JPS6121917Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention relates to the improvement of a speaker system.
The purpose is to flatten the energy (acoustic power) in the listening space of the speaker system.

A conventional speaker system consists of a woofer (bass speaker) and tweeter (treble speaker)
Regarding a two-way type speaker equipped with a speaker, in FIG. The radial axis of 2 coincides with the front direction of the cabinet.

Electric signals divided into bands that can be reproduced by each speaker are applied to the woofer and tweeter by a network circuit (not shown).

Figure 2 shows the frequency characteristics of the input signal divided by the network circuit, 21 is the woofer input signal,
22 indicates the tweeter input signal, and in order to flatten the overall frequency characteristics, it is usually configured so that each input level is attenuated by 3 dB at the frequency _c (crossover frequency) where the characteristics of both input signals intersect. .

However, the above characteristics are due to only the direct sound on the radiation axis in an anechoic chamber, and in the room where the user actually uses the room, the user hears not only the above direct sound but also indirect sound due to reflections from the ceiling, walls, etc. There is.

Therefore, when actually designing a speaker system, it is preferable to make sure that the sound pressure of the sum of the direct sound and indirect sound is constant regardless of the frequency, but as is well known, speakers As the playback frequency becomes higher, the directivity becomes sharper, and as a result, the amount of indirect sound decreases as the playback frequency becomes higher.

If we consider this in terms of acoustic power (integral value of the sound pressure level on a spherical surface centered on the sound source), we find that the third
As shown in the figure, the acoustic power value begins to decrease as shown in FIG. 331 from the frequency at which directivity begins to appear.

This frequency ₁ has been determined from various experiments as ₁ = (0.5~
0.6) c/2πa ₁ (where c: speed of sound, a ₁ : effective vibration radius of the woofer).

Therefore, the acoustic power in the conventional two-way speaker system is as shown in Fig. 33.
Unable to obtain flat characteristics.

This is undesirable in terms of auditory sense, as it causes phenomena such as sound dropout.

A similar phenomenon (Fig. 3, 32) also occurs with tweeters, which has the disadvantage of insufficient reproduction of high-pitched sounds.

Therefore, this invention increases the indirect sound in the frequency band where the acoustic power level decreases,
The system is equipped with a compensating speaker that reproduces only the above-mentioned frequency band and radiates it to the rear of the cabinet to increase indirect sound mainly due to reflection from the rear wall.Examples will be described in detail below.

In FIG. 4, 1, 2, and 3 are the same as those shown in FIG.

Reference numeral 41 denotes a first compensation speaker disposed in a hole bored in the top plate of the cabinet 3, facing upward from the radiation axis.

Reference numeral 42 designates a shielding reflector plate disposed to cover the opening of the first compensation speaker 41, and is formed into a substantially half-truncated quadrangular pyramid shape with an opening on the surface located at the rear of the cabinet.

Reference numeral 43 denotes a second compensating speaker, and the speaker 43 is arranged so that its radiation axis is oriented in the direction of the outer wall surface of the reflecting plate 42.

The first compensation speaker 41 is connected to an electrical network circuit having a capacitance of _L = (0.5 to 1.0 kHz).
0.6) c/ _2πa1 to _H = _c = (0.5 to 0.6) c/
A frequency component of 2πa ₃ (where c is the speed of sound, a ₁ is the effective vibration radius of the woofer 1, a ₃ is the effective vibration radius of the first compensation speaker 41, _{and c} is the crossover frequency between the woofer 1 and the tweeter 2) is input,
Similarly, the compensation speaker 43 is set to _L =
(0.5-0.6) c/2πa ₂ (where a ₂ is tweeter 2
Frequency components equal to or greater than the effective vibration radius of the input.

According to the above configuration, the direct sound of the woofer 1 and the tweeter 2 and the indirect sound caused by the reflection of the speaker sound from the side wall or the rear wall of the listener can be heard, and the frequency band in which the indirect sound from the speakers 1 and 2 is reduced is heard. At this point, indirect sound from the sounds radiated from the first and second compensation speakers 41 and 43 is superimposed.

That is, the sound emitted from the first compensation speaker 41 is reflected backward by the reflecting plate 42, and further radiated forward by the rear wall of the cabinet 3.
It reaches the listener as indirect sound.

Further, the sound emitted from the second compensation speaker 43 is reflected diagonally backward by the reflecting plate 42, and further reflected forward by the wall surface, reaching the listener as indirect sound.

Therefore, in the frequency band where the indirect sound from the speakers 1 and 2 decreases, the indirect sound from the first and second compensation speakers 41 and 43 is compensated, so that the acoustic power is kept constant over the entire reproduced frequency range. Therefore, it is possible to prevent the sound dropout phenomenon in a specific frequency band as in the conventional example.

Furthermore, first and second compensation speakers 41,
Since the reflecting plate 42 having an inclined surface is disposed on the common radiation axis of the 43, a wide range of diffusion due to reflection can be expected, which has the advantage that a uniform indirect sound field can be obtained.

Furthermore, in the first compensating speaker 41, due to the cavity resonance phenomenon caused by the capacitance of the space surrounded by the reflector 42, together with the action of the network circuit, the radiated sound is extremely effectively limited to the necessary frequency band. Therefore, it is possible to adjust the balance between direct sound and indirect sound. Further, if necessary, a sound absorbing material or the like may be placed inside the reflecting plate 42 to change the frequency characteristics.

Furthermore, the shape of the reflector is not limited to that explained in the above embodiments, but if one with a truncated sphere shape 52 is used, for example, as shown in FIG. Even better.

Furthermore, as shown in FIG. 6, the reflecting plate may be formed into a hemispherical shape 62, and a large number of holes 63 may be bored in the rear surface of the spherical surface to form openings.

In this case, the reproduction frequency characteristics of the first compensation speaker 41 can be changed depending on the size of the hemisphere 62, the size of the hole 63, etc.

As explained above, according to this invention, it is possible to stop the reduction of indirect sound at specific frequencies in the listening space, and it is possible to achieve extremely excellent reproduction without missing sounds, which is extremely useful in practice. This is a great idea.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional speaker system.
Figure 2 is a sound pressure-frequency characteristic diagram, Figure 3 is a sound power-frequency characteristic diagram, and Figures 4, 5, and 6 are perspective views of the speaker system implemented with this invention, viewed from the rear. . 1 is a woofer, 2 is a tweeter, 3 is a cabinet, 41 is a first compensation speaker, 43 is a second compensation speaker, 42 is a reflector, 52 is a quarter-section spherical reflector, 62 is a hemispherical reflector, 63 is a hole.

Claims (1)

[Claims for Utility Model Registration] 1. A cabinet 3 in which a woofer 1 and a tweeter 2 are mounted so that their radiation axes face toward the front.
and the first compensation speaker 41 whose reproduction frequency band ₁ is (0.5 to 0.6) C/2πa ₁ ≦ ₁ ≦ _c = (0.5 to 0.6) c/2πa ₃ and the reproduction frequency band ₂ which is ₂ ≧ (0.5 to 0.6). ) c/2πa ₂ where c: Sound speed a ₁ , a ₂ , a ₃ : Effective vibration radius of woofer, tweeter, and first compensation speaker _c : Second compensation speaker 43 which is the crossover frequency of woofer and tweeter Equipped with
A speaker system characterized by the following configuration. a The first compensation speaker 41 is mounted on the top plate of the cabinet 3 so that its radiation axis faces upward. b A shielding reflector plate 4 having an opening on the rear surface so as to cover the radiation opening of the first compensation speaker 41
It has 2. c. The second compensation speaker 43 is arranged so that the radiation axis is oriented on the outer wall surface of the reflecting plate 42. 2. The speaker system according to claim 1, wherein the reflecting plate has a half-cut square pyramid shape 42. 3. The speaker system according to claim 1, wherein the reflector has a four-truncated sphere shape 52. 4. The speaker system according to claim 1, wherein the reflecting plate has a hemispherical shape 62, and a hole 63 is formed in the rear surface of the spherical surface.