JPS6228920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve sound quality and clarity 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 purpose of this invention is to suppress disturbances in radiation impedance and flatten the frequency characteristics of a horn speaker capable of reproducing sound with high fidelity.

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. Figures 1a and 1b show a conical horn disclosed in Japanese Unexamined Patent Publication No. 12724/1983. This horn has a straight sidewall curve and is a combination of two conical horns. However, this horn has the disadvantage that the radiation impedance is greatly disturbed.

Figure 2a shows the wall shapes of typical horns, such as the exponential, conical, and Petssel horns, and Figure 2b 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. 2b, as n becomes smaller, the disturbance in the radiation impedance becomes larger, and the disturbance in the radiation impedance of the conical horn is the largest.

The present invention eliminates the above-mentioned conventional drawbacks, and will be described in detail below.

First, we performed a simulation of the directivity of a rectangular horn with a straight sidewall curve. this is,
As shown in Figure 3, Wolb&
This was done using Malter's formula.

Here, 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), and k=2πf/c.

The calculation results performed using the above formula are shown in FIGS. 4 and 5. FIG. 4 shows the case where the tangential angle of the aperture is changed, and FIG. 5 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 the directivity control factor in this band, We hypothesized that the tangent angle would be approximately √3θ. A horn was created based on this temporary structure and the results of actual measurements are shown in FIG. As is clear from FIG. 6, in the Besselhorn, by setting the tangent angle of the aperture to approximately √3θ, the directivity angle in the low range becomes θ, and the hypothesis has been verified.

In addition, as a result of making a horn with the tangential angle of the horn opening between 1.5θ and 2.0θ and actually measuring it, it was confirmed that the directivity angle in the low range was also θ. and,
I found that the best result was when I set it to √3θ.

The shape of the horn in one embodiment of the present invention is shown in FIGS. 7a and 7b. FIG. 7a shows the shape in the vertical direction, and FIG. 7b shows the shape in the horizontal direction.

The horn of this embodiment has four wall surfaces 1, 2, 3, 4.
If the horizontal and vertical directivity angles are equal, the connection angle of the side wall at the horn opening is approximately √3θ
shall be. 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 x from the throat α : Spreading coefficient (different between n ₁ part and n ₂ part) 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 , then θ from the throat
The curve is such that the change in cross-sectional area becomes hyperbolic up to point B in _{the H} direction. Also in this direction, the side wall curve changes from n ₁ to n ₂ at point c. 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 the eighth section.
Shown in Figures a and b. Furthermore, the radiation impedance and frequency characteristics are shown in FIGS. 9a and 9b. In FIGS. 9a and 9b, 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.

Figure 10 shows a comparison of the frequency characteristics of the present invention and the case where the change in cross-sectional area from the throat _{to two} points of distance l from the aperture on the center axis of the horn is taken as the exponential. Since the load is often applied in the low range, the frequency characteristics are flat.

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 hyperbolic, and the load will be applied quickly near the cut-off frequency, which will reduce the sound pressure. The flatness of frequency characteristics is improved. 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.

The present invention has the above configuration, and 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 there is little disturbance in the radiation impedance characteristics, so the sound pressure distribution does not vary greatly depending on the frequency. This has the advantage that the characteristics are flat.

[Brief explanation of the drawing]

Figures 1a and b are horizontal and vertical cross-sectional views, respectively, of the horn of a conventional horn speaker, Figure 2a is a half-sectional view of various horns, Figure 2b is a radiation impedance characteristic diagram of the same various horns, and Figure 2b is a diagram of the radiation impedance characteristics of the various horns. Fig. 3 is a diagram showing an arcuate line sound source model, Figs. 4 and 5 are directivity angle characteristic diagrams in the arcuate line sound source model shown in Fig. 3,
FIGS. 6a and 6b are a half-sectional view and a directivity angle characteristic diagram of a horn, FIGS. 7a and b are a vertical sectional view and a horizontal sectional view of a horn speaker in an embodiment of the present invention,
Figures 8a and b are directional characteristics diagrams of the same horn speaker.
9a and 9b are radiation impedance characteristics and sound pressure frequency characteristic diagrams of the same horn speaker, and FIG. 10 is a characteristic diagram of the speaker. 1, 2, 3, 4...Wall surface.

Claims (1)

[Claims] 1. A horn comprising four walls 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, Each wall surface curve of one opposing wall surface 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 expressed by the following equation, a=a ₀ (1+αx) ⁿ a ₀ : Dimension of throat a : Dimension of cross section at distance x from throat α : Value of spread coefficient n is n ₁ (n ₁ ≧ 2) on the opening side of the horn, n on the throat side ₂ (n ₂ > 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 defined as hyperbolic. Features a horn speaker.