JPH04170298A - speaker system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speaker system having an acoustic tube on the rear surface of a speaker unit.

BACKGROUND OF THE INVENTION One of the conventional techniques for expanding the low temperature range of a speaker system is an acoustic tube system.

Hereinafter, a conventional acoustic tube type speaker system will be explained with reference to the drawings.

FIG. 4 shows a structural sectional view of the above speaker system.

In FIG. 4, 1 is a speaker unit, 2 is a cavity provided on the back side of the speaker unit 1, 3 is an acoustic tube extending continuously from the cavity 2, and 4 is an opening of the acoustic tube 3.

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

Sound emitted from the rear surface of the speaker unit is guided to the acoustic tube and radiated from the opening 4 thereof. An acoustic tube resonates at a specific frequency determined by its length.

If the total length of the acoustic tube is C7 and the speed of sound in the air is C7, then n=o
, 1, 2.・・・・・・n, and when n=o, 1/4 wavelength is carried inside the acoustic tube, causing resonance, and acoustically amplified sound is radiated from the opening 4 of the acoustic tube, and the sound is emitted near the bass reproduction limit. This will greatly improve efficiency. Also, sound tube 1
/2 wavelength, the sound emitted from the front of the speaker unit 1 and the sound from the back of the speaker unit 1, which is originally in reverse phase, are radiated from the opening 4 of the acoustic tube, so that the sound is halved. A phase delay occurs in the wavelengths, which become in-phase and added together, increasing the sound pressure level. Furthermore, when n=2,
Similar to the case where 3/4 wavelength is placed inside the acoustic tube and n=o,
Acoustically amplified sound is radiated from the opening 4 of the acoustic tube. Therefore, it was possible to realize a speaker system with high efficiency in the bass range.

Problems to be Solved by the Invention However, with the length of the acoustic tube configured as described above, the low frequency reproduction limit frequency f. In a speaker system where fo is determined, if you try to lower fo further, you will need to increase the length of the sound tube L to the length determined by L = C/4fo, which will result in a large speaker system. There was an issue.

In view of the above-mentioned problems, the present invention has been developed to
- To provide a speaker system that can extend the low frequency reproduction limit frequency to a lower frequency.

Means for Solving the Problems To achieve this object, the speaker system of the present invention comprises a cavity provided at the back of a speaker unit and an acoustic tube continuously extended from the cavity, The opening area of the tube was configured to be reduced by multiplying the area by a value larger than O and less than 1.

Effect: With this configuration, an acoustic mass is added to the opening of the sound tube, and the mass component in the resonance system of the sound tube increases, and the resonance frequency shifts to a lower frequency. Therefore, in the present invention, the lowest resonant frequency of the conventional acoustic tube, which has a wavelength of 4 times the length of the acoustic tube, is moved to an even lower frequency, so the low-frequency reproduction limit frequency of the sound pressure is It can be extended to lower frequencies without changing the length of the acoustic tube.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a structural cross section of a speaker system according to an embodiment of the present invention. In Figure 1, 5
is a speaker unit, 6 is a cavity provided on the back side of the speaker unit 5, 7 is an acoustic tube extending continuously from the cavity 6, and 8 is a numerical value greater than 0 and less than 1 for the cross-sectional area of the acoustic tube 7. The aperture is narrowed down to an area multiplied by .

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

Sound radiated from the rear surface of the speaker unit 5 is guided to the acoustic tube 7 and radiated from the opening 8 therebetween. At this time, although the aperture area is not narrowed down, the operation is as described in the conventional example. In addition, in the case where the aperture area is narrowed down as in this example, acoustic mass is added by narrowing down the aperture, as shown in the frequency characteristic diagram of the radiation impedance of the acoustic tube in Figure 2. , the resonant frequency of the acoustic tube moves to a lower frequency. Therefore, as shown in the sound pressure characteristic diagram of FIG. 3, the bass reproduction limit frequency moves to a lower frequency band.

In this embodiment, the acoustic tube is a straight tube, but it may also be a horn-shaped tube whose cross section gradually widens from the throat toward the opening due to an exponential or other function.

Effects of the Invention The present invention can be realized with an excellent speaker system that can achieve the effect of moving the bass reproduction limit frequency to a lower frequency by narrowing down the opening area of the acoustic tube.

[Brief explanation of the drawing]

-〇- Fig. 1 is a diagram showing a structural cross section of a speaker system according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing acoustic impedance when viewed from the throat side of the acoustic tube to the opening side, and Fig. 3
The figure is a sound pressure characteristic diagram of a speaker system according to an embodiment of the present invention and a conventional example, and FIG. 4 is a diagram showing a structural cross section of the speaker system according to a conventional example. 5...Speaker unit, 6...Empty room, 7...Acoustic tube, 8...Opening.

Claims (4)

[Claims] (1) A speaker system comprising a cavity provided on the back side of a speaker unit and an acoustic tube continuously extending from the cavity, and characterized in that the area of the opening of the acoustic tube is narrowed. (2) The speaker system according to claim 1, wherein the cross-sectional area of the acoustic tube gradually increases from the throat toward the opening. (3) The distance of the acoustic tube from its throat to the opening is
When the cross-sectional area at is S_x, the throat area is S_t, the opening area is S_m, and the pipe length is l, then
2. The speaker system according to claim 1, wherein the speaker system is an exponential horn having a shape represented by: m/St)}. (4) The speaker system according to claim 1, wherein the aperture ratio α of the area of the opening satisfies 0<α<1.