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[Industrial field of application] The present invention is directed to a loudspeaker having
directivity, in which a strong sound pressure can be obtained in a specific direction by arranging
a plurality of loudspeakers at an appropriate distance so that the interference of the acoustic
waves can be obtained. It relates to the improvement of the device. 2. Description of the Related
Art As a conventional speaker apparatus having this kind of directivity, it is known that the I.
Enzoile system of FIG. 2 in which a large number of speakers are arranged in a line. (Problems to
be Solved by the Invention) In this tone-raylay system, as shown in FIG. 3, since the speakers sp
are arranged in a row at a predetermined distance d apart, the sound pressures from the two
speakers sp P. The frequency f is d1π / 2 (π1 wavelength) in the PIIO direction from 90 ° to
90 °. Since the phase difference is 90 degrees in this case, the two cancel each other, and the
sound pressure becomes zero. And the central axis P. In order to strengthen each other, a peak of
sound pressure gel is generated, and the central axis P. At an angle Pθ between P and 0 in the
90 ° direction and from P0 to Pqo, the angle becomes weaker from P o to P q o, and the
directivity shown by the solid line in FIG. 4 is obtained. However, the frequency f of the speaker
sp. P, when -d 1 π. In order to reinforce each other, the directivity characteristics as shown by
the dotted line in FIG. 4 are obtained. For this reason, the speaker apparatus of the 2M 1-n-ray
system has the directivity shown by the solid line 8 in FIG. 5 in the middle range, and the
directivity shown by the dotted line B in the low range. It was not obtained. In addition, since the
distance between the speakers sp or d = − · π / 2 is required, there is also a drawback that the
entire apparatus becomes large. In addition to this, although parame- tial lysopic power using
highly directional ultrasound has been put to practical use, it is difficult to obtain a large sound
pressure response, as it needs an ultrasound generation device (modulation device). In addition,
there is a problem such as the reproduction of the low range or the difficulty in principle and it
has not been widely spread. SUMMARY OF THE INVENTION The present invention eliminates the
above-mentioned drawbacks of the conventional loudspeaker apparatus having directivity by a
plurality of loudspeakers, and can ensure sufficient directivity in the low frequency range even if
the arrangement interval of the loudspeakers is narrow. An object is to provide a speaker device
having directivity. SUMMARY OF THE INVENTION The present invention relates to a loudspeaker
apparatus having poor directivity to achieve the above-mentioned object, wherein a low-pass
filter of -12 dB per octave is applied at a cross-over frequency fc and an interval d of wavelengths
of fc. , A high-pass filter with the same attenuation characteristics is provided at the center of the
two sets of first speakers, and the two sets of second speakers are arranged at intervals of d and
/ 4, at least The first speaker is housed in a back open type cabinet.
An embodiment of the invention will now be described with reference to FIG. The low-range
speakers 1 and 1 'and the high-range speakers 2 and 2' are the same as the wavelength λc of
the crossover frequency fc with respect to the hash plate 3, and the spacing d1 and λC / 4 = (the
spacing d2 of (II / 4) The phase adjusting plate 4 or hl in the forward direction and h2 in the
backward direction are provided on the hanful plate 3. Then, the crossover frequency f of the low
range speaker 1 'and the high range speaker 2 and 2'. On the other hand, the low frequency
range reproduction limit frequency f7! をf1! −f7! If you set it to / 4, set it to the next
dimension. 輔 -1 200 sound receiving point P. からスピーカーまでのf? Ij. U: I [ρ 1, P from the
back of the speaker. Distance (dotted line in Fig. 1)! If it is 2, d (g '' '' l.z f2 + = 1---λ p I! 2-n, -1------λ p λ p :: fp wave length and low frequency band speaker, low pass filter to 1 is [C at -6 dB, 2
fc at -18 dB, for high frequency band The high pass filters to the loudspeakers 2, 2 'have an
attenuation characteristic of 12 clB per octave of fc-5 d Il, 2 L-18 dll. When this setting is made,
when considering the low frequency range speaker 1 and the high frequency range speaker 2 on
one side, the frequency f. On-axis sound pressure P at. Therefore the sound pressure P, in the
direction of 90 degrees. Is the distance from the front of the low-range speaker 1 to the point p,,
o of 90 degrees and 10! 4 ・ Point P of 90 degrees 7 from the rear face of the low frequency
range speaker 1. Therefore, in the case of h 1 ′ ′ ′ ′ hz, ° C, シ C, and therefore for the 90
° direction, as in the case of f, then f − 2 f p − f c / 2 In, d, corresponds to 3/4 λ p, so that the
axis "two sound pressure P. Is old as in the case of equation (1), and then, at f = fC, dρ
corresponds to 3 / 2λ2, so that the axis 20 sound pressure P. Because of this, it will be
directional because it will be shorter in wavelength. The directivity factor D representing this
directivity is represented by kasin θJ 1; the first-order Hessel function in a pis ··· disk of radius a.
For example, in the case of a position inclined by θ from the axis, for example 90 degrees, that
is, at a position a, it is possible to sufficiently attenuate the sound from the rear surface from the
speaker 1 at fc. The upper sound pressure is almost only the sound from the front. At f> 2 fc, the
directivity characteristic of the speaker 2 itself on the high-pitch range side attenuates naturally.
Therefore, it is possible to realize a spin device having a sharp directivity over the whole range.
[Effects of the Invention] In the present invention, as in the second embodiment, the attenuation
characteristics at the crossover frequency, the distance between two pairs of two speakers, and
the low range speaker are stored in a cabinet with an open rear surface. By doing this, sharp
directivity can be obtained over the entire sound range. The spacing of the speakers on the low
frequency side is sufficient for the spacing of the wavelength of the "1" speaker frequency, and
downsizing of the entire speaker apparatus can be achieved, and in the conventional speaker
apparatus having directivity by a plurality of speakers It has an effect that the directivity of the
low range which was difficult can be obtained.
Brief description of the drawings
Fig. 1 is an explanatory view of the principle of one embodiment of the present invention, Fig. 2
is an explanatory view of the principle of the conventional 1 ・-ヅ ヅ ile system, Fig. 3 is an
explanatory view of sound pressure of two speakers, and Fig. 4 is its polar coordinates. 5 is a
display diagram of directivity characteristics according to the fifth embodiment, and is a display
diagram of directivity characteristics by polar coordinates according to the fifth embodiment.
1, 1 '... speaker for low frequency range, 2, 2' ... speaker for high frequency range, 3 ... full plate,
4 ... phase adjusting plate. 0 ° Fig. 4 Fig.