JP5083703B2 - Parallel-arranged air chamber type speaker reproducing device - Google Patents

Description

The present invention relates to a speaker reproducing apparatus for reproducing a rich bass even if it is small.

A conventional bass reflex type speaker reproducing apparatus is a Helmholtz resonance box, and is the most widely used method for reinforcing the low frequency range of the speaker reproducing apparatus.

In the conventional bass reflex system, since there is only one duct, the natural frequency of the duct has to be set higher, and therefore a woofer with a large aperture must be used to reproduce the low sound range. There wasn't.

There is a double bass reflex type as a method for reinforcing the bass range of a general bass reflex type. In the double bass reflex type, an air chamber (corresponding to the back pressure distribution chamber of the present invention) to which the speaker unit is attached is attached with one sub air chamber via a duct, and the sub air chamber is opened to the outside. One duct is provided. Therefore, there are only two resonance frequencies of the duct.
In general, since the interval between the resonance frequencies becomes large, it is difficult to obtain a sufficient sound pressure in the frequency range therebetween.

Patent Document 1 has been proposed as having a structure similar to that of the double bass reflex type. In this method, since the duct of the air chamber to which the speaker unit is attached is opened to the atmosphere, the back pressure of the speaker unit is released to the atmosphere, and other air chambers do not work sufficiently. Further, although there are two sub air chambers, only one of them is connected to the first air chamber, and the concept is different from the present invention.
In addition, there are several non-patent literatures such as Nagaoka's works, such as Non-Patent Documents 1 and 2, but each has a double bass reflex structure in which air chambers are arranged in series and has only two resonance frequencies. It is clearly described in the literature that the reproduction sound pressure level during
JP2003-169386A (P2003-169386A) Tetsuo Nagaoka "Latest Original Speaker Work 20" Tomosha, Music 1986 Tetsuo Nagaoka "Original speaker design technique I have never seen such a speaker" Music Friendship 1996

The problem to be solved is that the conventional double bass reflex speaker reproducing apparatus has only two resonance frequencies, and the band between them is wide, so that the frequency response over the entire low frequency range is not good.

According to the present invention, in the speaker reproducing apparatus, at least two or more sub air chambers are connected in parallel via a duct to an air chamber (back pressure distribution chamber) to which a speaker unit is attached. Each of the sub air chambers is directly connected to the back pressure distribution chamber via the duct, and each of the sub air chambers is different from the duct and applies sound pressure to the atmosphere. A speaker reproducing apparatus characterized by having a duct for radiating. "By arranging two or more auxiliary air chambers connected through the duct in parallel with an air chamber that distributes back pressure. The main feature is that reproduction is performed with a good frequency response up to a low frequency range by providing four or more resonance frequencies for bass reflex operation and freely determining the frequency band between the resonance frequencies.

The parallel-arranged air chamber structure speaker reproducing apparatus of the present invention can add the bass reflex resonance frequency by the number of the bass reflex ducts provided in the plurality of connected air chambers by providing the back pressure distribution chamber. For this reason, there exists an advantage that the favorable frequency response characteristic of a low sound range is realizable.
Furthermore, by designing the resonance frequency to appear in the low sound range where the sound pressure from the speaker diaphragm is insufficient, a good sound pressure characteristic can be obtained over a wide sound range.

A speaker reproducing apparatus having a cabinet having a structure in which two or more auxiliary air chambers are connected in parallel to a back pressure distribution chamber.

FIG. 1 is a structural view of an embodiment of the device of the present invention viewed from the back side. The outer skin on the back side is omitted to show the internal structure. 0 is a back pressure distribution chamber for dispersing the back pressure of the speaker unit, and 1a, 2a, 3a, and 4a are ducts that connect the back pressure distribution chamber 0 and the sub air chambers 1, 2, 3, and 4 to each other. It is. The sound pressure radiated from the back surface of the speaker unit is distributed to the sub air chambers 1, 2, 3, and 4 through the ducts 1a, 2a, 3a, and 4a, respectively, and the back pressures are distributed in the duct 1b, 2b, 3b, And 4b, respectively.
In this example, T3-band W3-517SA type was used for the speaker unit. The W3-517SA type is a full-range unit having a 3 inch diameter, and the reproduction frequency band is 100 Hz to 19 kHz according to the manufacturer's specifications.
The volume of the back pressure distribution chamber 0 is 1.01 liter, and the volumes of the auxiliary air chambers 1 to 4 are 1.99 liter, 2.00 liter, 2.08 liter, and 2.08, respectively.
Liters. The ducts 1a to 4a and 1b to 4b are all circular in cross-sectional shape, and the cross-sectional diameters and lengths of 1a to 4a are 25 mm × 51 mm, 27 mm ×
52 mm, 29 mm × 24 mm, 32 mm × 25 mm, and the diameter × length of 1b to 4b are 25 mm × 65 mm, 27 mm × 52 mm, 29 mm ×, respectively.
24 mm and 32 mm × 25 mm. In this production example, since any of the ducts 1b to 4b can be closed and adjusted, a reference example was used with 3b and 4b closed. As a result, the resonance frequencies of the ducts were 422 Hz, 194 Hz, 172 Hz, 141 Hz, 73 Hz, and 37 Hz.
In this reference example, the frequency characteristics are as shown in FIG. In FIG. 4, the sound pressure level of 170 Hz or higher is generally lowered. This is because the used sweep signal itself is so lowered, and considering this, the response characteristic of the speaker system is 40 Hz or more and 19 kHz. Until then, it was almost flat and was able to reproduce the manufacturer's specification of 100 Hz or less at a sufficient level.

In the operation principle diagram of FIG. 2, a speaker unit is attached to the back pressure distribution chamber 0.
The sound pressure radiated from the back surface of the speaker unit is distributed to the sub air chambers through the ducts 1a to 4a. The sound pressure that has passed through each sub air chamber is radiated into the atmosphere through the ducts 1b to 4b. Since the back pressure distribution chamber 0 and the sub air chambers 1 to 4 function as air springs, and the air in each duct functions as a mass, the entire speaker system forms a natural vibration system.
In this figure, since the number of ducts is 8, a vibration system with 8 degrees of freedom is configured. k represents the spring constant of the air in each air chamber, and m represents the mass of air in each duct. For simplification, only five types from k0 to k4 are shown for simplification. However, since the cross-sectional areas of the respective ducts are different, the actual calculation is performed as a value inversely proportional to the cross-sectional area of each duct. . The details of the calculation formula are shown in Equation 1. In the case of the reference example, since the ducts 3b and 4b were closed, it was calculated that these ducts were not present. In this case, approximate calculation was performed by sufficiently increasing the mass of air in these ducts.

In general, when a duct is attached to a sealed box, it is known that the box constitutes a natural vibration system as a spring and the air in the duct constitutes one lump (Helmholtz resonance box).
In the present invention, the Helmholtz equation is extended to a multi-degree-of-freedom vibration system.
In FIG. 2 showing the operation principle, the mass m _j of air in each duct is expressed by the equation (1) in Table 1. In addition, the spring constant k _j ^* for each duct of each air chamber including the back pressure distribution chamber is determined by using the spring constant K _j formally defined by the expression (3) in Table 1, the cross-sectional area a _{j of} each duct, and the diaphragm. Using the area ratio r _j with the area a _0, it is expressed as in equation (2) in Table 1.
Here, when the number of sub air chambers is N, the equation of motion of the free vibration of the system is expressed by equation (5). Expressions (5) in a matrix form are Expressions (6) to (12) in Expression 1, and the resonance frequency can be obtained by solving the characteristic equation (13) in Expression 1. The eigen equation was solved numerically by Jacobian method.
At the resonance frequency obtained by solving the eigen equation, the sound pressure of the speaker playback device increases, so by designing the resonance frequency to appear in the low range where the sound pressure from the speaker diaphragm is insufficient, And good sound pressure characteristics can be obtained.

In the above formulas (7) to (12), the number of sub air chambers is four as in the case of the first example.

By solving the proposed equation, the resonant frequency can be distributed arbitrarily, and as a result, the sound pressure due to the natural vibration of the speaker cabinet is loaded even in the frequency band where the sound pressure radiated from the front of the speaker unit is low. can do.

FIG. 3 is a structural diagram of an embodiment in which the auxiliary air chamber is simplified to 2. The operation principle is simplified by omitting the sub air chambers 3 and 4 and the connecting ducts 3a, 4a, 3b and 4b in the operation principle diagram of FIG.
In this example, the volume of the back pressure distribution chamber 0 is 1.39 liters, and the volumes of the auxiliary air chambers 1 and 2 are approximately 1.24 liters and 1.56 liters, respectively.
The ducts 1a, 2a, 1b, and 2b have a square cross-sectional shape, and the length of one side × the length of the duct is 26 mm × 70 mm, 26 mm × 70 mm, 26 mm ×
104 mm and 26 mm × 104 mm. A speaker diaphragm having a diameter of 60 mm was used. As a result, the resonance frequency of the duct is 218 Hz, 151 Hz,
It became 85 Hz and 46 Hz.
Since the number of ducts is smaller than that of the first embodiment and the degree of freedom of vibration is 4, the resonance frequency is four. Similar to the reference example, the natural frequency can be obtained from the governing equation when N = 2, and thus the resonance frequency can be obtained.

Structural diagram (Example 1) is a structural diagram in the case where there are four sub air chambers of the parallel-arranged air chamber structure speaker reproducing apparatus. Principle Diagram (Embodiment 1) FIG. 6 is an operation principle diagram in the case where there are four sub air chambers of the parallel-arranged air chamber structure speaker reproducing apparatus. Structural diagram (Example 2) is a structural diagram in the case where there are two sub air chambers of the parallel-arranged air chamber structure speaker reproducing apparatus. Frequency characteristics for the reference example

Explanation of symbols

0 Back pressure distribution chamber 1 Sub air chamber (1)
1a Duct 1b connecting the back pressure distribution chamber (0) and the sub air chamber (1) Duct 2a for radiating sound pressure from the sub air chamber (1) to the atmosphere 2a Back pressure distribution chamber (0) and sub air chamber (2) Connecting duct 2b Duct 3a radiating sound pressure from the sub air chamber (2) to the atmosphere Duct 3b linking the back pressure distribution chamber (0) and the sub air chamber (3) Dissipating sound pressure from the sub air chamber (3) to the atmosphere Duct 4a Duct for connecting back pressure distribution chamber (0) and sub air chamber (4) 4b Duct for dissipating sound pressure from sub air chamber (4) to the atmosphere

Claims (1)

In the speaker reproducing apparatus, at least two or more sub air chambers are connected in parallel to each other through the duct to an air chamber (back pressure distribution chamber) to which the speaker unit is attached. A chamber is directly connected to the back pressure distribution chamber via the duct, and each of the sub air chambers is provided with a duct for dissipating sound pressure to the atmosphere, which is different from the duct. A speaker reproducing apparatus characterized by comprising:

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