JPS63234700A - Composite type direct radiation speaker system - Google Patents

Abstract

PURPOSE:To cope with the specification change of a main speaker without modifying circuit constitution by measuring in advance an equivalent mechanical impedance of an auxiliary speaker and applying a signal proportional to the product between the velocity signal of the main speaker detected by the sensor and the mechanical impedance to the auxiliary speaker. CONSTITUTION:A sensor 13 detecting the diaphragm velocity of the main speaker 1, and an auxiliary speaker drive amplifier 12 receiving a detection signal of the sensor 13 and applying a signal proportional to the product between the diaphragm velocity of the main speaker 1 and the equivalent mechanical impedance of the auxiliary speaker 2 mounted in the cabinet 3 to the auxiliary speaker 2 are provided. That is, the signal proportional to the product between the diaphragm velocity of the main speaker 1 and the mechanical impedance of the auxiliary speaker 2 mounted in the cabinet 3 is fed to the auxiliary speaker 2 and the change in the back pressure caused by the operation of the main speaker 1 is eliminated by the vibration of the speaker 2. Thus, the design is not independent of the specification change in the main speaker 1 and the composite direct radiation speaker system with stable operation is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a main speaker that is mounted on a speaker cabinet and radiates sound directly to the outside, and a speaker that radiates sound to the back of the main speaker. This invention relates to a composite direct radiation speaker system consisting of an auxiliary speaker installed in a cabinet.

[Prior Art] Since a speaker system is generally composed of a single speaker and a speaker cabinet, its bass range characteristics are greatly influenced by the internal volume of the cabinet. For example, when looking at the resonant frequency, the resonant frequency when installed in a cabinet increases significantly compared to when only a single speaker is used. Therefore, bass reproduction methods have been developed in which the resonant frequency of a single speaker does not change even when it is installed in a cabinet.

Conventionally, as a bass reproduction method that can meet such demands, a composite direct radiation speaker system as shown in FIGS. 3 and 4 has been proposed. Figure 3 shows the English trace rA CU
S T I CA, vo1, 39 (1978) J P
P.

"Pseudo-infinite baffle speaker system (Loudspeaker enclosus)" described in 316-322
re to Simulatean Infinite
Schematic configuration diagram showing the conventional composite direct radiation speaker system introduced in the paper entitled Baff1e) J, No. 4
Figures (a) and (b) are speaker drive circuit diagrams thereof. In the figure, (1) is the main speaker for radiating sound to the outside, (2) is the auxiliary speaker installed inside the speaker cabinet so as to radiate sound to the back of the main speaker (1), and (3) is a speaker cabinet, (4)
is an air chamber between the main speaker (1) and the auxiliary speaker (2), and (5) is the back air chamber of the auxiliary speaker (2).

The conventional composite direct radiation speaker system is constructed as described above, and the change in back pressure that occurs to operate the main speaker (1) is removed by the auxiliary speaker (2), thereby preventing an increase in the resonant frequency.

Therefore, the electric signal applied to the auxiliary speaker (2) is controlled using an electronic circuit, and the above paper proposes two methods for this as shown in FIGS. 4(a) and 4(b). The first method is as shown in Figure 4(a).
The mechanical impedance Z1 of the main speaker (1) and the mechanical impedance Z2 of the auxiliary speaker (2) when installed in the speaker cabinet (3) are measured in advance, and the signal to be added to the auxiliary speaker (2) is input. This is a method of generating signals by multiplying them by the ratio Z2/Z□ of these mechanical impedances.

In Fig. 4(a), (6) is the audio signal input terminal, and (7) is the mechanical impedance Z of the main speaker (1).
(8) is the electrical impedance 72'' which is proportional to the mechanical impedance z2 of the auxiliary speaker (2), (9) is the resistance R1 to stabilize the circuit (10) is the electrical impedance 72'' which is proportional to the mechanical impedance z2 of the auxiliary speaker (2). Ratio Z 2
/Zx, (11) is an amplifier for driving the main speaker (1), and (12) is an amplifier for driving the auxiliary speaker (2).

This method has advantages such as the simple circuit configuration, stable operation of the speaker system, and easy adjustment.However, on the other hand, it is difficult to accurately approximate Z-HZ2. However, there are disadvantages such as not being able to obtain sufficient control accuracy, the need to change the design each time the specifications of the speaker system change, and the size becoming larger especially when the inductance and capacitance are made with passive elements. .

On the other hand, in the second method, as shown in FIG. ) to generate a signal to be applied to the auxiliary speaker (2). Figure 4(b)
, (13) is a sensor for detecting the speed of the diaphragm of the main speaker (1), (14) is a sensor for detecting the speed of the diaphragm of the auxiliary speaker (2), (15) is a subtracter, (16) is a main amplifier, (17) is a control amplifier, El is the voltage applied to the main speaker (1), E2 is the voltage applied to the auxiliary speaker (2),
vl is the diaphragm speed of the main speaker (1), v2 is the diaphragm speed of the auxiliary speaker (2), and k is the sensitivity of the sensor.

The feature of this method is that the main speaker (1) and the auxiliary speaker (
Even if the specifications in 2) are changed, these changes are converted as changes in the diaphragm speed signal, so there is no need to change the speaker drive circuit itself, and the circuit can be designed to be smaller because it can be configured entirely with active elements. However, on the other hand, there are disadvantages such as the operation of the speaker system becomes unstable because the gain of the control amplifier (17) must be increased to obtain a sufficient effect, and noise is easily mixed in. There is.

[Problems to be Solved by the Invention] The conventional composite direct radiation speaker system is configured as described above, and the first method described above requires a design change each time the specifications change; The second method has practical problems such as the need for two impedance elements that require high precision, which increases the size, and the second method causes unstable speaker system operation. there were.

This invention has been made to solve the above-mentioned problems, and to provide a composite direct radiation speaker system that is not affected by changes in the specifications of the main speaker, has stable operation, and can be formed into a small size. With the goal.

[Means for Solving the Problems] The composite direct radiation speaker system according to the present invention includes a sensor that detects the diaphragm speed of the main speaker, and a detection signal of this sensor that is input to detect the diaphragm speed of the main speaker. , and an auxiliary speaker drive circuit that applies a signal to the auxiliary speaker that is proportional to the product of the equivalent mechanical impedance of the auxiliary speaker when it is installed in the cabinet.

[Function] In this invention, a signal proportional to the product of the diaphragm speed of the main speaker and the mechanical impedance of the auxiliary speaker when installed in the cabinet is applied to the auxiliary speaker, and the signal generated by the operation of the main speaker is applied to the auxiliary speaker. Changes in backpressure are eliminated by vibration of the auxiliary speaker.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a speaker driving circuit diagram showing an embodiment of the composite direct radiation speaker system of the present invention, and FIG. 2 is an equivalent circuit diagram thereof. In the figure, (1) is the main speaker, (2
) is the auxiliary speaker, (6) is the audio input voltage Ein
(8) is the electrical impedance Z2', (8) which is proportional to the mechanical impedance Z2 of the auxiliary speaker (2).
9) is a resistor R1 for stabilizing the circuit (10) is an operational amplifier, (11) is an amplifier with gain G1 for driving the main speaker (1), and (12) is for driving the auxiliary speaker (2). (13) is a sensor with a sensitivity to detect the diaphragm speed V of the main speaker (1), (18) is a compensation resistor Rs, and V2 is an auxiliary speaker (2).
diaphragm speed, E is the voltage applied to the main speaker (1),
F2 is the voltage applied to the auxiliary speaker (2), Zl is the equivalent mechanical impedance of the main speaker (1), and Z is the voltage applied to the auxiliary speaker (2).
The equivalent mechanical impedance of the air chamber (4) in a), Fl is the vibration force of the main speaker (1), and F2 is the auxiliary speaker (2).
, B□ is the magnetic flux density of the main speaker (1), B2 is the magnetic flux density of the auxiliary speaker (2), and Ql is the magnetic flux density of the main speaker (1).
), Q2 is the effective voice coil length of the auxiliary speaker (2), rl is the voice coil resistance of the main speaker (1), F2 is the voice coil resistance of the auxiliary speaker (2), and n is the effective voice coil length of the main speaker (1). ) for the auxiliary speaker (2
) is the diaphragm area ratio.

In Figure 1, the voltage E2 applied to the auxiliary speaker (2)
Focusing on , F2 is the diaphragm speed v of the main speaker (1)
1 and impedance 22', F2 = k vlZ2' G 2 / Rs """
It is expressed as ""' (1). On the other hand, the relationship between E and F2 is as follows from the equivalent circuit in Figure 2: (BJt/rt)Et=(Zt+Za)Vz nZ2
'/2"..." (2) (Bz Q 2/ r 2)
F2 ” n F3 Vl + (F2 + n 2
Z3 )F2 ''' (3).In equation (1), (3
) by substituting the equation for v1 and ■2, and in order to completely eliminate the change in back pressure caused by the main speaker (1) with the auxiliary speaker (2), v1=nv2...・・・・・・・・・・・・
By adding the condition (4), we obtain the following equation.

(B2QJr2)k(Z2'/Rs)a2=Z2/n-
......- (5) Here, k, B2. f12.
Since r,,G,,n are constants independent of frequency,
If the impedance 22' is selected to be proportional to the mechanical impedance Z2 of the auxiliary speaker (2), equation (5) can be completely satisfied by adjusting the compensation resistor Rs. In other words, the change in back pressure caused by the main speaker (1) can be completely eliminated by the auxiliary speaker (2). Further, since the signal to be applied to the auxiliary speaker (2) is selected so that Z2' and 72 are proportional, it can be seen from equation (1) that the signal is proportional to the product of V□ and 22.

As can be seen from FIG. 1, this embodiment is based on the first method shown in FIG. 4(a) in a conventional composite direct radiation speaker system. Therefore, the circuit configuration is simple, and the speaker system operates stably and is easy to adjust. In addition, in this embodiment, the drawbacks of the first method are as follows.
The problem that the circuit configuration needs to be changed in response to changes in speaker specifications has been resolved with respect to the main speaker (1). That is, in this embodiment, the main speaker (1
) by detecting the speed signal, it is possible to respond to changes in the specifications, so there is no need to change the circuit configuration. On the other hand, when changing the specifications of the auxiliary speaker (2), it is necessary to change the electrical impedance 22'. However, the purpose of the auxiliary speaker (2) is to eliminate the back pressure variations caused by the main speaker (1), and as long as this operation is performed perfectly, it will not contribute to the sound emission of the speaker system, so its specification is There is almost no need to change it. Therefore, there is no practical problem even if the specifications of the auxiliary speaker (2) are not changed.

Note that if a passive element is used as the impedance element (8) in this embodiment, it is possible that the impedance element (8) will be large in size. However, whereas the first method shown in FIG. 4(a) requires two impedance elements (7) and (8), only one impedance element is required, which is half of this, resulting in a smaller size. In addition, the inductance and capacitance used in the impedance element Z2' (8) can be equivalently configured using active elements, and the size can be reduced. It is well known that inductance is constructed from an active element circuit, for example, "Op Amp Practical Technology" by Shigeru Tanimoto (Seibundo Shinkosha)
It is shown on page 174 [Figure 6-53] [Figure 6-54], etc.

[Effects of the Invention] As described above, according to the present invention, the equivalent mechanical impedance of the auxiliary speaker is measured in advance, and a signal proportional to the product of the speed signal of the main speaker detected by the sensor and the mechanical impedance is generated. is added to the auxiliary speaker, the circuit configuration is simple, it can respond to changes in the main speaker specifications without changing the circuit configuration, it is easy to adjust, and it is a composite type that allows the speaker system to operate stably. This has the effect of providing a direct radiation speaker system.

[Brief explanation of the drawing]

Fig. 1 is a speaker drive circuit diagram showing an embodiment of the present invention, Fig. 2 is an equivalent circuit diagram thereof, Fig. 3 is a schematic configuration diagram showing a conventional composite direct radiation speaker system, and Fig. 4 (
a) and (b) are the speaker drive circuit diagrams thereof. In the figure, (1) is the main speaker, (2) is the auxiliary speaker, (3) is the speaker cabinet, (6) is the input terminal, (8) is the electrical impedance proportional to the equivalent mechanical impedance of the auxiliary speaker, (10) is an operational amplifier, (
11) is a main speaker drive amplifier, (12) is an auxiliary speaker drive amplifier, (13) is a main speaker diaphragm speed detection sensor, and (18) is a compensation resistor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (4)

[Claims] (1) A composite type direct speaker comprising a main speaker mounted on a speaker cabinet and directly radiating sound to the outside, and an auxiliary speaker mounted inside the speaker cabinet so as to radiate sound to the back of the main speaker. In a radiant speaker system, a sensor detects the diaphragm speed of the main speaker, and a detection signal from this sensor is input, and the diaphragm speed of the main speaker and the mechanical equivalent of the auxiliary speaker when installed in the cabinet are input. A composite direct radiation speaker system comprising: an auxiliary speaker drive circuit that applies a signal proportional to the product of impedance to the auxiliary speaker. (2) As the output signal of the auxiliary speaker drive circuit, when the diaphragm speed of the main speaker is v_1, the diaphragm speed of the auxiliary speaker is v_2, and the diaphragm area ratio of the auxiliary speaker to the main speaker is n, v_1=nv_2 Claim 1, characterized in that the circuit constants of the auxiliary speaker drive circuit are adjusted so as to satisfy the following relationship:
The composite direct radiation speaker system described in Section 1. (3) The auxiliary speaker drive circuit connects the output signal of the sensor to one input terminal of the operational amplifier via a compensation resistor, and creates an equivalent mechanical impedance of the auxiliary speaker between the input terminal and the output terminal of the operational amplifier. The composite type direct speaker according to claim 1 or 2, characterized in that an impedance having a proportional value is connected and the output signal of the operational amplifier is applied to the auxiliary speaker via the amplifier. Radiant speaker system. (4) A composite direct radiation speaker according to claim 3, characterized in that the composite direct radiation speaker is equivalently constructed using an active element as an inductance element with an impedance having a value proportional to the equivalent mechanical impedance of the auxiliary speaker. system.