Speaker system

Abstract

To reproduce natural sound that is faithful to the original sound. [Solution] An original sound signal output from a sound source is input to an input terminal 100. A woofer 10 is driven by the original sound signal to reproduce low-frequency sounds. A vibration detection unit 12 outputs a first reproduction signal corresponding to the vibration of a vibration system of the woofer 10. A subtractor 14 generates a first differential signal by subtracting the first reproduction signal from the original sound signal. A full-range speaker 20 is driven by the first differential signal. A vibration detection unit 22 outputs a second reproduction signal corresponding to the vibration of the vibration system of the full-range speaker 20. A subtractor 24 generates a second differential signal by subtracting the second reproduction signal from the first differential signal. A tweeter 30 is driven by the second differential signal to output high-frequency sounds.

Description

[Technical field]

[0001] The present invention relates to a speaker system that reproduces sounds that are faithful to the original sounds. [Background technology]

[0002] A full-range speaker reproduces sounds from low to high ranges using a single speaker. A multi-way speaker reproduces sounds using speakers suitable for each of several ranges. For example, a three-way speaker uses a woofer suited to reproducing low range sounds, a squawker suited to reproducing mid-range sounds, and a tweeter suited to reproducing high range sounds. In addition, a subwoofer (also called a super woofer) suited to reproducing extremely low range sounds and a super tweeter suited to reproducing extremely high range sounds may also be used.

[0003] In addition, MFB (Motional Feedback) detects the vibration of the vibration system of the speaker and feeds back a signal corresponding to the vibration to the driving circuit of the speaker to correct the driving signal. This allows the speaker to output sound that is faithful to the original sound. The vibration system of the speaker includes a diaphragm (e.g., a cone paper), a voice coil bobbin, a damper, a center cap, etc.

[0004] Known vibration detection circuits that detect vibrations of a speaker's vibration system for MFB include a vibration detection circuit that detects changes in an electrical signal generated in a piezoelectric element due to vibrations of the vibration system, a vibration detection circuit that detects changes in the sound pressure level received from the diaphragm using a microphone, and a vibration detection circuit that detects vibrations by irradiating light emitted from a light-emitting element onto a light-reflecting member attached to the vibration system and receiving the reflected light with a light-receiving element (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 the voice coil of a speaker near the voice coil, and the MFB detection coil detects vibrations of the speaker. MFB speakers equipped with this vibration detection circuit are on the market (for example, see Non-Patent Document 1).

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

[0007] Patent Document 2 also describes a 3D speaker device that includes a pair of left and right high-frequency speakers, first and second amplifiers that drive the speakers, first and second detectors that detect the vibration acceleration of the speakers, a comparator that compares the outputs of the first and second detectors with an input original signal to the high-frequency speaker, a high-cut filter that cuts high-frequency components of the output signal of the comparator, a third amplifier that amplifies the output signal of the high-cut filter, and a low-frequency speaker driven by the third amplifier. This 3D speaker device has motional feedback that inputs the vibration acceleration detection signal of the high-frequency speaker and the input original signal to the high-frequency speaker to the comparator and controls the drive of the low-frequency speaker by the output of the comparator. Patent Document 2 also describes a woofer and a super woofer as examples of the high-frequency speaker and the low-frequency speaker, respectively.

[0008] Patent document 3 also describes a speaker system that includes a main speaker that is driven by an original sound signal output from a sound source, a vibration detection unit that detects vibrations of the vibration system of the main speaker and outputs a playback signal corresponding to the vibration, a subtractor that outputs an error signal indicating the difference between the original sound signal and the playback signal, and a sub-speaker that, based on the error signal, outputs a sound in the same phase as the sound of the main speaker to increase the sound pressure level if the sound pressure level of the main speaker is insufficient, and outputs a sound in the opposite phase to the sound of the main speaker to reduce the sound pressure level if the sound pressure level of the main speaker is excessive. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 6-284492 [Patent Document 2] Japanese Utility Model Application Publication No. 57-51390 [Patent Document 3] Patent No. 6898538 [Non-patent literature]

[0010] [Non-Patent Document 1] "CW250D Active Subwoofer", [online], Foster Electric Co., Ltd. website, [searched on November 26, 2024], Internet<URL: https: / / www.fostex.jp / products / cw250d / > [Non-Patent Document 2] "Orphian", [online], Takumi Co., Ltd. website, [searched on November 26, 2024], Internet site)<URL: https: / / www.cocojc.com / orphean / structure.html#mfb> Summary of the Invention [Problem to be solved by the invention]

[0011] In a multi-way speaker, the same sound is output from the two speakers in the crossover range of each speaker. In the crossover range, the sound from each speaker is attenuated by low-pass and high-pass filters included in the network circuit, for example, but this can easily result in unnatural changes in sound pressure levels. To prevent this, strict filter design is required.

[0012] An object of the present invention is to provide a three-way or more speaker system capable of comprehensively reproducing natural sounds that are faithful to the original sounds. [Means for solving the problem]

[0013] In order to achieve the above object, the speaker system of the present invention comprises: A bass speaker that reproduces low-frequency sounds; a first vibration detection unit that outputs a first reproduction signal corresponding to a vibration of a vibration system of the woofer; a first subtractor configured to subtract the first playback signal from a signal that drives the woofer to generate a first difference signal; a full-range speaker driven by the first differential signal; a second vibration detection unit 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 differential signal by subtracting the second reproduced signal from the first differential signal; a treble speaker that is driven by the second differential signal and outputs a treble sound; Equipped with.

[0014] Preferably, the speaker system of the present invention comprises: The high-pass filter removes, from the second differential signal, frequency components that may cause damage to the vibration system of the treble speaker.

[0015] Preferably, the speaker system of the present invention comprises: The amplifier further includes a first low-pass filter having a cut-off frequency higher than the cut-off frequency of the high-pass filter, the first low-pass filter supplying the first differential signal from which high-frequency components have been removed to the full-range speaker.

[0016] Preferably, the speaker system of the present invention comprises: The signal that drives the woofer is the original sound signal output from the sound source.

[0017] Preferably, the speaker system of the present invention comprises: The device further includes a second low-pass filter having a cutoff frequency lower than the cutoff frequency of the first low-pass filter, the second low-pass filter supplying the original sound signal from which high-frequency components have been removed to the woofer.

[0018] Preferably, the speaker system of the present invention comprises: a subwoofer that is driven by an original sound signal output from a sound source and reproduces a subwoofer having a lower frequency than the bass sound reproduced by the subwoofer; a third vibration detection unit that outputs a third reproduction signal corresponding to a vibration of a vibration system of the ultra-low frequency speaker; a third subtractor that generates a third difference signal by subtracting the third reproduction signal from the original sound signal; Equipped with The signal that drives the woofer is the third differential signal.

[0019] Preferably, the speaker system of the present invention comprises: a fourth vibration detection unit that outputs a fourth reproduction signal corresponding to the vibration of the vibration system of the high-frequency speaker; a fourth subtractor that generates a fourth differential signal by subtracting the fourth reproduced signal from the second differential signal; an ultra-high frequency speaker that is driven by the fourth differential signal and outputs an ultra-high frequency sound having a higher frequency than the high frequency sound reproduced by the treble speaker; Equipped with. Effect of the Invention

[0020] According to the present invention, it is possible to comprehensively reproduce natural sounds that are faithful to the original sounds. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a speaker system according to an invention disclosed in Patent Document 3. [Diagram 2] 2 is a diagram showing an example of the relationship between frequency and sound pressure in the speaker system of FIG. 1. [Diagram 3] 1 is a diagram showing an example of a configuration of a speaker system according to a first embodiment of the present invention. [Figure 4] 4 is a diagram showing an example of the relationship between frequency and sound pressure in the speaker system of FIG. 3. [Diagram 5] FIG. 11 is a diagram showing an example of a configuration of a speaker system according to a second embodiment of the present invention. [Figure 6] 6 is a diagram showing an example of the relationship between frequency and sound pressure in the speaker system of FIG. 5. [Figure 7] FIG. 11 is a diagram showing an example of the configuration of a speaker system according to a third embodiment of the present invention. [Figure 8] 8 is a diagram showing an example of the relationship between the frequency and sound pressure of a sound reproduced by a woofer in the speaker system of FIG. 7. [Figure 9] 8 is a diagram showing an example of the relationship between the frequency and sound pressure of sounds reproduced by one full-range speaker and a tweeter in the speaker system of FIG. 7. [Figure 10] 8 is a diagram showing an example of the relationship between the frequency and sound pressure of sounds reproduced by the other full-range speaker and tweeter in the speaker system of FIG. 7. FIG. [Figure 11] FIG. 11 is a diagram showing an example of the configuration of a speaker system according to a fourth embodiment of the present invention. [Figure 12]FIG. 13 is a diagram showing an example of the configuration of a speaker system according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 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 explaining the embodiment, the same components are given the same reference numerals, and the repeated description will be omitted.

[0023] In the 3D speaker device described in Patent Document 2, a detector that detects vibration acceleration is provided in the high-frequency speaker. This 3D speaker device inputs the vibration acceleration detection signal of the high-frequency speaker and the input original signal to the high-frequency speaker to a comparator, and controls the driving of the low-frequency speaker based on the output of the comparator. In other words, this 3D speaker device corrects the sound of the high-frequency speaker using the sound of the low-frequency speaker.

[0024] However, the vibration system of the low-frequency speaker is usually heavier than that of the high-frequency speaker. Due to the action of inertia, the vibration system of the low-frequency speaker moves slower than the vibration system of the high-frequency speaker. For this reason, when the sound of the high-frequency speaker is corrected by the sound of the low-frequency speaker, the correction is delayed in time compared to correcting the sound of the low-frequency speaker by the sound of the high-frequency speaker, and the sound is likely to become unnatural.

[0025] 1 shows an example of the configuration of a speaker system 1 according to the invention disclosed in Patent Document 3. The speaker system 1 includes a woofer 10, an amplifier 11, a vibration detector 12, a subtractor 14, a full-range speaker 20, an amplifier 21, an LPF (low pass filter) 23, a tweeter 30, an amplifier 31, and an HPF (high pass filter) 35.

[0026] An original sound signal output from a sound source is input to the input terminal 100. The original sound signal is amplified by the amplifier 11 and drives the woofer 10. The vibration detection unit 12 detects the vibration of the vibration system of the woofer 10 and outputs a playback signal corresponding to the vibration. The vibration system includes, for example, the diaphragm (for example, cone paper) of the woofer 10, a voice coil bobbin, a damper, and a center cap. The same applies to the full-range speaker 20 and the tweeter 30. The same applies to the subwoofer 60 and the super tweeter 70 described later. The vibration detection unit 12 has a configuration similar to that of a vibration detection circuit used in motional feedback. The subtractor 14 is, for example, a differential amplifier. The original sound signal is input to the non-inverting input terminal (+) of the subtractor 14, and the playback signal is input to the inverting input terminal (-). The subtractor 14 outputs a difference signal indicating the difference between the original sound signal and the playback signal. The difference signal is defined as the following equation (1).

[0027] Difference signal = original signal - reproduced signal (1)

[0028] The LPF 23 passes the differential signal whose frequency is lower than a predetermined upper limit frequency. The differential signal that has passed through the LPF 23 is amplified by the amplifier 21 and drives the full-range speaker 20. The HPF 35 passes the differential signal whose frequency is higher than a predetermined lower limit frequency. The differential signal that has passed through the HPF 35 is amplified by the amplifier 31 and drives the tweeter 30. The LPF 23 and the HPF 35 constitute a network circuit 110. The network circuit 110 is the same as that used in a normal three-way speaker.

[0029] FIG. 2 shows an example of the relationship between frequency and sound pressure in the speaker system 1. FIG. 2 shows an example in which an original sound signal with a constant sound pressure level is input at all frequencies. The full-range speaker 20 outputs sound based on the difference 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 original sound 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 a 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 a sound with an 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 a sound with the same sound pressure level as the sound pressure level of the original sound signal.

[0030] 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 that is in phase with the sound of the woofer 10, increasing the sound pressure level of the speaker system 1 as a whole to the sound pressure level defined by the original sound signal. The sound pressure level of the sound obtained by superimposing the sound of the woofer 10 and the full-range speaker 20 becomes the same as the sound pressure level of the original sound signal. Therefore, in the speaker system 1, no unnatural change in sound pressure level occurs between the range of sound reproduced by the woofer 10 and the range of sound reproduced by the full-range speaker 20. No network circuit is required between the range of sound reproduced by the woofer 10 and the range of sound reproduced by the full-range speaker 20.

[0031] Based on the differential signal, the network circuit 110 causes the full-range speaker 20 to mainly reproduce frequency components lower than a predetermined crossover frequency (fc), and causes the tweeter 30 to mainly reproduce frequency components higher than fc. However, in the crossover range, the full-range speaker 20 and the tweeter 30 autonomously output sound based on the differential signal. For this reason, the speaker system 1 may cause an unnatural change in sound pressure level in the crossover range between the range reproduced by the full-range speaker 20 and the range reproduced by the tweeter 30.

[0032] The speaker system 1 compensates for the sound of the woofer 10 with the sound of the full-range speaker 20. The vibration system of the full-range speaker 20 is usually lighter than that of the woofer 10. The vibration system of the full-range speaker 20 moves faster than that of the woofer 10. For this reason, compared to a configuration in which the sound of the full-range speaker 20 is compensated for with the sound of the woofer 10, such as the 3D speaker device described in Patent Document 2, the speaker system 1 compensates for the sound of the woofer 10 with the full-range speaker 20 more quickly, and can reproduce a more natural sound.

[0033] Furthermore, resonance of the speaker or within the speaker box can have a serious effect on sound quality. Particularly in the low-frequency range, resonance can make the sound muddy and impair the clarity of the sound. This is because resonance emphasizes sound waves at a specific frequency and suppresses other frequency components. With the speaker system 1, for example, when the level of a sound at a specific frequency increases due to resonance in the woofer 10, the full-range speaker 20 emits sound so that the level of the sound at that specific frequency decreases. For this reason, the speaker system 1 suppresses the effects of resonance.

[0034] Furthermore, the playback characteristics of the cone paper (paper material) used in many speakers change over time (even with age) depending on the usage environment, particularly humidity. The mass of the cone paper is greater for a speaker that reproduces low-pitched sounds. This makes it more susceptible to the effects of humidity. The mass of the edge and damper is also greater. This makes it more susceptible to changes in the physical properties of the edge and damper (hardening over time, etc.). This can cause changes in the sound output by the speaker. In speaker system 1, full-range speaker 20 compensates for changes in sound caused by changes over time in the vibration system including the cone paper and damper of woofer 10 (hereinafter referred to as changes over time in the vibration system) within the range of sound that it can output.

[0035] 3 shows an example of the configuration of a speaker system 2 according to the first embodiment of the present invention. The speaker system 2 has a woofer 10, an amplifier 11, a vibration detection unit 12, a subtractor 14, a full-range speaker 20, an amplifier 21, a vibration detection unit 22, a subtractor 24, a tweeter 30, an amplifier 31, and an HPF (high pass filter) 120. The speaker system 2 differs from the speaker system 1 in FIG. 1 in that it has the vibration detection unit 22 and the subtractor 24 for the full-range speaker 22, and in that it does not have a network circuit 110. In other respects, the configuration of the speaker system 2 is the same as the configuration of the speaker system 1 in FIG. 1.

[0036] An original sound signal output from a sound source is input to the input terminal 100. The original sound signal is amplified by the amplifier 11 and drives the woofer 10. 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 first differential signal corresponds to the differential signal in the speaker system 1 of FIG. 1. The subtractor 14 is, for example, a differential amplifier. The original sound signal is input to the non-inverting input terminal (+) of the subtractor 14, and the reproduction signal is input to the inverting input terminal (-). The subtractor 14 outputs a first differential signal indicating the difference between the original sound signal and the reproduction signal. The first differential signal is defined as the following equation (2).

[0037] First differential signal = original signal - first reproduced signal (2)

[0038] The first differential signal is amplified by the amplifier 21 and drives the full-range speaker 20. The vibration detection unit 22 detects 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 a configuration similar to that of a vibration detection circuit used in motional feedback. The subtractor 24 is, for example, a differential amplifier. The first differential signal is input to the non-inverting input terminal (+) of the subtractor 24, and the second reproduction signal is input to the inverting input terminal (-). The subtractor 24 outputs a second differential signal indicating the difference between the first differential signal and the second reproduction signal. The second differential signal is defined as the following equation (3).

[0039] Second differential signal = First differential signal - Second regenerated signal (3)

[0040] The HPF 120 passes the differential signal having a frequency higher than a predetermined lower limit. The HPF 120 removes from the second differential signal a frequency component that may damage the vibration system of the tweeter 30. The second differential signal is amplified by the amplifier 31. The tweeter 30 is driven by the amplified second differential signal from which the low frequency components have been removed.

[0041] Fig. 4 shows an example of the relationship between frequency and sound pressure in the speaker system 2. Fig. 4 shows an example of the case where an original sound signal with a constant sound pressure level is input at all frequencies. The relationship between the sound of the woofer 10 and the sound of the full-range speaker 20 in the speaker system 2 is the same as that in the speaker system 1 in Fig. 1.

[0042] The tweeter 30 is driven by the second differential signal and outputs a high-frequency sound. The sound of the full-range speaker 20 is compensated 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 original sound signal, the tweeter 30 does not output sound. When the sound pressure level of the full-range speaker 20 is insufficient, the tweeter 30 outputs a sound in phase with the sound of the woofer 10 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 in phase opposite to the sound of the full-range speaker 20 to decrease the sound pressure level.

[0043] 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 that is in phase with the sound of the full-range speaker 10, and the sound pressure level of the speaker system 2 as a whole increases to the sound pressure level defined by the original sound signal. The sound pressure level of the sound in which the sound of the full-range speaker 20 and the sound of the tweeter 30 are superimposed becomes the same as the sound pressure level of the original sound signal. Unlike the speaker system 1 in FIG. 1, the speaker system 2 does not require the network circuit 110. In the speaker system 2, no unnatural change in sound pressure level occurs between the range of sound reproduced by the full-range speaker 20 and the range of sound reproduced by the tweeter 30.

[0044] In the speaker system 2, the tweeter 30 corrects the sound of the full-range speaker 20 within the range of sound that the tweeter 30 can output. For example, even if the sound changes due to a change over time in the vibration system of the full-range speaker 20, the sound of the full-range speaker 20 is corrected by the sound of the tweeter 30.

[0045] Furthermore, in the speaker system 2, it is essential to prevent the tweeter 30 from outputting low-frequency sounds and to prevent damage to the tweeter 30. To achieve this purpose, the HPF 120 is provided. As shown in Fig. 4, the lower limit frequency of the range in which the tweeter 30 can output sounds is set by the HPF 120 to a frequency at which the tweeter 30 will not be damaged. The HPF 120 may be a simple high-pass filter, and may be composed of, for example, only a capacitor.

[0046] 5 shows an example of the configuration of a speaker system 3 according to the second embodiment of the present invention. The speaker system 3 has a woofer 10, an amplifier 11, a vibration detection unit 12, an LPF 13, a subtractor 14, 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, and an HPF 120. The speaker system 3 differs from the speaker system 2 of FIG. 3 in that it has an LPF 13 and an LPF 23. In other respects, the configuration of the speaker system 3 is the same as the configuration of the speaker system 2 according to the first embodiment. The following describes the differences between the speaker system 3 and the speaker system 2.

[0047] FIG. 6 shows an example of the relationship between frequency and sound pressure in the speaker system 3. FIG. 6 shows an example in which an original sound signal with a constant sound pressure level is input at all frequencies. The LPF 13 removes high frequency components from the original sound signal. The original sound signal from which the high frequency components have been removed is amplified by the amplifier 11 and supplied to the woofer 10. The cutoff frequency (cutoff frequency) of the LPF 23 is set higher than the cutoff frequency of the HPF 120. The cutoff frequency of the LPF 23 is also higher than the cutoff frequency of the LPF 13. The LPF 23 removes high frequency components from the first differential signal. The first differential signal from which the high frequency components have been removed is amplified by the amplifier 21 and supplied to the full-range speaker 20. The cutoff frequencies of the LPF 13 and the LPF 23 can be set to the same cutoff frequencies as those of the low-pass filters included in the network circuits of the conventional three-way speakers, for example. However, the cutoff frequencies of the LPF 13 and the LPF 23 may be different from the cutoff frequencies of the low-pass filters included in the network circuits of the conventional three-way speakers. Furthermore, the speaker system 3 does not require a strict (steep) crossover frequency setting as in the past. Therefore, the LPF 13 and the LPF 23 may each be a simpler filter than in the past. Note that the LPF 13 and the LPF 23 are examples of the second low-pass filter and the first low-pass filter of the present invention, respectively.

[0048] In the speaker system 3, the range of sounds reproduced by the woofer 10, the full-range speaker 20, and the tweeter 30 can be set to be the same as the range of sounds reproduced by, for example, a conventional three-way speaker.

[0049] 7 shows an example of the configuration of a speaker system 4 according to a third embodiment of the present invention. The speaker system 4 is an extension of the speaker system 3 according to the second embodiment to a stereo system. The speaker system 4 includes a woofer 10, an amplifier 11, a vibration detection unit 12, an LPF 13, a subtractor 14, a subtractor 15, an amplifier 16, an amplifier 17, 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 full-range speaker 40, an amplifier 41, a vibration detection unit 42, an LPF 43, a subtractor 44, a tweeter 50, an amplifier 51, an HPF 120, and an HPF 121. The speaker system 4 is obtained by adding a subtractor 15, an amplifier 16, an amplifier 17, a full-range speaker 40, an amplifier 41, a vibration detection unit 42, an LPF 43, a subtractor 44, a tweeter 50, an amplifier 51, and an HPF 121 to the speaker system 3 according to the second embodiment. The following describes the differences between the speaker system 4 and the speaker system 3.

[0050] A first original sound signal and a second original sound signal output from a sound source are input to input terminal 101 and input terminal 102, respectively. Amplifier 16 amplifies the first original sound signal, and amplifier 17 amplifies the second original sound signal. The output terminal of amplifier 16 and the output terminal of amplifier 17 are connected at connection point 18. The amplified first original sound signal and second original sound signal are added together at connection point 18. The added first original sound signal and second original sound signal are passed through LPF 13, amplified by amplifier 11, and input to woofer 10.

[0051] The first original sound signal is input to the non-inverting input terminal (+) of the subtractor 14, and the first reproduced signal is input to the inverting input terminal (-). The subtractor 14 outputs a first differential signal indicating the difference between the first original sound signal and the first reproduced signal. The first differential signal is defined as the following equation (4).

[0052] 1st differential signal = 1st original signal - 1st reproduced signal (4)

[0053] The subtractor 15 is, for example, a differential amplifier. The second original sound signal is input to a non-inverting input terminal (+) of the subtractor 15, and the first reproduced signal is input to an inverting input terminal (-). The subtractor 15 outputs a fifth differential signal indicating the difference between the second original sound signal and the first reproduced signal. The fifth differential signal is defined as the following equation (5).

[0054] 5th difference signal = 2nd original signal - 1st playback signal (5)

[0055] The full-range speaker 40, the amplifier 41, the vibration detection unit 42, the LPF 43, and the subtractor 44 operate in the same manner as the full-range speaker 20, the amplifier 21, the vibration detection unit 22, the LPF 23, and the subtractor 24, respectively. The LPF 43 removes high-frequency components from the fifth differential signal. The fifth differential signal from which the high-frequency components have been removed is amplified by the amplifier 41 and supplied to the full-range speaker 40. The cutoff frequency of the LPF 43 is set higher than the cutoff frequency of the HPF 121. The cutoff frequency of the LPF 43 is also higher than the cutoff frequency of the LPF 13. The vibration detection unit 42 outputs a fifth reproduction signal. The fifth differential signal is input to the non-inverting input terminal (+) of the subtractor 44, and the fifth reproduction signal is input to the inverting input terminal (-). The subtractor 44 outputs a sixth differential signal indicating the difference between the fifth differential signal and the fifth reproduction signal. The sixth differential signal is defined as the following equation (6).

[0056] 6th differential signal = 5th differential signal - 5th regenerated signal (6)

[0057] The HPF 121 operates in the same manner as the HPF 120. The HPF 121 removes frequency components that may damage the vibration system of the tweeter 50 from the sixth differential signal. The tweeter 50 and the amplifier 51 operate in the same manner as the tweeter 30 and the amplifier 31. The sixth differential signal from which the high-frequency components have been removed is amplified by the amplifier 51 and supplied to the tweeter 50. The tweeter 50 is driven by the amplified sixth differential signal from which the low-frequency components have been removed.

[0058] Fig. 8 shows an example of the relationship between the frequency and sound pressure of the sound reproduced by the woofer 10 in the speaker system 4 of Fig. 7. Fig. 8 shows an example in which there is a difference between the levels of the first original sound signal and the second original sound signal, and the level of the first original sound signal is greater than the level of the second original sound signal. The woofer 10 is driven by the sum of the first original sound signal and the second original sound signal. Therefore, the woofer 10 reproduces a sound at a level equal to the average of the first original sound signal and the second original sound signal.

[0059] Fig. 9 shows an example of the relationship between the frequency and sound pressure of the sound reproduced by one of the full-range speaker 20 and the tweeter 30 in the speaker system 4 of Fig. 7. The full-range speaker 20 and the tweeter 30 reproduce sound based on a first original sound signal. The example of Fig. 9 shows a case where the first original sound signal shown in Fig. 8 is input. Since the level of the sound reproduced by the woofer 10 is smaller than the level of the first original sound signal, the full-range speaker 20 outputs a sound in phase with the sound of the woofer 10, thereby increasing the sound pressure level.

[0060] FIG. 10 shows an example of the relationship between the frequency and sound pressure of the sound reproduced by the other full-range speaker 40 and the tweeter 50 in the speaker system 4 of FIG. 7. The full-range speaker 40 and the tweeter 50 reproduce sound based on the second original sound signal. The example of FIG. 10 shows a case where the second original sound signal shown in FIG. 8 is input to the input terminal 102. In the area A surrounded by the dashed ellipse, the level of the sound reproduced by the woofer 10 is higher than the level of the second original sound signal. Therefore, in the area A, the full-range speaker 40 outputs a sound in the opposite phase to the sound of the woofer 10 to reduce the sound pressure level. In the area with a higher frequency than the area A, the sound reproduced by the woofer 10 gradually becomes smaller due to the action of the LPF 43. In this area, the level of the sound reproduced by the woofer 10 is lower than the level of the second original sound signal, so the full-range speaker 40 outputs a sound in the same phase as the sound of the woofer 10 to increase the sound pressure level.

[0061] In the 3D speaker device described in Patent Document 2, the low-frequency speaker is driven based on the sum of two signals indicating the vibrations of the vibration systems of a pair of left and right high-frequency speakers and the sum of two input original signals. Then, the sound reproduced by one low-frequency speaker corrects the sound reproduced by a pair of left and right high-frequency speakers. Therefore, strictly speaking, it cannot be said that the sound levels of the left and right high-frequency speakers are corrected to the levels of the two input original signals. In contrast, as shown in Figures 9 and 10, in a speaker system 4 according to a third embodiment of the present invention, the level of the sound reproduced by the woofer 10 is corrected to the level of the first original sound signal and the level of the second original sound signal by a pair of full-range speakers 20 and 40, respectively.

[0062] In the first to third embodiments, the woofer is an example of a low-frequency speaker of the present invention, but the present invention is not limited to this, and the low-frequency speaker may be, for example, a subwoofer (super woofer). In the first to third embodiments, the tweeter is an example of a high-frequency speaker of the present invention, but the present invention is not limited to this, and the high-frequency speaker may be, for example, a super tweeter.

[0063] FIG. 11 shows an example of the configuration of a speaker system 5 according to a fourth embodiment of the present invention. The speaker system 5 is obtained by adding a subwoofer 60 to the speaker system 3 according to the second embodiment. The speaker system 5 includes a woofer 10, an amplifier 11, a vibration detection unit 12, an LPF 13, a subtractor 14, 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 subwoofer 60, an amplifier 61, a vibration detection unit 62, an LPF 63, a subtractor 64, and an HPF 120. The speaker system 5 differs from the speaker system 3 according to the second embodiment in that the speaker system 5 includes a subwoofer 60, an amplifier 61, a vibration detection unit 62, an LPF 63, and a subtractor 64. In other respects, the configuration of the speaker system 5 is the same as that of the speaker system 3 according to the second embodiment. The following describes the differences between the speaker system 5 and the speaker system 3.

[0064] An original sound signal is input to the input terminal 100. The LPF 63 removes high frequency components from the original sound signal. The cutoff frequency of the LPF 63 is set lower than the cutoff frequency of the LPF 13. The original sound signal from which the high frequency components have been removed is amplified by the amplifier 61 and drives the subwoofer 60. The vibration detection unit 62 detects vibrations of the vibration system of the subwoofer 60 and outputs a third reproduction signal corresponding to the vibrations. The vibration detection unit 62 has a configuration similar to that of a vibration detection circuit used in motional feedback. The subtractor 64 is, for example, a differential amplifier. The original sound signal is input to the non-inverting input terminal (+) of the subtractor 64, and the third reproduction signal is input to the inverting input terminal (-). The subtractor 64 outputs a third difference signal indicating the difference between the original sound signal and the third reproduction signal. The third difference signal is defined as the following equation (7).

[0065] 3rd differential signal = original signal - 3rd reproduced signal (7)

[0066] Unlike the speaker system 3 according to the second embodiment, the third differential signal is supplied to the LPF 13. The LPF 13 removes high frequency components from the third differential signal. The third differential signal from which the high frequency components have been removed is amplified by the amplifier 11 and supplied to the woofer 10. The cutoff frequencies of the LPF 63, the LPF 13, and the LPF 23 can be set to the same cutoff frequencies as the low pass filters included in the network circuits of the conventional four-way speakers, for example. However, the cutoff frequencies of the LPF 63, the LPF 13, and the LPF 23 may be different from the cutoff frequencies of the low pass filters included in the network circuits of the conventional four-way speakers. Furthermore, the speaker system 5 does not require the setting of strict (steep) crossover frequencies as in the conventional system. Therefore, the LPF 63, the LPF 13, and the LPF 23 may each be a simpler filter than the conventional system. The LPF 13 and the LPF 23 are examples of the second low pass filter and the first low pass filter of the present invention, respectively.

[0067] The woofer 10 outputs a sound based on the third difference signal. The sound of the subwoofer 60 is compensated by the sound of the woofer 10. When the sound pressure level of the subwoofer 60 is the same as the sound pressure level of the original sound signal, the woofer 10 does not output a sound. When the sound pressure level of the subwoofer 60 is insufficient, the woofer 10 outputs a sound in the same phase as the sound of the subwoofer 60 to increase the sound pressure level. When the sound pressure level of the subwoofer 60 is excessive, the woofer 10 outputs a sound in the opposite phase to the sound of the subwoofer 60 to decrease the sound pressure level. When the sound pressure level of the subwoofer 60 is 0, the woofer 10 outputs a sound with the same sound pressure level as the sound pressure level of the original sound signal.

[0068] As the frequency increases, the sound pressure level of the subwoofer 60 decreases. However, at this time, the woofer 10 outputs a sound that is in phase with the sound of the subwoofer 60, increasing the sound pressure level of the speaker system 5 as a whole to the sound pressure level stipulated by the original sound signal. The sound pressure level of the sound obtained by superimposing the sounds of the subwoofer 60 and the woofer 10 is the same as the sound pressure level of the original sound signal. For this reason, in the speaker system 5, no unnatural change in sound pressure level occurs between the range of sounds reproduced by the subwoofer 60 and the range of sounds reproduced by the woofer 10.

[0069] In the speaker system 5, the range of sounds reproduced by the subwoofer 60, the woofer 10, the full-range speaker 20, and the tweeter 30 can be set to be the same as the range of sounds reproduced by, for example, a conventional four-way speaker.

[0070] In this embodiment, the woofer 10 is an example of a low-frequency speaker of the present invention, and the subwoofer 60 is an example of an extremely low-frequency speaker of the present invention.

[0071] FIG. 12 shows an example of the configuration of a speaker system 6 according to the fifth embodiment of the present invention. The speaker system 6 is a speaker system 5 according to the fourth embodiment to which a super tweeter 70 is added. The speaker system 6 includes a woofer 10, an amplifier 11, a vibration detection unit 12, an LPF 13, a subtractor 14, 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 vibration detection unit 32, an LPF 33, a subtractor 34, a subwoofer 60, an amplifier 61, a vibration detection unit 62, an LPF 63, a subtractor 64, a super tweeter 70, an amplifier 71, and an HPF 120. The speaker system 6 differs from the speaker system 5 according to the fourth embodiment in that the speaker system 6 includes the vibration detection unit 32, the LPF 33, the subtractor 34, the super tweeter 70, and the amplifier 71. In other respects, the configuration of the speaker system 6 is the same as the configuration of the speaker system 5 according to the fourth embodiment. Below, the points where the speaker system 6 differs from the speaker system 5 will be described.

[0072] The LPF 33 removes high frequency components from the second differential signal. The cutoff frequency of the LPF 33 is set higher than the cutoff frequency of the LPF 23. The second differential signal from which the high frequency components have been removed by the LPF 33 is amplified by the amplifier 31 and drives the tweeter 30. The vibration detection unit 32 detects vibration of the vibration system of the tweeter 30 and outputs a fourth reproduction signal corresponding to the vibration. The vibration detection unit 32 has a configuration similar to that of a vibration detection circuit used in motional feedback. The subtractor 34 is, for example, a differential amplifier. The second differential signal that has passed through the HPF 120 is input to the non-inverting input terminal (+) of the subtractor 34, and the fourth reproduction signal is input to the inverting input terminal (-). The subtractor 34 outputs a fourth differential signal indicating the difference between the second differential signal and the fourth reproduction signal. The fourth differential signal is defined as the following equation (8).

[0073] 4th differential signal = 2nd differential signal - 4th regenerated signal (8)

[0074] The fourth difference signal is amplified by the amplifier 71 and supplied to the super tweeter 70. The cutoff frequencies of the LPF63, LPF13, LPF23, and LPF33 can be set to the same cutoff frequencies as the low-pass filters included in the network circuits of the conventional five-way speakers, for example. However, the cutoff frequencies of the LPF63, LPF13, LPF23, and LPF33 may be different from the cutoff frequencies of the low-pass filters included in the network circuits of the conventional five-way speakers. Furthermore, the speaker system 6 does not require a strict (steep) crossover frequency setting as in the conventional system. For this reason, the LPF63, LPF13, LPF23, and LPF33 may each be a simpler filter than the conventional system. The LPF13 and LPF23 are examples of the second low-pass filter and the first low-pass filter of the present invention, respectively.

[0075] The fourth differential signal is amplified by the amplifier 71 to drive the super tweeter 70. The super tweeter 70 outputs sound based on the fourth differential signal. The sound of the tweeter 30 is compensated by the sound of the super tweeter 70. When the sound pressure level of the tweeter 30 is the same as the sound pressure level of the original sound signal, the super tweeter 70 does not output sound. When the sound pressure level of the tweeter 30 is insufficient, the super tweeter 70 outputs a sound in 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 70 outputs a sound in the opposite phase to 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 70 outputs a sound with the same sound pressure level as the sound pressure level of the original sound signal.

[0076] As the frequency increases, the sound pressure level of the tweeter 30 decreases. However, at this time, the super tweeter 70 outputs a sound that is in phase with the sound of the tweeter 30, and the sound pressure level of the speaker system 6 as a whole increases to the sound pressure level stipulated by the original sound signal. The sound pressure level of the sound in which the sounds of the tweeter 30 and the super tweeter 70 are superimposed is the same as the sound pressure level of the original sound signal. For this reason, in the speaker system 6, no unnatural change in sound pressure level occurs between the range of sounds reproduced by the tweeter 30 and the range of sounds reproduced by the super tweeter 70.

[0077] In the speaker system 6, the range of sounds reproduced by the subwoofer 60, the woofer 10, the full-range speaker 20, the tweeter 30, and the super tweeter 70 can be set to be the same as the range of sounds reproduced by, for example, a conventional five-way speaker.

[0078] In this embodiment, the woofer 10 is an example of a low-frequency speaker of the present invention, the subwoofer 60 is an example of an extremely low-frequency speaker of the present invention, the tweeter 30 is an example of a high-frequency speaker of the present invention, and the super tweeter 70 is an example of an extremely high-frequency speaker of the present invention.

[0079] As described above, according to the present invention, it is possible to comprehensively reproduce natural sounds that are faithful to the original sound. Since the movement of the vibration system has inertia, delays occur with respect to movements that are faithful to the original sound signal. For this reason, delays and overshoots (excessive amplitudes) occur in the sounds reproduced by each speaker, but by sequentially correcting these delays with speakers that have lighter vibration systems, the effects of inertia can be minimized.

[0080] Although the embodiments of the present invention have been described above, various modifications and combinations required due to convenience in design or manufacturing 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. [Explanation of symbols]

[0081] 1...speaker system according to the invention, 2, 3, 4, 5, 6...speaker systems according to the embodiments of the present invention, 10...woofer, 11...amplifier, 12...vibration detection unit, 13...LPF (low pass filter), 14, 15...subtractor, 16, 17...amplifier, 20...full-range speaker, 21...amplifier, 22...vibration detection unit, 23...LPF, 24...subtractor, 30...tweeter, 31...amplifier, 32...vibration detection output section, 33...LPF, 34...subtractor, 35...HPF (high pass filter), 40...full-range speaker, 41...amplifier, 42...vibration detection section, 43...LPF, 44...subtractor, 50...tweeter, 51...amplifier, 60...subwoofer, 61...amplifier, 62...vibration detection section, 63...LPF, 64...subtractor, 70...tweeter, 71...amplifier, 100, 101, 102...input terminal, 120, 121...HPF

Claims

1. A bass speaker that reproduces low-frequency sounds; a first vibration detection unit that outputs a first reproduction signal corresponding to a vibration of a vibration system of the woofer; a first subtractor configured to subtract the first playback signal from a signal that drives the woofer to generate a first difference signal; a full-range speaker driven by the first differential signal; a second vibration detection unit 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 differential signal by subtracting the second reproduced signal from the first differential signal; a treble speaker that is driven by the second differential signal and outputs a treble sound; A speaker system comprising:

2. 2. The speaker system according to claim 1, further comprising a high-pass filter for removing, from the second differential signal, frequency components that may cause damage to a vibration system of the treble speaker.

3. 3. The speaker system of claim 2, further comprising a first low-pass filter having a cutoff frequency higher than the cutoff frequency of the high-pass filter, the first low-pass filter supplying the first differential signal from which high-frequency components have been removed to the full-range speaker.

4. 4. The speaker system according to claim 2, wherein the signal for driving the woofer is an original sound signal output from a sound source.

5. a subwoofer that is driven by an original sound signal output from a sound source and reproduces a subwoofer having a lower frequency than the bass sound reproduced by the subwoofer; a third vibration detection unit that outputs a third reproduction signal corresponding to a vibration of a vibration system of the ultra-low frequency speaker; a third subtractor that generates a third difference signal by subtracting the third reproduction signal from the original sound signal; Equipped with a signal for driving the woofer is the third differential signal; 2. The speaker system according to claim 1.

6. a fourth vibration detection unit that outputs a fourth reproduction signal corresponding to the vibration of the vibration system of the high-frequency speaker; a fourth subtractor that generates a fourth differential signal by subtracting the fourth reproduced signal from the second differential signal; an ultra-high frequency speaker that is driven by the fourth differential signal and outputs an ultra-high frequency sound having a higher frequency than the high frequency sound reproduced by the treble speaker; The speaker system according to claim 1 .

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