JPS60208198A - Speaker system - Google Patents

Abstract

PURPOSE:To eliminate reflection sound at a listening point by providing a sub- woofer in addition to a main woofer being a cause to generation of reflection sound and taking the phase of the reflecting sound from the main speaker inverse to the direct sound from the sub-woofer. CONSTITUTION:There is not phase shift in a signal fed to the main woofer 4 and the sub-woofer 5 via LPF7, 8 at a low frequency smaller than a frequency fa and the woofers 4, 5 are operated in parallel. When the frequency is increased and reaches the fa, the phase of the signal fed to the LPF8 is shifted by 180 deg. and the phase is opposite to that of the output of the LPF7. Thus, the low frequency range generated from the main speaker 4 and the sub-woofer 5 is opposite in phase to each other, the direct sound from the woofer 5 and the reflected sound from the woofer 4 are cancelled together at the listening point LP, thereby giving the same effect that no reflecting sound reaches the listening point LP.

Description

[Detailed description of the invention] Technical field The present invention relates to a speaker system.

Background technologySpeaker systems are designed to provide smooth characteristics in a sound field without reflections, such as an anechoic chamber, but in an actual sound field, they cannot be used in a room without special acoustic treatment. It is generally installed directly on the floor or via a stand.

In such speaker settings, sound reflection from walls such as the floor, ceiling, and walls becomes a problem. In particular, when the speaker/stem is installed on the floor, reflections from the floor cannot be ignored.

FIG. 1 is a diagram for explaining the reflection of sound by the floor surface. Direct sound (indicated by a solid line) reaches the listening point LP from the speaker 2 of the speaker/stem placed on the floor surface 1.
Sound reflected by the floor 1 (indicated by a broken line) reaches the listening point LP. This reflected sound can be considered to be sound emitted from a virtual sound image 3 (hereinafter referred to as a virtual image speaker) that is virtualized at a symmetrical position with respect to the floor surface. If the path lengths from speaker 2 and virtual image speaker 3 to listening point LP are respectively t and A2, there is a path difference of 12
-1. exists. Wavelength of the frequency at which this path difference occurs]/
2, that is, if the wavelength at frequency fa is λα (fa-C/λa, c is the speed of sound), 12-1. =λa/2, a dip in the sound pressure level occurs at the listening point LP at the frequency fa.

1, when the path difference is equal to one wavelength λb of the frequency fb, that is, 12-1. -λb, the sound pressure level peaks at the listening point LP at the frequency fb. Thereafter, the r inog and peak will be repeated at 3λC/2, 2λd, etc. However, as the frequency increases, the influence of reflected sound becomes smaller, so dips and peaks in the sound pressure level can be ignored.

In Fig. 2, a dip occurs at frequency fa, and a dip occurs at frequency fb.
This shows the frequency characteristics of the sound pressure level that has a peak at . In particular, the dip in the sound pressure level at the frequency fα is large and has a significant effect on sound quality.

In order to prevent such dips from occurring, it is difficult to make the floor a perfect sound-absorbing surface to eliminate reflected waves, and such a method is at least not suitable for general households.

SUMMARY OF THE INVENTION An object of the present invention is to provide a speaker system that does not cause deterioration of the sound pressure level at a listening point due to sound reflected from a wall surface, and therefore can obtain smooth sound pressure characteristics.

According to the speaker/stem of the present invention, in addition to the main speaker for the bass range which causes reflected sound generation, a bass speaker for the bass range is provided, and at the listening point, the reflected sound from the main speaker at frequency fα and the direct sound from the sub speaker are provided. The sound is out of phase with the reflected sound and the direct sound, canceling it out.
It is designed to eliminate reflected sound at the listening point.

Embodiment FIG. 3 is a diagram showing an embodiment of the speaker/stem of the present invention. This speaker/stem consists of two bass speakers, namely main speaker 4 and sub speaker 5.
, one mid-to-high frequency range speaker 6, and networks 7, 8, and 9 connected to these speakers, respectively. It is assumed that this speaker/stem is installed on the floor surface 10. The three speakers are arranged along a straight line perpendicular to the floor surface in the order of the main speaker 4 for low frequency range, the speaker 6 for medium and high frequency range, and the sub speaker 5 for low frequency range from a position close to the floor surface lO. It is provided inside the M node 11.

It is assumed that the listening point LP is located parallel to the floor 10 from the mid-high range speaker 6, and the angle of depression from this listening point toward the bass main speaker 4 is θ4, and the distance from the listening point to the speaker 4 is Let be A3. The virtual image speaker 12 with respect to the main speaker 40 for bass range and the floor 10 is indicated by 12, and the angle of depression when looking at the virtual image speaker 12 from the listening point LT is 0.
2. Let the distance from the listening point to the virtual image speaker 121 be A4.

When driving by giving a signal only to the bass speaker 4,
Direct sound from the speaker 4 and reflected sound reflected by the floor surface 10 reach the listening point LP.

Therefore, as explained in FIG.
At a frequency fa such that t, =λα/2, a dip in the sound pressure level occurs at the listening point LP.

In order to prevent the occurrence of this dip, the following measures are adopted in this embodiment. First, the elevation angle of the bass sub-speaker 5 from the listening point LP is the same as that of the virtual image speaker 1.
2 so that the depression angle θ2 is the same. That is, the bass sub-speaker 5 and the virtual image speaker 12 are positioned symmetrically with respect to the line connecting the mid-high frequency range speaker 6 and the listening point LP. In this case, it can be seen that the distance from the listening point LP to the sub speaker 5 is the same as the distance t4 to the virtual image speaker 12.

Next, for networks 7.8, 9, and especially network 8, their characteristics are selected as follows. The main speaker 4 for low frequency range and the speaker 6 for medium and high frequency range are for crossover, and if the crossover frequency is fx, the network 7 connected to the speaker 4 is a low frequency filter with a cutoff frequency fx. As such, the network 9 connected to the speaker 6 is configured as a bypass filter with a cutoff frequency fx. The parts constituted by the speakers 4, 6 and the filter 7.9 are the same as those of a normal speaker system 1.

On the other hand, the network 8 connected to the bass sub-speaker 5 has a cutoff frequency fa that is lower than the crossover frequency fx, and an attenuation characteristic of 36 dB/o.
It consists of a ct low gas filter. The o-/' space filter 8 has a function of shifting the phase of the input signal to the filter by 180 at the frequency fa, that is, shifting the phase by 180. The low-speed filter 8 and the high-speed filter 9 are connected in parallel to the signal input terminal 13.

Next, the operation of this embodiment will be explained. In the bass range lower than the frequency fα, there is almost no phase shift between the signals supplied to the main speaker 4 and the sub speaker 5 via the low frequency filter and 8, and these speakers for the bass range operate in complete parallel connection. In addition, in the frequency range smaller than fa, the floor lO from the bass main speaker 4
There are no changes in sound pressure level caused by reflected sound, and the sound quality is stable.

When the frequency increases to fa, the signal supplied to the low f filter is output with a phase shift of 180, and has an opposite phase to the signal output from the low f filter. Therefore, the phases of the bass frequencies generated by the main speaker 4 and the sub speaker 5 are shifted by 180 degrees. The low-frequency sound from the main speaker 4 that is reflected by the floor surface 10 and reaches the listening point LP can be considered as the low-frequency sound generated by the virtual image speaker 12.

As mentioned above, the bass sub-speaker 5 is located at the listening point L.
Since the virtual image speaker 12 is placed at the same distance as the distance t4 from the perspective of the speaker 11, a phase shift due to a path difference occurs.The direct sound from the speaker 5 and the reflected sound from the speaker 4 are at the listening point LP reach. Since the direct sound and the reflected sound are out of phase by 1.80, that is, in an antiphase relationship, they cancel each other out at the listening point LP. Therefore, it is the same as if the reflected sound did not reach the listening point LP, and no distortion of the sound pressure level at the frequency fα occurs.

7. Low frequency filter 8, where the frequency is greater than fa
As a result, the signal to the sub-speaker 5 is attenuated and only the main speaker 4 operates, but since the influence of reflected sound is small, the sound pressure level diyf does not occur.

In FIG. 4, the frequency characteristic of the sound pressure level at the listening point LP in this embodiment is shown by a solid line. For comparison, the frequency characteristics when dizziness occurs at frequency fα are shown by broken lines. As described above, according to this embodiment, smooth sound pressure characteristics can be obtained.

Next, another embodiment of the present invention will be described based on FIG. This embodiment is substantially the same as the embodiment described in FIG. 3 except for the following points, and the same elements as those in FIG. 3 are denoted by the same numbers.

In this embodiment, with respect to the distance t4 between the virtual image speaker 12 and the listening point LP, the distance t5 between the sub-speaker 5 and the listening point LP is set from the distance t4 within a range that can be ignored compared to the wavelength of the bass range. The sub-speaker 5 is arranged so that when the frequency is large and the frequency fa, t, -14='/4λα. Toyo K
By doing so, at around the frequency fα, the direct sound from the sub-speaker 5 is delayed by K by 90 phase with respect to the reflected sound from the main speaker 4.

On the other hand, the low gas filter 8 has a cutoff frequency fa,
(It is made to have a gentle attenuation characteristic of 2 dB 10 ct, and a phase shift of 90 is caused at the frequency fa.

In a speaker system with a configuration such as μ10, when the frequency increases to fa, the output signal of the low frequency filter 8 has a phase of 9 with respect to the output signal of the low frequency filter 8.
As a result of the delay of 0, the direct sound from the sub speaker 5 is delayed in phase by 90 relative to the reflected sound from the main speaker 4.

Furthermore, due to the path difference between the distances t5 and t4, the direct sound from the sub-speaker 5 is delayed in phase by 90 degrees with respect to the reflected sound, so the direct sound that finally reaches the listening point LP is reflected from the reflected sound that reaches the listening point LP. The phase will be delayed by 180 degrees relative to the sound. Therefore, as in the embodiment described above, the direct sound from the sub-speaker 5 and the reflected sound from the main speaker 4 are canceled out at the listening point LP, and the reflected sound is eliminated. Thereby, it is possible to prevent the generation of disk 0 caused by reflected sound at the frequency fα.

In the above two embodiments, the low gas filter and 8 are connected in parallel, but they can also be connected in series as shown in FIG. Since the cutoff frequency fa of the low pass filter 8 is smaller than the cutoff frequency x of the low pass filter 8, the signal that has passed through the low pass filter 8 is phase shifted by the low pass filter 8. The filter 8 can output a signal that is out of phase with the output of the Lavarow filter.

Moreover, although a low-pass filter is used in the network 8 to shift the phase, it is clear that a phase filter can also be used.

Furthermore, if level control is performed to match the level of the low-frequency sound from the sub-speaker 5 to the level of the friendly sound from the mace beaker 4, it is possible to completely eliminate reflected sound.

The speaker system of the present invention can deal with not only reflections from the floor but also reflections from large pieces. The speaker system is not limited to being installed on the floor, but can also be installed on the wall.

Effects According to the speaker system of the present invention, a sub-speaker for low frequency range is provided, and the direct sound from the sub-speaker is 180 degrees out of phase with the reflected sound at the listening point LP. Since the sound can be canceled out and eliminated, and the dip at the frequency fa caused by the reflected sound can be prevented from occurring, smooth sound pressure characteristics can be obtained.

In the bass range smaller than the frequency fα, two bass speaker units operate in parallel in the same phase, so the radiation area is twice as much as when there is only one bass speaker unit, which increases the sensitivity. 2. The allowable input also doubles, and the maximum output sound pressure rises to 6 dB. This enables rich bass reproduction with excellent linearity.

Furthermore, with a typical parallel-connected double woofer system, the sound image becomes too large in the midrange, or the distance between the two woofers is 1.
, 14. In contrast, in the speaker system of the present invention, the signal to the bass sub-speaker is attenuated in the middle range of frequency 16 or above, compared to the case where sound pressure synthesis is not performed properly due to the phase difference due to the path difference of 14. Since only the main speaker for bass frequencies operates, it is possible to prevent the interference that occurs with conventional double woofers/stem, and the reproducibility of the sound image is also improved.

According to the present invention, good sound quality and characteristics can be obtained without requiring a special room or acoustic treatment, so it has great practical value.

Furthermore, since the three speaker units are arranged in a straight line, the space factor of the speaker box is also good.

[Brief explanation of the drawings] Figure 1 is a diagram for explaining the reflection of sound by the floor surface, Figure 2 is a diagram showing the sound pressure characteristics at the listening point in the case of Figure 1, and Figure 3 is a diagram for explaining the sound pressure characteristics at the listening point in the case of Figure 1. FIG. 4 is a diagram showing the configuration of an embodiment of the present invention, and FIG. Fig. 6 is a diagram showing the configuration of another embodiment, and Fig. 6 is a diagram showing another example of network connection. Explanation of symbols of main parts 4...Main speaker for bass range 5...Sub for bass range Speaker 6...Speaker for mid-high range 7.8.9 - Network IO/Floor 11 Speaker + Lyx 12...Virtual image speaker 13/Signal input terminal. Applicant: Guionia Co., Ltd. Agent Patent attorney Motohiko Fujimura 2 Ku book 3 figure LA, concave fa, f (Hz) hair 4 ku,!, -, 3 people 6Z

Claims (1)

[Scope of Claims] l) A main speaker and a sub-speaker for bass reproduction arranged sequentially along a straight line perpendicular to the sound-reflecting wall surface starting from the one closest to the reflecting wall surface, and connected to the sub-speaker; The difference between the distance from the listening point to the virtual image speaker of the main speaker and the distance from the listening point to the main speaker, which are assumed to be in a symmetrical position with respect to the reflecting wall surface, is a frequency fa corresponding to a half wavelength of the sound. a cutoff frequency, and a network that causes a phase shift in the supplied signal so that the signal to the main speaker is out of phase with respect to the signal to the main speaker, and the sound reflected by the reflecting wall surface from the main speaker at the frequency fα. A speaker system characterized in that the phase difference between the direct sound from the sub-speaker and the direct sound is 180 degrees at a listening point. 2) The sub-speaker is arranged so that the distance from the listening point is equal to the distance from the listening point to the virtual image speaker, and the phase shift amount of the network is 180°. A speaker system having the configuration described in Scope 1. 3) Arrange the sub-board so that the distance from the listening point is 1/4 wavelength larger in the KJ fixed wave number fa than the distance from the listening point to the imaginary f3 speaker,
2. The speaker system according to claim 1, wherein the phase shift amount of the network is 90.