JPH0453398A - Speaker system - Google Patents

Abstract

PURPOSE:To reproduce sound with a flat sound pressure characteristic over a broad band by selecting a diaphragm area, its mass and its torque of 1st and 2nd speakers so that they satisfy a specific condition equation. CONSTITUTION:A 1st speaker having a large diaphragm 1 is arranged to a front face of a cabinet 7 and a 2nd speaker having a diaphragm 8 whose area is smaller than that of the 1st speaker is arranged to a rear part of the diaphragm 1 of the 1st speaker through an enclosed SPACE. Let a diaphragm area be S1 (S2), a torque produced in a voice coil be F1 (F2), and a weight of the diagram be M1, (M2) of the 1st (2nd) speaker constants, then they have a relation nearly shown in equation I. Thus, the sound is reproduced with a flat characteristic over a broad band.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speaker system that reproduces high efficiency and flat characteristics from low frequencies despite having a small and thin cabinet.

BACKGROUND OF THE INVENTION In recent years, there has been a strong demand for speaker systems to be made thinner and smaller, and moreover, there has been a demand for reproduction down to low frequencies.

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

FIG. 4 shows a structural cross-sectional view of a conventional speaker system for the above purpose. In the figure, 1 is a diaphragm,
2 is a voice coil coupled to the diaphragm 1, 3 is a damper 4 coupled to the voice coil 2 is a magnetic circuit, 5 is a speaker frame, 6 is a free edge coupled to the periphery of the diaphragm, and 7 is a cabinet. .

The operation of the speaker system made up of the above-mentioned components will be explained below.

When an electric signal is applied to the voice coil 2 provided in the magnetic gap of the magnetic circuit 4, the voice coil 2
A driving force is generated to drive the diaphragm 1, and a sound wave is generated. Since the speaker system shown in FIG. 4 is of a closed type, the sound pressure/impedance frequency characteristics of this speaker system are as shown in FIG. 5. Human is a sound pressure frequency characteristic, and B is an impedance frequency characteristic. The lowest resonant frequency f determines the low frequency reproduction limit frequency of the speaker system. It is represented by . Here, M is the mass of the vibration system, MA is the acoustic additional mass, S□ is the stiffness of the vibration system, and SM
B is the internal volume of the cabinet VB and the vibration area SD of the diaphragm
The stiffness is determined by And S□ and V1
, the relationship between SD is as follows. ρ0 is the density of air, and C is the speed of sound.

Problems to be Solved by the Invention However, with the above configuration, the internal volume VB of the cabinet is limited, and in a speaker system with a large diaphragm area S, the stiffness SMB of the cabinet is limited.
becomes large, making it difficult to reduce the lowest resonant frequency fo. In other words, in a speaker system where the internal volume of the cabinet VB is small, the stiffness S of the vibration system
The cabinet spacing SMB is larger than MS, and equation (1) becomes as follows. The mass M of the vibration system affects the efficiency, so it cannot be made unnecessarily large, and the minimum resonant frequency f. In order to lower the SMB, it was necessary to reduce the area of the diaphragm.

However, reducing the area of the diaphragm requires increasing the vibration amplitude in order to obtain the same sound pressure level, resulting in an increase in distortion due to nonlinearity of the support system. Furthermore, the area of the diaphragm also affects the richness of the bass during bass reproduction; using a large-area diaphragm will reproduce rich bass, but using a large-area diaphragm will inevitably result in stiffness of the cabinet. increases, and the lowest resonant frequency f. Until now, it has not been possible to increase the area of the diaphragm because the diaphragm area becomes larger and the bass frequencies are not reproduced.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a speaker system that reproduces rich bass sounds using a large-area diaphragm even when the speaker system has a cabinet with a small internal volume.

Means for Solving the Problems In order to achieve this object, in the speaker system of the present invention, a first speaker having a large diaphragm is arranged at the front of the cabinet, and a closed speaker is placed at the rear of the diaphragm of the first speaker. In this configuration, a second speaker having a diaphragm having a smaller area than the first speaker diaphragm is arranged via a space between the two speakers.

Effect: The present invention allows the lowest resonance frequency of the speaker system to be determined by the second speaker diaphragm and the internal volume of the cabinet, and the second speaker diaphragm can be freely selected to be small, thereby lowering the bass reproduction limit. be able to. Since the sound field to be reproduced can be reproduced by a diaphragm with a large area, rich bass reproduction is possible.

By selecting the driving force for driving the first speaker and the second speaker as shown in the claims of the present invention, the characteristics of the speaker system of the present invention can be reproduced with flat characteristics over a wide band.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a structural sectional view of a speaker system according to a first embodiment of the present invention. Note that the same reference numerals are used for the same components as those shown in FIG. 4 of the conventional example. In the figure, ■
is a diaphragm of the first speaker, which is disposed at the front of the cabinet 1-7 and supported by the free edge 6. At the center of the back of the diaphragm 1 is a voice coil 2 of a first speaker.
The voice coil 2 is connected to the frame 5 by a damper 3. and voice coil 2
is adapted to be driven by the magnetic circuit 4 of the first speaker.

The frame 5 forms a sealed space between the diaphragms 1 of the first speaker, and the diaphragm 8 of the second speaker is supported on the frame 5 by a free edge 12. The second speaker includes a voice coil 9, a second speaker damper 10, a magnetic circuit 11, and a frame 13, respectively. Although two second speakers are arranged in FIG. 1, it may be one, or three or more. It is also desirable to have a symmetrical positional relationship between the first speaker and the second speaker in order to prevent abnormal vibrations from occurring.

Here, the internal volume surrounded by the second speaker and the cabinet 7 is assumed to be 6. Ignoring the load on the first speaker, the lowest resonant frequency f. is the internal volume of the second speaker and space H■3
The resonant frequency is determined by

Here, the fact that no load is applied to the diaphragm of the first speaker means that when the diaphragm of the second speaker moves forward, the diaphragm of the first speaker also moves forward and drives the second speaker. If the volume displacement of the diaphragm obtained by driving the first speaker is set equal to the volume displacement of the diaphragm obtained by driving the first speaker, the space I surrounded by the diaphragm of the first speaker and the diaphragm of the second speaker is This means that compression and expansion will not work. That is, if the driving forces of the first speaker and the second speaker and the relationship between the respective constants are selected so as to satisfy the following, no compression/expansion force will act on the space (2).

However, S1 and Sz are the first. Second speaker diaphragm area,
F1 and F2 are the first. Driving force of the second speaker, M1, M2
is the first. This is the mass of the vibration system of the second speaker.

FIG. 2 is a sound pressure frequency characteristic diagram that does not show how the frequency characteristics change depending on the magnitude of the driving force. (A) is a sound pressure frequency characteristic diagram when the conditions are set to satisfy the above conditions, and (B) is a diagram when the conditions are met. That is, it can be seen that a flat sound pressure frequency characteristic can be obtained over the range. If this conditional expression is selected to satisfy, the first speaker can be ignored, the vibration area of the second speaker diaphragm can be freely selected to be small, and the lowest resonant frequency can also be lowered. It can be seen that the area of the diaphragm of the first speaker that radiates into the sound field can be freely increased as long as the above conditional expression is satisfied. Furthermore, nonlinear distortion in the support system and drive system that occurs due to the increase in vibration amplitude caused by reducing the vibration area of the second speaker is blocked by the low-pass filter formed by the space I and the diaphragm of the first speaker. , has the advantage that it is not radiated from the diaphragm surface of the first speaker.

FIG. 3 shows another embodiment of the invention. This device is characterized by the provision of a connecting bow 1-14 that connects the first connecting space and the second connecting space. In this case, an optimal bass reflex design can be achieved using the second speaker and the internal volume of the cabinet, and the bass range can be expanded and reproduced more than in the sealed system shown in the first embodiment. If the relationship between the diaphragm area, mass, and driving force of the first speaker and the second speaker is similarly selected as follows, it is possible to obtain flat characteristics over a wide band as shown in Figure 2. It is possible. If the positions of the ports are shifted so that one or more ports are provided at symmetrical positions with respect to the first speaker diaphragm, the sound pressure distribution in the space I will be uniform, and a uniform load will be applied to the first speaker diaphragm. It will take a while.

By providing a structure for attaching the second speaker to the frame portion of the first speaker and a structure for attaching the acoustic port, assembly can be easily performed.

In addition, the voice coils of the first speaker and the second speaker are connected in parallel or in series, and the impedance of the voice coil is such that the power applied to the second speaker is greater than the power W applied to the first speaker. If the power W2 is selected to be large, the speaker system can efficiently reproduce low frequencies even in a small cabinet.

Effects of the Invention As is clear from the explanation of the embodiments above, the present invention provides a uniformly rich sound from the low frequency range even in a system in which a large-area diaphragm is attached to a cabinet with a limited internal volume. The sound pressure can be reproduced in the first. By selecting the diaphragm area, mass, and driving force of the second speaker as described in [Claims 2], it is possible to reproduce flat sound pressure characteristics over a wide band.

[Brief explanation of drawings]

Fig. 2 is a sound pressure frequency characteristic diagram of the speaker system, Fig. 3 is a sectional view of another embodiment of the invention, and Fig. 4 is a sectional view of a conventional speaker system. FIG. 5, which is a sectional view of the speaker system, is a sound pressure/impedance frequency characteristic diagram of a conventional speaker system. 1... Speaker diaphragm, 2... Voice coil, 3... Damper, 4... Magnetic circuit, 5... Frame, 6 ...Free Edge, 7...Cashnet, 8...
Speaker diaphragm, 9...Voice coil, 10.
... Damper, 11 ... Magnetic circuit, 12
...Free Edge, 13...Frame, 14...Sound Boat. Name of agent: Patent attorney Shigetaka Awano Haka 1 person 4a-Recommendation 1 and 2, '? --°Horse coil 3.10-・Tan R- 4, ff-1 structure circuit 5.13--・-4 6, tz-11 F-edge diagram [Hr”J Sokyo boat diagram diagram] Chi Q, f (H7)

Claims (5)

[Claims] (1) A first speaker placed on the front part of the speaker cabinet, and one or more second speakers placed on the rear face of the diaphragm of the first speaker, that is, inside the cabinet, The back of the diaphragm and the second
The space I between the speaker and the diaphragm is closed with a frame or the like, and the first and second speaker constants are the diaphragm areas S_1 and S_2, and the driving force generated in the voice coil is F_1. , F_2, diaphragm weight M_1
, M_2, approximately S_1・(F_1)/(M_1)=S_2・(F_2)
A speaker system configured so that /(M_2). (2) A first speaker placed on the front part of the speaker cabinet, and one or more second speakers placed on the rear face of the first speaker diaphragm, that is, inside the cabinet, to vibrate the first speaker. The space I between the back surface of the plate and the diaphragm of the second speaker has a closed structure with a frame, etc., and the closed space I, the back surface of the second speaker, and the inside of the cabinet are connected. A speaker system with an acoustic port that acoustically connects the enclosed space II. (3) The relationship between the diaphragm areas S_1 and S_2 of the first and second speakers, the driving forces F_1 and F_2, and the diaphragm weights M_1 and M_2 is approximately S_1・(F_1)/(M_2)=S_2・(F_2)
3. The speaker system according to claim 2, wherein the speaker system is configured such that /(M_2). (4) One or both of one or more second speakers and an acoustic port that acoustically connects the first space and the second space can be attached to the frame of the first speaker. A speaker system with a structure that allows. (5) connecting the voice coil of the first speaker and the voice coil of the second speaker in parallel or in series;
The power ratio of the electrical input applied to the first speaker and the electrical input applied to the second speaker is W_1<, where W_1 is the power applied to the first speaker, and W_2 is the power applied to the second speaker. The speaker system according to claim 1 or 2, wherein the speaker system is selected to be W_2.