JPH0691680B2 - Speaker system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a speaker system having an acoustic tube on the rear surface of a speaker unit.

2. Description of the Related Art As one of the conventional speaker systems for expanding the bass range, there is an acoustic maze type speaker system.

Hereinafter, the conventional acoustic maze type speaker system described above will be described with reference to the drawings.

FIG. 5 is a structural sectional view of the speaker system.

In FIG. 5, 1 is a cabinet, 2a, 2b, 2c, 2d, 2e are partition plates provided on the front and rear plates of the cabinet 1, and 3 is an opening provided at the bottom of the front plate of the cabinet 1. Is a speaker unit provided above the front plate.

The operation of the acoustic maze type speaker system configured as described above will be described below.

Partition plates 2a, 2b, 2c, 2d, 2e provided in the cabinet 1
Constitutes an acoustic tube, and the sound emitted from the rear surface of the speaker unit 4 is guided to the acoustic tube and radiated from its opening. The acoustic tube resonates at a specific frequency determined by its total length. Resonance frequency n = C / 4L * (2n + 1), where n =, where L is the total length of the acoustic tube and C is the speed of sound in the air.
0, 1, 2, ... N, and 1/4 in the acoustic tube when n = 0
The wavelength is increased to cause resonance, and the acoustically increased sound is radiated from the opening 3 of the acoustic tube, and the efficiency is greatly improved in the vicinity of the bass reproduction limit. Further, at a frequency of 1/2 wavelength in the acoustic tube, a speaker radiated from the opening 3 of the acoustic tube that is originally in opposite phase to the sound radiated from the front surface of the speaker unit 4 and the sound from the front surface. The sound from the rear surface of the unit 4 is added in the same phase due to the phase delay of a half wavelength, and the sound pressure level increases. Further, when n = 2, 3/4 wavelength is spread in the acoustic tube, as in the case of n = 0,
Acoustically enhanced sound is emitted from the opening 3 of the acoustic tube. Therefore, it was possible to realize a highly efficient speaker system in the low sound range.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, when the frequency further rises and its wavelength becomes equal to the length of the acoustic tube, the sound radiated from the front surface of the speaker unit 4 and the opening of the acoustic tube. Sound radiated from the rear surface of the speaker unit 4 interferes with each other, and as shown in FIG. 6, ridges and valleys having a large sound pressure are generated and the sound quality is deteriorated.

In view of the above-mentioned problems, the present invention provides a speaker system having an improved radioactivity in the low sound range, less disturbance of sound pressure characteristics, and excellent sound quality.

Means for Solving the Problems In order to achieve this object, a speaker system according to the present invention has a plurality of acoustic tubes of different lengths continuously extended from the back surface of a speaker unit in parallel with a sound traveling direction. Need not be radiated from the acoustic tube into the shared acoustic tube, which is arranged in a shared manner and connects the respective outlets of the acoustic tube to form a further continuously extending shared acoustic tube It is configured to include at least one acoustic filter that cuts off the mid-high range.

Operation According to the present invention, the acoustic characteristics of the acoustic tubes having different lengths are determined by the tube lengths from the entrance to the opening of the shared acoustic tube. That is, looking at the operation of one acoustic tube, at a frequency having one wavelength in the acoustic tube, the sound on the front surface of the speaker unit and the sound on the rear surface of the speaker unit radiated from the opening of the acoustic tube have opposite phases and cancel each other out. As a result, a valley with a large sound pressure is generated. On the other hand, for other acoustic tubes, for example, if the length of the acoustic tube is 1/2, a half wavelength is placed in the acoustic tube at the same frequency and is radiated from the front of the speaker unit and the acoustic tube opening. The sounds are added in the same phase due to the half-wave phase delay, and the sound pressure level increases. If the number of acoustic tubes with different lengths is increased and the resonance of the acoustic tubes and the above-mentioned phase delay effect are continuously generated, it is possible to improve the radioactivity over a comprehensive wide band. Further, an acoustic filter that blocks unnecessary sound in the middle and high frequencies on the back surface of the speaker radiated from the acoustic tube is provided in one shared acoustic tube. Therefore, it is possible to reduce the sound pressure level emitted from the acoustic tube in the mid-high range without damaging the bass range characteristics, to prevent interference with the sound in front of the speaker unit, and to reduce the sound pressure disturbance. It is possible.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially cutaway perspective view of a speaker system according to an embodiment of the present invention. In FIG. 1, reference numeral 5 is a cabinet, and 6a to 6h are partition plates, which constitute two acoustic tubes having different lengths in the middle of the cabinet 5 and one acoustic tube shared at the exit thereof. 7
Is an opening of the acoustic tube, 8 is a speaker unit, and 9 is a partition plate 6a.
It is an acoustic filter provided in one shared acoustic tube composed of ~ 6h, and is composed of a drone cone composed of a shielding plate 10, a diaphragm 11 and a suspension 12. Further, the solid line arrow indicates the flow of sound passing through the longer acoustic tube, and the broken line arrow indicates the flow of sound passing through the shorter acoustic tube.

The operation of the speaker system configured as above will be described below.

First, the partition plates 6a to 6h in the cabinet 5 constitute two acoustic tubes having different lengths continuously extended from the back surface of the speaker unit 8 and one acoustic tube shared at the exit thereof. At a frequency of ₁ with one wavelength on the acoustic tube, the sound on the front surface of the speaker unit 8 and the sound radiated from the opening of the shared acoustic tube have opposite phases, and as shown in FIG. Cause By selecting the length of the short acoustic tube, the acoustic characteristic is such that the valley of the sound pressure of the long acoustic tube is canceled, and in this embodiment, ₁ is 3/4.
As shown in Fig. 2, by using a tube length with a wavelength
It is possible to flatten the sound pressure characteristics in the low frequency range, and to greatly expand the reproduction band.

FIG. 3 shows a mechanical system equivalent circuit of the speaker system. In the figure, F is the driving force, Z _S is the impedance presented by the speaker unit 8, Z _H1 is the impedance presented by the short acoustic tube, Z _H2 is the impedance presented by the long acoustic tube, and C is the acoustic filter 9 and the above-mentioned length. Compliance exhibited by the spaces formed at the outlets of two different acoustic tubes, M is a reactor tank exhibited by the mass of the diaphragm 11 of the drone cone. Since the compliance exhibited by the suspension 12 is designed to be extremely large, it is ignored in the equivalent circuit. It operates as a high-frequency cutoff filter having an arbitrary cutoff frequency according to the values of C and M, and since the mass of the diaphragm 11 acts as a reactance component, when the frequency of the sound passing through the drone cone becomes high, The impedance becomes large, the high frequency range component flows to the compliance C, and the sound pressure level radiated from the common acoustic tube opening 7 becomes extremely attenuated. As shown in FIG. Only the sound on the front surface is radiated, and a flat sound pressure characteristic can be obtained.

On the other hand, in the low frequency range, the impedance presented by the diaphragm 11 is small and the presence of the acoustic filter 9 can be ignored, so that the low frequency range component is radiated from the opening 7 without impairing the operation of the two acoustic tubes having different lengths. It is a thing.

Although the drone cone is used as the acoustic filter 9 in the embodiment of the present invention shown in FIG. 1, it is smaller than the cross-sectional area of the shared acoustic tube attached to the shield plate 13 as shown in FIG. By providing the port 14 having a cross-sectional area, it is possible to configure the acoustic filter 9 by using the reactance exhibited by the air mass of the port 14, and to simplify the structure than the acoustic filter 9 using the drone cone. Is something that can be done.

In this embodiment, the acoustic tube has a constant cross-sectional area. However, if the acoustic tube has a horn shape in which the cross-sectional area increases toward the opening, the sound pressure level increases due to the horn effect, and the bass range increases. It is possible to improve the radioactivity rate at.

Effect of the Invention As described above, according to the present invention, a plurality of acoustic tubes continuously extending from the back surface of the speaker unit and having different lengths are arranged in parallel with respect to the traveling direction of the sound. By combining the outlets of the two tubes to form a single continuous acoustic tube that extends continuously, resonance of the acoustic tube is continuously generated, and the sound pressure characteristic is flattened over a wide range of bass. By providing an acoustic filter that blocks high frequencies in the shared acoustic tube, the bass enhancement effect of the acoustic tube is maintained as it is, and only the middle and high frequencies are
The sound pressure level radiated from the acoustic tube is greatly attenuated to eliminate the interference with the mid-high range sound radiated from the front of the speaker unit. Compared to the past, the sound pressure characteristic has less peaks and valleys and there is no deterioration in sound quality. The system can be realized.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of an embodiment of the speaker system of the present invention, FIG. 2 is a sound pressure frequency characteristic diagram of the speaker system, and FIG. 3 is a mechanical system equivalent circuit diagram of the speaker system. FIG. 4 is a perspective view showing another embodiment of the acoustic filter, FIG. 5 is a structural sectional view of a conventional speaker system, and FIG. 6 is a sound pressure frequency characteristic diagram of the same speaker system. 5 ... Cabinet, 6a-6h ... Partition plate, 7 ... Opening,
8 …… Speaker unit, 12 …… Vibration plate, 14 …… Port.

Claims (4)

[Claims] 1. A plurality of acoustic tubes having different lengths continuously extended from the rear surface of a speaker unit are arranged in parallel with respect to a sound traveling direction, and the respective outlets of the acoustic tubes are coupled to each other. Further, one shared acoustic tube extending continuously is formed, and at least one acoustic filter for blocking unnecessary mid-high range emitted from the acoustic tube is provided in the shared acoustic tube. Characteristic speaker system. 2. The speaker system according to claim 1, wherein the acoustic tube has a horn shape whose cross-sectional area increases as it goes to the opening. 3. The acoustic filter according to claim 1, wherein the acoustic filter is composed of a shield plate and a drone cone composed of a vibrating plate supported by a suspension provided in a central portion of the shield plate. Speaker system. 4. The speaker system according to claim 1, wherein the acoustic filter comprises a port having a cross-sectional area smaller than that of the shared acoustic tube.