JPH05183978A - Motional feedback speaker device - Google Patents

Abstract

PURPOSE:To provide a motional feedback speaker device in which characteristic for motional feedback(MFB) can be stabilized with few distortion and superior bass reproducing characteristic. CONSTITUTION:A speaker 12 is made up by dividing a cabinet 11 into upper and lower space by a baffle plate 11a, and mounting a speaker unit 5 on the lower space and a passive radiator 12 on the upper space. Furthermore, detectors 13a, 13b which detect the vibration of the speaker unit 5 and the passive radiator 12 are mounted on each diaphragm. A feedback signal is generated based on the phase and amplitude of signals detected by the detectors 13a, 13b, and it is supplied to a power amplifier 2. Superior sound pressure vs, frequency characteristic can be obtained by radiating the audio signal of an input signal source 1 from the speaker unit 5, and also, detecting the vibration of each diaphragm, and applying MFB feedback to the power amplifier 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motional feedback (hereinafter referred to as MFB) speaker device having a passive radiator for improving bass reproduction capability.

[0002]

2. Description of the Related Art In recent years, speaker devices have been required to be improved in characteristics such as high sound quality, high output, and expansion of low sound range with the digitization of audio output devices.
A B speaker device is used. Below is the conventional MFB
The speaker device will be described.

FIG. 4 is a block diagram showing an example of a conventional MFB speaker device. As shown in the figure, the audio signal from the audio input signal source 1 is amplified by the power amplifier 2 and given to the phase inversion type speaker 3. The phase inversion speaker 3 includes a phase inversion cabinet 4 and a speaker unit 5,
The speaker has a bass reflex port 6 opened at the bottom of its mounting surface, and is a speaker capable of reproducing low-pitched sound with a relatively small internal volume. The bass reflex port 6 emits a sound of which the phase is inverted and which is radiated from the back surface of the diaphragm of the speaker unit 5 to emphasize the low frequency range.

A detector 7 is attached to the dust cap of the diaphragm of the speaker unit 5. The detector 7 is a sensor that detects the vibration acceleration of the speaker unit 5 and converts it into a voltage, and the output thereof is given to the feedback circuit 8.
If the detector 7 detects, for example, the speed of the diaphragm of the speaker unit 5, the feedback circuit 8 generates a speed signal, an acceleration signal obtained by differentiating the speed signal, and a position signal (amplitude) obtained by integrating the speed signal. Then, it is a circuit that changes the gain and phase of these signals and outputs a feedback signal. Feedback circuit 8
Is output to the power amplifier 2 as a negative feedback signal.

In the MFB speaker device having such a configuration, the amplitude and phase of the audio signal input to the power amplifier 2 are controlled so that resonance or anti-resonance is suppressed at each specific portion of the reproduction frequency, and the low frequency portion is controlled. It compensates the playback characteristics of and also corrects the distortion in the high frequency range. FIG. 5 is a diagram showing frequency characteristics of the speaker unit 5 alone and resonance frequency characteristics of the bass reflex port 6. A curve A shows the frequency characteristic of the speaker unit 5 itself, and the vibration sharply drops around 50 Hz. A curve B shows the resonance frequency characteristic of the cabinet 4 having the bass reflex port 6 and has a resonance peak near 50 Hz.

[0006]

However, in such a conventional configuration, the air vibration in front of the speaker unit 5 can be detected by the detector 7 attached to the diaphragm of the speaker unit 5, but from the bass reflex port 6. The emitted air vibration could not be detected. Therefore, the phase-reversed speaker 3 including the speaker unit 5 and the bass reflex port 6 having the frequency characteristics shown in FIG.
When B is applied, the phase of the speaker unit 5 becomes unstable at the anti-resonance frequency (around 50 Hz). That is, when a feedback signal is generated by the feedback circuit 8 by the output of the detector 7, the feedback signal may have the same phase when it should have the opposite phase when the power amplifier 2 is input. Therefore, there has been a problem that the MFB control near this frequency becomes unstable. Further, there has been a problem that distorted sound such as wind noise from the bass reflex port 6 is generated.

The present invention has been made in view of the above conventional problems, and in a phase inversion type speaker,
Even when the anti-resonance frequency of the speaker unit 5 when the MFB is not applied matches the resonance frequency of the bass reflex port 6, the MFB can be applied stably, and the MFB speaker device having excellent low-frequency characteristics with little distortion is provided. Aim to achieve.

[0008]

According to a first aspect of the present invention, a baffle plate that divides the interior of a cabinet into a first space and a second space, and an opening portion of the baffle plate in the first space are attached. , A speaker unit that radiates air vibrations to the divided second space, a speaker that has a passive radiator in the front opening of the second space of the cabinet, and corrects the low frequency characteristics of the audio output of the input signal source A characteristic correction circuit, a power amplifier that amplifies the output of the characteristic correction circuit to drive the speaker unit, and a detector that is attached to the diaphragm of the passive radiator to detect the vibration.
A feedback circuit that generates a feedback signal based on the amplitude and phase of the output signal of the detector and supplies the feedback signal to the power amplifier.

According to a second aspect of the present invention, a baffle plate dividing the interior of the cabinet into first and second spaces, and a first baffle plate
A speaker unit that is attached to the opening of the baffle plate in the above space and radiates air vibrations to the divided second space; and a speaker that has a passive radiator at the front opening of the second space of the cabinet, A characteristic correction circuit that corrects the low-frequency characteristics of the audio output of the signal source, a power amplifier that power-amplifies the output of the characteristic correction circuit and drives the speaker unit, and is attached to the diaphragm of the speaker unit and the passive radiator. A first detector and a second detector that detect vibrations, and a first feedback that generates a feedback signal based on the amplitude and phase of the output signal of the first detector and provides the feedback signal to a power amplifier. A second feedback circuit for generating a feedback signal based on the amplitude and phase of the output signal of the second detector, and providing the feedback signal to the power amplifier. It is an feature.

[0010]

According to the present invention having such a feature, the sound signal from the input signal source is supplied to the power amplification circuit after the sound pressure in the low range is corrected by the characteristic correction circuit. When the power amplifier circuit drives the speaker unit, the detector detects the vibration of the speaker unit or the diaphragm of the passive radiator. Then, the feedback circuit generates a feedback signal based on the amplitude and phase of the output signal of the detector and supplies it to the power amplifier. The feedback signal output from the feedback circuit and the original audio signal are combined, and the power amplifier outputs the drive signal corrected in the low frequency range to the speaker unit. Next, the sound pressure radiated from the speaker unit is output to the outside through the passive radiator. As a result, the bass reproduction limit frequency of the speaker is expanded, and feedback is also applied to the harmonic components, so that the harmonic distortion is also reduced in the treble reproduction frequency band.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the MF according to the first embodiment of the present invention.
It is a block diagram which shows the structure of a B speaker apparatus. In this figure, the input signal source 1, the power amplifier 2, and the speaker unit 5 are the same as those in the conventional example. A characteristic correction circuit 9 is provided between the input signal source 1 and the power amplifier 2. Characteristic correction circuit 9
Is a circuit for correcting the frequency characteristic of an audio input signal, and particularly a circuit for emphasizing an audio signal in the low frequency band shown in FIG. 5, which is constituted by a low-pass filter or the like.

Unlike the conventional example, the speaker 10 has a cabinet 11 having an inner space partitioned by a baffle plate 11a into upper and lower first and second spaces. The central portion of the baffle plate 11a is opened, and the speaker unit 5 is mounted in the lower second space so that air vibration can be radiated from the opening to the upper first space. Again cabinet 1
A passive radiator 12 is attached to the front opening of the upper space of 1. The passive radiator 12 is a diaphragm having no drive coil, converts air vibration in the upper space into reciprocating motion of a flat plate, and radiates sound pressure to the outside by a vibrating flat plate having a large area. A detector 13 is attached to the diaphragm of the passive radiator 12. The detector 13 detects the vibration acceleration of the diaphragm, and its output is the feedback circuit 1
Given to 4.

The feedback circuit 14 is similar to the feedback circuit 8 of FIG.
Acceleration signal output from the detector 13, velocity signal obtained by integrating the acceleration signal, position signal obtained by further integrating the velocity signal (amplitude)
Are generated, the gain and phase of these signals are changed, and a feedback signal is output. The output of the feedback circuit 14 is given to the power amplifier 2 as a negative feedback signal.

FIG. 2 shows the difference in the frequency characteristics of the phase inversion type speaker 10 depending on the presence or absence of the feedback of the signal of the detector 13 attached to the passive radiator 12 in the MFB speaker device having such a configuration. Curve C is MFB speaker 1
The frequency characteristic is shown when the MFB of 0 is not applied.
A curve D shows a frequency characteristic when MFB is applied without using the characteristic correction circuit 9, and a curve E uses the characteristic correction circuit 9 and M.
The frequency characteristic when FB is applied is shown.

When the feedback of MFB is not applied, a peak occurs in the frequency band of 30 to 50 Hz as shown by the curve C, but when feedback is applied, it is 30 to 8 as shown by the curve D.
Flat sound pressure characteristics can be obtained in the ultra-low frequency band of 0 Hz. This is because the acceleration of the diaphragm of the speaker unit 5 and the passive radiator 12 is controlled to be constant by negatively feeding back the acceleration of the passive radiator 12 to the power amplifier 2 of FIG. That is, by increasing the effective vibration mass of the passive radiator 12, its reproduction limit is expanded as the low-frequency reproduction speaker. Further, by inputting the audio signal of the input signal source 1 to the characteristic correction circuit 9, as shown by the curve E,
It can be seen that the gain increases by 5 db or more in the low range of 100 Hz.

As described above, according to the present embodiment, by applying MFB, the low-pitched sound reproduction limit frequency of the speaker is widened, the sound pressure level is also increased, and feedback is also applied to the harmonic component, so that the high-frequency sound reproduction range is tuned. Wave distortion can also be reduced. Also, by using a passive radiator instead of the bass reflex port, not only distortion noise such as wind noise generated from the bass reflex port can be eliminated, but also sound waves can be emitted from a wider cross-sectional area than the bass reflex port, so it is possible to hear. You can obtain bass with a sense of quality.

Next, an MFB speaker device according to the second embodiment of the present invention will be described. FIG. 3 shows the M of the second embodiment of the present invention.
It is a block diagram which shows the structure of an FB speaker apparatus. In the figure, an input signal source 1, a power amplifier 2, a speaker 10,
The characteristic correction circuit 9 is the same as that of the first embodiment, and the description thereof is omitted. Unlike the first embodiment, the cabinet 11
The speaker unit 5 and the passive radiator 12 mounted on the first detector 13a for detecting the vibrations
And a second detector 13b are provided respectively. The detectors 13a and 13b are the same as the detector 13 of FIG. 1, and are sensors that detect the vibration acceleration of each diaphragm.

The outputs of the detectors 13a and 13b are given to the first feedback circuit 14a and the second feedback circuit 14b. Similar to the feedback circuit 14 shown in FIG. 1, the feedback circuits 14a and 14b respectively generate an acceleration signal of the diaphragm output by the detectors 13a and 13b, a velocity signal obtained by integrating the acceleration signal, and a position signal obtained by further integrating the velocity signal. Then, it is a circuit that changes the gain and phase of these signals and outputs a feedback signal. The outputs of the feedback circuits 14a and 14b are added to each other and given to the power amplifier 2.

As described above, in the sound pressure frequency characteristic of only the speaker unit 5 of the speaker 10 when the MFB is not applied, a sharp sound pressure drop of the speaker unit 5 occurs at the same portion as the resonance frequency of the passive radiator 12. Even in some cases, the acceleration signals of the speaker unit 5 and the passive radiator 12 are processed and fed back together. Then, the detector 13b detects a change in the phase of the passive radiator 12 and suppresses a sudden change in the phase of the speaker unit 5 and the passive radiator 12, and
The frequency characteristic can be flattened.

In the first and second embodiments, the detector 13
And 13b and 13a detect the acceleration of the passive radiator 12 and the speaker unit 5, respectively.
These detectors may detect the velocity of the diaphragm, the amplitude, or a combination of these signals. If the detector is a Zensa that detects the speed of the diaphragm, it is effective when the damping of the speaker unit 5 is to be equivalently increased. If the detector is a sensor that detects the amplitude, the suspension of the speaker unit 5 is used. This is effective when you want to make it equivalently stiff.

[0021]

As described above, according to the present invention, it is possible to widen the bass reproduction limit frequency of the speaker device and reduce the harmonic distortion in the treble reproduction region. Especially when the sound pressure frequency characteristics of the speaker unit when MFB is not applied sharply drops near the resonance frequency of the bass reflex port or the passive radiator, when the vibration of the passive radiator is detected and a feedback signal is given to the power amplifier, It is possible to suppress a sudden phase change of the diaphragm of the speaker unit and stabilize the MFB feedback characteristic. Further, by extracting the sound pressure from the passive radiator to the outside, it is possible to radiate the sound wave from a wide cross-sectional area, so that there is an effect that an excellent MFB speaker device with a sense of volume can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an MFB speaker device according to a first embodiment of the present invention.

FIG. 2 is a graph showing sound pressure frequency characteristics of the first embodiment of the present invention and the conventional MFB speaker device.

FIG. 3 is a block diagram showing a configuration of an MFB speaker device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a conventional MFB speaker device.

FIG. 5 is a speaker unit when MFB is not applied,
It is a graph which shows the sound pressure frequency characteristic of a bass reflex port or a passive radiator, respectively.

[Explanation of symbols]

 1 Input Signal Source 2 Power Amplifier 5 Speaker Unit 9 Characteristic Correction Circuit 10 Speaker 11 Cabinet 11a Baffle Plate 12 Passive Radiator 13, 13a, 13b Detector 14, 14a, 14b Feedback Circuit

Claims (2)

[Claims] 1. A baffle plate that divides the interior of the cabinet into a first space and a second space, and an air vibration to a second space that is attached to the opening of the baffle plate in the first space and is divided. A speaker unit that radiates, a speaker that has a passive radiator in the front opening of the second space of the cabinet, a characteristic correction circuit that corrects the low-frequency characteristic of the audio output of the input signal source, and the characteristic correction circuit A power amplifier that amplifies the output power to drive the speaker unit, a detector that is attached to the diaphragm of the passive radiator to detect the vibration, and a feedback signal based on the amplitude and phase of the output signal of the detector. And a feedback circuit that supplies the feedback signal to the power amplifier. 2. A baffle plate that divides the interior of the cabinet into first and second spaces, and air vibrations in a second space that is attached to the opening of the baffle plate in the first space and is divided. A speaker unit that radiates, a speaker that has a passive radiator in the front opening of the second space of the cabinet, a characteristic correction circuit that corrects the low-frequency characteristic of the audio output of the input signal source, and the characteristic correction circuit A power amplifier for amplifying the output power to drive the speaker unit; a first detector and a second detector attached to the speaker unit and the diaphragm of the passive radiator to detect the vibration; and A first feedback circuit that generates a feedback signal based on the amplitude and phase of the output signal of the first detector, and supplies the feedback signal to the power amplifier; and the second detector. Generating a feedback signal based on the output signal amplitude and phase, motional feedback speaker apparatus characterized by comprising a second feedback circuit for providing the feedback signal to the power amplifier, the.