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JPS5829295

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DESCRIPTION JPS5829295
[0001]
The present invention relates to a speaker drive device for improving the low frequency range
characteristics. Conventionally, there is known a method for expanding the bass reproduction
range by making the output impedance of a speaker driving amplifier negative, but since the
target to be driven is a specific speaker system, in terms of amplifier imageability. In addition,
there is a drawback that sufficient improvement of the bass characteristic can not be realized.
The present invention provides a novel speaker driving device which ameliorates such
conventional drawbacks, and will be described below with reference to the drawings. First, an
electro-mechanical acoustic conversion system in an electrodynamic speaker will be considered.
The equivalent circuit of the electro-mechanical acoustic conversion system is represented as
shown in FIG. 1 (electrical system) and FIG. 2 (mechanical acoustic system). In such a system,
generally, EO = (Zo + Zl) Q. F=(zo+zl))−ム−q=。 The vibration velocity of the
diaphragm is calculated according to both methods. However, EO: input voltage F: driving force:
Re product zo: output impedance of the driving source zl: moving coil electrical impedance 12
fields: motion electrical impedance zO: medium acoustic impedance zl: vibrating electrical
impedance zm: motion mechanical impedance In the figure, Le: Indag dance of moving coil Re:
DC resistance of moving coil Pm: Mechanical resistance of vibration system Mo: Equivalent mass
of vibration system CO: Equivalent coscidence of vibration system, and There is a relationship of
zt. In both equations, the first term is the operation to convert the inflow current q from the
power supply voltage, the second term is the operation to convert the flow input current q into
the driving force F, and the eighth term is the operation to convert the driving force F into r
motion velocity). Respectively. In other words, when considering the electro-mechanical acoustic
conversion system, it indicates that it is necessary to consider the electrical system and the
mechanical acoustic system mutually, and in the electrical system, the motion mechanical
impedance Zm is It does not have to be taken into consideration, and conversely, it is shown that
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1
in the mechanical acoustic system, it is not necessary to take into consideration the movement
electrical impedance Zm. Since such an electro-mechanical acoustic conversion system is usually
driven at a constant voltage, the case of constant voltage driving will be considered below. In the
case of constant voltage drive, the output impedance ZoI / iZl of the drive source, the ZmK ratio
is sufficiently small, and the (1) and (2) 弐 'are equal. Next, a bass range near the lowest
resonance frequency fo is devised. Below the lowest resonance frequency fo, in the equivalent
circuit of FIG. 2, since the vibration velocity 5 is approximately 09 =--A, jωC0le from equation
(4), therefore, 1 sound pressure (acceleration) 1 = -A ..- c.
Reとなる。 That is, below the lowest resonance frequency fo, the vibration velocity is elasticcontrolled, and the sound pressure drops at 12 dB10 Ct as shown by the solid line a in FIG. The
present invention is made by considering the above-mentioned lowest resonance frequency f O (=
J near the low frequency range more deeply), and will be misrepresented as follows. In
describing the present invention, its technical background will be described. In the equation (I)
(4) or FIG. 79, when the DC resistance Re of the moving coil is used as a variable and Re is
decreased, the DC resistance pe of the i '+ J moving coil is reduced below the lowest resonance
frequency IO. The vibrational velocity is approximately E, R because 2Re involved is sufficiently
large compared to other factors. Also, the sound pressure is Eo 1 sound pressure (acceleration) 1
− 1 ω m 2 and the vibration velocity) is reduced as the DC resistance Re of the moving coil is
decreased. The resistance is controlled and becomes constant, and the sound pressure drops at 6
d B / oct as shown by the dotted line in FIG. (It) On the other hand, viewed from the electrical
system (equivalent circuit in FIG. 1), the electrical inductance of the moving coil] 1. The
relationship between + e and the movement electrical impedance Zm is as shown in FIG. In the
figure, (1; O (2π10)) is a parallel resonance point of Zm, and a series resonance point of cal C2z
f 1) by Zm (−j term) and Le (+ j term). Therefore, above the lowest resonance frequency fo, as
the DC resistance R of the movable coil is decreased, the resonance Q at the above-mentioned
series resonance point ω1 becomes high, and the sound pressure is peaked around the series
resonance point product 1 The result is shown in FIG. 8 dotted line. As apparent from the above
consideration, the sound pressure can be lowered by 6 dB 10 ct in a low frequency range lower
than the lowest resonance frequency fO by reducing the DC resistance Re of the movable coil, but
on the other hand, the electric inductance of the movable coil A peak is generated on the sound
pressure characteristic at the series resonance point ω1 of Le and the kinetic electrical
impedance Zm. In view of the above consideration, the first invention of the present invention
connects the electrodynamic speaker (2) to the output of the amplifier (1) as shown in FIG. 5, and
the electrodynamic speaker (2) In the configuration in which the negative resistance circuit (8) is
connected in series, the negative resistance circuit (3) is negative at a predetermined frequency
(the lowest resonance frequency fO or its vicinity) or lower as shown in FIG. It is intended to have
sexual resistance. That is, negative resistance circuit (3) is formed of, for example, a known
voltage inversion type, that is, a grounded base type transistor circuit combining voltage positive
feedback and current negative feedback, and in this embodiment a predetermined frequency in
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2
the feedback loop. It is not a configuration in which a low pass filter (4) having a cutoff frequency
of fa is inserted and connected.
This negative resistance circuit (3) has the characteristic of having negative resistance in the
region below the cut-off frequency fC of the low pass filter (4) as shown in FIG. As shown in the
figure dotted line (Re), the lowest resonance frequency f. As shown in FIG. 7, the sound pressure
drops by 6 dB 10 ct in the region near and below, and the negative resistance circuit (3) does not
have negative resistance in the region above the predetermined frequency. There is no peak on
the sound pressure characteristic at the series resonance point ωl of the electrical inductance Le
of the moving coil and the kinetic electrical impedance Zm. Next, in the first invention described
above, as shown in FIG. 8, an impedance circuit (5) comprising a capacitor C and a resistor R
between the electrodynamic speaker (2) and the negative resistance circuit (8). Consider the case
of adding. Assuming that the output impedance zo of the drive source is sufficiently small in the
case of constant voltage driving, the equivalent circuit of the mechanical acoustic system is as
shown in FIGS. In the figure, in the region O below the lowest resonance frequency fo, the
impedance (jωLe) of the moving coil is sufficiently small and the DC resistance Be of the IIJ
moving coil is controlled sufficiently small by the negative resistance circuit (3) The lowest
resonance frequency fO 'is given by the following equation, since the equal mingled mass M O' of
the diaphragm of this system is MO '= M, + OA "and the apparent appearance of K increases, and
the conventional lowest resonance frequency i. fo = 2 · It drops for Ji punishment. FIG. 10 shows
the change of the lowest resonance frequency when the value of the capacitor C of the
impedance circuit (5) is changed. The figure shows a specific example in the case where the value
of the capacitor C is increased in the order of 200 μF 1500 μF, 1000 μF and 2000 μF
1801100 μF at the m resonance of the lowest resonance frequency fo = 100 H 2 and the
resistance R = 100 Ω of the impedance circuit. Further, since the resonance Q at the lowest
resonance frequency fo is given by the equation, the resonance Q can be controlled by adjusting
the value of the resistance R of the impedance circuit (5). FIG. 11 shows a specific example where
the value of the resistance R is gradually increased in the order of 2 oΩ, 35 Ω and 65 Ω in the
case of the lowest resonance frequency fo = 70 Hz and the capacitor c of the impedance circuit
(5) = 500 μF. That is, in the present invention, as the value of capacitor C of the impedance
circuit increases, the lowest resonance frequency decreases, and as the value of resistor R
decreases, the resonance Q at the lowest resonance frequency decreases, and capacitor C1
resistance R decreases. By setting the value of L appropriately, it is possible to lower the lowest
resonance frequency and realize an ideal characteristic close to or at the critical damping in this
region, and to expand the low JP-A 58-29295 (4) sound reproduction area. Be able to
The negative resistance circuit (3) is not limited to the embodiment of FIGS. 5 and 8, and the load
of the negative resistance circuit (8) as shown in FIG. 12 (FIGS. 5 and 6) It may be a modified
circuit in which 2) in the figure and the impedance of the electrodynamic speaker (2) are shared.
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3
As described above, according to the present invention, in the configuration in which an
electrodynamic speaker is connected to the output of the amplifier and a negative resistance
circuit is connected in series with the electrodynamic speaker, the negative resistance circuit has
a frequency lower than a predetermined frequency. Since the region has negative resistance, the
sound pressure drops by 6 dB 10 at in the region below the lowest resonance frequency, and the
lowest resonance frequency can be lowered by adding an impedance circuit in series with the
negative resistance circuit. , Has excellent use that can expand the bass playback range.
[0002]
Brief description of the drawings
[0003]
1 and 2 show the equivalent circuit of the electro-mechanical acoustic system, FIGS. 3 and 4
show the same characteristics, and FIG. 5 shows the configuration of the speaker drive device of
the present invention 3 6 shows the characteristics of the negative resistance circuit, FIG. 7
shows the frequency characteristics, and FIG. 8 shows the configuration of another speaker drive
device according to the present invention. 9 shows the equivalent circuit, FIG. 10, and FIG. 11
show the frequency characteristics, and FIG. 12 shows the other embodiment.
(1) is an amplifier, (2) is a speaker, (3) is a negative resistance circuit, and (5) is an impedance
circuit. Patent Assignee Onkyo Co., Ltd. Attorney Attorney Satoshi Satsuma Part 1 VIj 20th 4th
Close-up Figure 5 Figure 60 During Liquid Recovery Figure 7 Not Figure 811i 6 □□-487 10
figures around number 11 concave
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