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JPS5252601

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DESCRIPTION JPS5252601
1 ? Name of invention
Audio playback device
The present invention relates to an audio reproducing apparatus using a multi-unii speaker
system, and more particularly to an improvement of a channel dividing means for distributing a
signal to each speaker. Audio playback devices generally use many so-called multi-unii speaker
systems that use dedicated speakers for the bass and treble band or the bass and mid band and
treble band respectively. There are various systems as shown in FIG. 1 to FIG. FIG. 1 shows an
example using an LC network, in which a record disc reproduction signal input to the first input
terminal 11c is input to the second input terminal 2 or a signal whose frequency characteristic
has been corrected by the equalizer circuit 3 based on the RIAA standard. The already flat signal
of frequency characteristics such as receiver output (hereinafter, these signals are referred to as
signals to be reproduced) is increased by EndPage: 1 by one power amplifier 4 and this amplified
output is configured using LC The high frequency cutoff filter 5 and the low frequency cutoff
filter 6 are divided and added to the bass speaker (hereinafter referred to as woofer) 7 and the
high tone speaker (hereinafter referred to as tow eater) 8. However, in this method, an LC
network consisting of the filter 5.6 is inserted between the amplifier 4 and the speaker, and the
impedance of the network is added to the output impedance of the amplifier 4 when viewed from
the speaker. There is a drawback that 7 actors are reduced. Also, since the impedance of the
speakers varies with frequency, the design of the network is often less rigorous. Moreover, L
used in this network is large one! Since it is necessary to withstand the flow and have a large
inductance, it tends to cause non-linearity. For this reason, for example, L is used as an air core,
but in that case, there is a problem that the number of turns of the coil must be increased. The
systems shown in FIGS. 2 and 3 are examples of a so-called multi-panel drive system using a
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dedicated power amplifier for each speaker, and channel division is performed at the front stage
of the power amplifier. It can be eliminated. That is, in FIG. 2, the signal to be reproduced is
divided by the high-pass filter 9 and the low-pass filter 10, the outputs of these filters 9.10 are
amplified by the power amplifier 11.12 and the woofer 7 and It is supplied to the squawker 8.
However, according to this method, the level changes near the crossover frequency, and the
phase also tends to change.
When this is explained using a mathematical expression, when, for example, the -order filter is
used as the filter 9.10, the output levels pw and pT of the woofer 7 and the toe-tor 8 are
expressed by the following equations. However, S = j? = 2j?fW (sl: response of woofer 7 T (sl :)
response of weak 8 e: filter 9 ', input level of JO) Therefore, the combined output P is P = Pw +
PT. = W (sl, i.e., if the efficiency of the woofer 7 and the tweeter 8 is equal b), it is necessary to
equal k = 1, i.e. the outputs of the amplifiers 9, 10 equal. In other words, it is necessary to use an
amplifier equivalent to 9 ░ 10, which increases the cost burden. Furthermore, when a secondorder filter is used as the filter 9.10, 'Pw = 8 Wfsl (4) S + a S + b P--i ? 78 T (и) ░ "--.Degree..degree.-.degree. +51 P = Pw + PT" Therefore, in this case, it becomes Wis) = Tlsl, and making the
level characteristics and the phase characteristics near the crossover frequency be a problem. On
the other hand, FIG. 3 shows a multi-channel drive system adopting a shadowing network, in
which level characteristics and phase characteristics in the vicinity of the crossover frequency
are considered. That is, the signal to be reproduced is amplified by the amplifier 13 and then
supplied to the woofer 7 through the high-pass cutoff filter 14 and the power amplifier 11, and
the difference between the input and output of the filter 4 is taken by the subtraction circuit 15
It is supplied to the tweeter 8 through J2. According to this, if the filter 4 is a second order filter,
for example, PT = (1? - BatsuRyo) eTlsl ииииииииииииииииии (9) EndPage: 2 and Do jl), WIs) = if T (s) P =
P1wl + Pttl is a constant Become. However, in this case as well, amplifiers 11.12 must use the
same output. Furthermore, the circuit configuration is also complicated, and there is a defect
accompanied by deterioration of S / 'H. The present invention has been made to address the
above-mentioned points, and it is an object of the present invention to provide a multi-channel
drive type audio reproducing apparatus which has good phase characteristics and level
characteristics and can simplify the configuration. (1) In general, audio playback devices are most
often used for playing back a record board. Record board is currently defined to record according
to the standard by RIAA (RecordIndustrialAs 5ociation of Arnerlea), and when the pickup
cartridge with a flat frequency characteristic is used on the reproduction side, the frequency
characteristic opposite to RIAA recording characteristic (this is RIAA reproduction characteristic
In general, playback is performed after correcting the playback output of the record board by an
equalizer having the
According to the present invention, a channel dividing circuit (also referred to as a network) for
dividing a signal to a multi-way speaker into a low band signal and a high band signal is
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constituted by a pair of first-order high-pass cutoff filters having specific different time constants.
Also, the output level of the tweeter is set to be smaller than the output level of the woofer by a
fixed amount. According to the configuration of the present invention, not only the level
characteristic and the phase characteristic of the reproduction output can be flattened, but also
the amplifier used on the high-pitched side can be a small one. Since it is not necessary, there is
an advantage that the circuit becomes extremely simple.
Audio playback device
The present invention will be described in detail by way of the following examples. FIG. 4 is a
view showing an embodiment of the present invention, in which the reproduction of the record
disc is received at the first input terminal 21 and the frequency characteristic of the receiver
output etc. is substantially flat at the second input terminal 22. Signals are input respectively.
The signal to the input terminal 22 is further corrected by a frequency characteristic correction
circuit 23 substantially equal to the recording disc recording characteristic, ie, the RIAA
recording characteristic. These record board reproduction signals and signals corrected by the
correction circuit 23 (hereinafter collectively referred to as signals to be reproduced) or
selectively taken out, and further, a preamplifier, a tone control circuit (shown in FIG. And the
like, and then led to the first and second primary high-pass cutoff filters 24.25. At the input side
of the filter 24, an attenuator 26 is inserted. And each output of the filter 24.25 is amplified by
the power amplifier: 11.28 respectively and then the woofer 29. It is supplied to the tequator 30.
Here, the time constant of the filter 24.15 11. ? is set to Tl = 3180 ?s 1 ?t = 75 ?s. ????
?????? The frequency characteristic of 4.25 is set as shown by curves ^ and B in FIG. Here,
1 = ?f ? is the filter 24. F1 = 17.tau. = 50 Hz / 1 == 1 / .tau.t = 2122 Hz at a turnover frequency
of 26 (cutoff frequency), and the slopes of the curves A and H are 6 dBloct. On the other hand,
when the amplification factor of the amplifier 24 ░ 25 is equal to the attenuator of the
attenuator 26 and the efficiencies of the woofer 29 and the tweeter 30 are equal, k is set to 20
da. In this way, the output level of the filter 25 becomes as shown by the broken line in FIG. 5
relative to the output level of the filter 24. Therefore, the reproduction frequency characteristic
of the combination of the woofer 29 and the tweeter 30 is K as shown in FIG. In FIG. 6, f и is the
crossover frequency /, = 500 Hz. This reproduction frequency characteristic is the same as that
of the recording RIAA curve]. Therefore, when the recording disc reproduction signal to the input
terminal 21 is reproduced, a flat reproduction frequency characteristic can be obtained as the
whole apparatus. Further, when reproducing a flat signal of frequency characteristics to the input
terminal 22, this signal is subjected to the same correction as the RIAA recording characteristic
by the frequency characteristic correction circuit 23, so the reproduction frequency
characteristics of the whole apparatus are similarly flat. It becomes. EndPage: 3 The operation of
this device will be described as follows using mathematical expressions.
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???????? Assuming that the frequency response of the tweeter 30 is W (?) and T (?)
respectively, where ? = A?f) and the signal level to be reproduced is e, the woofer 29. Output
level Pwl?1 of tweeter 3?. Pd?) is given by the following equation. PWf?1 = eW (?) / (? +
?1) ииииииииииии [IPt (?1 = ekTt?) / (? + ?,) ииииииииииии Sumika: Therefore, the combined output P (?) is
P (?1 = Pw (?1 + kPr4) (T1 where ? is taken. If k is selected so that = 318 ?B (? 1/10 in the
above example), the (? + ?0) / (? + ?I) (? + ?) of the equation 04 will give a reproduction
RIAA curve. As described above, according to the present invention, the signal division into the
woofer 29 and the tweeter 30 is performed by the channel division circuit comprising the next
high-pass cutoff filter 24.25 and the attenuator 26 in the above configuration, and the RIAA
reproduction characteristic is simultaneously obtained. In view of the reproduction
characteristics of the entire apparatus, the reproduction level is continuous, ie, constant, even
near the crossover frequency. The phase characteristics can also be made almost constant as
compared with those in FIG. 2 in which channel division is performed using the high-pass cutoff
filter and the low-pass cutoff filter. Moreover, since the reproduction output of the tow gear 30 is
set to be approximately 1/10 of the reproduction output of the woofer 29, the power amplifier
28 for driving the towter may have a smaller output capacity than the power amplifier 27 for
driving the woofer 27 The reduction can be achieved. Therefore, the sex also decreases. In
addition, in the case of the playback of a source recorded through the RIAA recording
characteristics when the record board is used, there is an advantage that the playback can be
performed without providing an equalizer. On the other hand, with regard to a flat signal of
frequency characteristics such as receiver output, since the correction for enhancing the high
range is performed by the frequency characteristic correction circuit 23 having the same
characteristic as the RIAA recording characteristic, it is inputted to the channel division circuit.
The effect is equivalent to that given emphasis, and an improvement in S / N can be expected. In
the above embodiment, although the reproduction band of the woofer 29 is only the low band,
the reproduction band of the tow tracker 30 is mainly the high band, but the low band
component is also reproduced. However, in this case, the output of the toe gear 30 is about 1710
of the output of the woofer 21, and it can be practically supported even if the toe gear 30 does
not emit sound mechanically or acoustically in the low band. That is, for example, if the tweeter
30 is in a horn shape and its cutoff frequency is selected to be about 500 Hz or less, there is no
unnaturalness in reproduction.
FIG. 7 shows another embodiment of the present invention, which is an example in which a 3way speaker system is adopted. That is, the output of the power amplifier 28 drives the mid-tone
speaker (squaker) 31 and the subtraction circuit 32 for detecting the difference between the
person and the output of the filter 25 and the power for amplifying the output of the subtraction
circuit 32 An amplifier 33 is provided, and the output of this amplifier 33 drives the tweeter 30.
Also in this case, although the configuration is somewhat complicated, there is an advantage that
the capacity of the power amplifier 211.33 can be made smaller than before. According to the
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present invention, it is also possible to divide the output of the filter 24.25 at an appropriate
busy frequency and extend the speaker system to four or more windows. In each of the above
embodiments, the attenuator 26 is used to set the output level of the tweeter 30 or the squawker
31 to approximately 1/10 of the woofer 29, but the amplification factor of the amplifier 28 or 33
is equal to the end factor of the amplification factor of the amplifier 27: Similar results can be
obtained by setting the value to approximately 1/10. In addition, the present invention can be
variously modified and implemented without departing from the scope of the invention.
4. Brief Description of the Drawings FIGS. 1 to 3 are schematic block diagrams for explaining
various channel dividing means in the conventional audio reproducing apparatus, and FIG. 4 is a
schematic block diagram showing one embodiment of the present invention. Fig. 5 shows the
frequency characteristics of the primary high-pass cutoff filter in Fig. 4, Fig. 6 shows the overall
reproduction frequency characteristics of the woofer and tow eater in Fig. 4, and Fig. 7 the other
of the present invention It is a schematic block diagram which shows the Example of. 23 иии
Frequency characteristic correction circuit, 24.25 иии Next high band cutoff filter, 26 иии Attenuator,
27 ░ 28.83 иии Power amplifier, 29 иииииииииииииииииииииииииииии 3 Towita 3rd ... Skooka, 32 ... Subtraction
circuit. Applicants Attorney Attorneys Suzue Takeshi 4 pieces 1 figure piece 2 figures yf 3 figure
7 iP 4 figure 7 i '5 figure pieces. Figure EndPage: ?
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