the amplifier shown in the figure is Zo = Rs (1-Rt/Ry).

Here, since R,=30 is Ω, R,<30 is Ω
When , the negative resistance component -RA can be included isometrically in the output impedance 0.

In addition, in the above, CX and RX have been treated as using actual capacitors and resistors, but since voltage loss and heat generation occur in these resistors, which reduces the total efficiency, these CX and RX Ha-RA
Same as <(-RA is not an element that actually exists, so it can only be created isometrically by a circuit) It is more efficient to create it isometrically by a circuit.

FIG. 27 shows an example of a circuit that creates such Cx and RX isometrically.

In this way, according to the drive device having the equivalent impedance shown in FIG. 1, it is possible to drive the speaker system with fo and Qo isometrically changed to fx and Qx. Therefore, even if the unit and the cabinet are not highly matched, driving with a drive device having an output impedance as shown in Figure 1 is equivalent to or better than the case where the unit and the cabinet are highly matched. In addition to the above characteristics, many other benefits can be obtained, such as increased freedom in designing speaker units and cabinets.

[Other Examples] In the above, examples of miniaturization with a closed type, miniaturization with a bass reflex type, and expansion of design freedom have been given, but other methods such as a horn type and tube resonance are also possible. Naturally, there are many benefits when applied to speaker systems.

In addition, although the above example shows an example of lowering fo, the second
If a drive circuit having the equal output impedance shown in the figure is used, it is also possible to raise fo to an arbitrary frequency using Lx and set Q to an arbitrary value using Rx.

In this case as well, it is more efficient to create t and x isometrically using an electric circuit, as in -RA.

Furthermore, although the case where the impedance specific to the speaker unit is only a resistance component has been described above, it goes without saying that the present invention can also be applied to a case where the impedance specific to the speaker unit is composed of only a reactance component or a reactance component and a resistance component. In this case, instead of the detection resistor RS in FIG.
Connecting a detection impedance of the same type as the specific impedance, or connecting a detection impedance of a different type from these detection resistors or the specific impedance,
By differentiating or integrating the terminal voltages of these detection impedances, a desired negative impedance can be obtained, and the specific impedance can be reduced or nullified.

[Effects] As described above, by driving a vibrator, for example, a speaker unit using the drive device of the present invention having an equivalent impedance as shown in FIG. 1 or FIG. 2 in the output impedance, the following effects can be achieved. You can get an effect like this.

That is, the unit driven in this way has fx, Q
Since it can be treated as a speaker unit with x, the design method for installing it in various cabinets can be done using the conventional calculation method, and the constants of the unit are fx and Q.
Just use x.

In addition, since there is a degree of freedom in setting fx and Qx, if you design the cabinet first, you can set fx and Qx without changing the unit by simply changing the constants of the electric circuit, even if you burden the unit with the characteristics. Since it can be varied, the degree of freedom in design increases.

In addition, equivalent fo, which cannot be realized in real units,
, and Qo, it is possible to develop a speaker system with sizes and characteristics that are currently impossible by combining with various cabinets.

[Brief explanation of the drawing]

1 and 2 are equivalent circuit diagrams showing the basic configuration of a drive device according to an embodiment of the present invention, respectively. FIG. 3 is a diagram showing the negative resistance -RA of FIGS. 1 and 2. FIG. 4 is an equivalent circuit diagram of the negative impedance generating circuit shown in FIG. 3. FIGS. Equivalent circuit diagrams when driven by a generator circuit, Figures 8 to 13 are explanatory diagrams showing that the resonance frequency can be lowered by electrically connecting a capacitor CX to the equivalent mass of a speaker unit. 17 is an explanatory diagram showing that the Q value can be lowered by further connecting a resistor in parallel to the capacitor shown in FIG. 13, and FIG. Figure 19 is a mechanical equivalent circuit diagram when the speaker unit is attached to an infinite baffle and driven at a constant voltage. Figure 20 is a frequency characteristic diagram of the speed of the circuit in Figure 19. Figure 21 is a frequency characteristic diagram of the output sound pressure of the circuit in Figure 19. Figure 22 is a mechanical equivalent circuit diagram when the speaker unit is installed in a closed cabinet and driven at a constant voltage. Figure 23 is: Circuit and frequency characteristics diagram when a speaker unit installed in a small cabinet is driven at a constant voltage with a signal with boosted bass. Figure 24 shows the mechanical equivalent when a speaker unit is installed in a bass reflex type cabinet and driven at a constant voltage. 25 is an electrical equivalent circuit of the mechanical equivalent circuit of FIG. 19, FIG. 26 is a circuit diagram showing an example of an amplifier having an output impedance as shown in the equivalent circuit of FIG. 1, and FIG. FIG. 27 is a circuit diagram showing an example in which CX and RX of FIG. 1 are created without connecting actual elements to the output terminals. -RA: Negative impedance, Cx: Capacitor, L
x: inductor, Rx: resistance, Rv: inherent internal resistance of the vibrator.

Claims (2)

[Claims] (1) In a drive device that drives a vibrator having a unique internal impedance, this drive device includes a negative impedance component that equivalently reduces or nullifies the internal impedance of the vibrator, and a negative impedance component connected in series to this negative impedance component. A drive device characterized by having an output impedance consisting of a connected capacitive or inductive reactance component. (2) In a drive device that drives a vibrator having a unique internal impedance, this drive device includes a negative impedance component that equivalently reduces or nullifies the internal impedance of the vibrator, and a negative impedance component connected in series to this negative impedance component. A drive device characterized by having an output impedance consisting of a capacitive or inductive reactance component connected to the reactance component and a resistance component connected in parallel to the reactance component.