A bass-reflex loudspeaker system

<img file="AT376351B_D0001.tif" />

AUSTRIAN

PATENT OFFICE

Int.Cl³.: H04R 001/02

H04R 001/34 © AT PATENTSCHRIFT © Nr.376 351 ® Patent owner: JAMO HI-FI A / S

GLYNGORE »DENMARK © Subject: BASSREFLEX SPEAKER © Addendum to Patent No.

© Elimination from:

Registered: 1932 02 02 »9008/82 0K82 / 00007 © Exhibition priority:

©©© Union Priority: DENMARK (DKI 1981 02 03

475/81 CLAIMED © Beginning of the period of paternity: 1984 03 15 Longest possible duration:

© Issued: 19 84 II 12 © Inventor:

© dependence:

© Pamphlets considered to delineate the prior art:

TCO Ql O TV

OK-PS 46426 FR-PS 2370400 US-PS 1742016 US-PS 3115947

US-PS 3638753 US-PS 3666040 EP-Al 8274

Nr.376351

The invention relates to a bass-reflex loudspeaker having a housing whose front plate is formed with an approximately circular opening for the installation of a bass or woofer and which is provided with a bass reflex opening which has the shape of an annular gap surrounding the loudspeaker, which is formed by the space between a rigidly attached to the front panel first pipe socket and a coaxially within the same provided second pipe socket space, the speaker is rigidly fixed to the front panel end of the second pipe socket.

Efforts are underway for many years to construct loudspeaker cabinets which are acoustically completely inactive, ie soundless, and this also applies to the reproduction of music pieces with very high sound levels, so that a neutral reproduction of the electrical signals supplied to the loudspeaker without Deterioration of the sound image by cabinet resonances or other disturbing noise sources takes place. It is known housing heavy or produce thick boards of solid wood and stiffen them by means of struts. This is an effective but costly method since wood of this quality is expensive. It is also known to make the housing as a double-walled box, for example made of chipboard and to fill the cavity between the outer and the inner box with sand, whereby the housing receives a large weight. In terms of acoustics, this represents an excellent solution, since this vibration of the housing is avoided with certainty. Due to the high weight, however, significant transport problems are required. The same applies to the proposal known from the literature to use concrete or marble.

The invention is therefore an object of the invention to provide a bass-reflex speaker, which meets the above-described sound technical conditions, which is economical to manufacture and which nonetheless has a low weight. This is inventively achieved in that the second pipe socket is fastened at its front plate-side end to the front panel by means of a vibration-absorbing device and that it is free ends at the respective other ends of the two pipe sockets. Preferably, the vibration absorbing fastening means is formed by rubber pads disposed along the peripheral edge of the loudspeaker and clamped at their ends between the second pipe socket and an associated first mounting ring.

Speakers according to the invention are much more inactive in acoustic terms than previously known speakers, although their housing has the same wall thickness. In particular, the occurrence of distortions in the mid and high audio frequency ranges due to the Doppler effect of the low frequency or woofer is avoided. A reduction in the thickness of the plates or boards, however, is not allowed, since the air pressure conditions inside the housing are not changed by the new way of installing the bass reflex speaker.

The object of the invention is explained below with reference to an embodiment shown in the drawings. 2 shows a front view of the loudspeaker according to FIG. 1 and FIG. 3 shows a section along the line AA of FIG.

In the drawings, only those details are shown that relate to the particular way in which the woofer is mounted, since the formation of the remaining part of the housing for the invention is immaterial. The front panel -10- is formed with a circular opening -11- whose diameter is larger than the largest diameter of the speaker located in this opening. From the opening -11- extends a first pipe socket -13- into the housing. This first pipe socket -13- is fixed along the edge of the opening -11- on the front panel -10-, whereby it forms an integral part of this plate. The pipe socket -13- can be made of iron, whereby the mass of the front plate -10- greatly increased and thus their vibration sensitivity is reduced. Alternatively, the required stiffness can be achieved by integrally fabricating the first pipe socket -13- and the front panel -10- from a plastic material.

Coaxially with the first pipe socket -13-, a second pipe socket -14- is provided which has a smaller diameter than the first pipe socket -13-. Trim the second pipe

Nr.376351

- 3 - 14- is at the end facing the outside of the housing, attached to a mounting ring -15-, at the periphery of which also a bass or woofer -16- is attached. The axis 12 of the second pipe socket -14- is shown by a dashed line.

The profile of the mounting ring -15- depends on the design of the edge suspension of the speakers used. The mounting ring -15- has a first flange -17- which is parallel to the front plate -10-, and a second flange -18- which extends at right angles thereto and extends into the housing. Accordingly, the mounting ring is profiled approximately L-shaped. In the first flange -17- grooves -19- for receiving the edge suspension -20- of the speaker -16- are provided. In the second flange -18- a groove -21- is provided for receiving the edge of the second pipe socket -14-.

The assembly of the mounting ring -15- with the edge suspension -20- or with the second pipe socket -14- can be done in any known manner, ie either by gluing, by welding or by means of rivets or screws. However, it must be ensured that the second pipe socket -14- and the mounting ring -15- are rigidly connected together. Also, the second pipe socket -14- may be made of iron to increase the total mass of that part to which the speaker is attached.

The unit formed from the second pipe socket -14-, the mounting ring -15- and the loudspeaker -16- is fixed to the front panel -10- so that vibrations caused by movements of the loudspeaker membrane or loudspeaker cone are largely prevented from reaching the front panel -10- and continue to propagate to the remaining parts of the housing. One way in which this can be achieved is shown in FIGS. 2 and 3. In this case, four rubber blocks -22- are provided as vibration-damping fastening or suspension means, which are distributed uniformly along the periphery of the loudspeaker. Each rubber block -22- is inserted with one of its ends in a recess -23- in the second flange -18- of the mounting ring -15- and fixed in this example by sizing against movements in the lateral direction. At their other ends are the rubber blocks -22- between the

Front plate -10- and an outer mounting ring -24- clamped. To accommodate the respective end of the rubber blocks -22- -24- recesses -25 and 26- are provided in the front panel -10- and in the outer mounting ring. The outer mounting ring -24- is attached, for example by means of screws on the front panel -10-. In Figure 2 on each side of the rubber block -22- a fastening screw -27-- indicated.

The number of rubber blocks -22- and the number of screws are dependent on the requirements, according to the weight to be supported, the width of the annular gap -28- between the two pipe sockets -13 and 14- and the properties of the material from which the Gummiklötze -22- are made, selected. By itself, natural rubber has the best vibration-damping effect. In a series production of loudspeakers, however, by using a synthetic rubber, a higher economy is achievable, since the properties of synthetic rubber, such as its hardness, are easier to determine in an extrusion process than the properties of natural rubber, which is produced in a completely different way. It may also be advantageous to use rubber with different hardnesses adapted to the different speaker sizes.

Thus, considerable demands are placed on these rubber blocks, since it must be ensured by them that vibrations generated by the speaker are not transmitted to the front panel, and that the second pipe socket -14 coaxial with the first pipe socket -13- remains and does not tilt. This second requirement can be met by at least one supporting rubber block, which is inserted into the annular gap -28- between the pipe socket -13 and 14-.

It should be noted that the annular gap -28- between the front panel -10- and the edge of the speaker, which is formed by this special vibration-damping suspension of the woofer -16-, is exploited in a known manner as a bass reflex opening through the two coaxial pipe socket -13 and 14- is formed, whereby the arrangement of an additional opening in the front panel -10- is unnecessary as a bass reflex opening.

- 4 No.376351

Inside the housing, the pipe sockets -13 and 14- end in one and the same vertical

Plane, as shown in Fig.l by a solid line, their lengths are in

Correspondence with the well-known technique in this field according to the ratio between the area of ​​the bass reflex port and the volume of the housing ge5 selected.