DE2046776C3 - Interference loudspeaker system for stereophonic reproduction - Google Patents

Description

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The invention relates to an interfaced loudspeaker system for stereophonic playback that has both a center signal and two side signals radiates, and in which all speakers are housed in a single housing

The invention aims at broadband subjective stereophonic reproduction by means of a single loudspeaker box, which is particularly suitable for a cost-effective equipment of small appliances, door that way Improvement of the usual stereophonic reproduction through the additional use of the interference loudspeaker system and for more effective reproduction of artificial head stereophonic performances.

According to the principle of summing localization of coherent signals to find W ar η blocks (Audible Z, Vol 6, _1941., Pp. 174-188) sound sources intensity · and maturity conditionally so located, as if only one signal between two sound sources aired would. The conventional playback in the ΛΥ-technique uses this principle; where ΛΥ-technique means that two loudspeakers are set up separately and controlled with the signals X (right signal) or Y (left signal).

It is known that the following deficiencies occur:

- the "broadening of the center", d. H. the sound body appears on both sides during playback

moved to the speakers,

- the lack of spatial resolution in the dimension of depth,

- the limitation of the base to the area between the two speakers,

- the need to separate two speaker enclosures to have to set up.

To counteract these deficiencies, the following methods are known and used:

The broadening or the lack of the center was countered by setting up several loudspeakers using MS and .YY signals (M = X + Y; center signal; S = XY; side signal). It was, inter alia, an M itten speaker with the Summensienal M and the side speakers with Χ / λ or Y / l fed (see DT-PS 12 20 895).

The depth resolution that is sought in subjective (head-related) stereophony is significantly disturbed by the acoustic crosstalk, d. H. in that part of the X signal is delayed and, depending on the frequency, acoustically superimposed on the V signal and vice versa. Remedy can e.g. T. can be achieved by electrical compensation circuits.

Lauridsen and Schlegel have already pointed out the possibility of widening the base (Gravesaner Blätter, Volume 11, 1956, H. 5, P. 28 - 50), and A controllable base widening was made using the runtime and phase-related locating capabilities used - in the DT-AS 11 60 503.

The transmission of stereo signals from a single loudspeaker housing is possible using the presented by Lauridsen and Schlegel (1956) Cross loudspeaker principle known per se, see also Funk Technik No. 2, p. 52 (1970). The one used here Process in which the transversely radiating loudspeakers with the S signal and the forward radiating Loudspeakers are controlled with the M signal, has the disadvantage that the lateral resolution is frequency-dependent and only satisfactory in the lower frequency range (up to about 1 kHz) can work.

The per se known anti-phase control arranged side by side, essentially after Front radiating loudspeaker (cf. DT-AS 10 73 036), which is used to generate pseudo-stereophonic effects is useless for the purpose of acoustic redissolubility of stereophonic signals; only additional frequency-dependent acoustic superposition of coherent signals can this be expected.

The invention is based on the object of a loudspeaker combination accommodated in a housing to be arranged and controlled electrically in such a way that it is possible to use the stereophonic signals emitted for Listener in front of the loudspeaker combination is as realistic as possible from the side and acoustically in depth to appear resolved, so that the original spatial sound image is subjectively true to frequency and time of flight is reproduced.

This object is achieved according to the invention in that all speakers are essentially in one plane are arranged offset and radiate from, and that in the frequency range relevant for the location (over 300 Hz) the amplifier channel for the side signals a strong increase in the lower ones Frequencies compared to the amplifier channel for the center signal, in such a way that the frequency-dependent

Depending on the amplitudes and phase positions of the side signals compared to the Miuensignal, separate right (X) and unk signals arise for the listener according to their acoustic superposition.

The most advantageous embodiments of the invention are specified in the subclaims.

The advantages that can be achieved with the invention are that - especially in small appliances - the stereophonic playback with a loudspeaker housing is made possible, and that with additional Use of ate center speaker system in a conventional stereo system

- the local dissolvability also in the dimension of Depth can be significantly improved,

- Compensates for the unnatural broadening of the center can be,

- and in artificial head stereophony during playback a higher degree of naturalness can be achieved using loudspeakers.

The invention is explained in more detail below with reference to drawings; it shows

F i g. 1 the arrangement and control of three loudspeakers in one housing as an interference loudspeaker system,

F i g. 2 the control and arrangement of only two loudspeakers in one housing as an interference loudspeaker system and

Fig.2a) a general circuit example for the signal overlay required for this.

The following terms are used in the description:

X:

Y:

S = X-Y:

M = X + Y:

ρ (ω):

j:

ω = 2πί:

C-.
ΔΙ:

b:
a:

Ya; Gain of the λ signal opposite

of the Af signal at relatively low levels Frequencies (about 500 Hz);

V; variable frequency-independent reason

reinforcement of the S-channel opposite the M channel

(G F i. 1) in the 1st embodiment, the two outer loudspeakers L 1 and L 2 in opposite phase to the signal ρ (ω) · S and the center speaker L 3 is driven with the signal M, whereby the frequency response ρ (ω) in essentially has a low-pass behavior that can be specified as follows:

Right signal;

Left signal;
Side signal;
Center signal;

Frequency response of the channel for the side signal 5 in relation to the channel for M;

imaginary unit;
Angular frequency, l ·. Frequency;
Period of an upper limit frequency; Speed of sound;
Difference in the distances of the centers of vibration of loudspeakers L 1 and L 2 from the ear that receives - ^;
Distance of the centers of vibration of loudspeaker L 1 from that of L 2;
Distance of ears;

For an optimal adaptation of the overlay, it is advantageous to make the basic reinforcement of the S channel variable compared to the iVf channel. This means that ρ (ω) is replaced by ρ (ω) = V · ρ (ώ), where V indicates a constant that can be realized by a potentiometer

Note: Under X and V we mean the right and Left-hand signals as they are present on the loudspeaker membrane. If one interprets A "'or VaIs the X, Y equivalent amplitudes, as they are superimposed on the right and left ear, then the sum can be given approximately by

X " = (X - Y) p (m) j- sin Wt ₀ A- i- (X + Y),

so that in the frequency range that is important for localization with the formula given above for ρ (ω) it approximately follows: X '= X \ since because ω &<1 and 2wfo> -l / vb applies:

For transmission below 300 Hz you need It is well known that one should not pay attention to localized radiation: it can be ρ (ω) = 0 or all three loudspeakers can be controlled so that they emit in phase - for optimal use of the loudspeakers.

In the second embodiment (FIG. 2), one loudspeaker is controlled with the signal M + p (a) S and the other with the signal Μ-ρ (ω) 5; transformers or (internal) resistors can be used for this. For low frequencies below 300 Hz, approximately /) (w) = 0 can again be provided.

By changing the amplification ratio V , the impression of width and depth of the sound can be changed slightly.

1 sheet of drawings

Claims (4)

Claims; t, interference loudspeaker system for stereophonic reproduction, which emits both a center signal (voice signal) and two side signals (positive or negative difference signal), and in which all loudspeakers are housed in a single housing, characterized in that all loudspeakers are essentially in one plane are arranged offset and radiate forward and that in the frequency range relevant for localization (above 300 Hz) the amplifier channel for the side signals has a strong increase in the lower frequencies compared to the amplifier channel for the center signal, in such a way that the frequency-dependent amplitudes and phase positions of the side signals compared to the center signal, according to their acoustic superposition, separate right (X) and left signals fl9 arise for the listener. 2. Interfcrenzlautsprechersystem according to claim 1, characterized in that three speakers arranged side by side are provided, of which the middle one emits the center signal (M) , while the two outer speakers each emit a side signal (Sfipy), - Sp (u))) . 3. Interference loudspeaker system according to claim 1, characterized in that two identical speakers arranged side by side are provided, each of which has both the center signal (M) and one of the side signals (S ■ ρ {ω \ -S- p (fi}) )) radiates 4. Interference loudspeaker system according to one of the The preceding claims, characterized in that all speakers below 00 Hz are in phase emit the center signal.