DE2351423C2 - Stereophonic player - Google Patents

Description

marked by

d) a frequency characteristic compensation circuit (10), by means of which the level of the difference signals (L - R) and (R - L) is large in the range of low frequencies and small in the range of high frequencies compared to the sum signal (L + );

e) a matrix circuit (18), which from the difference signals ( L - R), (R - L) and the sum signal (L + R) generates stereophonic left and right signals L and R for the headphones, if these with the additional Output terminals are connected and

f) a circuit (20, 20 ') or a switching element (SW) to cancel the effect of the frequency characteristic compensation circuit (10) when the headphones are connected to the additional output terminals (h, 13).

2. Apparatus according to claim 1, characterized in that the circuit (20, 20 ') for canceling the Effect of the frequency characteristic compensation circuit (10) its frequency characteristic in compensated in the opposite direction

3. Apparatus according to claim 2, characterized in that the circuit (20) for canceling the effect of the frequency characteristic compensation circuit consists of two series-connected capacitors (Cs, Q) and a resistor (Rt $ ) connected in parallel to one of the capacitors (Ci) , this circuit (20) of a preamplifier (3b) for the difference signal between the emitter of the transistor (Q]) (L - R) and the ground is switched on.

4. Apparatus according to claim 2, characterized in that the circuit (20 ') for canceling the effect of the frequency characteristic compensation from a capacitor (Cs) is formed, this circuit (20') between the emitter of the transi-

stors (Qi) of a preamplifier {3b) for the difference signal (L - R) w \ d mass can be switched on

5. Apparatus according to claim 1, characterized in that the switching element (SW) for canceling the effect of the frequency characteristic compensation circuit (10) is formed by an on-off switch arranged in this frequency characteristic compensation circuit (10).

The invention relates to a stereophonic player according to the preamble of claim 1.

In a known stereophonic reproducing apparatus of the presupposed in the preamble of claim 1 kind (DE-PS 12 20 895) are a center speaker, a sum signal and two side speakers anti-phase difference signals supplied in the difference signals (L - R) and (R - L) occur in the high frequency This area often exhibits distortion, which attenuates the differential signals. The sound reproduction is accordingly not entirely natural with this device; the spatial sound impression is not optimal.

It is also known (DE-OS 20 46 776), in one Interference loudspeaker system for stereophonic reproduction three loudspeakers relatively close together to be accommodated in a single housing and also those to be emitted by the side speakers To distort signals in such a way that by the acoustic superposition of the emitted signals approximately that The sound produced by the stereo recording microphone requires a number of settings and readjustments are necessary, which complicate the operation of the device. The one in general The surround sound actually achieved is therefore not sufficiently natural.

The invention is based on the object of a stereophonic player according to the preamble of claim 1 so that a sound with an improved spatial impression is created and with Using headphones, the left and right signals are picked up with unchanged frequency characteristics can be.

According to the invention, this object is achieved by the characterizing features of claim 1.

The frequency characteristic compensation circuit according to the invention amplifies the difference signals (L - R) and (R - L) compared to the sum signal (L + R) in the range of low frequencies and attenuates in the range of high frequencies , in which directional hearing is strongly developed, is increased in relation to the level of the center loudspeaker. This makes the lateral position of the left and right sound images clearer. The sound image is therefore perceived to be better stereophonic.

If, in the playback device according to the invention, the headphones are connected to the additional output terminals, then stereophonic left and right signals (L and R) are generated by the matrix circuit

The effect of the frequency characteristic compensation circuit is here by a switching device canceled.

Appropriate refinements of the invention are the subject matter of the subclaims.

jS Some exemplary embodiments of the invention are thus also the electrical frequency response

jt drawing illustrates it shows for the signals coming from the input terminals Ti

g Fig-1 a schematic representation of the loudspeakers ei- and T ₂ to the output connections of the amplifier 3c

'* nes stereophonic playback or 4c run according to the invention.

J advises; 5 The frequency characteristic compensation switch

'£ F i g. 2 is a diagram showing the reproduction of the individualization iu preamplifier 3b of the differential signal system 3

; j nen frequencies illustrated; "has a damping characteristic, for example

"? Fig. 3 is a block diagram of a first embodiment of 12 dB per octave and thus attenuates the playback

h example of the stereophonic reproduction according to the invention bc of the difference signal when it is in the higher range

; 2 devices: io frequencies are coming

F i g. 4 shows the circuit diagram of the main part of the embodiment F i g. 4 shows a practical embodiment of the according to FIG. 3; Preamplifier 36 with the frequency characteristic F i g. 5 and 6 diagrams of listening tests with a compensation circuit 10. With the aid of a capacitor Q according to the invention, the stereophonic playback device Q is from the collector of a transistor <? one betrays and with another playback device; 15 strong signal picked up and an output connector F ig. 7 a block diagram of the experimental arrangement, finally supplied to T _0. The series connection of a Kon-F i g. 8 is a graphical representation of the frequency capacitor Tj and a resistor Ri (which is connected in parallel with the test arrangement according to FIG. 7; capacitor C ₃ ) lies between FIG. 9 is a circuit diagram showing an exemplary embodiment of the output terminal To and ground. In this way, stereophonic playback device according to the invention; 20 the difference signal in the range of low frequencies F i g. 10 the circuit of the main part of a further amplified, in the range of high frequencies, however, strong embodiment. attenuated so that the frequency response according to curve a

Fig. 1 shows the loudspeaker system of an invention inFig.2 results

stereophonic playback device according to the invention. The effect achieved by the invention can be indicated by P a listener while the loudspeaker is a comparison experiment. As in the more on the left and right side of the listener with SPz. Figs. 5 and 6 are shown in front of a listener P in and SPk, respectively. The speakers SPl and a distance of 40 to 50 cm, a speaker SPk be a located from the left signal L and the right of the width d of about 35 cm placed in this box signal R of a stereophonic signal obtained differential, a center speaker SPm, a left renzsignal (L - R) and a difference signal (R - L) with 30 loudspeakers SPl and a right loudspeaker 5Pr. fed to the former opposite phase position. Like F i g. 7 shows, with the aid of an oscillator 5 The off gnales from the speakers will be reached via an amplifier 6 to the center of radiated sounds an A center speaker SPm is a sum signal of low-frequency signal generated A portion of this Si- (L + R) is supplied acoustically Room to the left loudspeaker SPm, another part is matriculated via phase and right sound information The listener P 35 reversing circuit and an amplifier 8 on the left thus has the impression that he is listening to the sounds from the loudspeaker SP _L and SPk (these Both left and right sides of the loudspeaker SPt or SPk loudspeakers are imaginary points L ', R' with opposite polarity. It results in closed). F i g. 5 shows the test result (sound perception thus also when using a very compact that of the listener P) in a freestereophonic playback device according to the invention, a pronounced frequency response according to FIG. 2, while FIG. 6 shows the spatial sound impression. Search result with a usual frequency response ent-The levels of the difference signals (L-R) are corresponding F i g. 8 shows, the curve a 'again and (R - L) being large in the range of low frequencies and the frequency response of the difference signal and the curve being small in the range of high frequencies compared to the frequency response of the sum signal, see sum signal (L + R) done as this F i g. 2 shows 45 light

Curve a illustrates the levels of the differences. In the case of FIG. 6 creates the sound image on the

reference signals and curve b the level of the sum signal side of the loudspeaker, which is connected to the center loudspeaker

les. The curve / ″ illustrates the phase position that is more in phase, ie the left one, for example

Difference signals (L - R) in relation to the phase position of the loudspeaker SPl and the center loudspeaker SPm with

Sum signal (L + R). In the present case, 50 signals are fed that are in phase, so the

the difference signals compared to the sum signal make listener P the feeling of getting the sound from the left,

hesitates. The apex of curve a is in the symbol χ in FIG. 5 and 6 indicate the positions

Area of the frequency range from 200 to 400 Hz. In which the listener P perceives the sound generator,

curves a and b intersect at about 4 kHz. if the sound is created on the left side (the

In an FM radio receiver according to FIG. 3 55 number of listeners is chosen to be 20). The character 0

becomes a composite stereophony signal, on the other hand it represents the positions in which the listener P

holding the difference signal (L - R), the sum signal perceives the sound image on the right side. The cure-

(L + R) and a control signal via an FM demodulator / and / 'are mean values of the various

lator 2 from a tuner 1 (containing for an IF amplifier listener perceived sound image distances from the

ker) the input terminals Ti and Ti of a differential central axis. The F i g. 5 and 6 thus show the sensation

Signal system 3 and a sum signal system 4 trains for the spatial expansion of the sound on the part of a

leads. The differential signal system 3 contains an auxiliary number of listeners in the frequency range from 300 Hz to

channel demodulator 3a, a preamplifier 3b with a 1 kHz. It turns out that a sufficiently stereophonic

Frequency characteristic compensation circuit and impression is achieved.

an output amplifier 3c for low frequencies. 65 If one now carries out a qualitative evaluation, see this

The sum signal system 4 has a low-pass filter 4a, can be seen from the measurement results according to FIG

a preamplifier 4ft and an amplifier 4c for F i g. 5 and 6 that useful at frequencies above 4 kHz

low frequencies. Curves a and b of FIG. 2 there is no more directional hearing. The listener has

at these higher frequencies the sensation as if the sound was being produced practically in the middle is therefore the volume level of the side speakers for frequencies above 4 kHz compared to the volume level of the center speaker and the volume level of the side speakers for Frequencies from 300 to 400 Hz increased compared to the volume level of the center speaker, see above the lateral position of the left and right sound images is made clearer The expansion of the stereophonic The sound image is thus better perceived by the listener.

In the lower frequency range, the left and right sound signals are generated with approximately the same phase position. The difference signals (L - R) and (R - L) therefore contain almost no low frequency components. In contrast, the difference signals contain sufficient tones in the higher frequency range. Therefore, if the frequency characteristic is flat over the entire frequency range, as shown in FIG. 8 shows, the sound strength of the left and right loudspeakers is amplified in the high-frequency range, as indicated by the dashed curve c in FIG. 8 illustrates In the frequency range between 300 Hz and 4 kHz, which has a special influence on the stereophonic perception, nothing is produced by the left and right loudspeakers that would improve the spatial sound perception.

This results in the change in the frequency characteristic according to the invention (increasing the Difference signals in the range of low frequencies and attenuation in the range of high frequencies) achieved a significant improvement in the stereophonic impression.

In the above description, an FM broadcast receiver has been taken as an example. Of course, however, the stereophonic playback device according to the invention can also be used in the same way can be used with a record player or tape recorder.

In the above description it was assumed that the levels of the difference and sum signals are the same at around 4 kHz. However, tests have shown that this frequency value can generally be in the range between 3 and 6 kHz.

If additional output terminals for the connection of headphones are provided in such a stereophonic playback device, the left signal L and the right signal R cannot be output by simply mixing the difference signals (L - R) and (R - L) and the sum signal (L + R) if the difference signals and the sum signal have a different frequency response. According to the invention, the effect of the frequency characteristic compensation circuit is therefore canceled by a switching device when the headphones are connected to the additional output terminals.

F i g. 9 shows a practical embodiment of the stereophonic playback device according to the invention, where the reference numerals according to FIGS. 3 and 4 are used.

Input terminals 11, 12 are fed to the difference signal (L - R) and the sum signal (L + R). The preamplifiers 3f> or 46 contain transistors Qi, Qi. The preamplifier 36 corresponds to that of FIG. 4, that is, contains a frequency characteristic compensation circuit 10. A load resistor R2 is provided between the collector of the transistor Qi and a current source + B. A resistor R ₃ is connected between the emitter of transistor Qi and ground. The connection point between capacitors C \ and Ci is connected to ground via a potentiometer A4. The tap of the potentiometer Ra is connected to the input of the amplifier 3c for low frequencies.

In the preamplifier 46 a load resistor Rs is connected between the collector of the transistor Q2 and the current source + B , while a resistor R% is connected between the emitter of the transistor Q ₂ and ground. Between the collector of the transistor Qi and the ground there is a capacitor G in series with a potentiometer Rj, the tap of which is connected to the input of the amplifier 4c for low frequencies.

The primary windings 13a, 14a of converters 13, 14, the secondary windings of which are denoted by 136, 146, are connected to the outputs of the amplifiers 3c and 4c. Resistors Rs and Ri form a negative feedback circuit between the secondary windings 136, 146 and the amplifiers 3c, 4c.

The right and left loudspeakers SPl and SPr are parallel to one another on the secondary winding 136 of the converter 13, via a polarity switch 16. The left loudspeaker SPl thus receives the difference signal (L - R) and the right loudspeaker SPr the difference signal (R - L). With the aid of the polarity switch 16, the polarity of the differential signal fed to the right loudspeaker SPr can be reversed, so that a signal of the same phase can be fed to both loudspeakers SPr and SPt when receiving mono. The center loudspeaker 5Pm is connected to the secondary winding 146 of the converter 14 and receives the sum signal (L + R).

A matrix circuit 18 is used to generate the left signal L and the right signal R from the difference signals (L - R) and (R - L) and the sum signal (L + R). This matrix circuit 18 contains resistors Rio, Ru, Rn and Ru. Additional output terminals are designated by t ₂ and (3, which are used to connect headphones and to which the left signal L and the right signal R are output by the matrix circuit 18. 20 designates a circuit through which the effect of the frequency characteristic compensation circuit 10 is canceled, fi in the socket arrangement / is a terminal connected to ground.

One end of the secondary winding 136 of the converter 13 is connected to ground via a resistor A15. The center point of the secondary winding 136 is directly connected to ground. The left output terminal h is connected via the resistor /? I3 to the end of the secondary winding 136 to which the resistor Rn is also connected. The end of the secondary winding 146 of the converter 14 that is not connected to ground is also connected to this output circuit via the resistor Ru & connected. The other output terminal h is connected to the secondary winding 136 of the converter 13 via the resistor /? I2 and to the secondary winding 146 of the converter 14 via the resistor Rw.

The socket arrangement / contains a left switch SWi and a right switch SW ₂ . They each contain a movable contact a and fixed contacts 6 and c. In the normal position (when playing over loudspeakers) the contacts a are connected to the fixed contacts 6. If, on the other hand, headphones are connected, with an insulating piece ti engaging between the output terminals fe and t ₃ , the movable contacts a are brought into contact with the fixed contacts c

The movable contact a of the left switch SIV ₁ is connected to the secondary winding 136 of the converter 13

Connection, while the fixed contact b of the switch 5Wi is connected to the common connection point of the left speaker SPt and the right speaker SPr . Fixed contact c of switch 5Wi is not connected. The moving contact a of the right switch SVV ₂ is grounded; the contact b of the switch 5W ₂ is connected to the secondary winding 14Z> of the converter 14 via the center loudspeaker SP _M. The fixed contact c of the switch SW ₂ is connected via the circuit 20 to the emitter of the transistor Q \ of the preamplifier 3b .

The circuit 20 for canceling the effect of the frequency characteristic compensation circuit 10 contains the series connection of two capacitors Cs and C ₆ and a resistor Äi6- connected in parallel to the capacitor C _6.

Since the frequency characteristic compensation circuit 10 is provided in the preamplifier 3b , the difference signals (L - R) and (R - L) have the values shown in FIG. 2 illustrated by the curve a frequency response. The phase position with respect to the sum signal (L + R) has the course according to curve Φ in FIG. 2. By the circuit 20, the effect of the frequency characteristic compensation circuit 10 is canceled, so that the difference signals (L - R) and (R - L) practically the same frequency response as the sum signal (L + R) according to curve b in F i g. 2 own. The phase of the difference signals is also the same as that of the sum signal.

If the loudspeakers 5Pl, 5Pr and SP _{M are used} to reproduce stereophony signals, the difference signal (L - R) is sent to the left loudspeaker SP ^, the difference signal (R - L) to the right loudspeaker (SPr) and the sum signal (L + R ) fed to the center loudspeaker 5Pm, since the movable contact a of the switches SWi and SW _{2 is} connected to the fixed contacts b , while at the same time the circuit 20 is disconnected from ground at one end and is therefore ineffective

If headphones are now connected to the additional output terminals, the movable contacts a of the switches 5Wi and SW _{2 come} into contact with the fixed contacts c. The right and left loudspeakers SPl or SPr are separated from the transducer 13; of the center speaker SPm is from the transducer 14 are separated, the circuit 20 is connected between the emitter of the transistor Q \ of the amplifier 3b and mass turned on by the output signal obtained from the preamplifier 3b and the difference signal (L - R) has a flat frequency response and the same phase position as the sum signal (L + R). The difference signal (L - R) emitted by the secondary winding 146 of the transducer 13 and the sum signal (L + R) emitted by the secondary winding 146 of the transducer 14 are mixed by the matrix circuit 18 so that the left signal L and an at the output terminal t ₂ of the output terminal h the right signal J? occurs

The circuit 20 can be implemented by a simplified circuit 20 ', which only contains a capacitor Cy (see FIG. 9).

Instead of the circuit 20, 20 ', the frequency characteristic compensation circuit 10 an on-off switch can be provided to the effect of the frequency characteristic compensation circuit when the headphones are connected to cancel.

In the case of the FIG. Such an on-off switch SW 'is provided in the exemplary embodiment shown in FIG. It is located in the socket arrangement / and is switched when the headphones are connected in such a way that the frequency characteristic compensation circuit 10 is separated from the output of the transistor Q.

The loudspeakers SPl, SPr and SPm can of course be replaced by loudspeaker systems which each contain a number of individual loudspeakers. In such a case, the sound ranges of the individual loudspeakers of each loudspeaker system are generally selected to be different.

In addition 5 sheets of drawings

Claims (1)

Patent claims:
1. stereophonic player, nut a) a left loudspeaker (SPl), a right loudspeaker (SPr) and a center loudspeaker (SP _M ) b) a device for supplying a difference signal (L - R) obtained from the left * and the right signal (L and R) of a stereophonic signal and a difference signal (R - L) with the opposite phase position to the left and right loudspeaker and to the Feeding of a sum signal (L 4- R) to the center loudspeaker in such a way that the emitted sounds are acoustically matrixed in the room to form left and right sound information, and c) additional output terminals (t ₂ , t ₃ % which are used to connect headphones and are provided with a switching device (SW _U SW2) through which the connection of the loudspeakers to the additional output terminals is interrupted when the headphones are connected to the additional output terminals will,