DE1049918B - - Google Patents

Description

The invention provides a loudspeaker arrangement for closed rooms that is inexpensive a uniform sound distribution in the playback room and thus a good surround sound effect is guaranteed.

So far it has been customary to achieve such an effect through additional tweeters, the z. B. are attached to the side walls of a radio receiver and shine obliquely forward while the woofer shines straight forward.

It is also known to arrange the single loudspeaker on the vertical rear wall and one to let a small part of the sound energy radiate forward through an opening in the front wall (British Patent 665 163). Sound-reflecting and sound-dispersing screens should be behind the rear wall, that direct the sound upwards at an angle. Such an arrangement is quite cumbersome and also does not sufficiently solve the problem underlying the invention, because the housing of the Propagation of the backward emitted sound stands in the way.

It is also known to have the single loudspeaker or the main loudspeaker in the upper part of the rear wall to arrange the housing so that it shines obliquely upwards. In one of these known arrangements the rearward sound radiation is hindered by the protruding upper wall of the housing (U.S. Patent 2,539,327). This disadvantage falls in another arrangement of this type, because the rear wall corresponds to the position of the loudspeaker runs obliquely (Swiss patent specification 303 107). The sound distribution is quite good, but apparently not yet sufficient, because it is recommended to mount a tweeter on the front wall.

Finally, it is known to have such a baffle positioned obliquely forwards in the interior of the housing to arrange that the loudspeaker attached to it near the upper edge through the openings in the Front wall shines diagonally downwards (British patent specification 652 377). In the bottom and in the top of the case there are openings for heat dissipation through the chimney effect. Through the upper openings part of the sound radiated backwards by the loudspeaker emerges at an angle to the rear. But there the If a substantial part of the sound is radiated forward, there is no uniform sound distribution in the room.

The invention solves the problem posed in the following way. It relates to a loudspeaker arrangement for enclosed spaces in which the loudspeaker is mounted in the upper part of the rear wall of a housing so that the front of its diaphragm is loudspeaker arrangement
for closed rooms

Applicant:

Telefunken GmbH,
Berlin NW 87, Sickingenstr. 71

Roland Rabl, Göttingen,
has been named as the inventor

shines diagonally upwards without obstruction from protruding housing walls. According to the invention are on the front wall of the housing made openings in comparison to the sound radiated backwards Only let through so little sound energy that without additional tweeters a uniform Sound distribution of all sound frequencies in the room is achieved.

Appropriately, these openings \ verde at the same time used to dissipate the heat developed in the housing through the chimney effect.

The drawing shows an embodiment of the invention. In
Fig. 1 is a section parallel to the side surface and in Fig. 2 the front wall is shown.

In Fig. 1 and 2, T is a table or the like. On which the device is placed; W is the wall of the playback room behind it. Individual characteristic sound beams and the first mirror image of the loudspeaker L are also shown in FIG. 1, including the diffraction of a beam grazing the top of the housing. As is known per se, the loudspeaker L is arranged on the rear upper edge of the housing, in such a way that it still covers the upper part of the rear wall R. In order to save space, this is bent and runs more steeply than flat in its upper part, and almost vertically in the lower part; it is not protruded from the cover plate of the housing, and only slightly protruded from the side walls. The upper front and rear edges of the housing are preferably rounded so that the side walls have an approximately parabolic profile.

Openings O are provided on the front. You are supposed to put the sound shadow in front of the housing at the high frequencies at which the sound diffraction occurs

809 '748/319

Claims (4)

the edges of the cabinet are removed by making the sound emitted by the loudspeaker directly audible in addition to the sound reflected from the walls. The openings O must, however, be dimensioned in such a way that the rearward radiation remains predominant. The result is a balanced sound image that is equivalent throughout the room, without the need for additional loudspeakers or sound-dispersing means. The use of several openings causes a diffuse sound distribution to the front, which promotes the intended effect. In addition to the spatial sound effect, the arrangement according to the invention has the advantage that the distorting directional impression is equal to that of a natural sound source. If only reflected sound is used, a false and undesirable position of the sound source would be simulated, e.g. B. on the ceiling or behind the device, or it gives the impression of sitting in a concert hall behind a pillar. On the other hand, the directional impression is not as unnaturally strong as with a single loudspeaker radiating directly towards the front, because the reflected sound creates a surround sound effect. The fact that despite the small proportion of the sound radiated forwards compared to the reflected sound, a directional impression is still generated can be explained by the echo masking effect found by Haas in 1951 during speech intelligibility studies, which states, among other things, that the original sound and a reflected sound by a few Millisecond delayed sound can be merged by the hearing into a uniform sound and directional impression, but that the original sound (front radiation) defines the directional impression far more than it would correspond to its energy-related part. The upper openings in the drawing are made small to avoid an acoustic short circuit. They then act as an acoustic inductance and not as a short circuit. They are conveniently arranged on both sides of the large scale 5 *. In the exemplary embodiment, an opening is also made below the scale, through which the sound can exit to the front. These three openings also cause heat to be dissipated through the chimney effect. If necessary, openings can also be made on the side walls. The openings O can be covered by a grid. It is indicated in Fig. 2 by hatching. The device chassis, not shown in FIG. 2, can be inserted from the rear; the rear wall R, including the loudspeaker and paneling, must be made removable. Insertion from the front or from below is also possible. An oval loudspeaker is advantageously used, in which case the housing does not need to be made larger than when the loudspeaker is mounted on the front wall. The operating means - rotary knobs and pushbuttons - and the rear housing connections keep their previous position. at. P A T E N T Λ N S P R C) C H E: 1. Loudspeaker arrangement for closed rooms with the loudspeaker in the upper part the rear wall of a housing is attached so that the front of its membrane is unobstructed radiates diagonally upwards through protruding housing walls, especially radio receivers, characterized in that openings (O) are attached to the front wall of the housing, which In comparison to the sound emitted backwards, only so little sound energy can pass through that without additional tweeter an even sound distribution of all sound frequencies in the room is achieved. 2. Loudspeaker arrangement according to claim 1, characterized in that the in the upper part of the Openings located on the front wall are so small that they do not act as a short circuit, but rather act as acoustic inductance. 3. Loudspeaker arrangement according to claim 1, characterized in that the openings in the Front wall are distributed over the lower and upper part so that there is a discharge due to the chimney effect the heat developed in the housing takes place. 4. loudspeaker arrangement according to claim 1, characterized in that the side walls of the Housing have the shape of a parabola, the apex of which is at the top. Considered publications:
Dr. Eugen Nesper, "Loudspeaker", 1925, p. 45; British Patent Nos. 665 163, 652 377;
U.S. Patent Nos. 2,056,305, 2,315,896,
539,327; Swiss patent specification No. 303 107. 1 sheet of drawings