JPS6311840B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a method for improving sound quality depending on the listening position when creating a uniform sound field for a large number of listeners in indoor and outdoor sound reproduction such as halls, station premises, and grounds. The present invention relates to a horn speaker capable of reproducing high-fidelity sound with no difference in clarity.

Prior Art Conventional horns include radial horns, conical horns, and the like. Radial horns are designed so that the wavefront forms an arc in the horizontal plane, and this arc-shaped wavefront propagates concentrically inside the horn, so it radiates directly from the aperture surface without any directivity. Although it has excellent directivity, it has the disadvantage that it is not good in the vertical direction. Also, conical horns have excellent directivity in the horizontal and vertical directions, but
The disadvantage is that the radiation impedance characteristics are disturbed. FIGS. 8a and 8b show a conical horn disclosed in Japanese Patent Application Laid-Open No. 12724/1983. This horn has a straight sidewall curve and is a combination of two conical horns.

Problems to be Solved by the Invention However, the above-described conventional horn has the drawback of large disturbance in radiation impedance.

Figure 9a shows the wall shapes of typical horns, such as the exponential, conical, and Bessel horns, and Figure 9b shows their radiation impedance characteristics.
Shown below. These horns are expressed as the general formula of Webster's Bessel horn as shown below.

S _M = S _O (1 + αX) ⁿ S _M : Cross-sectional area of the cut S _O : Cross-sectional area of the throat α: Spreading coefficient In between is Bethusel.

As is clear from FIG. 9b, as n becomes smaller, the disturbance in the radiation impedance becomes larger, and the problem is that the disturbance in the radiation impedance of the conical horn becomes the largest.

In view of the above conventional problems, the present invention aims to suppress disturbances in radiation impedance and flatten frequency characteristics.

Means for Solving the Problems In order to achieve the above object, the present invention includes a horn consisting of four walls in which the target pointing angle θ _H in the horizontal direction and the target pointing angle θ _V in the orthogonal direction are in different relationships. Then, each wall surface curve of one opposing wall surface of the horn that faces each other and each wall surface curve of the other opposing wall surface of the horn that faces each other up to a distance l ₂ from the opening on the central axis of the horn are as follows. It is expressed by the formula, a=a ₀ (1+αX) ⁿ _{a 0} : Dimension of throat a : Dimension _of cross section at distance ), is a combination of functions with n ₂ (n ₂ > n ₁ ) on the throat side,
When the target pointing angle is 2θ, the tangential angle of the horn aperture is set to 1.5θ to 2.0θ, and the change in cross-sectional area from the throat of the horn to the distance _l from the aperture is calculated from the throat of the horn to the aperture. The horn has a straight shape, and within the straight shape, a partition wall having a shape such that the change in cross-sectional area is exponential is arranged in parallel and connected to one opposing wall surface of the horn.

Effects The present invention has the above-described configuration, so that the sound pressure distribution does not vary greatly depending on the frequency, the sound quality is uniform depending on the listening position, and the frequency characteristics are flat because there is little disturbance in the radiation impedance characteristics. be.

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

First, we performed a simulation of the directivity of a rectangular horn with a straight sidewall curve. this is,
As shown in Figure 4, Wolb&
This was done using Malter's formula.

However, R〓 is the directivity coefficient of the angle α, r is the radius of curvature, d is the length of the line sound source divided into (2m + 1),
K=2πf/c.

The calculation results performed using the above formula are shown in FIGS. 5 and 6. FIG. 5 shows the case where the tangential angle of the aperture is changed, and FIG. 6 shows the case where the arc radius r is changed. From this result, it can be seen that in the low range, the aperture angle and the directivity angle match at the frequency where Ka≒1.89/sinθ. Furthermore, the directivity angle approaches the aperture angle at high frequencies. In order to make the directivity angle uniform, the directivity angle in the low range centered around Ka≒450/2θ is approximately θ/√3, but the horn aperture, which is a directivity control factor in this band, We hypothesized that the tangent angle would be approximately √3θ. A horn was created based on this hypothesis and the results of actual measurements are shown in FIG.
As is clear from Fig. 7, in the Besselhorn, by setting the tangent angle of the aperture to approximately √3θ, the directivity angle in the low range becomes θ.
The hypothesis was proven.

In addition, the tangential angle of the horn opening is 1.5θ to 2.0θ,
As a result of making a horn and actually measuring it, it was confirmed that the directivity angle in the low range is θ. And √3
We found that the best results were obtained when θ was set.

The horn shape of a horn speaker in an embodiment of the present invention is shown in FIGS. 1a and 1b. FIG. 1a shows the shape in the vertical direction, and FIG. 1b shows the shape in the horizontal direction.

The horn of this embodiment has four wall surfaces 1, 2, 3, 4.
and a partition wall 5, and when the directivity angles in the horizontal and vertical directions are equal, the connecting angle of the side walls at the horn opening is approximately √3θ. Each side wall curve of the horn is expressed as a function of a = a ₀ ( ₁ + αX) ⁿ a ₀ : Throat dimension a : Cross _- sectional dimension at distance and the value of n is n ₁ (n ₁ ≧
2) is a combined form with n ₂ (n ₂ > n ₁ ) on the throat side. Point A is determined by the flatness of the deviation of the directional characteristics.

On the other hand, if the horizontal directivity angle θ _H and the vertical directivity angle θ _V are different, the longer the directivity angle, the shorter the length. If θ _V < θ _H , the change in cross-sectional area from the throat to point B in the θ _H direction is a straight shape, and within that straight shape, a partition wall 5 with a shape such that the change in cross-sectional area is exponential is provided on the wall surface. These are arranged in parallel and connected to the vertical upper and lower walls 1 and 2. Also, in the portion extending from point B to the opening side, the side wall curve changes from n ₁ to n ₂ at point C. Note that point C is determined by the flatness of the deviation of the directivity angle characteristics.

The directional characteristics of the horn speaker according to the present invention are
Shown in Figures a and b. Furthermore, the radiation impedance and frequency characteristics are shown in FIGS. 3a and 3b. In FIGS. 3a and 3b, solid lines indicate the present invention, and broken lines indicate the conventional conical horn.

In this example, 2θ _V = 40° and 2θ _H = 90° are selected, and within these ranges, the sound pressure distribution does not vary greatly depending on the frequency, nor does it vary greatly depending on the listening position. , which indicates that the sound quality is uniform depending on the listening position. Furthermore, since there is little disturbance in the radiation impedance characteristics, this indicates that the frequency characteristics are flat.

In addition, as shown in Figure 7b, the side wall shape from the _two points on the center axis of the horn to the throat is straight, and the opposing wall surfaces are parallel, making it easy to manufacture the horn itself. Become.

By making the cross-sectional area change on the throat side different from the wall curve on the opening side in this way, the radiation impedance of the horn will be less disturbed if the cross-sectional area change is exponential or hypobolic, and the load will be faster near the cutoff frequency. This improves the flatness of the sound pressure frequency characteristics. Furthermore, since the directivity is controlled, the sound pressure distribution does not vary greatly depending on the frequency, and the sound quality has the advantage of being uniform depending on the listening position.

Effects of the Invention As described above, according to the present invention, the sound pressure distribution does not vary greatly depending on the frequency, the sound quality is uniform depending on the listening position, and the frequency characteristics are flat because there is little disturbance in the radiation impedance characteristics. This has the following advantages.

Further, since the side wall shape is straight for a predetermined length from the horn opening, and the opposing wall surfaces are parallel, the horn itself can be manufactured easily.

[Brief explanation of the drawing]

FIGS. 1a and 1b are vertical and horizontal sectional views of a horn speaker according to an embodiment of the present invention, and FIG.
Figures a and b are directional characteristics diagrams of the same horn speaker.
Figures a and b are radiation impedance and sound pressure frequency characteristic diagrams of the same horn speaker, Figure 4 is a diagram showing the arcuate line sound source model, and Figures 5 and 6 are the directivity in the arcuate line sound source model shown in Figure 4. FIGS. 7a and 7b are a half-sectional view of the horn and a directivity angle characteristic diagram; FIGS. 8a and b are horizontal and vertical sectional views of the horn of a conventional horn speaker, respectively;
Figure a is a half-sectional view of various horns, and Figure 9b is a radiation impedance characteristic diagram of the various horns. 1, 2, 3, 4...Wall surface, 5...Partition wall.

Claims (1)

[Claims] 1. A horn comprising four wall surfaces in which the target pointing angle θ _H in the horizontal direction and the target pointing angle θ _V in the vertical direction have different relationships, and the horns face each other. Each wall surface curve of one opposing wall surface and each wall surface curve of the other opposing wall surface of the horn from the opening to a distance l ₂ on the central axis of the horn are expressed by the following formula, a=a ₀ (1+αX) ⁿ a ₀ : Throat dimension a : Cross-sectional dimension at distance _X from the throat _α : _{Spreading coefficient} ＞n ₁ ),
When the target pointing angle is 2θ, the tangential angle of the horn aperture is set to 1.5θ to 2.0θ, and the change in cross-sectional area from the throat of the horn to the distance _l from the aperture is calculated from the throat of the horn to the aperture. A horn characterized in that the horn has a straight shape, and a partition wall having a shape such that the change in cross-sectional area is exponential is arranged in parallel within the straight shape and is connected to one opposing wall surface of the horn. speaker.