JPH11150787A - Bass amplifying device for speaker system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily radiate bass through a speaker of a small diameter and a miniaturized casing. SOLUTION: A passive radiator 5 composed of a speaker having a voice coil 7 is arranged at a place for receiving the sound pressure of a main speaker 1 driven by a main amplifier 4, and a motional feedback circuit independent of the main amplifier 4 for driving the main speaker 1 is connected to this passive radiator 5. On the input side of the main amplifier 4 for driving the main speaker 1, a mixing amplifier 16 is connected for mixing a signal for a center speaker and a signal for sub woofer. Bass can be amplified by the motional feedback circuit without deteriorating the sound quality of the main speaker 1 and further, sounds in a center speaker area and a sub woofer area can be reproduced by the main speaker 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bass enhancement device for a speaker system used for an audio system or a personal computer.

[0002]

2. Description of the Related Art In an audio system, since it is better to reproduce an original sound more faithfully, various devices have been devised for reproducing a high fidelity without using a simple amplifier circuit. An NFB (negative feedback) circuit usually applied to an amplifier circuit is one of them. This NFB
Although the circuit was initially implemented only in the amplifier circuit, it is gradually implemented to include a speaker system. This is because the worst performing audio system is the speaker, so this speaker is driven without any means (of course, the speaker itself has been studied and improved). This is because there is a limit even if only the circuit is improved.

[0003] By the way, in order to faithfully reproduce sound quality, especially low-frequency sound, a large-diameter speaker is inevitably used. This is because the cone paper must be vibrated with a large amplitude in order to reproduce low-frequency sounds.
However, there are many cases where a large-diameter speaker cannot be used for actual applications. For example, it is a small audio system, and a speaker for an audio monitor of a personal computer corresponds to this. This is because low frequency reproduction is strongly demanded while both have small diameters.

[0004] Therefore, a speaker having a certain diameter is used.
As a measure for reproducing lower-frequency sounds, a bass enhancement device called a passive radiator has been devised and put to practical use. This means that another speaker (this speaker does not need to have a magnetic circuit with only cone paper for vibration) is placed where the sound pressure of the main speaker (active speaker) driven by the output of the amplifier is received. Then, the speaker resonates with the sound pressure generated by the main speaker to generate a sound (low-frequency sound). This resonance speaker is called a passive radiator.

[0005] This technology has also been studied and various patent applications have been filed. Of these, Japanese Patent Application Laid-Open No. 5-176389
JP-A-5-176390 and JP-A-5-176390 each disclose a box body (enclosure) that divides the interior into two parts.
A sensor for detecting vibration of a driver unit in a structure in which a driver unit (speaker) driven by an amplifier is mounted in a first cavity in the inside and a passive radiator is mounted in a second cavity independent of the first cavity. And feeds back to the amplifier in accordance with the output of the sensor.

Another prior art is disclosed in Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent No. 32399. In this method, a means for detecting the vibration is provided in a passive radiator, and an amplifier for driving a main speaker is fed back according to the output.

[0007]

All of these inventions can exhibit an excellent effect in reproducing low frequencies.
The present invention is based on a completely different idea from these techniques and does not apply feedback to the drive amplifier system of the main speaker as described in [0005] or [0006] above, and is different from the signal system of the main speaker. A technique for compensating for low-frequency band compensation has been developed by an independent passive radiator compensation method.

[0008] On the other hand, recently, even in homes, etc., there are more and more opportunities to watch software such as movies on a large screen. In such a case, a Dolby Digital / AV system or the like is adopted as an image / audio facility. Are increasing. In order to adopt this system, front speakers are placed on the left and right of the screen placed in the center of the front wall of the room, center speakers are placed at the bottom of the screen, and rear speakers are placed on the left and right of the back wall of the room. Become. The problem is how to place a sub woofer (super woofer) that is responsible for heavy bass that cannot be reproduced by these speakers, and is generally arranged along a wall.

Since the subwoofer also reproduces sound closely related to the image, it is better not to arrange the subwoofer along the side wall of the room, but to place it at the upper center or lower part of the screen if possible. Nor. However, as a general technical common sense, it is necessary to use a large-diameter speaker in order to reproduce a deep bass, and accordingly, a box (enclosure) becomes large. Then, it must be arranged along the side wall, and the listener in the center of the room cannot wipe out the unnatural impression due to the relationship with the image.

As described in the above [0007], the present invention has developed a technique capable of satisfying low-frequency compensation by a passive radiator-side compensation method independent of the signal system of the main speaker. Depending on the system,
It is also possible to provide a technique for reproducing a medium tone and a bass sound that are sufficient with a small-diameter main speaker without providing a separate subwoofer.

[0011]

According to the present invention, as a means for solving the above-mentioned problems, a passive radiator comprising a speaker having a magnetic circuit is provided at a position receiving a sound pressure of a main speaker driven by an amplifier. And, to the passive radiator, while connecting a motional feedback circuit independent of the drive circuit of the main speaker, the input side of the amplifier that drives the main speaker,
A mixing amplifier for mixing a signal for a center speaker and a signal for a subwoofer is connected.

The cone paper of the passive radiator vibrates with the operation of the main speaker. This vibration is captured by the magnetic circuit of the passive radiator and becomes an audio current. This audio current is signal-processed by a differential input buffer amplifier, an integrating MFB amplifier, a speed MFB amplifier, and a summing amplifier, and then power-amplified and applied again to the magnetic circuit of the passive radiator. As a result, the passive radiator continues to operate.

[0013] The passive radiator is servo-controlled by the above circuit, and the stiffness acting on the passive radiator is canceled. If the main speaker and the passive radiator are mounted on a sealed or bass-reflex box, the effects of the servo control and the effects unique to these boxes are synergistic, and the reproduction of lower frequencies is more excellent.

A speaker unit having a magnetic circuit is used as a passive radiator, and a motional feedback loop (MFB loop) closed only by the passive radiator is formed independently of the main unit.
B effectively cancels the stiffness acting on the passive radiator. As a result, the operating band of the passive radiator can be extended to a low frequency region, the low-frequency sound reproduction limit frequency of the speaker system can be greatly reduced, and ultra-low sound can be reproduced with a small system.

The main speaker also functions as a center speaker and a subwoofer by connecting a mixing amplifier for mixing a signal for a center speaker and a signal for a subwoofer to an input side of an amplifier for driving the main speaker. In other words, the passive radiator also functions for this sound, so that the overall sound range is extended and high sound quality can be obtained.
Therefore, especially when the installation area of the speaker is limited, such as in an audio system mainly composed of visuals, the medium and heavy bass can be sufficiently reproduced without separately installing a subwoofer that requires a large area. become.

[0016]

Embodiments of the present invention will be described below. In the circuit of FIG. 1, a portion surrounded by a broken line is a characteristic portion of the present invention, and other portions are portions of the base technology. The applicant has already filed a patent application for this prerequisite technology (Japanese Patent Application No. 9-165146). FIG.
1 is a main speaker, 2 is cone paper, 3
Is a voice coil serving as a magnetic circuit. Voice coil 3
Is connected to the output side of the main amplifier 4. Although not shown, the output side of the acoustic circuit is connected to the input side of the main amplifier 4. A passive radiator 5 is disposed in the vicinity of the main speaker 1 where the sound pressure is received when the main speaker 1 operates. The passive radiator 5 is composed of a speaker having cone paper 6 and a voice coil 7 serving as a magnetic circuit. When the main speaker 1 operates, a voice current is generated in the voice coil 7.

The output side of the power amplifier 8 and one end of a resistor 9 are connected to one end (positive side) of the voice coil 7 of the passive radiator 5. The other end of the resistor 9 is connected to the positive input terminal of a differential input buffer amplifier (balanced input buffer amplifier) 10 and one end of a resistor 11. Resistor 1
The other end of 1 is connected to the ground circuit together with the other end (negative side) of the voice coil 7 and the other end of the resistor 12 having one end connected to the negative input end of the differential input buffer amplifier 10. The differential input buffer amplifier 10 eliminates the difference between the input levels at both input terminals, and has an amplification level of 0 dB.

The output side of the differential input buffer amplifier 10 is connected to the input terminals of an integrating MFB amplifier 13 and a speed MFB amplifier 14. The integrating MFB amplifier 13 converts the input signal to a high frequency of -6 dB / oct through a built-in integrating circuit.
And a signal having a phase difference of 90 degrees is created. By returning this signal,
Since the stiffness acting on the diaphragm of the passive radiator 5 is equivalently negated, the lowest resonance frequency of the passive radiator 5 is lowered, and the bass reproduction limit frequency is lowered. The speed MFB amplifier 14 amplifies a signal proportional to the diaphragm speed of the passive radiator 5 and feeds back the signal. A state is obtained in which the electromagnetic braking resistance of the passive radiator 5 is equivalently reduced, and the stiffness due to the integral MFB is obtained. Passive radiator 5 equivalently smaller due to reduction of
The Q value of the vibration of the diaphragm is increased to compensate for the decrease in the bass reproduction level.

The output terminals of the amplifiers 13 and 14 are connected to the input terminal of a summing amplifier 15 having an amplification factor of 0 dB and a flat characteristic.
The signals are added by the summing amplifier 15, and an added signal is output. The output terminal is connected to the input side of the power amplifier 8 having an amplification of 26 dB.

The prerequisite technical portion of the circuit thus configured is a voice coil 7 of the passive radiator 5.
Since the sound current generated in the voice coil 7 is reduced, the electromagnetic braking force generated by the sound current flowing through the voice coil 7 itself is reduced and the vibration is increased. Proven by drawing a diagram. Therefore, the self-oscillation will cause the voice coil 7 to be damaged. Therefore, by applying the Nyquist stability discrimination method, the gain of the speed MFB and the gain of the integral MFB are determined in a strict and practical manner so as to be optimal values within a range in which the stability can be obtained in advance, and this is prevented. It is.

Main speaker 1 and passive radiator 5
Is used by being attached to a closed box or attached to a bass reflex box having a port at the bottom. In either case, the passive radiator 5 is driven by the sound pressure behind the main speaker. In the hermetically sealed box, the opposite phases of the front and rear surfaces of the cone paper 2 of the main speaker 1 and the cone paper 6 of the passive radiator 5 are blocked, so that there is an advantage that the sound pressure attenuation due to interference between them is eliminated. ], The advantages of the return mentioned in the section are added. On the other hand, in the bass reflex type, the vibration amplitude of the main speaker 1 and the cone paper 6 of the passive radiator 5 is limited in the vicinity of the anti-resonance frequency at which Helmholtz resonance between the air in the box and the air in the port occurs. Therefore, by setting this anti-resonance frequency lower than the resonance frequency of the passive radiator 5 to which the feedback is applied, the sound pressure in the ultra-low sound region where the vibration amplitude of the cone paper 6 becomes large without substantially affecting the sound pressure. Distortion can be reduced.

When a portion (prerequisite portion of the present invention) of the circuit shown in the drawing except for a portion surrounded by a broken line is activated, the passive radiator 5 does not simply resonate with the main speaker 1 to emit sound, but a power amplifier 8. Will output sound positively. For this reason, even if a small-diameter speaker is used for both the main speaker 1 and the passive radiator 5 and the speaker is mounted on a small-capacity box, it is possible to sufficiently cover the low frequency range.

The circuit shown in the drawing includes a portion surrounded by a broken line, which is an embodiment of the present invention, and is particularly suitable when a subwoofer is required for a speaker system. In this circuit, an output side of a mixing amplifier 16 is connected to an input side of a main amplifier 4 for driving a main speaker 1, and a signal for a center speaker input via a resistor 17 is connected to an input side of the mixing amplifier 16. The sub-woofer signal input via 18 is mixed and added. The ordinary input circuit of the main amplifier 4 is not shown in the figure as in FIG. 19 is a feedback resistor.

In this circuit, there is no difference in basic operation from that described above. However, since the signal applied to the main speaker 1 is the one in which the middle and low frequencies are enhanced, a very wide area, including the sound generated by the passive radiator, is particularly emphasized, especially from the middle to low frequencies. The obtained high sound quality can be obtained.

[0025]

As described above, according to the present invention, the motional feedback (MF) is applied only to the passive radiator.
Since the MFB loop is closed only by the passive radiator, since the MFB loop is closed only by the passive radiator, bass can be enhanced without deteriorating the sound quality of the main unit, and the drive of the main unit can be performed. Free choice of amplifier. And by making it a servo controlled passive radiator,
Since the stiffness acting on the passive radiator is canceled by the MFB, and the band occupied by the passive radiator can be widened in the low frequency direction, the sound pressure characteristic can be extended to an ultra-low sound range of 50 Hz or less.

Since the volume of the box required by the main unit is sufficient, the passive radiator can be operated in an ultra-low sound range with a small box, and a small-diameter main unit with a light vibration mass and a very small box can be used. Can play bass. There is no need to divide the cavity for bass reproduction. Since the medium and heavy bass can be reproduced with the small-diameter main speaker, a subwoofer is separately provided by arranging the main speaker above the visual monitor (large-screen television or screen, etc.). Without this, it is possible to obtain a sound field with a medium tone and a deep bass. Thereby, the matching between the image and the sound becomes very good.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main speaker 4 Main amplifier 5 Passive radiator 7 Voice coil 8 Power amplifier 10 Differential input buffer amplifier 13 Integrating MFB amplifier 14 Speed MFB amplifier 15 Summing amplifier 16 Mixing amplifier

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koji Osuga 1-112-17 Kamedarijaku, Mitaka City, Tokyo Inside Atsu Den Co., Ltd. (72) Inventor Akihiro Ozono 1-12-17, Kamedarijaku, Mitaka City, Tokyo Atsu Inside Den Co., Ltd. (72) Inventor Yuichi Shoda 1-112-17 Kamedarijaku, Mitaka City, Tokyo Inside Atsu Den Co., Ltd.

Claims (1)

[Claims] 1. A passive radiator comprising a speaker having a magnetic circuit is provided at a location where a sound pressure of a main speaker driven by an amplifier is received, and the passive radiator is provided with a motional independent of the main speaker driving circuit. -A bass enhancement device for a speaker system, wherein a feedback circuit is connected, and a mixing amplifier for mixing a signal for a center speaker and a signal for a subwoofer is connected to an input side of an amplifier for driving the main speaker. .