GB2288513A - Mounting loudspeaker grilles - Google Patents

Abstract

A loudspeaker cabinet has a baffle for supporting a loudspeaker unit in a front opening of the cabinet. A grille 40 is positioned in front of the baffle, and the baffle has a rebate or groove 23a for receiving respective members of a frame 45 bounding the grille. The grille is substantially flush with the front opening of the cabinet. Accordingly, sound waves emanating from the speaker are less impeded than in the prior art where reflections occur in the confined space in front of the speaker, and this improves the quality of reproduction of the sound. <IMAGE>

Description

LOUDSPEAKER CABINETS The present invention relates to a loudspeaker cabinet.

The front wall or baffle of a loudspeaker cabinet is conventionally covered by a grille to enhance the appearance of the speaker. The grille can be made of foam, expanded or perforated metal or plastic, or a woven cloth stretched over a frame. Ideally, the presence of the grille arrangement should have little or no effect on the sound quality performance of the loudspeaker.

In one known arrangement, the baffle is set back slightly into the cabinet so as to form a rebate which receives a foam grille of similar or slightly greater thickness than the depth of the rebate.

In another known arrangement, the baffle is set back only slightly from, or is flush with, the front of the cabinet, and a thin cloth grille stretched over a frame is secured over the front of the baffle.

The grille is held in place by pegs extending from the rear of the frame which are received in corresponding sockets in the baffle.

Although known grilles give a satisfactory appearance to the front of the speaker, they do have some adverse effect on the sound produced by the speaker. In particular, investigations have shown that the grille arrangement can disturb soundwaves being reproduced by the speaker, typically in the 2-1OkHz range which are particularly undesirable to a smooth and extended frequency response and to the human ear.

It is thought that the reason for the production of these disturbances results from sound waves being "trapped" inside the rebate or frame bounding the grille. The reflected waves may then form a number of independent sources of soundwaves within the grille which produce interference patterns on the baffle and outside the speaker. At frequencies where constructive and destructive interference occurs, the contribution of the reflections to the overall sound is especially undesirable.

It would be desirable to provide a grille for a loudspeaker cabinet which, while providing an aesthetically pleasing appearance and offering some protection to the speaker units, does not produce the above-described constructive and destructive interference which affects the quality of reproduction of the sound.

According to one aspect of the present invention, the perimeter of a front baffle for a loudspeaker cabinet is formed with a rebate or groove for receiving respective members of a frame at least partially bounding a loudspeaker grille. In this manner a grille is provided for the speaker unit(s) in the cabinet without creating a confined space within which sound waves emanating from the speaker unit(s) can be trapped.

The rebate or groove preferably extends around the entire perimeter of the baffle but may extend around only a predetermined portion of the perimeter. For example, it may extend around only the upper half of the baffle when a grille is required for a tweeter speaker unit.

The width of the groove or rebate is preferably such that the groove or rebate is not completely filled by the respective frame member. The resulting gap is then preferably formed between the frame member and the baffle, and is preferably of approximately the same width as the thickness of the frame member so that the frame member occupies only about half the width of the groove or rebate.

According to a second aspect of the invention, it has been found that the presence of such a gap significantly improves the performance of the speaker by reducing any disturbance to the soundwaves being reproduced by the speaker unit(s).

A loudspeaker cabinet embodying each aspect of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figures 1 and 2 are diagrammatic central longitudinal crosssections through speaker cabinets of the prior art.

Figure 3 is a diagrammatic central longitudinal cross-section through a speaker cabinet embodying the present invention; Figure 4 is an enlarged detail of part C of the cross-section highlighted in Figure 3.

Referring to these drawings, in which like references are used to denote like parts, Figure 1 is a cross-section through a prior art loudspeaker cabinet with a foam grille 10 covering the front baffle 23 to conceal the speaker units 11, 12. The baffle 23 is set back from the front of the cabinet to form a rebate which receives and retains the foam grille 10.

Figure 2 shows a cross-section through another prior art loudspeaker cabinet. In this cabinet the baffle 23 is only set back slightly, if at all, into the cabinet so that the baffle is almost flush with the front of the cabinet. A cloth grille 40 stretched over a rectangular frame 41 is secured over the baffle by means of pegs 9 provided on the frame 41 which are received in complementary apertures in the baffle.

Alternatively, the frame 40 can be made smaller so that it fits within a lip formed by the cabinet walls 24, 25 protruding beyond the baffle 23.

In all these prior art constructions, there is therefore a space immediately in front of the baffle 23 bounded by a rigid frame preventing the escape of sound waves. The trapped waves will be reflected at the bounding walls and may produce an unwanted interference pattern of sound which interferes with the main propagation of sound waves from the speaker units 11, 12 in the forward direction.

Figures 3 and 4 show a loudspeaker cabinet embodying the present invention. The rectangular speaker cabinet has a top wall 24, a bottom wall 25, opposed side walls, a rear wall 26 and a front baffle 23. The baffle 23 carries a pair of speakers, a bass/midrange unit 11 and a tweeter 12 located above the bass/midrange unit 11. The baffle 23 is mounted in the speaker cabinet so that its outer surface 43 is substantially flush with the front edges of the top, bottom and side walls of the cabinet, only the chamfered front edges 44 of the top and bottom walls 24, 25 being shown in the drawings.

As shown in more detail in Figure 4, the outer periphery of the baffle 23 has a rebate 23a which, together with the surrounding cabinet walls forms a groove which serves to receive the respective members of a rectangular frame 45 (Fig. 3), each frame member consisting of a flat strip 46.

The thickness of each strip 46 is about half the width of the rebate 23a (measured parallel to the front face 43) while the frame 45 fits snugly within the front opening formed by the walls of the cabinet.

Accordingly, there is a residual gap 26 formed between the baffle 23 and the frame 45, the width of the gap being approximately equal to the thickness of the strip 46. This gap 26 assists in overcoming the problems associated with the prior art cabinets of Figs. 1 and 2.

A woven cloth 40, or a similar acoustically transparent material, is stretched over the frame 45 so that it lies adjacent the front surface 43 of the baffle wall 23 and conceals the speaker units 11,12.

With this arrangement, sound waves emanating from the speaker units 11, 12 are free to travel in any direction without risk of being trapped within a confined space in front of the speaker.

Claims (4)

1. A loudspeaker cabinet comprising: a baffle for supporting a loudspeaker unit in a front opening of the cabinet, and a grille positioned in front of the baffle; the baffle or the front opening having a peripheral rebate or groove for receiving respective members of a frame at least partly bounding the grille.

2. A loudspeaker cabinet as claimed in claim 1, in which each frame member is of rectangular cross-section.

3. A loudspeaker cabinet as claimed in claim I or claim 2. in which the groove or rebate is formed in the baffle. and in which each frame member only partly fills the respective rebate or groove so that a gap is formed between the frame member and the baffle.

4. A loudspeaker cabinet substantially as hereinbefore described with reference to. and as shown in. Figures 3 and 4 of the accompanying drawings.