WO1999055117A1

WO1999055117A1 - Electro-acoustical transducer

Info

Publication number: WO1999055117A1
Application number: PCT/SE1999/000655
Authority: WO
Inventors: Erik Liljehag
Original assignee: Long Tall Ribbon Co. Ab; Westermark, Tomas
Priority date: 1998-04-22
Filing date: 1999-04-22
Publication date: 1999-10-28
Also published as: SE9801414L; SE9801414D0; AU4300099A

Abstract

An elector-acoustic transducer comprising a baffle having a number of electro dynamic bass units mounted in holes in the baffle. The invention is characterized in that the bass units (2) are essentially identical, and are mounted such that the surface projected by the oscillating part of the bass units (2) in the plane of the baffle (1), have a surface coverage of at least 35 % of the surface of the baffle.

Description

Electro-acoustica 1 transducer

The present invention relates to an electro-acoustic transducer.

It is known to arrange two or more loudspeaker elements or other electro- acoustic elements in one and the same baffle. A baffle is a front disc wherein holes have been made and in which loudspeaker elements have been mounted. Normally the baffle is provided in a closed loudspeaker box as a front wall.

Such loudspeaker boxes have a relatively low efficiency because the coupling to the mass of air that is to be put in motion is relatively poor. In addition, when the various loudspeaker elements co-operate, interferences occur which distort the sound.

The present invention relates to a substantial improvement in large electro- acoustic bass units comprising a plurality of loudspeaker elements.

Thus, the present invention relates to an electro-acoustic transducer comprising a baffle having a number of electro-dynamical bass units mounted in holes in the baffle, and is characterized in that the bass units are substantially identical and mounted such that the surface projected in the plane of the baffle by the oscillating part of the bass units, has a surface coverage of at least 35% of the surface of the baffle.

Below, the present invention will be further described partly with reference to embodiments of the invention shown on the appended drawing, wherein 2

- fig. 1 shows an electro-acoustic transducer according to the invention as seen straight from the front

- fig. 2 shows an electro-acoustic transducer according to the invention seen straight from the back.

In fig. 1 there is shown an electro-acoustic transducer comprising a baffle 1 having a number of electro-dynamic bass units 2 mounted in holes 3 in the baffle. The baffle 3 comprises a disc of a suitable material. The bass units can be conventional cone loudspeakers, but other electro-acoustic transducers may also be employed.

According to the invention the bass units are substantially identical. By this is meant that the bass units should be as similar to each other as possible and preferably identical. The purpose is that all bass elements at each moment in time should function totally synchronously and identically.

Furthermore, in accordance with the invention the bass units 2 are mounted such that the surface projected by the oscillating part of the bass units 2 in the plane of the baffle 1 has a surface coverage amounting to at least 35% of the surface of the baffle.

The surface projected by the oscillating part of the bass units 2 in the plane of the baffle 1 is thus the surface of the circles in fig. 1. In fig. 1 the circles comprise approximately 35% of the surface of the baffle, that is 35% of the surface of the square in fig. 1. Of course the oscillating surface could be made larger than 35%, whereby the effect of the invention increases.

According to a preferred embodiment the bass units 2 are mounted in a baffle 1 , to which side pieces 4, 5, 6, 7 can be attached but where a back piece is missing, whereby the baffle constitutes a so called acoustic dipole, see fig. 2. In fig. 2 the device is shown from the back. In fig. 2 only one bass element 2 is shown, but of course there should be provided bass elements in each hole 3 in the baf- 3

fle. This embodiment facilitates set-up and a transport due to the presence of the side pieces.

The present invention thus relates to an electro-acoustic transducer, wherein a large number of bass loudspeakers or other electro-acoustic bass elements are mounted in a baffle. These bass elements together form a large oscillating membrane surface, which gives a very good coupling to the air, such that a source of sound with a high efficiency is obtained.

The source of sound furthermore yields a planar wave front, a clear virtual acoustic image, high power handling, small amplitude in the bass elements, low distortion of the sound, and an extended frequency response with high accuracy down to below the audible region.

The electro-acoustic transducer according to the invention makes it possible reproduce very low frequency musical signals with low distortion, at long distances and with very high sound pressures. This was previously not possible with known bass elements because of a too high amplitude on the cones of the bass loudspeakers. In addition, the lowest octave, i.e. 20 - 40 Hz, has not been possible to reproduce with the same acoustic pressure level as the remaining frequency region.

In regard of the acoustic pressure that can be achieved according to the invention, each of the smaller loudspeaker elements gives a smaller cone amplitude for the same acoustic pressure compared to the conventional, large loudspeaker element. Thus, it is extremely advantageous to provide a number of smaller loudspeaker elements having the same total surface calculated at the opening of the loudspeakers, instead of one large loudspeaker element.

According to a preferred embodiment two or more baffles are arranged in the same plane to form a unit which is larger in height and/ or width. Baffles are arranged in close proximity to each other such that spaces between the baffles essentially are avoided. By this measure it is contemplated to prevent air from 4

flowing in and out of the plane of the paper between adjacent baffles. If air is allowed to flow in the way indicated, distortion will occur due to interferences Thus, the intention is to prevent air pressure differences at the front and the back of the loudspeaker elements respectively, to cause a flow of air between the baffles that is high and which gives rise to distortion. In addition the sound will be short circuited having cancellation phenomena as a consequence, since the phase progress of the music signal is negative at the back and positive at the front

Thus, with the present invention one achieves an improved electro-acoustic transducer, wherein the coupling to the air has been markedly increased by mounting many bass elements on a relatively small surface. In addition to the above-mentioned advantages, the high coupling to the air gives a good acoustic damping.

Above various embodiments have been disclosed. However, the invention can be varied with respect to the location and design of the electro-acoustic elements.

Thus, the present invention should not be regarded as limited to the above disclosed embodiments, but can be varied withm the scope of the appended claims.

Claims

5CLAIMS

1. An electro-acoustic transducer, comprising a baffle having a number of electro-dynamic bass units mounted in holes in the baffle, characterized in that the bass units (2) are substantially identical and mounted such that the surface projected by the oscillating part of the bass units (2) in the plane of the baffle (1), has a surface coverage of at least 35% of the surface of the baffle (1).

2. The electro-acoustic transducer according to claim 1 , characterized in that the bass units (2) are mounted in a baffle (1), to which side pieces (6- 9) can be mounted, but where a back piece is missing, whereby the baffle (1) constitutes a so called acoustic dipole.

3. The electro-acoustic transducer according to claim 1 or 2, characterized in that two or more baffles (1), are provided in the same plane to a unit which is larger in height and /or width, and in that the baffles are provided in close proximity to each other, such that spaces between the baffles essentially are avoided.