DE2351423A1 - STEREOPHONIC PLAYBACK DEVICE - Google Patents

Description

It 2630

Sony Corporation, Tokyo, Japan

Stereophonic player

The invention relates generally to stereophonic reproducers and in particular such a stereophonic player by which the left, a right and sounds emitted by a central loudspeaker are acoustically superimposed in the room in matrix form.

In stereophonic playback devices of the conventional type, a left and a right speaker system are supplied with a difference signal (LR) between a left signal L and a right signal R or such a signal in phase inversion (RL), in which they are then converted into sound while a sum signal (L + R) from the right and the left signal is fed to a central speaker system, which is converted into sound there, the sounds generated in this way are then superimposed acoustically in the room ₉ so that the listener has the feeling that the Sounded differently to the left and right in the room. With the help of a compensation circuit for the frequency characteristic, a frequency reproduction of the sounds generated by the difference signals (LR) and (RL) is made comparatively high compared to that of the sum signal (L + R) in a band of low frequency, while the frequency reproduction is comparatively low in a high frequency band to reduce noise in the high frequency band. If the sound of such a stereophonic player is monitored with headphones connected to the auxiliary output terminals of the device,

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then, since the headphones sit directly on the ear cups of the listener, the matrix-like propagation of the sound can occur not expected in the room. When listening to headphones with headphones, a sound is produced that has a difference in frequency characteristics between the difference signals (L-R) and (R-L) and the sum signal (L + R) by the action of Frequency characteristic compensation attitude, so that the left signal L and the right signal R, acoustically from each other are separated, cannot be preserved.

The stereophonic player according to the invention mixes in a tree the difference signals (L-R) and (R-L) and a sum signal (L + R), which are emitted by loudspeakers, acoustically in a matrix form and also has a frequency characteristic compensation circuit, by the frequency characteristics determined by the difference signals (It-R) usa (R-L) are given. However, if the signal from the auxiliary output terminals of the device is removed, the! frequency— characteristic lk compensation circuit switched ineffective.

With the invention, the aim is thus aimed at a To get rid of the deficiencies of the previously known devices.

The object of the invention is to provide a stereophonic player in which, even when the output signals removed from the auxiliary output terminals of the device the degree of separation into left and right signals is not deteriorated.

The further task is to provide a stereophonic player to create, in which only by inserting a plug of a headphone into a socket of the Auxiliary output connections to the frequency characteristic compensation circuit is switched to ineffective.

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From the description of exemplary embodiments that now follows of the invention in conjunction with the drawing the features, properties and advantages of the invention again clearly revealed. Show it:

Fig. 1 shows the arrangement of loud-

speaker systems as used in a stereophonic player according to the invention is provided to sound in the form of an acoustic matrix to achieve ^

the graphic representation of the generated frequency reproduction in the stereophonic player;

3 shows a schematic block diagram of a first

Ausftthrmngsbeispiels the stereophone according to the invention! e-playback devicesi

the circuit diagram of the main part of the in Mg. 3 ge showed exemplary embodiment of the device;

FIGS. 5 and 6 show diagrams of listening tests on the stereophonic playback device according to the invention and a stereo playback device with other Elangmatrixi

7 shows a block switch during the experiment; turned put

Fig. B a graph? Position: the Freepesz; characteristics of the arrangement according to FIG. ¹

Pig. 9 is a circuit diagram of an embodiment

of the stereophonic player according to the invention; and

Eig.10 a circuit arrangement of the main part of a another embodiment of the stereophonic playback device according to the invention.

1 shows a loudspeaker system of a stereophonic player. A listener is indicated by P, while the loudspeakers arranged to the left and to the right of the listener are indicated by SP,. and SP _{R are} designated. A difference signal (LR) between the left and right signals L and R or a difference signal (RL) which is in phase opposition to the former is fed to the loudspeakers SP 1 and SP ″, which convert the loudspeakers into sound, while a center loudspeaker SP _M a sum signal (l + R) is fed, which this converts into sound. The sounds generated in this way are mixed acoustically in the room in the form of a matrix, so that the listener gets the impression of the imaginary starting points 1 'and R ¹ , which are to the left and right of the speakers SPx and SP-g, respectively To receive sounds, whereby an even stronger spatial sound impression is created. In this way, a stereophonic playback device that is relatively small in size, for example a portable device that has a left and a right and a center loudspeaker in a common loudspeaker box, can generate a sound with a sufficiently spatial impression. In order to achieve a sound impression that is as spacious as possible and to improve the sound balance by correcting the lack of the difference signals (LR) and (RL), which may be amplified and distorted in the high frequency range compared to the sum signal (L + R)

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the reproduction or level of the difference signals (L-R) and (R-L) caused by the speakers SP, - and SP ^ is, in the same way as the reproduction of the sum signal (L + R), generated by the center speaker SP ^ in the low frequency range the reproduced frequencies made large (see curve b in Fig. 2) but small compared to the reproduction of the sum signal (L + R) in the range of high frequencies, which curve a in FIG. 2 shows. The curve / S in Fig. 2 shows the ' Phase position of the difference signals (L-R) and (R-L) in relation to the phase position of the sum signal (L + R). In the present case it is the difference signal is delayed compared to the sum signal, and the apex of curve a is in the area of Frequency range of 200 ^ 40O Hz. The value of curve a is at about 4 kHz the same as the value of the sum signal at this frequency.

The frequency values shown in Fig. 2 are electrical frequency characteristics in signal paths of the difference signals (LR) and (RL) and the sum signal (L + R). In an FM radio receiver according to FIG. 3, a composite stereophony signal which contains the difference signal (LR), the sum signal (L + R) and a control signal is transmitted via an FM demodulator 2 from a tuner 1 which contains an IF amplifier , the input terminals I .. and T ″ of a differential signal system 3 and a sum signal system 4 supplied. The differential signal system 3 includes an auxiliary channel demodulator 3a, a gate amplifier 3b with a frequency characteristic compensation circuit and an output amplifier 3c for low frequency, while the sum signal system 4 has a low-pass filter 4a, a preamplifier 4b and an amplifier 4c for low frequency. Curves a and b of FIG. 2 represent the electrical frequency responses for the signals from the input _{terminals T 1} and T ₂ to the output sides of the amplifiers 3o and 4e for low frequencies.

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235U23

The frequency characteristic compensation circuit in the preamplifier of the differential signal system 3 has, for example, a delay characteristic for one octave of 12 dB and delays the reproduction of the difference signal when it enters the high frequency range.

Pig. 4 shows a practical exemplary embodiment of the preamplifier 3b with a frequency compensation circuit 10. In this exemplary embodiment, an amplified signal is derived from the collector electrode of a transistor Q with the aid of a capacitor C., the emitter electrode of the transistor being connected to ground; the signal is then passed to the output terminal S «. The series connection of a capacitor Cp and a resistor R .. is between the output terminal Tq and ground, with a capacitor C- connected in parallel with the resistor R /. In this way, the transmitted signal or the difference signal is amplified in the low frequency range, while it is greatly attenuated when it reaches high frequency ranges. Thereby, the frequency sensitivity of the overall differential signal system 3 is about the same as the curve a in Fig. Z.

In the stereophonic player in which the difference signals (L-R) and (R-L) are left and right, respectively Speaker system are fed, in which they are converted into sound, while the sum signal (L + R) to the center speaker system is supplied, all sounds generated in this way are mixed into a sound matrix in the room, if the playback sensitivity for the difference signal in the range of low frequencies high and in the range of high frequencies is low compared to the reproduced sum signal, which creates a clearer stereophonic impression will.

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This phenomenon can be ascertained by the following Ifec search. As in the Pig. 5 and also in Pig. 6, in front of a listener P at a distance of about 40-50 cm, a loudspeaker ox of width d of about 35 cm is set up, with a left loudspeaker box SP ^ and a right loudspeaker box SP “attached _{to both sides of a central loudspeaker SP M} 7 shows, a signal with a single frequency component is generated with the aid of a low frequency oscillator 5. Part of the signal generated in this way is fed through an amplifier 6 to the central loudspeaker SPjj, while another part is carried out by a phase reversal circuit and an amplifier 8 to the left and right speakers SP ^ BZI * SPj 7. out ₁ which are connected with opposite polarization. the signal of the oscillator 5 is thus from the speakers SP ^ and SP _R of opposite polarity in sound and the sound perception is measured, which is determined by the listener P. Figure 5 shows the test result for a frequency behavior according to Figure 2, during Pig. 6 the test result according to Pig. 8 shows in which the reproduction ^{sensitivity t a 1 of} the difference ^{signal system and b 1 of} the sum signal system were the same or the sensitivity a ^{1 was selected to be} greater than the sensitivity Ib ¹ .

In this pail, the sound output from the left and right speakers SPt and SPp becomes the same as that of the center speaker SP ™ with no phase shift, and the sound image is formed on the side whose speaker is in phase with the center speaker. If the left loudspeaker SP _L and the center loudspeaker SB ^ are fed in such a way ^ that their sound is in phase, the listener P has the feeling of receiving the sound from the left _{Medium loudspeaker or} SPjp vjas with the help of the PJaase sweep 7

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happens, the listener P has the feeling of receiving the sound from the right.,

The characters x in Figures 5 and 6 indicate the positions in which the listener P perceives the sound generator when the sound image is formed by .the corresponding frequencies on the left (the number of listeners is selected to be 20), while the characters ο represent the positions in which the listener P perceives the sound image generated on the right-hand side. The curves 1 and l ^f indicate mean values of the sound image distances perceived by the various listeners from the central axis. With the representations of FIGS. 5 and 6, the feeling for the expansion of the sound reproduction by a number of listeners in the frequency range from 30.0 Hz to 1 kHz is reproduced. This shows that a sufficient stereophonic impression is achieved. '

The description should now be made qualitatively. The measurement results recorded in FIGS. 5 and 6 show that at frequencies higher than 4 kHz there is practically no directional hearing and the listener has the feeling that the sound is being produced practically in the middle; in other words, the listener only has a stereophonic sound perception in a frequency range below 4 kHz. It follows that if the volume level for frequencies higher than 4 kHz is reduced in comparison to the center speaker and instead the volume level of the frequencies is increased by 300 - 400 Hz compared to the level of the center speaker in the side speakers, i.e. in frequencies that have a strong influence on the stereophonic sound perception, the lateral position of the left and right sound images can be made clearer, so that the expansion of the stereophonic sound image is better perceived. .

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In the lower frequency range, where the wavelength is relatively large, the left and right sound signals are in sound complementary than sounds with approximately the same Phase position generated. The difference signals (L-R), and (R-L) contain thus almost none. Low frequency components. In contrast even if the wavelength of the sounds is short and the distance is short, e.g. the distance to a sound recording microphone, sufficient tones are reproduced in the higher frequency range, where phase differences are generated. So where the sound reproduction characteristics of the side speakers and the center speaker over the entire frequency range flat, d. H. is without significant differences, as shown in FIG. 8, the sound strength mainly produced is amplified by the left and right loudspeakers in the high-frequency range, as indicated by the dashed curve c 'in Fig. is indicated, while in the frequency range between 300 Hz and 4 kHz, which is special to the stereophonic sensation The left and right speakers have no influence generated, which could amplify the spatially perceived sound reproduction - as the difference signals (L-R) and (R-L) tend to be attenuated in the high frequency range, the above-described phenomenon becomes from this point of view from not wünff-cht.

If the reproduction sensitivity of the left and right loudspeakers is increased in the range of low frequency values and is attenuated for high frequencies, a sound image is generated which gives the listener a sufficient stereophonic impression. The sound becomes clearer ; and the listener feels the spatial expansion of the sound reproduction arrangement and, in addition, the acoustic BjLance is improved.

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The above description is given in connection with an M broadcast receiver as an example. It rule however, the same conditions when the difference and sum signals of stereophony signals are obtained from a record player or a tape recorder, from which a sound matrix is then generated.

In the above description, the reproduction levels of the difference and sum signals were in the range of about 4 kHz same, done, but experiments have shown that this JPre— frequency value can be in the range between 3 and 6 kHz.

If auxiliary output terminals are provided in a stereophonic player of the type described above, on The two-channel headphones can be connected to get stereophonic playback, then the left signal L and the right signal R by simply mixing the difference signals (L-R) and (R-L) and the sum signal (L + R), which at the Matrix playback are fed to the left or laughed loudspeaker and the center loudspeaker, not simply derived, if there is a difference in frequency response between the difference signals (L-R) and (R-L) and the sum signal (L + R) is.

Pig. 9 shows a practical embodiment of the invention in which those already used in FIGS Reference numerals are used for the same elements.

With the digits 11 and 12 are in the Pig. 9 denotes input terminals to which the difference signal (LR) and the sum signal (L + R) are fed, which are led out from the base electrodes of the transistors Q ₁ and Q ₂ , the emitter electrodes of the transistors being connected to ground and the transistors being a preamplifier 3b and 4b form.

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235-23

The preamplifier 3b corresponds to the one shown in fig. 4 structure, is thus determined by the frequency characteristic k-Kompen ^. sationskreis 10 shown. The reference number R ₉ represents. . . -A load resistor which is connected between the collector electrode of the transistor QL and an energy source + B, while the resistor R _{7 is} between the emitter electrode of the transistor Q. and ground. The connection point between the capacitors C. and CL.is, t is connected to ground via a variable resistor R , via which the volume is regulated; the movable tap of the control resistor Pw is connected to the input side of the amplifier 3c for low frequencies. In the other preamplifier 4b, a load resistor R is connected between the collector electrode of the transistor Q ₂ and the energy source + B-, while a .Widerstand R ^ - is between the emitter electrode of the transistor Qu and ground. Between the collector electrode of the transistor Q ₂ and ground, the capacitor C. is in series with a variable resistor R ₇ . The tap of the variable resistor R ₇ leads to the input of the. "Amplifier-4c for low.frequencies.

The output transducers 1 3 and 14 are, with. the Aus. input sides of the amplifiers 3e, and 4.for. low frequencies in connection. . In the present case the transducers 13 and 14 having primary windings 13a, 14a and secondary windings _13b: equipped 14b. As negative feedback circuits, resistors 8 and 9 connect the secondary windings 13, b and 14b with the Vers tärkerii 3q or, respectively. 4ß »" .. · ...

The right and left speakers SP-. and SP _R are parallel to each other on the secondary winding 13b of the converter 13 via a socket with polarization switch, which will be described in more detail below. The left loudspeaker SPj- thus receives the difference signal (LR) fed, while the right loudspeaker SP "the difference signal (RL) is fed. The polarization switch 16 is connected to the right loudspeaker SP _R , with the aid of which the polarization of the signal fed to it can be reversed so that it too receives a signal with the same phase as the left loudspeaker SP ^ if a monaural signal arrives in mono reception. The central loudspeaker SP _M is connected to the secondary winding 14b of the transformer 14 via a socket with a changeover switch, via which the sum signal (L + R) is fed to it.

The numeral 18 in FIG. 9 generally designates a matrix circle in which the difference signals (LR) and (RL) and the sum signal (L + R) are mixed and the left signal L and the right signal R are generated therefrom; In the present case, this matrix circle consists of the resistors R ₁₀ , R ₁₁ , R ₁₂ and R ₁₅ . With t ₂ and t ~ output auxiliary terminals (left and right output terminals) are referred to, to which the matrix circuit 18 outputs the left and right signals L and R, these terminals being designed as a socket with a switch for a stereo headphone. With 20 'denotes a circuit, with the aid of which the frequency characteristic compensation effect of the difference signals (LR) and (RL) is canceled by the frequency characteristic compensation circuit 10, ifofoei the circuit arrangement 20 is a kind of frequency characteristic compensation reversal circuit. t ₁ in the Steek socket arrangement J is what is most commonly a ne, ac. grounded terminal.

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One end of the secondary winding 15b of the transformer is connected to ground via a resistor R .., - while the center point of the secondary transformer winding is directly connected to ground. The left output _{terminal t 2 of} the socket arrangement J is connected via the resistor R ^ of the matrix circuit 18 to the secondary winding 13b of the transformer 13 at its one end (to which the resistor R ₁ , - is also connected), Terbundea, while one end of the secondary winding 14b of the transformer 14 (which is not connected to ground) is also connected to this terminal _{via the resistor R 11.} The right output terminal t, the socket arrangement J is above the. Resistor R ₁₂ of matrix circuit 18 is connected to secondary winding 13b of transformer 13 at its other end and also via resistor R ₁₀ to secondary winding 14b of transformer 14 at its end that is not connected to ground. .

The socket arrangement J, in which with SW ₁ and SW ₂ a left and a right Sehalter are designated, each having a movable contact a and fixed contacts b and c, has normal pitch connection of the contacts a of the switches SW ₁ and SWp with the fixed contacts b. The movable contacts a are however brought into connection with the other fixed ^ contacts c via the left and right output terminals tp or t ^, with the interposition of insulating pieces 22 when the plug contact (not shown) of the stereo headphones is inserted into the socket arrangement J. is used.

The movable contact a of the left switch is connected to the secondary winding 13b of the transformer 13 at one end (on which the resistor R ₁₅ is also connected), while the fixed contact b of the switch is connected to a common terminal of the left speaker

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and the right speaker SP ^ is connected and the other fixed contact C ₁ ^ of SW. remains free. While the movable contact a of the right switch SWp is grounded, its fixed contact b is connected to the secondary winding 14b of the transformer 14 at one end (not connected to ground) via the center speaker SPj, while the other fixed contact c is connected to the emitter electrode of the The transistor Q. of the preamplifier 3b is connected to the circuit for undoing the frequency characteristic compensation. The other ends of the left and right speakers SPx and SPn are connected to the other end of the secondary winding 13b of the transformer 13.

The circuit 20 for undoing the frequency characteristic compensation consists of a series connection of the capacitors C ₅ and Cg, with a resistor Rg being connected in parallel with the capacitor Cg.

Since the frequency characteristic compensation circuit 10 is provided in the preamplifier 3b, the frequency sensitivity of the difference signals (LR) and (RL) is as in Pig. 2 indicated by the curve a, while the phase characteristic with respect to the sum signal (L + R) has a course, as in Fig. 2 by the. Curve / ό shown. The circuit 20, d urch the Frequenzeharakteristik compensation is compensated for i makes frequency compensation of the difference signals (LR) and (RL) again reversed, so that they are substantially equal to the sum signal (L + R) (curve b in Fig. 2) , whereby the phase is also equal to the sum signal (L + R).

The operation of the stereophony signal reproducing apparatus shown in FIG. 9 will now be described. If the loudspeakers SP _3. , SP _R and SP ^ are used to reproduce stereophony signals, the difference signal (LR) ctem left speaker SP ^, the difference signal (RL)

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the right loudspeaker SPn and the sum signal (L + R) the 'center _{loudspeaker SP ^ forwarded, since the movable contact a of the switches SW ^ and SW 2 of} the socket arrangement J is connected to the fixed contacts b, while at the same time the circuit 20 to undo the Frequency characteristic compensation is cut off from ground at one end, so that it becomes ineffective? this produces a stereophonic sound reproduction in matrix form.

Now a plug of the headphones into the socket arrangement J is inserted, then the movable contacts a become the switches SW. and SWp on the fixed contacts c switched over. The right and left speakers SP, respectively, SPjv are separated from the transmitter 13, the center speaker SP "is separated from the transformer 14 and the circuit 20 for undoing the frequency characteristic compensation is connected between the emitter electrode of the transistor Q. of the preamplifier 3b and ground. This has the output signal of the preamplifier 3b or the difference signal (L-R) a flat frequency characteristic, which indicates the effect of the circuit “2jO for undoing the frequency characteristic compensation is due, the output signal also has the same phase position as the sum signal (L + R). The difference signal (L-R) coming from one end of the secondary winding 13b of the transformer 13 (to which end the resistor R .., - is also connected) is output, as well as the Sum signal (L + R) at one end of the secondary winding 14b of the transformer 14 (the end not connected to ground) can be tapped, both are via the resistors R.j, and R ^ attenuated and mixed in matrix form, so that the left signal L appears at the left output terminal tp as the result. At the same time, this will happen at the other end of the secondary winding 13b of the transmitter 13 appearing difference signal (R-L) and

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the sum signal (L + R) appearing at the other end of the secondary winding 14b of the transformer 14 is attenuated and _{mixed in matrix form by the resistors ILp and R 10} , so that the right-hand signal R appears at the right output terminal t. The left and right signals L and R are given to the stereophonic headphones - where an acoustic stereophonic sound signal with the same frequency and phase is generated. -. ■

In the exemplary embodiment described, the circuit arrangement 20 is for reversing the frequency characteristic compensation formed from the capacitors 5 and -6, with the capacitor Cg still the resistor R-jg. is connected in parallel, but it is also possible to build the same circuit 20 'with only one capacitor Cj-', as indicated in FIG. 9.

Instead of the undo circuits 20 or 20 ' The frequency characteristic compensation can also do this compensation on the difference signals (L-R) and (R-L) can be switched off in that a ΕΠΓ-OFF switch is provided in the frequency characteristic compensation circuit 10.

In a circuit example shown in FIG. 10, such an EIF-AUS-Sehalter SW ^{1 is} provided, which is located in the socket arrangement J and which is switched when the plug (not shown) of the headphones is inserted into the socket arrangement J, that while the frequency characteristic compensation circuit 10 is separated from the output of the transistor Q.

It is also possible to replace the running speakers SP ^, SP _R and SP _M for left, right and center with a loudspeaker system ^, each of which has a plurality of individual loudspeakers.

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contain brazen. In such a case, the individual sound ranges are the different speakers of each Speaker system selected differently.

In a stereophonic player of the 'described According to the invention, the difference signal (L-R) from the left and right signals L "and R and the difference signal (R-L), which has phase reversal to the first one, entered into the left or right speaker system and there converted into acoustic sound, while the sum signal (L + R) is given to the center speaker system and is converted into sound there, with the sounds generated by the individual loudspeaker systems in the room in the form of a Matrix can be mixed acoustically. This is the frequency response sensitivity for the difference signals (L-R) and (R-L) in the range of low frequencies compared to the sum signal (L + R) made large but small in the high frequency range, and when signals from the auxiliary output terminals removed, the left and right signals can be an excellent separation from the listening point of view allow to be removed immediately.

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Claims (8)

_18_ 235U23 PATENT CLAIMS 1.W stereophonic playback devices with the combination of fölender Characteristics: a) a left speaker system (SP _T ), a right speaker system (SP-o) and a center speaker system (SP ^.); b) Means for supplying a difference signal (L-R) obtained from the left and right signals (L and R) and a difference signal (R-L) with opposite phase to the former to the left or right speaker system and for supplying a sum signal (L + R) to the center speaker system, the generated by them Sounds are mixed acoustically in the room in matrix form; c) a frequency characteristic compensation circuit (10) through which the difference signals (L-R) and (R-L) the Playback sensitivity in the low frequency range is made large and in the high frequency range small compared to the sum signal (L + R); d) a matrix circuit for mixing the difference signals (L-R), (R-L) and the sum signal (L + R) in matrix form to generate left and right signals (L, R) and e) Auxiliary output terminals to which the left and right signals (L, R) are fed from the matrix circuit, characterized in that circuit parts (20; 20 ';SW') are provided for preventing the frequency characteristic compensation by the frequency characteristic compensation circuit (10). 2.) Apparatus according to claim 1, characterized in that the means for preventing by switching a switch when inserting a plug into the auxiliary output terminals is operated. 4 0 9 8 17/0872 3.) Apparatus according to claim t, characterized in that the Device for preventing the frequency characteristic compensation from electrical circuit parts (20, 20 ·) "consists of the'prefrequenzc'häräkteristik-Eoinpensation reversible-." 4.) Device to. Claim 3, characterized in that the circuit (20) for undoing the frequency characteristic compensation consists of two capacitors (Cj-, CV) connected in series and a resistor '(R ₁ , -) Ta which is parallel to the second capacitor (Cg).' . .-. - ^{5.) Device according to claim 3} , characterized in that the circuit (2O 1 ") for reversing the frequency characteristic compensation from a" capacitor (C ₅ ¹ ) is formed ". 6.) Apparatus according to claim 1, characterized in that the device for ineffective compensation of the frequency characteristic compensation is a switch (SW ¹ ) through which the frequency characteristic compensation circuit (10) is separated. 7.) device "according to claim Ϊ, characterized in that the Matrix circuit and the device for undoing the frequency characteristic compensation become effective, '. if an output signal is picked up at the auxiliary output terminals will. . "" "■" "'' ■■■ -" "'■" 8.) Apparatus according to claim 1, characterized in that at Acceptance of an output signal from the auxiliary output terminals, the matrix circuit taad the device for ineffective communication the frequency characteristic compensation in the same area take effect in "where the speaker systems switched off. 4 0 9 8 1 7 / 087-2 Blank page