DE3130234A1 - Loudspeaker enclosure or combination for stereo reproduction - Google Patents

Abstract

In contrast to the usual loudspeaker arrangement for stereo sound reproduction involving separate loudspeaker enclosures set up with adequate spacing, which are fed with the left-hand (L) and right-hand (R) sound signal, the loudspeaker arrangement proposed here operates with loudspeakers which are arranged closely to one another and the radiating directions of which are offset with respect to one another by 90 DEG and which are fed with the M = L + R and S = L - R signals. Using a single loudspeaker enclosure which radiates the M signal at the front and the positive or respectively negative S signal at the side, a largely true stereophonic sound image can be reproduced in the room by this means. Such a loudspeaker configuration is suitable in the various construction variants, described in greater detail, for, among others, equipment having small dimensions and in-built loudspeakers such as, for example, portable receivers, portable television sets, but also especially for single-enclosure loudspeakers for hi-fi systems when there are conditions of restricted space, and particularly also for installation in a motor vehicle in the centre of the rear shelf. A suitable matrix is supplied for feeding loudspeaker enclosures of such construction with the regular left-hand (L) and right-hand (R) signals.

Description

DESCRIPTION

Loudspeaker box or combination for stereo playback For stereophonic Sound reproduction is generally at least two separate loudspeaker boxes used, which is placed at a suitable distance of approx. 3 to 4 m in front of the listener and with the two separate signals for the left (L) and right (R) stereo information be fed. Embodiments of the known loudspeaker boxes are very diverse, several loudspeakers are used within the individual loudspeaker box, which are preferably arranged on the vertical front surface, in special cases but are also placed so that they also radiate upwards or obliquely to the side. This often affects the tweeters in particular.

It is also known for reproducing the low frequencies below about 300 Hz to use a common loudspeaker for both channels and only for the reproduction of the middle and high frequencies above 300 Hz two separate Use loudspeaker boxes at a corresponding distance of a few meters be set up. The common woofer is then placed anywhere in the room.

Preserved with all known speaker combinations and arrangements always use the loudspeakers intended for directional sound reproduction separate left (L) and right (R) signals, so that from the superposition of the two Sound fields the stereophonic sound field is reproduced.

It is also known, using stereophonic links (L) - and right (R) signals to achieve pseudo-quadrophone playback by that in the rear part of the listening room another one or two loudspeaker boxes are set up which are either also fed with the left (L) and right (R) signals or with one of the two combined signals. As such it was too the difference signal S = L - R is used. This latter pseudo-quadrophone Process is under designations such as "Quadro-Sound", "Multi-Sound'l," Quasi-Quadro " i.a. has been used frequently.

The disadvantage of the known speaker arrangements for stereo or Pseudo-Quadro playback is mainly due to the considerable space required for the several Loudspeaker boxes.

Even if these have small dimensions and you have appropriate Accepts loss of quality, at least the corresponding installation points are in the Listening room required, which are reasonably favorable for the sitting position of the listener, so a stereophonic reproduction impression is made possible at all. In all of those Cases where there are not at least two such installation points due to the given Furniture arrangement can be found, the achievable quality of the stereo transmission remains clearly falls short of expectations.

The invention is concerned with the task, especially for those living space conditions, where there is practically only a single installation space for a loudspeaker box is to find a solution with which a convincing stereophonic playback quality is nonetheless possible is achieved for the full range of the given listening or sitting positions.

The invention relates to a loudspeaker box or combination with several loudspeakers intended for front and side sound radiation and has the object that the or the loudspeakers radiating from the front are fed with the sum signal M = L + R and that the other for lateral Sound radiation provided speakers preferably at an angle of about 900 are aligned with the front speakers and that these speakers Signals are fed which are essentially the stereophonic difference signal S = L - R represent.

At the time of the introduction of stereophony on records and radio the so-called M / S technique was intensively experimented with, especially on the recording side. A combined stereo microphone, which a cardioid microphone for picking up the mid-range signals and for the recording of the side signals contains such an oo-shaped characteristic, both of which were placed at the central point in front of the sound box. This technique theoretically allows signal acquisition with the correct stereophonic resolution of the Total signal according to amplitude and direction of the individual signals. It exists theoretically fully equivalent to the so-called A / B stereo technique, in which 2 separate, in the appropriate Microphones placed at a distance from the sound body for picking up the right and left signals be used.

Because of the indispensable requirement in the studio for a subsequent Signal correction to emphasize individual instruments and solo voices was implemented classic M / S technology in the course of the further development of studio technology the multichannel recording technology derived from A / B technology has been completely displaced, with a directional characteristic suitable for a large number of support microphones any composition of the overall signal is made possible.

Wicdergalrescitig has from the beginning on in the Stcreo technique Use of separate loudspeaker boxes for playback of the left and right Individual signals enforced, although on the transmission side, both for the record as well as the signals in broadcasting for reasons of compatibility with mono transmission M = L + R and S = L - R formed and recorded or transmitted in the multiplex signal will.

The loudspeaker combination according to the invention can in principle be shown in FIG individual loudspeaker boxes are formed, which are placed next to each other in such a way that that one forward and the other two sideways at an angle of 90 ° radiate. While the forward-facing loudspeaker group with the composite signal M = L + R is fed to the side-aligned loudspeaker groups the signal S = L - R, advantageously with such a polarity that the one directed to the left the positive and the one directed to the right the negative S signal is supplied.

With the antiphase and symmetrical radiation of the differential signals A very correct reproduction of the spatial sound image is possible on both sides. At the same time it is avoided that quality losses, especially in the range of low frequencies occur through extinctions. The symmetrical reproduction of the sound field has Incidentally, the advantage that also lateral sitting and listening positions outside of the optimalexl frontal area offer favorable and equivalent quality ratios.

Theoretically, a true-to-image reproduction of the stereophonic takes place Sound field in harmony with that of the recording room only if the Recording takes place according to the M / S principle, as this is done with today's standard studio technology If this is not the case, the instrumental resolution gives way to the directed direct sound parts when using the loudspeaker combination according to the invention from the optimum value, and in such a way that the expansion of the sound body in width restricted is, but its central position is largely independent of the point of view the listener remains firmly oriented in the room.

On the other hand, it causes the extremely lifelike reproduction the spatial configuration characterized by the side reverberation components of the original sound field a special emphasis and deepening of the stereophonic Spatial impression, the z. B.

is extremely demonstrative when switching between mono and stereo. A further development of the loudspeaker box according to the invention is that all Front and side speakers are housed in a single housing.

This embodiment represents in terms of effort and space requirements an optimal solution, with which even under very limited spatial conditions a qualitatively good stereo reproduction can still be achieved.

Another further training is based on the above and includes, that the individual loudspeaker groups intended for frontal and lateral sound radiation are acoustically separated from each other within the box by partition walls and operated as closed individual systems. By within the only one CehHuse's proposed partition walls to acoustically separate the groups of radiators these can be individually coordinated with regard to their transmission behavior and optimize, so that time-consuming, empirical measures that may be necessary are no longer necessary would be if, in an execution without partitions, a loss of quality would result Extinctions and repercussions between the emitter groups as far as possible should be avoided.

The further suggestion is based on the last-mentioned geographic version with partitions and has the object that the mutual acoustic Separation of the loudspeaker groups provided partition walls with so arranged Breakthroughs are provided that a down to the lower transfer limit for the entire system substantially linear sound pressure frequency response is achieved and the lower limit frequency is approximately determined by the total volume of the loudspeaker box.

With corresponding, in the sense of the classic bass-reflex principle provided in the intermediate walls breakthroughs that with the insert the partition walls associated reduction of the for the individual radiator groups available volume to approx. 1/3 of the total volume, no equivalent increase the lower limit frequency results in a significant deterioration in quality of the overall system. The possibility of these disadvantages through application Avoiding corresponding reflex couplings appears in particular from the Basically sensible, because the low frequencies below approx. 250 Hz do not have any anyway make a physiological contribution to the stereophonic room transparency, so that the acoustic Adjustment of the overall system in this frequency range is only for consideration can take place on optimal transmission parameters.

The following 3 training courses relate to a loudspeaker box or -Combination in a special design and shape for use in motor vehicles.

First of all, it is proposed that the radiating surfaces of the frontal and lateral sound radiation provided loudspeaker deviating from the theoretically optimal right-angled inclinations with respect to the horizontal plane this form a smaller angle of inclination of only approx. 300 to 600.

With the reduction of the baffle inclination angle compared to the horizontal plane is made possible to keep the loudspeaker box in the Höhekl, so that in the cheapest Case when using only one loudspeaker each for the front and side radiation a relatively flat structure is created, which e.g. the installation or structure in the middle the rear window storage allows. At an angle of inclination the baffles of e.g. 450 and use of 3 loudspeaker chassis with a diaphragm diameter of 100 mm each an overall height of the loudspeaker box of 90 mm can be easily achieved.

The proposed design and arrangement of the with M and S signals powered speaker box in the rear window shelf has a number of advantages.

The frontal1 inclined upward radiation causes the Sum signal M = L + R very good speech intelligibility in the front seats, without disturbing the occupants in the back seats with direct sound. In order to it is possible to dispense with an additional loudspeaker in the dashboard area entirely.

The lateral, oblique upward emission of the differential signals S = L-R or -S = R-L simultaneously conveys a largely optimal stereophonic spatial transparency, especially with regard to the side sound components of the stereo signal.

Due to the proposed alignment of the baffle surfaces, the rest assured that none of the occupants by directly directed direct sound is harassed and at the same time an extremely pleasant and fully stereophonic Sound reproduction is given in all seats.

The following special design for the installation in the motor vehicle proposed embodiment also includes that the baffle surfaces for frontal and side sound radiation provided speakers one down open three-sided pyramid, preferably form a tetrahedral body.

With the design of the housing of the loudspeaker box as 3-sided Pyramid in the manner of a tetrahedral body, which is open at the bottom, succeeds in the entire area of the rear window shelf as a baffle fitted in the middle to use, so that a good bass reproduction despite the use of only small speakers is achieved. Furthermore, through the obliquely rearwardly directed radiation from the difference signals S = L-R and PS = R-L have an even greater installation tolerance the exact placement, because the risk is werner direct, annoying Sound in the rear seats is further reduced - also in the event that that it is installed on the front edge of the rear window shelf.

As a further variant of this type, it is also scored, that the baffle surfaces are intended for front and side sound radiation Loudspeaker together with a further sloping surface one afterwards Four-sided pyramid open at the bottom, preferably a half-octahedron. These In terms of design, form appears to offer the most favorable conditions, since it is relative flat edge angles occur, so that a visually less conspicuous execution can be realized.

The last development of the invention deals with the problem the signal processing for the control of the front and side-facing loudspeaker groups with the signals M = L + R and S = L-R.

In addition to the basically possible and known receiver and amplifier side The task of providing and processing these signals is also one specify a passive circuit solution in which the output is more conventional Stereo system available Siganle L (left) and R (right) directly for the M and S control can be used. According to the invention, this takes place in Way that the two groups of speakers intended for lateral sound radiation in opposite directions in series between the hot poles of the left (L) and right (R) signal source lie and that the loudspeaker group intended for frontal Schallab radiation with one pole at the junction of the two side panels connected in series Loudspeaker groups and with the other pole connected to ground. The proposed Circuit approximately meets the requirements.

For the special case that the impedance dc 3 loudspeakers have the same value R, the result is for the signal power NtM) of the M component; and for the signal power N (s) of the S component as where: R = loudspeaker impedance U (L) = level of the left signal U (R) = level of the right signal t (M) = level of the sum signal U (s) = level of the difference signal It can be seen that the coefficients of the M and S components are equal, so that the correct ratio is achieved with the same absolute values of U (M) and U (s).

The S components are superimposed by pure L and R components with half the level, i.e. the side speakers also play the pure signals U (L) to the left or U to the right with 1/4 of the forward emitted Transfer the power of the M signal.

This deviation from the pure M and S reproduction can be seen in in practice as insignificant and does not reduce the quality of the stereo reproduction noticeably.

In the case of mono operation, this proves to be an advantage, because the side speakers are then automatically controlled, with each 1/4 of the power of the front loudspeaker in phase with it. This will make the Mono playback significantly improved. In the proposed Schaltun is preferred by choosing a correspondingly reduced impedance value R for the loudspeakers used ensure that overall approximately the same amplifier power rating can be seen as when connecting conventional loudspeakers for the channels Left (L) and Right (R).

With the choice of different impedance values for the front and side speakers can be further variants in the signal distribution as well as he the ratio of Realize M and S components as well as for the superimposed pure L and R signals, depending on the quantitative weighting on the quality of stereo and mono playback have a correspondingly negative or positive effect.

Fig. 1 shows a plan view of the basic composition of a Loudspeaker combination for M / S playback from individual boxes with the I "rontalbox l and the two side boxes 2 and 3.

From. 2 shows the execution in the single housing from the same perspective 4 with the front speaker 5, the side speakers 6 and 7, as well as the occasional existing partition walls 8, which are optionally provided with openings.

Fig. 3 and Fig. 4 show a version for motor vehicle installation in Shape of a tetrahedron body in plan view (9) and perspective (13). The speaker 10, 11, 12 are located in the inclined triangular surfaces. 5 and Fig. 6 show an equivalent design in the form of a 4-sided pyramid in plan view (14) as well as perspective (18). The front speaker 15 is located in the front inclined triangular (Ilichc, the Sciten loudspeakers in the lateral triangular surfaces. The rear triangular surface is closed.

The pyramid bodies 3, 4, 5, 6 are for installation in a horizontal Baffle preferably open at the bottom.

Fig. 7 shows the special interconnection in the event that the M / S loudspeaker combination not supplied with the signals M = L + R and S = L - R should be, but with the conventional output signals L and R of a normal Stereo NF amplifier.

The two side speakers 19 and 20 are in opposite directions in series between the hot poles of the left (21) and right (22) amplifier output signals. The front loudspeaker 23 receives the sum signal M = L + R from the connection point of the two side speakers to ground.

Claims (8)

PATENT CLAIMS U Loudspeaker box or combination for stereo playback with several loudspeakers intended for frontal and side sound emission, dad. gek. that the speaker or speakers emitting from the front with the composite signal M = L + R are fed and that the other intended for lateral sound radiation Speaker preferably at an angle of about 900 to the front speakers are aligned and that these speakers are fed signals which essentially represent the stereophonic difference signal S = L - R. 2. Loudspeaker box or combination according to cont. 1, dad. gek. that all front and side speakers housed in a single housing are. 3. loudspeaker box or combination according to cont. 1 or 2, dad. gek. that the individual, for frontal and lateral sound radiation provided loudspeaker groups within the box acoustically through partition walls are separated from each other and operated as closed individual systems. 4. loudspeaker box or combination according to claim 3, dad. approved, that provided for the mutual acoustic separation of the loudspeaker groups Partitions are provided with openings arranged in such a way that for the entire system an essentially linear sound pressure frequency response down to the lower transmission limit is reached and the lower limit frequency is approximated by the total volume the loudspeaker box is intended. 5. loudspeaker box or combination according to claim 1, 2, 3 or 4 in special design and shaping for installation in motor vehicles, dad. marked, that the radiating surfaces are intended for frontal and lateral sound radiation Loudspeaker in deviation from the theoretically optimal right-angled inclination towards it the horizontal plane with this a smaller angle of inclination of only approx. 300 to 600 form. 6. loudspeaker box or combination according to claim 5, dad. characterized in that the baffle surfaces for the front and side Sound radiation provided loudspeaker a three-sided pyramid open at the bottom, preferably form a tetrahedral body. 7. loudspeaker box or combination according to claim 5 dad. marked, that the baffle surfaces are intended for frontal and lateral sound radiation Loudspeaker together with a further sloping surface one afterwards Four-sided pyramid open at the bottom, preferably a half-octahedron. 8. loudspeaker box or combination according to one of the preceding claims, in which a direct signal feed with conventional stereophonic links (L) - and right (R) signals are provided, dad. marked that the two for lateral sound radiation provided loudspeaker groups in opposite directions in series lie between the hot poles of the left (L) and right (R) signal source and that the loudspeaker group intended for frontal sound radiation with the one Pole to the connection point of the two loudspeaker groups connected in series and the other pole is connected to ground.