One of the aims of acoustic developments of the last decades was improving the fidelity of sound reproducing systems using commonly available loudspeakers. One possible way to approach this problem is filling the acoustic field by diffuse sound wave space started from small radiation surface.

Former acoustic systems had several trends. Beside the conventionally built up soundboxes, wherein the loudspeakers are in a single box and suitable sized separate spaces belong to each loudspeakers, some special sound reproducing systems have been built for achieving optimum acoustic quality.

The book titled, Hangdoboz6pft (§s, H. H. KLINGE, published by FRANZIS- MARKTECH, Budapest 1991. p-p. 33-35, Figs. 19-19a"discloses spherical sound boxes for eliminating the acoustic beam, each with one loudspeaker. An important drawback of this construction is that, by bringing the boxes in suitable positions the directional characteristic is improving, but the same time phase linearity is falling off due to the increased distance between the boxes.

To avoid these problems, systems of different principles have also been built. For example the Walsch's TL system or W. Meletzky's BS systems giving circular radiation disclosed by H. H. KLINGER in the book titled"Hangdobozepites, published by FRANZIS- MARKTECH. Budapest 1991. p-p. 90-93, Figs. 71-73".

Both of these solutions provide acoustic image remarkable better than that of the spherical soundboxes. The high manufacturing costs is one of the causes that impedes the spreading of these systems.

Other solutions are disclosed in HU 197111B and HU 208586A for achieving more diffuse sound distribution. In both of them the acoustic field is uniformly spread by using bell mouth. Reduction of the sound beam effect that appears in higher frequency is the main benefit of both systems.

The system disclosed in HU 208 586A is able to radiate the whole sound frequency band. The construction seriously abridges the quality sound reproduction. At least two loudspeakers, reproducing different frequency sound, operate in one common sound chamber. The more difference between the features of the loudspeakers the more

adaptation in dimensioning of sound chamber is necessary. i ne iransTormation or radiation impedance shows serious variation too. Loudspeakers working in the same chamber have considerable influence on each other. As a result of these effect serious distortion appears. In the case of correcting the distortion by bell mouths fitted to loudspeakers then the problem arise again, that the acoustic centers of loudspeakers get too far from each other.

The origin of distortion of before-cited system is the far position of different frequency loudspeakers. The systems aiming the correction of this drawback, among others which have been disclosed in HU 197 111B and HU 208 586A, use bell mouth to improve the sound quality on one hand but introduce further distortion on the other hand.

The object of the present invention is providing a sound reproducing system that fills the acoustic field by diffuse sound space, without any elements causing acoustic distortion (like bell mouth) and the same time bringing acoustic centers of loudspeakers as close to each other as possible so as to result pseudo single point acoustic source effect.

The invention based on the principle that loudspeakers arranged with their rear part facing to a common convex polygonal space determined by the centers of magnets in the way that the largest distance between farthest magnets is equal or less than the 20 times of the largest size of the largest magnet mounted with the loudspeakers, and a soundbox is fixed to the front of at least one loudspeaker. In that way, the acoustic centers of loudspeakers are sufficiently close to each other and all of the loudspeakers radiate into the acoustic field.

The geometric size of loudspeaker magnets (i. e. magnetic core) determined by their thickness and diameter. These dimensions determine the acoustic center of loudspeaker. One object of the present invention is to obtain an arrangement in which the acoustic centers of loudspeakers are as close as possible.

According to the present invention in the sound reproducing system as described in the opening paragraph maximal distance between the centers of mass of any two of the magnets of the loudspeakers arranged with their rear parts facing to a common convex polygonal space determined by the centers of magnets, is less than 20 times of the maximal size of the biggest magnet, and soundbox is attached to at least one of the loudspeakers on the front part of that.

The loudspeakers arranged with their rear parts facing to a common convex polygonal space determined by the centers of magnets in the way that the axis of loudspeakers on their rear part extend within said convex polygonal space determined by the centers of loudspeaker magnets.

The rear part of loudspeakers is understood as the part on wmcn siae me voice coil and magnet are arranged. The opposite side is considered as front part.

The axis of loudspeakers is regarded as the line perpendicular to the plane of magnetic core and intersect at the middle point of the plane of magnetic core.

The loudspeaker arrangement disclosed by the present invention makes such soundbox designs possible in which the soundbox encompasses both the rear and front part of loudspeakers or multiple soundbox constructions which are fixed to the rear part and to the front part of the loudspeakers. Under the fixing soundbox to the front part of loudspeaker such a soundbox arrangement is meant in that the front part of loudspeaker encircled by the soundbox.

Instead of or completing the loudspeakers other kind of acoustic radiators can also be used, such as electrodynamic or horn loudspeaker or any other electroacoustic transducer. In the case of a horn loudspeaker the rear part is which contains the driver of horn.

The loudspeakers radiating backward are of the low-frequency ones, while radiating forward are the treble loudspeakers conventionally. The soundboxes aligned with loudspeakers can be closed, bass-reflex or any other kind of them. The boxes used can be very different in their shape from the polygonal to cylindrical design. The actual soundbox design usually determines mainly the sound quality in the acoustic field. The material and shape of a soundbox, joining, bracing and the bevels and fillets could decrease the origin of interference distortions. The best sound quality achieved, if the acoustic centers are at the listener's ear height level.

According to an embodiment at least one loudspeaker is encompassed with the soundbox attached to the front part of the loudspeaker. This may improve sound image in certain frequency ranges.

One possible embodiment of the invention with three electrodynamic loudspeakers is disclosed in the following description referring to the drawings in which: Fig. 1 is a simplified view of an embodiment of the invention with three loudspeakers ; Fig. 2 is an illustration of mechanical fitting of the loudspeakers of Fig. 1.

In Fig. 1 and also in Fig. 2 the loudspeakers 1,2,3 are arranged with their rear parts facing to each other, more particularly facing to a common central point, which is located somewhere within the space between the loudspeakers 1,2,3. Alternatively the rear parts may be facing to different points which, however, are located within a common convex polygonal space determined by the centers of all used loudspeaker magnets. The

maximal distance amaX is the largest distance between any two or tne magnets +, o, a taking into consideration their centers of mass. This is less than the 20 times of the maximal size of the biggest magnet of the used loudspeakers 1,2,3. In this respect maximal size of a magnet will be the maximal distance between any two different geometrical points of the same magnet. In the case of the embodiment illustrated in Fig. 1 the magnets 4,5,6 of the loudspeakers 1,2,3 are cylindrical with a certain height. In this way the maximal size of a magnet 4,5, or 6 can be a diameter measured in a slant direction between the to parallel end planes of the cylindrical magnet body.

The soundboxes 7 and 8 have been attached to the front part of loudspeakers 2 and 3 respectively. The magnets 4,5,6 of the loudspeakers 1,2,3, as it is shown in Fig.

2, are attached to fixing caps 10,11,12 by adhesive binding or threading or in any other known manner. The fixing caps 10,11,12 can be made of wood or metal or any other material. The outer plane surface of the fixing caps are attached to a T shape 13 frame made of wood or metal or any other material. The loudspeakers 2 and 3 are attached to both sides of the leg of T shape frame 13 through the fixing caps 11 and 12. Similarly, the loudspeaker 1 is attached to the crossbar of the T shape frame 13 through the fixing cap 10. The fixing of loudspeakers can be, of course, carried out in any other known manner.

Alternatively the soundbox 7 or 8 could be attached to the relevant loudspeaker 2 or 3 in a manner where the loudspeaker itself is encompassed with the soundbox attached to the front part of the loudspeaker. This embodiment is not shown in Figs.

The main advantage of the invention is in the fact that the acoustic center of loudspeakers working in different frequency ranges are close enough to each other. This enables quality sound reproducing in a very economical way causing diffuse sound space without acoustic transformation elements and dispensable distortion.

Working of the system according to the present invention can be regarded as an inverse of microphonous sound recording method, because the radiation surfaces arranged in a small space surrounded by the acoustic centers. As a result of that the system has extremely good reproducing abilities especially with one or two microphonous audio records.

It is an advantage that the system according to the present invention can be built up using mainly conventional loudspeakers and the acoustic centers of loudspeakers arranged close to each other. Further advantage that there are no elements causing acoustic distortion.