Speaker system

Abstract

When there is a deviation between the sound reproduced by the low-range speaker and the original sound, the deviation is corrected by the sound reproduced by the high-range speaker, and the branched input signal is added in parallel to each speaker. 【Solution means】The woofer 10 is driven by an input signal. The vibration detection unit 12 outputs a first reproduction signal corresponding to the vibration of the vibration system of the woofer 10. The subtractor 24 generates a first difference signal by subtracting the first reproduction signal from the input signal. The full-range speaker 20 is driven by the first difference signal. The vibration detection unit 22 outputs a second reproduction signal corresponding to the vibration of the vibration system of the full-range speaker 20. The subtractor 34 generates a second difference signal by subtracting the second reproduction signal from the input signal. The HPF 35 removes the frequency components of the sound reproduced by the woofer 10 from the second difference signal. The tweeter 30 is driven by the second difference signal that has passed through the HPF 35.

Description

Technical Field

[0001] The present invention relates to a speaker system that reproduces sound faithful to the original sound.

Background Art

[0002] A full-range speaker reproduces sound with a single speaker from low-frequency sound to high-frequency sound. A multi-way speaker reproduces sound with speakers suitable for each of a plurality of sound ranges. For example, in a three-way speaker, a woofer suitable for reproducing low-frequency sound, a squawker suitable for reproducing mid-frequency sound, and a tweeter suitable for reproducing high-frequency sound are used. Further, a super tweeter suitable for reproducing ultra-high-frequency sound may be used.

[0003] Also, MFB (Motional feedback) detects the vibration of the vibration system of a speaker, and feeds back a signal corresponding to the vibration to the drive circuit of the speaker to correct the drive signal. Thereby, it is possible to output faithful sound from the speaker to the original sound. The vibration system of the speaker includes a diaphragm (for example, cone paper), a voice coil bobbin, a damper, and a center cap.

[0004] As a vibration detection circuit for detecting the vibration of the vibration system of a speaker for MFB, a vibration detection circuit that detects a change in an electrical signal generated in a piezoelectric element due to the vibration of the vibration system, a vibration detection circuit that detects a change in the sound pressure level received from the diaphragm with a microphone, and a vibration detection circuit that detects vibration by causing light emitted from a light emitting element to enter a light reflecting member attached to the vibration system and receiving the reflected light with a light receiving element are known (see, for example, Patent Document 1).

[0005] Also, a vibration detection circuit is known in which an MFB detection coil is provided in parallel with a voice coil near the voice coil of a speaker, and the vibration of the speaker is detected by this MFB detection coil. An MFB speaker equipped with this vibration detection circuit is on the market (see, for example, Non-Patent Document 1).

[0006] Also, a metal plate is fixed to a surface close to the center cap (metal) of the speaker so as not to contact the center cap, and a vibration detection circuit (based on the principle of a condenser microphone) that detects the vibration of the speaker from the change in capacitance between the center cap and the metal plate is known. An MFB speaker equipped with this vibration detection circuit is also on the market (see, for example, Non-Patent Document 2).

[0007] Also, Patent Document 2 describes a vibration detection device including a light source that emits light, a first light receiving element that receives the light emitted by the light source, a second light receiving element that receives the light emitted by the light source, a light reception amount adjustment means that changes the light reception amount of the first light receiving element and the light reception amount of the second light receiving element according to the movement of a vibration part that generates sound in an acoustic reproduction part, a pair of the first light receiving element and the second light receiving element that operates as a differential pair, and a signal detection part that outputs a reproduction signal according to the difference between the light reception amount of the first light receiving element and the light reception amount of the second light receiving element.

[0008] Also, Patent Document 3 describes a speaker system including a woofer driven by an input signal generated to reproduce an original sound, a first vibration detection part that outputs a first reproduction signal according to the vibration of the vibration system of the woofer, a first subtractor that generates a first difference signal by subtracting the first reproduction signal from the input signal, a full-range speaker driven by the first difference signal, a second vibration detection part that outputs a second reproduction signal according to the vibration of the vibration system of the full-range speaker, a second subtractor that generates a second difference signal by subtracting the second reproduction signal from the first difference signal, and a tweeter driven by the second difference signal.

[0009] In the speaker system described in this Patent Document 3, when there is a deviation between the sound reproduced by the low-frequency range speaker and the original sound, the sound reproduced by the high-frequency range speaker corrects the deviation. For example, the deviation between the sound reproduced by the woofer and the original sound is corrected by the sound reproduced by the full-range speaker.

[0010] In a multi-way speaker, the same sound is output from two speakers in the crossover frequency range of each speaker. In a general multi-way speaker, a network circuit including a low-pass filter and a high-pass filter is used to attenuate the sound of each speaker in the crossover frequency range. On the other hand, Patent Document 4 describes a linear phase network circuit using a low-pass filter and a subtractor. In a two-way speaker using this linear phase network circuit, the input signal is branched into two, one is applied to the woofer speaker via a low-pass filter, and the other subtracts from the input signal the signal to be applied to the woofer speaker using a subtractor, and the output of this subtractor is applied to the tweeter speaker. Patent Document 4 also describes a configuration example of a three-way speaker using this linear phase network circuit. In this configuration example, the input signal is branched into three and applied in parallel to three speakers.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0012]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0013] In the 3-way speaker described in Patent Document 3, the input signal input from the input terminal reaches the tweeter through the first subtractor and the second subtractor. Also, in the case of a 4-way speaker, the input signal passes through three subtractors before reaching the speaker that reproduces the highest pitched sound. On the other hand, in the configuration example of the 3-way speaker described in Patent Document 4, the input signal is branched and applied in parallel to three speakers, and reaches each speaker through only one subtractor.

[0014] An object of the present invention is to provide a speaker system of 3-way or more that can correct the deviation in the sound reproduced by the high-range speaker when there is a deviation between the sound reproduced by the low-range speaker and the original sound, and can apply the branched input signal to each speaker in parallel.

Means for Solving the Problems

[0015] To achieve the above object, the speaker system of the present invention includes a first speaker driven by an input signal to reproduce a low-range sound, and a first vibration detection unit that outputs a first reproduction signal corresponding to the vibration of the vibration system of the first speaker, and a first subtractor that generates a first difference signal by subtracting the first reproduction signal from the input signal, and a full-range speaker driven by the first difference signal, and a second vibration detection unit that outputs a second reproduction signal corresponding to the vibration of the vibration system of the full-range speaker, and A second subtractor that generates a second difference signal by subtracting the second reproduction signal from the input signal; A first high-pass filter that removes the frequency components of the sound reproduced by the first speaker from the second difference signal; A second speaker that is driven by the second difference signal that has passed through the first high-pass filter and reproduces high-frequency sound; It is provided with.

[0016] Preferably, the speaker system of the present invention A first low-pass filter that removes high-frequency components from the input signal and supplies the input signal with the high-frequency components removed to the first speaker; A second low-pass filter having a cut-off frequency higher than the cut-off frequency of the first low-pass filter, which removes high-frequency components from the input signal and supplies the input signal with the high-frequency components removed to the first subtractor; It is provided with.

[0017] Preferably, the speaker system of the present invention A third low-pass filter having a cut-off frequency higher than the cut-off frequency of the second low-pass filter, which removes high-frequency components from the input signal and supplies the input signal with the high-frequency components removed to the second subtractor; A third vibration detection unit that outputs a third reproduction signal corresponding to the vibration of the vibration system of the second speaker; A third subtractor that generates a third difference signal by subtracting the third reproduction signal from the input signal; A second high-pass filter that removes the frequency components of the sound reproduced by the first speaker and the full-range speaker from the third difference signal; A third speaker that is driven by the third difference signal that has passed through the second high-pass filter and reproduces extremely high-frequency sound higher than the sound reproduced by the second speaker; It is provided with.

[0018] Further, the speaker system of the present invention includes a first speaker that is driven by an input signal and reproduces a low-frequency sound, a vibration detection unit that outputs a reproduction signal corresponding to the vibration of the vibration system of the first speaker, a second low-pass filter that removes high-frequency components from the input signal, a first subtractor that generates a first difference signal by subtracting the reproduction signal from the input signal from which high-frequency components have been removed by the second low-pass filter, a full-range speaker driven by the first difference signal, a second subtractor that generates a second difference signal by subtracting the input signal from which high-frequency components have been removed by the second low-pass filter from the input signal, a second speaker driven by the second difference signal and reproducing a high-frequency sound, and is provided with.

[0019] Preferably, the speaker system of the present invention is a third low-pass filter having a cut-off frequency higher than the cut-off frequency of the second low-pass filter, removes high-frequency components from the input signal, and supplies the input signal from which the high-frequency components have been removed to the second subtractor, a third subtractor that generates a third difference signal by subtracting the input signal from which high-frequency components have been removed by the third low-pass filter from the input signal, a third speaker driven by the third difference signal and reproducing an extremely high-frequency sound higher than the sound reproduced by the second speaker, and is provided with.

[0020] Preferably, the speaker system of the present invention A first low-pass filter having a cut-off frequency lower than that of the second low-pass filter, which removes high-frequency components from the input signal and supplies the input signal from which the high-frequency components have been removed to the first speaker, is provided.

Advantages of the Invention

[0021] According to the present invention, when there is a deviation between the sound reproduced by the low-frequency range speaker and the original sound, the sound reproduced by the high-frequency range speaker can correct the deviation, and the branched input signal can be added to each speaker in parallel.

Brief Description of the Drawings

[0022]

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Figure 16

MODE FOR CARRYING OUT THE INVENTION

[0023] Hereinafter, a speaker system according to an embodiment of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, common components are denoted by the same reference numerals, and repeated explanations are omitted.

[0024] FIG. 1 shows an example of the configuration of a speaker system 1 according to the first embodiment of the present invention. FIGS. 2 to 6 show examples of the frequency characteristics of signals of each part or sounds reproduced by each speaker when an input signal of a certain level is input at all frequencies. The speaker system 1 includes a woofer 10, an amplifier 11, a vibration detection unit 12, an LPF (low - pass filter) 13, a full - range speaker 20, an amplifier 21, a vibration detection unit 22, an LPF 23, a subtractor 24, a tweeter 30, an amplifier 31, a subtractor 34, and an HPF (high - pass filter) 35.

[0025] An input signal is input to the input terminal 100. The input signal is a signal of the original sound output from a sound source. The LPF 13 removes high-frequency components from the input signal. The LPF 13 is an example of the first low-pass filter in the present invention. FIG. 2 shows an example of the frequency characteristics of the input signal that has passed through the first low-pass filter (LPF 13). The input signal from which the high-frequency components have been removed is amplified by the amplifier 11 and supplied to the woofer 10. That is, the woofer 10 is driven by the input signal input to the input terminal 100 and reproduces sound in the low-frequency range. The sound reproduced by the woofer 10 also exhibits frequency characteristics similar to those in FIG. 2.

[0026] The vibration detection unit 12 detects the vibration of the vibration system of the woofer 10 and outputs a first reproduction signal corresponding to the vibration. The vibration system includes, for example, the diaphragm (e.g., cone paper) of the woofer 10, the voice coil bobbin, the damper, and the center cap. The same applies to the full-range speaker 20 and the tweeter 30. The same also applies to the super tweeter 40 described later. The vibration detection unit 12 has the same configuration as the vibration detection circuit used in the motional feedback.

[0027] The cut-off frequency of the LPF 23 is higher than the cut-off frequency of the LPF 13. The LPF 23 removes high-frequency components from the input signal. The LPF 23 is an example of the second low-pass filter in the present invention. FIG. 3 shows an example of the frequency characteristics of the input signal that has passed through the second low-pass filter (LPF 23). The input signal from which the high-frequency components have been removed is supplied to the subtractor 24. The subtractor 24 is, for example, a differential amplifier. The input signal that has passed through the LPF 23 is input to the non-inverting input terminal (+) of the subtractor 24, and the first reproduction signal is input to the inverting input terminal (-). The subtractor 24 outputs a first difference signal indicating the difference between the input signal from which the high-frequency components have been removed and the first reproduction signal. That is, the subtractor 24 generates the first difference signal by subtracting the first reproduction signal from the input signal. FIG. 4 shows an example of the frequency characteristics of the first difference signal. The first difference signal is defined by the following equation (1).

[0028] First differential signal = Input signal with high-frequency components removed - First reproduction signal (1)

[0029] The first differential signal is amplified by the amplifier 21 and supplied to the full-range speaker 20. The full-range speaker 20 is driven by the first differential signal. The full-range speaker 20 can reproduce sounds in the entire frequency range from bass to treble. However, the sound reproduced by the full-range speaker 20 exhibits frequency characteristics similar to those in FIG. 4. The vibration detection unit 22 detects the vibration of the vibration system of the full-range speaker 20 and outputs a second reproduction signal corresponding to the vibration. The vibration detection unit 22 has the same configuration as the vibration detection circuit used in the motional feedback. The subtractor 34 is, for example, a differential amplifier. The input signal input to the input terminal 100 is input to the non-inverting input terminal (+) of the subtractor 34, and the second reproduction signal is input to the inverting input terminal (-). The subtractor 34 outputs a second differential signal indicating the difference between the input signal and the second reproduction signal. That is, the subtractor 34 generates the second differential signal by subtracting the second reproduction signal from the input signal. FIG. 5 shows an example of the frequency characteristics of the second differential signal in the speaker system 1 of FIG. 1. The second differential signal is defined by the following equation (2).

[0030] Second differential signal = Input signal input to the input terminal 100 - Second reproduction signal (2)

[0031] The second differential signal is input to the HPF 35. The second differential signal also includes the frequency components of the sound reproduced by the woofer 10. Therefore, the HPF 35 removes the frequency components of the sound reproduced by the woofer 10 from the second differential signal. The HPF 35 is an example of the first high-pass filter in the present invention. FIG. 6 shows an example of the frequency characteristics of the second differential signal that has passed through the first high-pass filter (HPF 35) in the speaker system of FIG. 1. The HPF 35 allows only the frequency components of the sound reproduced by the tweeter 30 to pass through. Thereby, it is possible to prevent the tweeter 30 from reproducing the sound reproduced by the woofer 10. The second differential signal that has passed through the HPF 35 is amplified by the amplifier 31 and supplied to the tweeter 30. The tweeter 30 is driven by the second differential signal that has passed through the HPF 35 and reproduces the sound in the high frequency range. The sound reproduced by the tweeter 30 also exhibits the same frequency characteristics as in FIG. 6.

[0032] FIG. 7 shows an example of the relationship between the frequency and the sound pressure level in the speaker system 1 of FIG. 1. FIG. 7 is an example in the case where an input signal with a constant sound pressure level is input at all frequencies. The full-range speaker 20 outputs sound based on the first differential signal. The sound of the woofer 10 is corrected by the sound of the full-range speaker 20. When the sound pressure level of the woofer 10 is the same as the sound pressure level of the input signal, the full-range speaker 20 does not output sound. When the sound pressure level of the woofer 10 is insufficient, the full-range speaker 20 outputs sound with the same phase as the sound of the woofer 10 to increase the sound pressure level. When the sound pressure level of the woofer 10 is excessive, the full-range speaker 20 outputs sound with the opposite phase to the sound of the woofer 10 to decrease the sound pressure level. When the sound pressure level of the woofer 10 is 0, the full-range speaker 20 outputs sound with the same sound pressure level as the input signal.

[0033] As the frequency increases, the sound pressure level of the woofer 10 decreases. However, at this time, the full-range speaker 20 outputs a sound with the same phase as the sound of the woofer 10, and increases the sound pressure level of the entire speaker system 1 to the sound pressure level defined by the input signal. The sound pressure level of the sound obtained by overlapping the sound of the woofer 10 and the sound of the full-range speaker 20 becomes the same as the sound pressure level of the input signal. Therefore, in the speaker system 1, no unnatural change in the sound pressure level occurs between the sound range reproduced by the woofer 10 and the sound range reproduced by the full-range speaker 20.

[0034] The tweeter 30 is driven by the second differential signal that has passed through the HPF 35 and outputs a sound in the high sound range. The sound of the full-range speaker 20 is corrected by the sound of the tweeter 30. When the sound pressure level of the full-range speaker 20 is the same as the sound pressure level of the input signal, the tweeter 30 does not produce a sound. When the sound pressure level of the full-range speaker 20 is insufficient, the tweeter 30 outputs a sound with the same phase as the sound of the full-range speaker 20 to increase the sound pressure level. When the sound pressure level of the full-range speaker 20 is excessive, the tweeter 30 outputs a sound with a phase opposite to that of the sound of the full-range speaker 20 to decrease the sound pressure level. When the sound pressure level of the full-range speaker 20 is 0, the tweeter 30 produces a sound with the same sound pressure level as the sound pressure level of the input signal.

[0035] As the frequency increases, the sound pressure level of the full-range speaker 20 decreases. However, at this time, the tweeter 30 outputs a sound with the same phase as the sound of the full-range speaker 10, and increases the sound pressure level of the entire speaker system 1 to the sound pressure level defined by the input signal. The sound pressure level of the sound obtained by overlapping the sound of the full-range speaker 20 and the sound of the tweeter 30 becomes the same as the sound pressure level of the input signal. In the speaker system 1, no unnatural change in the sound pressure level occurs between the sound range reproduced by the full-range speaker 20 and the sound range reproduced by the tweeter 30.

[0036] As described above, in the speaker system 1, the sound of the woofer 10 is corrected by the sound of the full-range speaker 20. The vibration system of the full-range speaker 20 is generally lighter than that of the woofer 10. The movement of the vibration system of the full-range speaker 20 is faster than that of the vibration system of the woofer 10. Therefore, the speaker system 1 can quickly correct the sound of the woofer 10 by the full-range speaker 20 and reproduce natural sound.

[0037] Also, resonance of the speaker and resonance in the speaker box may seriously affect the sound quality. Especially in the low frequency range, when resonance or resonance occurs, the sound may become muddy and the clear sound quality may be impaired. This is because resonance or resonance emphasizes sound waves at specific frequencies and suppresses other frequency components. According to the speaker system 1, for example, when the level of sound at a specific frequency increases due to resonance or resonance in the woofer 10, the full-range speaker 20 emits sound so that the level of sound at that specific frequency decreases. Therefore, in the speaker system 1, the influence of resonance and resonance is suppressed.

[0038] Furthermore, the cone paper (paper material) used in many speakers has its reproduction characteristics change over time (even over the years) depending on the usage environment, especially humidity. The heavier the cone paper of the speaker for reproducing low bass. Therefore, it is more susceptible to the influence of humidity. Also, the mass of the edge and damper increases. Therefore, it is more susceptible to the influence of physical property changes (aging hardening, etc.) of the edge and damper. As a result, the sound output by the speaker may change. In the speaker system 1, the full-range speaker 20 corrects the change in sound due to the time-dependent change (hereinafter referred to as the time-dependent change of the vibration system) of the vibration system including the cone paper and damper of the woofer 10 in the sound range that it can output.

[0039] Similarly, in the speaker system 1, the tweeter 30 corrects the sound of the full-range speaker 20 in the sound range that it can output. For example, even if the sound changes due to the time-dependent change of the vibration system in the full-range speaker 20, the sound of the full-range speaker 20 is corrected by the sound of the tweeter 30.

[0040] Compared with a high-range speaker, a low-range speaker has a heavy vibration system, and the volume of air pushed out by the cone paper or the like is also large. Therefore, the delay from when the force applied to the vibration system changes until its movement changes is large. Also, as the humidity increases, even if it is slight, the air contains moisture and its movement is further delayed. The tendency that a speaker with a heavier vibration system does not move with a smaller force, that is, a smaller music signal, becomes greater. Therefore, it is reasonable to transfer the signal from a speaker with a heavier vibration system to a speaker with a lighter vibration system.

[0041] The cut-off frequencies of LPF13 and LPF23 can be set, for example, to the same cut-off frequencies as the low-pass filters included in the network circuits in a conventional three-way speaker, respectively. Therefore, the speaker system 1 can set the sound ranges of the sounds reproduced by the woofer 10, the full-range speaker 20, and the tweeter 30, for example, in the same way as the sound ranges of the sounds reproduced by a conventional three-way speaker. However, the cut-off frequencies of LPF13 and LPF23 may be different from the cut-off frequencies of the low-pass filters included in the network circuits in a conventional three-way speaker. Also, in the speaker system 1, it is not necessary to set a strict (steep) crossover frequency as in the past. For this reason, LPF13 and LPF23 may be simpler filters compared with the conventional ones, respectively.

[0042] FIG. 8 shows an example of the configuration of the speaker system 2 according to the second embodiment of the present invention. The speaker system 2 includes a woofer 10, an amplifier 11, a vibration detector 12, a full-range speaker 20, an amplifier 21, a vibration detector 22, a subtractor 24, a tweeter 30, an amplifier 31, a subtractor 34, and an HPF 35. The speaker system 2 according to the second embodiment is different from the speaker system 1 according to the first embodiment in that it does not have the LPFs 13 and 23. In the speaker system 2, an input signal input to the input terminal 100 is amplified by the amplifier 11 and supplied to the woofer 10. Also, the input signal input to the input terminal 100 is input to the non-inverting input terminal (+) of the subtractor 24. In other respects, the configuration of the speaker system 2 is the same as that of the speaker system 1.

[0043] FIG. 9 shows an example of the relationship between the frequency and the sound pressure level in the speaker system 2 of FIG. 8. FIG. 9 is an example in the case where an input signal with a constant sound pressure level is input at all frequencies. In the speaker system 2, the woofer 10 reproduces all the sounds that can be originally reproduced as a speaker for reproducing the bass range. As the frequency increases, the sound pressure level of the woofer 10 decreases. At this time, the full-range speaker 20 outputs a sound having the same phase as the sound of the woofer 10, and increases the sound pressure level of the entire speaker system 1 to the sound pressure level defined by the input signal. The full-range speaker 20 also outputs sound in the high frequency range. However, in the high frequency range, the sound pressure level of the full-range speaker 20 slightly decreases as the frequency increases. In this high frequency range, the tweeter 30 outputs a sound having the same phase as the sound of the full-range speaker 20, and increases the sound pressure level of the entire speaker system 1 to the sound pressure level defined by the input signal. The tweeter 30 is driven by a second difference signal that has passed through the HPF 35. Although the second difference signal also includes the frequency components of the sound reproduced by the woofer 10, the HPF 35 removes the frequency components of the sound reproduced by the woofer 10 from the second difference signal. Therefore, it is prevented that the tweeter 30 outputs the sound output by the woofer 10.

[0044] FIG. 10 shows an example of the configuration of the speaker system 3 according to the third embodiment of the present invention. The speaker system 3 includes a woofer 10, an amplifier 11, a vibration detector 12, an LPF 13, a full-range speaker 20, an amplifier 21, a vibration detector 22, an LPF 23, a subtractor 24, a tweeter 30, an amplifier 31, a vibration detector 32, an LPF 33, a subtractor 34, an HPF 35, a super tweeter 40, an amplifier 41, a subtractor 44, and an HPF 45. The speaker system 3 according to the third embodiment is different from the speaker system 1 according to the first embodiment in that it includes a vibration detector 32, an LPF 33, a super tweeter 40, an amplifier 41, a subtractor 44, and an HPF 45. In other respects, the configuration of the speaker system 3 is the same as that of the speaker system 1. The speaker system 3 is an expansion of the speaker system 1 to a four-way speaker system. Hereinafter, the differences between the speaker system 3 and the speaker system 1 will be described.

[0045] The cut-off frequency of the LPF 33 is higher than that of the LPF 23. The LPF 33 removes high-frequency components from the input signal input to the input terminal 100. The LPF 33 is an example of the third low-pass filter in the present invention. The input signal from which the high-frequency components have been removed is supplied to the subtractor 34. The subtractor 34 is, for example, a differential amplifier. The input signal that has passed through the LPF 33 is input to the non-inverting input terminal (+) of the subtractor 34, and the second reproduction signal is input to the inverting input terminal (-). In the speaker system 1 according to the first embodiment, the input signal input to the input terminal 100 was input to the non-inverting input terminal (+) of the subtractor 34. In contrast, in the speaker system 3 according to the present embodiment, the input signal that has passed through the LPF 33 is input. The subtractor 34 outputs a second difference signal indicating the difference between the input signal from which the high-frequency components have been removed and the second reproduction signal. That is, the subtractor 34 generates a second difference signal by subtracting the second reproduction signal from the input signal. The second difference signal is defined by the following equation (3).

[0046] Second differential signal = Input signal with high-frequency components removed - Second reproduction signal (3)

[0047] The second differential signal is input to the HPF 35. FIG. 11 shows an example of the frequency characteristics of the second differential signal that has passed through the first high-pass filter (HPF 35) in the speaker system 3 of FIG. 10. The HPF 35 allows only the frequency components of the sound reproduced by the tweeter 30 to pass through. The second differential signal that has passed through the HPF 35 is amplified by the amplifier 31 and supplied to the tweeter 30. The tweeter 30 is driven by the second differential signal that has passed through the HPF 35 and reproduces the sound in the high-frequency range. The sound reproduced by the tweeter 30 exhibits frequency characteristics similar to those in FIG. 11. The vibration detection unit 32 detects the vibration of the vibration system of the tweeter 30 and outputs a third reproduction signal corresponding to the vibration. The vibration detection unit 32 has the same configuration as the vibration detection circuit used in the motional feedback. The subtractor 44 is, for example, a differential amplifier. The input signal input to the input terminal 100 is input to the non-inverting input terminal (+) of the subtractor 44, and the third reproduction signal is input to the inverting input terminal (-). The subtractor 44 outputs a third differential signal indicating the difference between the input signal input to the input terminal 100 and the third reproduction signal. That is, the subtractor 44 generates a third differential signal by subtracting the third reproduction signal from the input signal. FIG. 12 shows an example of the frequency characteristics of the third differential signal. The third differential signal is defined by the following equation (4).

[0048] Third differential signal = Input signal input to input terminal 100 - Third reproduction signal (4)

[0049] The third differential signal is input to the HPF 45. The third differential signal also includes the frequency components of the sound reproduced by the woofer 10 and the full-range speaker 20. Therefore, the HPF 45 removes the frequency components of the sound reproduced by the woofer 10 and the full-range speaker 20 from the third differential signal. The HPF 45 is an example of the second high-pass filter in the present invention. FIG. 13 shows an example of the frequency characteristics of the third differential signal that has passed through the second high-pass filter (HPF 45). The HPF 45 allows only the frequency components of the sound reproduced by the super tweeter 40 to pass through. Thereby, it is possible to prevent the super tweeter 40 from outputting the sound output by the woofer 10 and the full-range speaker 20. The third differential signal that has passed through the HPF 45 is amplified by the amplifier 41 and supplied to the super tweeter 40. The super tweeter 40 is driven by the third differential signal that has passed through the HPF 45 and reproduces a sound in an extremely high frequency range higher than the sound reproduced by the tweeter 30. The sound reproduced by the super tweeter 40 also exhibits frequency characteristics similar to those in FIG. 13.

[0050] The sound of the tweeter 30 is corrected by the sound of the super tweeter 40. When the sound pressure level of the tweeter 30 is the same as the sound pressure level of the input signal, the super tweeter 40 does not produce sound. When the sound pressure level of the tweeter 30 is insufficient, the super tweeter 40 outputs a sound with the same phase as the sound of the tweeter 30 to increase the sound pressure level. When the sound pressure level of the tweeter 30 is excessive, the super tweeter 40 outputs a sound with a phase opposite to that of the sound of the tweeter 30 to decrease the sound pressure level. When the sound pressure level of the tweeter 30 is 0, the super tweeter 40 produces a sound with the same sound pressure level as the sound pressure level of the input signal.

[0051] As the frequency increases, the sound pressure level of the tweeter 30 decreases. However, at this time, the super tweeter 40 outputs a sound with the same phase as the sound of the tweeter 30, increasing the sound pressure level of the entire speaker system 1 up to the sound pressure level defined by the input signal. The sound pressure level of the sound obtained by overlapping the sound of the tweeter 30 and the sound of the super tweeter 40 becomes the same as the sound pressure level of the input signal. In the speaker system 3, no unnatural change in the sound pressure level occurs between the sound range reproduced by the tweeter 30 and the sound range reproduced by the super tweeter 40.

[0052] In the speaker system 3, the super tweeter 40 corrects the sound of the tweeter 30 in its outputtable sound range. For example, even if the sound changes due to the sequential change of the vibration system in the tweeter 30, the sound of the tweeter 30 is corrected by the sound of the super tweeter 40.

[0053] The cut-off frequencies of the LPF13, LPF23, and LPF33 can be set, for example, to the same cut-off frequencies as the low-pass filters included in the network circuits in a conventional 4-way speaker, respectively. Therefore, the speaker system 3 can set the sound ranges of the sounds reproduced by the woofer 10, the full-range speaker 20, the tweeter 30, and the super tweeter 40 to be the same as those of the sounds reproduced by a conventional 4-way speaker, for example. However, the cut-off frequencies of the LPF13, LPF23, and LPF33 may be different from the cut-off frequencies of the low-pass filters included in the network circuits in a conventional 4-way speaker. Also, in the speaker system 3, a precise (sharp) crossover frequency setting as in the past is not required. For this reason, the LPF13, LPF23, and LPF33 may be simpler filters compared to the conventional ones, respectively.

[0054] FIG. 14 shows an example of the configuration of a speaker system 4 according to a fourth embodiment of the present invention. The speaker system 4 includes a woofer 10, an amplifier 11, a vibration detector 12, an LPF 13, a full-range speaker 20, an amplifier 21, an LPF 23, a subtracter 24, a tweeter 30, an amplifier 31, and a subtracter 34. The speaker system 4 according to the fourth embodiment is different from the speaker system 1 according to the first embodiment in that it does not include a vibration detector 22 and an HPF 35. Further, the speaker system 4 is different from the speaker system 1 in that the LPF 23 and the subtracter 34 constitute a linear phase network circuit. In other respects, the configuration of the speaker system 4 is the same as that of the speaker system 1. Note that the reproduction signal in FIG. 14 is the same as the first reproduction signal in FIG. 1. Hereinafter, the differences between the speaker system 4 and the speaker system 1 will be described.

[0055] In the speaker system 4, instead of supplying the second reproduction signal output from the vibration detector 22 to the inverting input terminal (−) of the subtracter 34 as in the speaker system 1, the input signal that has passed through the LPF 23 is supplied to the inverting input terminal (−) of the subtracter 34. As shown in FIG. 15, the LPF 23 removes high-frequency components from the input signal input to the input terminal 100. The subtracter 34 is, for example, a differential amplifier. The input signal input to the input terminal 100 is input to the non-inverting input terminal (+) of the subtracter 34, and the input signal from which the high-frequency components have been removed by the LPF 23 is input to the inverting input terminal (−). The subtracter 34 generates a second difference signal by subtracting the input signal from which the high-frequency components have been removed by the LPF 23 from the input signal input to the input terminal 100. That is, the subtracter 34 generates a second difference signal by subtracting the input signal from which the high-frequency components have been removed by the LPF 23 from the input signal input to the input terminal 100. The second difference signal is obtained by removing the frequency components of the signal for driving the woofer 10 and the first difference signal for driving the full-range speaker 20 from the input signal input to the input terminal 100. The tweeter 30 is driven by the second difference signal and reproduces high-pitched sounds. The second difference signal is defined by the following equation (5).

[0056] Second differential signal = Input signal input to input terminal 100 - Input signal from which high-frequency components have been removed by LPF23 (5)

[0057] Note that the cut-off frequency of LPF13 is lower than that of LPF23. LPF13 removes high-frequency components from the input signal input to input terminal 100 and supplies the input signal from which high-frequency components have been removed to woofer 10. However, LPF13 may be omitted. That is, woofer 10 may be directly driven by the input signal input to input terminal 100. LPF13 and LPF23 are examples of the first low-pass filter and the second low-pass filter in the present invention, respectively.

[0058] FIG. 16 shows an example of the configuration of a speaker system 5 according to a fifth embodiment of the present invention. The speaker system 5 includes a woofer 10, an amplifier 11, a vibration detection unit 12, an LPF13, a full-range speaker 20, an amplifier 21, an LPF23, a subtractor 24, a tweeter 30, an amplifier 31, an LPF33, a subtractor 34, a super tweeter 40, an amplifier 41, and a subtractor 44. The speaker system 5 according to the fifth embodiment is different from the speaker system 4 according to the fourth embodiment in that it includes an LPF33, a super tweeter 40, an amplifier 41, and a subtractor 44. In other respects, the speaker system 5 is the same as the speaker system 4. The speaker system 5 is an extension of the speaker system 4 to a four-way speaker system. Hereinafter, the differences between the speaker system 5 and the speaker system 4 will be described.

[0059] The cut-off frequency of LPF33 is higher than that of LPF23. LPF33 removes high-frequency components from the input signal input to input terminal 100. LPF33 is an example of the third low-pass filter in the present invention. In speaker system 5, instead of supplying the input signal input to input terminal 100 to the non-inverting input terminal (+) of subtractor 34, the input signal that has passed through LPF33 is supplied to the non-inverting input terminal (+) of subtractor 34. The second differential signal is defined by the following equation (6).

[0060] Second differential signal = Input signal from which high-frequency components have been removed by LPF33 - Input signal from which high-frequency components have been removed by LPF23 (6)

[0061] The input signal from which high-frequency components have been removed by LPF33 is supplied to subtractor 44. LPF33 and subtractor 44 constitute a linear phase network circuit. Subtractor 44 is, for example, a differential amplifier. The input signal input to input terminal 100 is input to the non-inverting input terminal (+) of subtractor 44, and the input signal from which high-frequency components have been removed by LPF33 is input to the inverting input terminal (-). Subtractor 44 outputs a third differential signal indicating the difference between the input signal input to input terminal 100 and the input signal from which high-frequency components have been removed by LPF33. That is, subtractor 44 generates a third differential signal by subtracting the input signal from which high-frequency components have been removed by LPF33 from the input signal input to input terminal 100. The third differential signal is obtained by removing the frequency components of the signal for driving woofer 10, the first differential signal for driving full-range speaker 20, and the second differential signal for driving tweeter 30 from the input signal input to input terminal 100. Super tweeter 30 is driven by the third differential signal and reproduces sounds in an extremely high frequency range higher than the sounds reproduced by tweeter 30. The third differential signal is defined by the following equation (7).

[0062] Third differential signal = Input signal input to input terminal 100 - Input signal from which high-frequency components have been removed by LPF33 (7)

[0063] Note that each process of the speaker system according to each of the above-described embodiments can be realized by analog processing or can be implemented by digital processing.

[0064] As described above, according to the present invention, when there is a deviation between the sound reproduced by the low-frequency range speaker and the original sound, the sound reproduced by the high-frequency range speaker can correct the deviation, and the branched input signal can be added to each speaker in parallel. Further, according to the present invention, it is possible to prevent an unnatural change in sound pressure level from occurring between the sound ranges reproduced by each speaker.

[0065] As described above, the embodiments of the present invention have been described. However, various modifications and combinations required due to design or manufacturing convenience or other factors are included in the scope of the invention described in the claims and the invention corresponding to the specific examples described in the embodiments of the invention.

Description of Reference Numerals

[0066] 1, 2, 3, 4, 5... speaker system, 10... woofer, 11... amplifier, 12... vibration detection unit, 13... LPF (low-pass filter), 20... full-range speaker, 21... amplifier, 22... vibration detection unit, 23... LPF, 24... subtractor, 30... tweeter, 31... amplifier, 32... vibration detection unit, 33... LPF, 34... subtractor, 35... HPF (high-pass filter), 40... super tweeter, 41... amplifier, 44... subtractor, 45... HPF, 100... input terminal

Claims

1. A first speaker driven by an input signal to reproduce low-frequency sound, a first vibration detector that outputs a first reproduction signal corresponding to the vibration of the vibration system of the first speaker, a first subtractor that generates a first difference signal by subtracting the first reproduction signal from the input signal, a full-range speaker driven by the first difference signal, a second vibration detector that outputs a second reproduction signal corresponding to the vibration of the vibration system of the full-range speaker, a second subtractor that generates a second difference signal by subtracting the second reproduction signal from the input signal, a first high-pass filter that removes the frequency components of the sound reproduced by the first speaker from the second difference signal, a second speaker driven by the second difference signal that has passed through the first high-pass filter to reproduce high-frequency sound, A speaker system comprising the above.

2. A first low-pass filter that removes high-frequency components from the input signal and supplies the input signal with the high-frequency components removed to the first speaker, A second low-pass filter having a cut-off frequency higher than the cut-off frequency of the first low-pass filter, which removes high-frequency components from the input signal and supplies the input signal with the high-frequency components removed to the first subtractor, The speaker system according to claim 1, comprising the above.

3. A third low-pass filter having a cut-off frequency higher than the cut-off frequency of the second low-pass filter, which removes high-frequency components from the input signal and supplies the input signal with the high-frequency components removed to the second subtractor, a third vibration detector that outputs a third reproduction signal corresponding to the vibration of the vibration system of the second speaker, a third subtractor that generates a third difference signal by subtracting the third reproduction signal from the input signal, a second high-pass filter that removes the frequency components of the sound reproduced by the first speaker and the full-range speaker from the third difference signal, a third speaker driven by the third difference signal that has passed through the second high-pass filter to reproduce ultra-high-frequency sound higher than the sound reproduced by the second speaker, The speaker system according to claim 2, comprising the above.

4. a first speaker driven by an input signal to reproduce low-frequency sound; a vibration detection unit that outputs a reproduction signal corresponding to the vibration of the vibration system of the first speaker; a second low-pass filter that removes high-frequency components from the input signal; a first subtractor that generates a first difference signal by subtracting the reproduction signal from the input signal from which high-frequency components have been removed by the second low-pass filter; a full-range speaker driven by the first difference signal; a second subtractor that generates a second difference signal by subtracting the input signal from which high-frequency components have been removed by the second low-pass filter from the input signal; a second speaker driven by the second difference signal to reproduce high-frequency sound; A speaker system comprising:

5. A third low-pass filter having a cut-off frequency higher than the cut-off frequency of the second low-pass filter, which removes high-frequency components from the input signal and supplies the input signal from which the high-frequency components have been removed to the second subtractor; a third subtractor that generates a third difference signal by subtracting the input signal from which high-frequency components have been removed by the third low-pass filter from the input signal; a third speaker driven by the third difference signal to reproduce extremely high-frequency sound higher than the sound reproduced by the second speaker; The speaker system according to claim 4, further comprising:

6. The speaker system according to claim 4 or 5, further comprising a first low-pass filter having a cut-off frequency lower than the cut-off frequency of the second low-pass filter, which removes high-frequency components from the input signal and supplies the input signal from which the high-frequency components have been removed to the first speaker.

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