speaker system
The speaker system uses vibration detection units and subtractors with filters to correct sound pressure levels and compensate for environmental changes, ensuring faithful reproduction of natural sound across different frequency ranges.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- 足立静雄
- Filing Date
- 2024-12-07
- Publication Date
- 2026-06-18
Smart Images
Figure 2026099690000001_ABST
Abstract
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 from a low-frequency sound to a high-frequency sound with a single speaker. 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 sub-woofer (also called a super-woofer) suitable for reproducing ultra-low-frequency sound or 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, faithful sound can be output 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 making light emitted from a light-emitting element incident on a light-reflecting member attached to the vibration system and receiving the reflected light with a light-receiving element are known (for example, see Patent Document 1).
[0005] Furthermore, a vibration detection circuit is known in which an MFB detection coil is provided near the voice coil of the speaker, parallel to the voice coil, and this MFB detection coil is used to detect vibrations of the speaker. MFB speakers equipped with this vibration detection circuit are commercially available (see, for example, Non-Patent Document 1).
[0006] Furthermore, a vibration detection circuit is known in which a metal plate is fixed to the surface adjacent to the speaker's center cap (metal) so as not to come into contact with the center cap, and the speaker's vibration is detected from the change in capacitance between the center cap and the metal plate (based on the principle of a condenser microphone). MFB speakers equipped with this vibration detection circuit are also sold (see, for example, Non-Patent Document 2).
[0007] Furthermore, Patent Document 2 describes a 3D speaker device comprising a pair of left and right high-frequency speakers, first and second amplifiers for driving the speakers, first and second detectors for detecting the vibration acceleration of the speakers, a comparator for comparing the outputs of the first and second detectors with the input signal to the high-frequency speakers, a high-cut filter for cutting the high-frequency component of the output signal of the comparator, a third amplifier for amplifying the output signal of the high-cut filter, and a low-frequency speaker driven by the third amplifier. This 3D speaker device has a motional feedback mechanism that inputs the vibration acceleration detection signal of the high-frequency speakers and the input signal to the high-frequency speakers to the comparator, and controls the driving of the low-frequency speakers by the output of the comparator. Patent Document 2 also describes a woofer and a subwoofer as examples of high-frequency speakers and low-frequency speakers, respectively.
[0008] Furthermore, Patent Document 3 describes a speaker system comprising: a main speaker driven by an original sound signal output from a sound source; a vibration detection unit that detects vibrations in the vibration system of the main speaker and outputs a playback signal corresponding to the vibrations; 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 with 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 with the opposite phase to the sound of the main speaker to decrease 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 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 November 26, 2024], Internet<URL: https: / / www.fostex.jp / products / cw250d / > [Non-Patent Document 2] "Orphian", [online], Takumi Co., Ltd. Homepage, [searched November 26, 2024], Internet site)<URL: https: / / www.cocojc.com / orphean / structure.html#mfb> [Overview of the Initiative] [Problems that the invention aims to solve]
[0011] In multi-way speakers, the same sound is output from both speakers within the crossover frequency range of each speaker. Within the crossover frequency range, for example, low-pass and high-pass filters in the network circuit attenuate the sound from each speaker, but this can easily lead to unnatural changes in sound pressure levels. To prevent this, precise filter design is necessary.
[0012] The objective of the present invention is to provide a three-way or more speaker system that can reproduce natural sound comprehensively while remaining faithful to the original sound. [Means for solving the problem]
[0013] To achieve the above objective, the speaker system of the present invention is A speaker for reproducing low-frequency sounds, A first vibration detection unit that outputs a first playback signal corresponding to the vibration of the vibration system of the low-frequency speaker, A first subtractor generates a first difference signal by subtracting the first playback signal from the signal that drives the low-frequency speaker, A full-range speaker driven by the first difference signal, A second vibration detection unit that outputs a second playback signal corresponding to the vibration of the vibration system of the full-range speaker, A second subtractor generates a second difference signal by subtracting the second regenerated signal from the first difference signal, A high-frequency speaker, driven by the second difference signal and outputting high-frequency sounds, It is equipped with.
[0014] Preferably, the speaker system of the present invention is The second difference signal is further enhanced by a high-pass filter that removes frequency components that could potentially damage the vibration system of the high-frequency speaker.
[0015] Preferably, the speaker system of the present invention is A first low-pass filter having a cut-off frequency higher than the cut-off frequency of the high-pass filter, and 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 The signal for driving the bass-range speaker is the original sound signal output from the sound source.
[0017] Preferably, the speaker system of the present invention A second low-pass filter having a cut-off frequency lower than the cut-off frequency of the first low-pass filter, and supplying the original sound signal from which high-frequency components have been removed to the bass-range speaker.
[0018] Preferably, the speaker system of the present invention A subwoofer speaker that is driven by the original sound signal output from the sound source and reproduces a sub-bass sound having a frequency lower than the bass sound reproduced by the bass-range speaker, A third vibration detection unit that outputs a third reproduction signal corresponding to the vibration of the vibration system of the subwoofer speaker, A third subtractor that generates a third differential signal by subtracting the third reproduction signal from the original sound signal, and The signal for driving the bass-range speaker is the third differential signal.
[0019] Preferably, the speaker system of the present invention A fourth vibration detection unit that outputs a fourth reproduction signal corresponding to the vibration of the vibration system of the tweeter speaker, A fourth subtractor that generates a fourth differential signal by subtracting the fourth reproduction signal from the second differential signal, A supertweeter speaker that is driven by the fourth differential signal and outputs a super-high-frequency sound having a frequency higher than the high-frequency sound reproduced by the tweeter speaker, It is equipped with. [Effects of the Invention]
[0020] According to the present invention, it is possible to reproduce a natural sound that is faithful to the original sound. [Brief explanation of the drawing]
[0021] [Figure 1] This figure shows an example of the configuration of a speaker system according to the invention described in Patent Document 3. [Figure 2] This figure shows an example of the relationship between frequency and sound pressure in the speaker system shown in Figure 1. [Figure 3] This figure shows an example of the configuration of a speaker system according to the first embodiment of the present invention. [Figure 4] Figure 3 shows an example of the relationship between frequency and sound pressure in a speaker system. [Figure 5] This figure shows an example of the configuration of a speaker system according to a second embodiment of the present invention. [Figure 6] Figure 5 shows an example of the relationship between frequency and sound pressure in a speaker system. [Figure 7] This figure shows an example of the configuration of a speaker system according to a third embodiment of the present invention. [Figure 8] Figure 7 shows an example of the relationship between the frequency and sound pressure of the sound reproduced by the woofer in the speaker system shown. [Figure 9] Figure 7 shows an example of the relationship between sound frequency and sound pressure reproduced by one full-range speaker and one tweeter in the speaker system shown. [Figure 10] This figure shows an example of the relationship between sound frequency and sound pressure reproduced by the other full-range speaker and tweeter in the speaker system shown in Figure 7. [Figure 11] This figure shows an example of the configuration of a speaker system according to the fourth embodiment of the present invention. [Figure 12]This figure shows an example of the configuration of a speaker system according to the fifth embodiment of the present invention. [Modes for carrying out the invention]
[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 illustrating the embodiments, common components are denoted by the same reference numerals, and repeated descriptions are omitted.
[0023] In the 3D speaker device described in Patent Document 2, a detector for detecting vibration acceleration is provided in the high-frequency speaker. This 3D speaker device inputs the vibration acceleration detection signal from the high-frequency speaker and the original input signal to the high-frequency speaker into 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 with the sound of the low-frequency speaker.
[0024] However, the vibration system of a low-frequency speaker is usually heavier than that of a high-frequency speaker. Due to inertia, the movement of the low-frequency speaker's vibration system is slower than that of the high-frequency speaker's vibration system. Therefore, when the sound of the high-frequency speaker is corrected using the sound of the low-frequency speaker, the correction is delayed in time compared to correcting the sound of the low-frequency speaker with the sound of the high-frequency speaker, which tends to result in an unnatural sound.
[0025] Figure 1 shows an example of the configuration of a speaker system 1 according to the invention described in Patent Document 3. The speaker system 1 includes a woofer 10, an amplifier 11, a vibration detection unit 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] The original sound signal output from the 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 vibrations in the vibration system of the woofer 10 and outputs a playback signal corresponding to those vibrations. The vibration system includes, for example, the diaphragm (e.g., cone paper), voice coil bobbin, damper, and center cap of the woofer 10. The same applies to the full-range speaker 20 and tweeter 30. The same also applies to the subwoofer 60 and super tweeter 70, which will be described later. The vibration detection unit 12 has a configuration similar to the 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 that shows the difference between the original sound signal and the playback signal. The difference signal is defined as equation (1) below.
[0027] Difference signal = Original sound signal - Reproduced signal (1)
[0028] The LPF23 allows difference signals below a predetermined upper frequency limit to pass through. The difference signals that have passed through the LPF23 are amplified by the amplifier 21 and drive the full-range speaker 20. The HPF35 allows difference signals above a predetermined lower frequency limit to pass through. The difference signals that have passed through the HPF35 are amplified by the amplifier 31 and drive the tweeter 30. The LPF23 and HPF35 constitute the network circuit 110. The network circuit 110 is the same as that used in a typical 3-way speaker.
[0029] Figure 2 shows an example of the relationship between frequency and sound pressure in speaker system 1. Figure 2 is an example where a source sound signal with a constant sound pressure level at all frequencies is input. The full-range speaker 20 outputs sound based on the difference signal. The sound from the woofer 10 is corrected by the sound from the full-range speaker 20. If the sound pressure level of the woofer 10 is the same as the sound pressure level of the source sound signal, the full-range speaker 20 does not produce sound. If the sound pressure level of the woofer 10 is insufficient, the full-range speaker 20 increases the sound pressure level by outputting a sound with the same phase as the sound from the woofer 10. If the sound pressure level of the woofer 10 is excessive, the full-range speaker 20 decreases the sound pressure level by outputting a sound with the opposite phase to the sound from the woofer 10. If the sound pressure level of the woofer 10 is 0, the full-range speaker 20 produces a sound with the same sound pressure level as the sound pressure level of the source 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 sound with the same phase as the sound from the woofer 10, increasing the overall sound pressure level of the speaker system 1 to the sound pressure level defined by the original sound signal. The sound pressure level of the combined sound from the woofer 10 and the full-range speaker 20 is the same as the sound pressure level of the original sound signal. Therefore, in the speaker system 1, there is no unnatural change in sound pressure level between the frequency range reproduced by the woofer 10 and the frequency range reproduced by the full-range speaker 20. A network circuit is not required between the frequency range reproduced by the woofer 10 and the frequency range reproduced by the full-range speaker 20.
[0031] The network circuit 110, based on the difference signal, primarily reproduces components with frequencies lower than a predetermined crossover frequency (fc) to the full-range speaker 20, and primarily reproduces components with frequencies higher than fc to the tweeter 30. However, in the crossover frequency range, the full-range speaker 20 and the tweeter 30 autonomously output sound based on the difference signal. As a result, the speaker system 1 may produce unnatural changes in sound pressure level in the crossover frequency range between the frequency range reproduced by the full-range speaker 20 and the frequency range reproduced by the tweeter 30.
[0032] Speaker system 1 corrects 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 movement of the vibration system of the full-range speaker 20 is faster than the movement of the vibration system of the woofer 10. For this reason, compared to a configuration in which the sound of the woofer 10 corrects the sound of the full-range speaker 20 with the sound of the woofer 10, as described in Patent Document 2, speaker system 1 corrects the sound of the woofer 10 by the full-range speaker 20 faster, and can reproduce a more natural sound.
[0033] Furthermore, speaker resonance and resonance within the speaker box can have a serious impact on sound quality. In particular, in the low-frequency range, resonance can cause the sound to become muddy and the clarity of the sound quality to be compromised. This is because resonance emphasizes sound waves at specific frequencies and suppresses other frequency components. In speaker system 1, for example, if the level of sound at a specific frequency increases due to resonance in the woofer 10, the full-range speaker 20 will emit sound in a way that lowers the level of sound at that specific frequency. Therefore, the effects of resonance are suppressed in speaker system 1.
[0034] Furthermore, the cone paper (paper material) used in most speakers changes over time (even with age) depending on the environment of use, especially humidity. Speakers that reproduce low frequencies have a larger cone paper mass. Therefore, they are more susceptible to the effects of humidity. Also, the mass of the edge and damper is larger. Therefore, they are more susceptible to the effects of changes in the physical properties of the edge and damper (such as hardening over time). As a result, the sound output by the speaker may change. In speaker system 1, the full-range speaker 20 compensates for changes in sound caused by changes in the vibration system including the cone paper and damper of the woofer 10 over time (hereinafter referred to as changes in the vibration system over time) within its output frequency range.
[0035] Figure 3 shows an example of the configuration of speaker system 2 according to the first embodiment of the present invention. Speaker system 2 includes 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. Speaker system 2 differs from speaker system 1 in Figure 1 in that it has a vibration detection unit 22 and a subtractor 24 for the full-range speaker 22, and does not have a network circuit 110. In other respects, the configuration of speaker system 2 is the same as that of speaker system 1 in Figure 1.
[0036] The original sound signal output from the 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 woofer 10's vibration system and outputs a first playback signal corresponding to that vibration. The first difference signal corresponds to the difference signal in speaker system 1 in Figure 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 playback signal is input to the inverting input terminal (-). The subtractor 14 outputs a first difference signal that shows the difference between the original sound signal and the playback signal. The first difference signal is defined as equation (2) below.
[0037] First difference signal = original sound signal - first reproduced signal (2)
[0038] The first difference signal is amplified by the amplifier 21 to drive the full-range speaker 20. The vibration detection unit 22 detects vibrations in the vibration system of the full-range speaker 20 and outputs a second regeneration signal corresponding to those vibrations. 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 difference signal is input to the non-inverting input terminal (+) of the subtractor 24, and the second regeneration signal is input to the inverting input terminal (-). The subtractor 24 outputs a second difference signal that shows the difference between the first difference signal and the second regeneration signal. The second difference signal is defined as equation (3) below.
[0039] Second difference signal = First difference signal - Second regenerated signal (3)
[0040] The HPF120 allows difference signals higher than a predetermined lower limit frequency to pass through. The HPF120 removes frequency components from the second difference signal that could damage the vibration system of the tweeter 30. The second difference signal is amplified by the amplifier 31. The tweeter 30 is driven by the amplified second difference signal from which the low-frequency components have been removed.
[0041] Figure 4 shows an example of the relationship between frequency and sound pressure in speaker system 2. Figure 4 is an example where a primary sound signal with a constant sound pressure level at all frequencies is input. The relationship between the sound from the woofer 10 and the sound from the full-range speaker 20 in speaker system 2 is the same as the relationship in speaker system 1 in Figure 1.
[0042] The tweeter 30 is driven by a second difference signal and outputs high-frequency sounds. The sound from the full-range speaker 20 is corrected by the sound from the tweeter 30. If 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 produce sound. If the sound pressure level of the full-range speaker 20 is insufficient, the tweeter 30 increases the sound pressure level by outputting a sound with the same phase as the sound from the woofer 10. If the sound pressure level of the full-range speaker 20 is excessive, the tweeter 30 decreases the sound pressure level by outputting a sound with the opposite phase to the sound from the full-range speaker 20.
[0043] As the frequency increases, the sound pressure level of the full-range speaker 20 decreases. However, at this time, the tweeter 30 outputs sound with the same phase as the sound from the full-range speaker 10, increasing the overall sound pressure level of the speaker system 2 to the sound pressure level defined by the original sound signal. The sound pressure level of the combined sound from the full-range speaker 20 and the tweeter 30 becomes the same as the sound pressure level of the original sound signal. Unlike speaker system 1 in Figure 1, the network circuit 110 is not required in speaker system 2. In speaker system 2, there is no unnatural change in sound pressure level between the frequency range reproduced by the full-range speaker 20 and the frequency range reproduced by the tweeter 30.
[0044] Furthermore, in speaker system 2, the tweeter 30 corrects the sound of the full-range speaker 20 within its output frequency range. For example, even if the sound changes due to the temporal changes 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 speaker system 2, it is crucial to prevent the tweeter 30 from outputting low-frequency sounds and thus prevent damage to the tweeter 30. To achieve this objective, an HPF120 is provided. As shown in Figure 4, the lower limit frequency of the frequency range in which the tweeter 30 can output sound is set by the HPF120 to a frequency that does not pose a risk of damaging the tweeter 30. The HPF120 can be a simple high-pass filter, and may even consist only of a capacitor, for example.
[0046] Figure 5 shows an example of the configuration of speaker system 3 according to the second embodiment of the present invention. Speaker system 3 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, and an HPF 120. Speaker system 3 differs from speaker system 2 in Figure 3 in that it has LPF 13 and LPF 23. In other respects, the configuration of speaker system 3 is the same as the configuration of speaker system 2 according to the first embodiment. The differences between speaker system 3 and speaker system 2 will be described below.
[0047] Figure 6 shows an example of the relationship between frequency and sound pressure in speaker system 3. Figure 6 is an example where a source sound signal with a constant sound pressure level at all frequencies is input. LPF13 removes high-frequency components from the source sound signal. The source sound signal from which the high-frequency components have been removed is amplified by amplifier 11 and supplied to woofer 10. The cutoff frequency (cutoff frequency) of LPF23 is set higher than the cutoff frequency of HPF120. Also, the cutoff frequency of LPF23 is higher than the cutoff frequency of LPF13. LPF23 removes high-frequency components from the first difference signal. The first difference signal from which the high-frequency components have been removed is amplified by amplifier 21 and supplied to full-range speaker 20. The cutoff frequencies of LPF13 and LPF23 can be set to the same cutoff frequencies as the low-pass filters included in the network circuit of a conventional 3-way speaker, for example. However, the cutoff frequencies of LPF13 and LPF23 may be different from the cutoff frequencies of the low-pass filters included in the network circuit of a conventional 3-way speaker. Furthermore, speaker system 3 does not require the strict (steep) crossover frequency setting required in conventional systems. For this reason, LPF13 and LPF23 can each be simpler filters compared to conventional systems. Note that LPF13 and LPF23 are examples of the second and first low-pass filters of the present invention, respectively.
[0048] The speaker system 3 allows the frequency range of the sound reproduced by the woofer 10, full-range speaker 20, and tweeter 30 to be set to be the same as, for example, the frequency range of the sound reproduced by a conventional 3-way speaker.
[0049] Figure 7 shows an example of the configuration of a speaker system 4 according to the third embodiment of the present invention. The speaker system 4 is a stereo extension of the speaker system 3 according to the second embodiment. 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. Speaker system 4 is the speaker system 3 according to the second embodiment, with the addition of 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. The differences between speaker system 4 and speaker system 3 will be described below.
[0050] Input terminals 101 and 102 receive the first and second original sound signals, respectively, output from the sound source. Amplifier 16 amplifies the first original sound signal, and amplifier 17 amplifies the second original sound signal. The output terminals of amplifier 16 and amplifier 17 are connected at connection point 18. At connection point 18, the amplified first and second original sound signals are added together. The added first and second original sound signals pass through LPF 13, are 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 re-played signal is input to the inverting input terminal (-). The subtractor 14 outputs a first difference signal that shows the difference between the first original sound signal and the first re-played signal. The first difference signal is defined as equation (4) below.
[0052] First difference signal = First original sound signal - First reproduced signal (4)
[0053] The subtractor 15 is, for example, a differential amplifier. The second original sound signal is input to the non-inverting input terminal (+) of the subtractor 15, and the first reproduced signal is input to the inverting input terminal (-). The subtractor 15 outputs a fifth difference signal that represents the difference between the second original sound signal and the first reproduced signal. The fifth difference signal is defined as equation (5) below.
[0054] Fifth difference signal = Second original signal - First reproduced signal (5)
[0055] The full-range speaker 40, amplifier 41, vibration detection unit 42, LPF 43, and subtractor 44 operate in the same manner as the full-range speaker 20, amplifier 21, vibration detection unit 22, LPF 23, and subtractor 24, respectively. The LPF 43 removes high-frequency components from the fifth difference signal. The fifth difference 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. Also, the cutoff frequency of the LPF 43 is higher than the cutoff frequency of the LPF 13. The vibration detection unit 42 outputs the fifth regenerative signal. The fifth difference signal is input to the non-inverting input terminal (+) of the subtractor 44, and the fifth regenerative signal is input to the inverting input terminal (-). The subtractor 44 outputs a sixth difference signal, which represents the difference between the fifth difference signal and the fifth regenerative signal. The sixth difference signal is defined by equation (6) below.
[0056] The sixth difference signal = the fifth difference signal - the fifth regenerated signal (6)
[0057] HPF121 operates similarly to HPF120. HPF121 removes frequency components from the sixth difference signal that could damage the vibration system of the tweeter 50. The tweeter 50 and amplifier 51 operate similarly to the tweeter 30 and amplifier 31. The sixth difference signal, from which the high-frequency components have been removed, is amplified by amplifier 51 and supplied to the tweeter 50. The tweeter 50 is driven by the amplified sixth difference signal from which the low-frequency components have been removed.
[0058] Figure 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 Figure 7. Figure 8 is an example where there is a difference in 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 the average level of the first original sound signal and the second original sound signal.
[0059] Figure 9 shows an example of the relationship between sound frequency and sound pressure in the speaker system 4 of Figure 7, specifically between one full-range speaker 20 and a tweeter 30. The full-range speaker 20 and tweeter 30 reproduce sound based on a first original sound signal. The example in Figure 9 shows the case where the first original sound signal shown in Figure 8 is input. Since the level of sound reproduced by the woofer 10 is lower than the level of the first original sound signal, the full-range speaker 20 outputs sound with the same phase as the woofer 10's sound to increase the sound pressure level.
[0060] Figure 10 shows an example of the relationship between sound frequency and sound pressure reproduced by the other full-range speaker 40 and tweeter 50 in the speaker system 4 of Figure 7. The full-range speaker 40 and tweeter 50 reproduce sound based on the second original sound signal. The example in Figure 10 shows the case when the second original sound signal shown in Figure 8 is input to the input terminal 102. In region A enclosed by the dashed ellipse, the level of sound reproduced by the woofer 10 is greater than the level of the second original sound signal. Therefore, in region A, the full-range speaker 40 outputs a sound with the opposite phase to the sound of the woofer 10, reducing the sound pressure level. In the part with a frequency higher than region A, the sound reproduced by the woofer 10 gradually decreases due to the action of the LPF 43. In this part, since the level of sound reproduced by the woofer 10 is less than the level of the second original sound signal, the full-range speaker 40 outputs a sound with the same phase as the sound of the woofer 10, increasing 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 representing the vibrations of the vibration systems of a pair of left and right high-frequency speakers, and the sum of two input original signals. The sound reproduced by one low-frequency speaker corrects the sound reproduced by the 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 the speaker system 4 according to the third embodiment of the present invention, the sound level reproduced by the woofer 10 is corrected to the levels of the first original sound signal and 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 it is not limited to this, and the low-frequency speaker may be, for example, a subwoofer (super woofer). Also, in the first to third embodiments, the tweeter is an example of a high-frequency speaker of the present invention, but it is not limited to this, and the high-frequency speaker may be, for example, a super tweeter.
[0063] Figure 11 shows an example of the configuration of speaker system 5 according to the fourth embodiment of the present invention. Speaker system 5 is the speaker system 3 according to the second embodiment with a subwoofer 60 added. 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. Speaker system 5 differs from speaker system 3 according to the second embodiment in that it 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 speaker system 5 is the same as that of speaker system 3 according to the second embodiment. The differences between speaker system 5 and speaker system 3 will be described below.
[0064] The original sound signal is input to input terminal 100. LPF 63 removes high-frequency components from the original sound signal. The cutoff frequency of LPF 63 is set lower than the cutoff frequency of LPF 13. The original sound signal from which the high-frequency components have been removed is amplified by amplifier 61 and drives the subwoofer 60. The vibration detection unit 62 detects vibrations in the vibration system of the subwoofer 60 and outputs a third playback signal corresponding to those vibrations. The vibration detection unit 62 has a configuration similar to the 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 playback signal is input to the inverting input terminal (-). The subtractor 64 outputs a third difference signal that shows the difference between the original sound signal and the third playback signal. The third difference signal is defined as equation (7) below.
[0065] Third difference signal = original sound signal - third reproduced signal (7)
[0066] Unlike the speaker system 3 according to the second embodiment, a third difference signal is supplied to the LPF13. The LPF13 removes high-frequency components from the third difference signal. The third difference 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 LPF63, LPF13, and LPF23 can be set to the same cutoff frequencies as the low-pass filters included in the network circuit of a conventional 4-way speaker, for example. However, the cutoff frequencies of LPF63, LPF13, and LPF23 may differ from the cutoff frequencies of the low-pass filters included in the network circuit of a conventional 4-way speaker. Furthermore, the speaker system 5 does not require the setting of a strict (steep) crossover frequency as in the conventional system. For this reason, LPF63, LPF13, and LPF23 may each be simpler filters compared to conventional systems. Note that LPF13 and LPF23 are examples of the second and first low-pass filters of the present invention, respectively.
[0067] Woofer 10 outputs sound based on the third difference signal. The sound from subwoofer 60 is corrected by the sound from woofer 10. If the sound pressure level of subwoofer 60 is the same as the sound pressure level of the original signal, woofer 10 does not produce sound. If the sound pressure level of subwoofer 60 is insufficient, woofer 10 increases the sound pressure level by outputting a sound with the same phase as the sound from subwoofer 60. If the sound pressure level of subwoofer 60 is excessive, woofer 10 decreases the sound pressure level by outputting a sound with the opposite phase to the sound from subwoofer 60. If the sound pressure level of subwoofer 60 is 0, woofer 10 produces a sound with the same sound pressure level as the sound pressure level of the original 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 with the same phase as the sound from the subwoofer 60, increasing the overall sound pressure level of the speaker system 5 to the sound pressure level defined by the original sound signal. The sound pressure level of the combined sound from the subwoofer 60 and the woofer 10 becomes the same as the sound pressure level of the original sound signal. Therefore, in the speaker system 5, there is no unnatural change in sound pressure level between the frequency range reproduced by the subwoofer 60 and the frequency range reproduced by the woofer 10.
[0069] The speaker system 5 allows the frequency range of the sound reproduced by the subwoofer 60, woofer 10, full-range speaker 20, and tweeter 30 to be set to be the same as, for example, the frequency range of the sound reproduced by a conventional 4-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 ultra-low-frequency speaker of the present invention.
[0071] Figure 12 shows an example of the configuration of a speaker system 6 according to the fifth embodiment of the present invention. Speaker system 6 is a speaker system 5 according to the fourth embodiment with a super tweeter 70 added. 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. Speaker system 6 differs from speaker system 5 according to the fourth embodiment in that it includes a vibration detection unit 32, an LPF 33, a subtractor 34, a super tweeter 70, and an amplifier 71. In other respects, the configuration of speaker system 6 is the same as that of speaker system 5 according to the fourth embodiment. The differences between speaker system 6 and speaker system 5 will be described below.
[0072] The LPF33 removes high-frequency components from the second difference signal. The cutoff frequency of the LPF33 is set higher than the cutoff frequency of the LPF23. The second difference signal, from which the high-frequency components have been removed by the LPF33, is amplified by the amplifier 31 and drives the tweeter 30. The vibration detection unit 32 detects vibrations in the vibration system of the tweeter 30 and outputs a fourth regeneration signal corresponding to those vibrations. The vibration detection unit 32 has a configuration similar to the vibration detection circuit used in motional feedback. The subtractor 34 is, for example, a differential amplifier. The second difference signal that has passed through the HPF120 is input to the non-inverting input terminal (+) of the subtractor 34, and the fourth regeneration signal is input to the inverting input terminal (-). The subtractor 34 outputs a fourth difference signal that shows the difference between the second difference signal and the fourth regeneration signal. The fourth difference signal is defined as equation (8) below.
[0073] The fourth difference signal = the second difference signal - the fourth regenerated signal (8)
[0074] The fourth difference signal is amplified by amplifier 71 and supplied to super tweeter 70. The cutoff frequencies of LPF63, LPF13, LPF23, and LPF33 can be set to the same cutoff frequencies as the low-pass filters included in the network circuit of a conventional 5-way speaker, for example. However, the cutoff frequencies of LPF63, LPF13, LPF23, and LPF33 may differ from the cutoff frequencies of the low-pass filters included in the network circuit of a conventional 5-way speaker. Furthermore, speaker system 6 does not require the setting of a strict (steep) crossover frequency as in the conventional system. For this reason, LPF63, LPF13, LPF23, and LPF33 may each be simpler filters compared to conventional systems. Note that LPF13 and LPF23 are examples of the second and first low-pass filters of the present invention, respectively.
[0075] The fourth difference signal is amplified by the amplifier 71 and drives the super tweeter 70. The super tweeter 70 outputs sound based on the fourth difference signal. The sound from the tweeter 30 is corrected by the sound from the super tweeter 70. If the sound pressure level of the tweeter 30 is the same as the sound pressure level of the original signal, the super tweeter 70 does not produce sound. If the sound pressure level of the tweeter 30 is insufficient, the super tweeter 70 increases the sound pressure level by outputting a sound with the same phase as the sound from the tweeter 30. If the sound pressure level of the tweeter 30 is excessive, the super tweeter 70 decreases the sound pressure level by outputting a sound with the opposite phase to the sound from the tweeter 30. If the sound pressure level of the tweeter 30 is 0, the super tweeter 70 produces a sound with the same sound pressure level as the original 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 with the same phase as the sound of the tweeter 30, increasing the overall sound pressure level of the speaker system 6 to the sound pressure level defined by the original sound signal. The sound pressure level of the sound produced by the superposition of the sound of the tweeter 30 and the sound of the super tweeter 70 becomes the same as the sound pressure level of the original sound signal. Therefore, in the speaker system 6, there is no unnatural change in sound pressure level between the frequency range reproduced by the tweeter 30 and the frequency range reproduced by the super tweeter 70.
[0077] The speaker system 6 allows the frequency range of the sound reproduced by the subwoofer 60, woofer 10, full-range speaker 20, tweeter 30, and super tweeter 70 to be set to be the same as, for example, the frequency range of the sound reproduced by a conventional 5-way speaker system.
[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 ultra-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 ultra-high frequency speaker of the present invention.
[0079] As explained above, the present invention makes it possible to reproduce a natural sound that is faithful to the original sound. Because the movement of the vibration system has inertia, a delay occurs in the movement that is faithful to the original sound signal. For this reason, delays and overshoots (excessive amplitude) occur in the sound reproduced by each speaker, but by sequentially correcting this with speakers that have lighter vibration systems, the effects of inertia can be minimized.
[0080] While embodiments of the present invention have been described above, various modifications and combinations necessary due to design or manufacturing considerations or other factors are included within the scope of the invention corresponding to the claims and 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 each embodiment 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 unit Output, 33...LPF, 34...Subtractor, 35...HPF (High-Pass Filter), 40...Full-Range Speaker, 41...Amplifier, 42...Vibration Detection Unit, 43...LPF, 44...Subtractor, 50...Tweeter, 51...Amplifier, 60...Subwoofer, 61...Amplifier, 62...Vibration Detection Unit, 63...LPF, 64...Subtractor, 70...Tweeter, 71...Amplifier, 100, 101, 102...Input Terminals, 120, 121...HPF
Claims
1. A speaker for reproducing low-frequency sounds, A first vibration detection unit that outputs a first playback signal corresponding to the vibration of the vibration system of the low-frequency speaker, A first subtractor generates a first difference signal by subtracting the first playback signal from the signal that drives the low-frequency speaker, A full-range speaker driven by the first difference signal, A second vibration detection unit that outputs a second playback signal corresponding to the vibration of the vibration system of the full-range speaker, A second subtractor generates a second difference signal by subtracting the second regenerated signal from the first difference signal, A high-frequency speaker driven by the second difference signal and outputting high-frequency sounds, A speaker system equipped with [features / equipment].
2. The speaker system according to claim 1, further comprising a high-pass filter that removes frequency components from the second difference signal that may damage the vibration system of the high-frequency speaker.
3. The speaker system according to claim 2, 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 difference signal from which high-frequency components have been removed to the full-range speaker.
4. The speaker system according to claim 2 or 3, wherein the signal that drives the low-frequency speaker is the original sound signal output from the sound source.
5. The speaker system according to claim 4, further comprising 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 low-frequency speaker.
6. A low-frequency speaker that is driven by the original sound signal output from the sound source and reproduces extremely low-frequency sounds with a frequency lower than the low-frequency sounds reproduced by the low-frequency speaker, A third vibration detection unit that outputs a third playback signal corresponding to the vibration of the vibration system of the aforementioned ultra-low frequency speaker, A third subtractor generates a third difference signal by subtracting the third playback signal from the original sound signal, Equipped with, The signal that drives the low-frequency speaker is the third difference signal. The speaker system according to claim 1.
7. A fourth vibration detection unit that outputs a fourth playback signal corresponding to the vibration of the vibration system of the high-frequency speaker, A fourth subtractor generates a fourth difference signal by subtracting the fourth regenerated signal from the second difference signal, A high-frequency speaker driven by the fourth difference signal and outputting extremely high-frequency sounds with a frequency higher than the high-frequency sounds reproduced by the high-frequency speaker, The speaker system according to claim 1, comprising: