GB2277008A

GB2277008A - Panels for improving acoustic performance of an enclosure

Info

Publication number: GB2277008A
Application number: GB9307186A
Authority: GB
Inventors: Michael Stuart Mason; John Morris
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-06
Filing date: 1993-04-06
Publication date: 1994-10-12
Anticipated expiration: 2013-04-06
Also published as: GB9307186D0; GB2277008B

Abstract

A panel 30 for improving acoustic performance of an enclosure e.g. a loudspeaker, the panel being used to line or to form at least part of at least one wall of the enclosure, presents a series of faces 38 each being other than parallel to a major plane of the panel. The angled faces reduce the occurence of standing waves within the enclosure. <IMAGE>

Description

Title: Panels for improving acoustic performance of an enclosure.

DESCRIPTION The present invention relates to panels for use in improving acoustic performance of an enclosure, such as a loudspeaker cabinet.

Loudspeaker cabinets are typically rectangular boxes having one or more loudspeakers fixed against an opening or openings in one face of the cabinet. Often the cabinet is filled with sound insulation material.

The cabinet walls are all usually flat and this can impair the sound quality emanating from the loudspeaker.

Sound is emitted from a loudspeaker in all directions contributing to the total sound effect.

If not controlled properly unwanted acoustic output can give subjective sound coloration. An undamped rear wall of a loudspeaker cabinet can give peaks which are only several decibels below the front axial output of the loudspeaker.

If resonance control or "damping" is applied the ratio of reactance to resistance of the intrinsic panel resonance can be significantly reduced and hence the choice of material for the walls of a loudspeaker cabinet is inconsequential. In the case of an undamped enclosure high mass may be an advantage, whereas in a damped cabinet it is actually detrimental Loudspeaker cabinets having flat walls can produce standing waves, ie. stationary maxima or minima of intensity due to interactions of incident and reflected sound waves within the cabinet. At frequencies whose wavelength is comparable to internal dimensions of the cabinet, reflections will occur between inner surfaces of the cabinet which will be additive at some frequencies and cancelling at others causing irregularities in response. Therefore, the production of standing waves needs to be reduced as much as possible to improve sound quality from a loudspeaker.

An object of this invention is to provide a panel for improving acoustic performance of an enclosure.

According to the invention there is provided a panel for improving acoustic performance of an enclosure, the panel being used to line or to form at least part of at least one wall of the enclosure, the panel presenting a series of faces each being other than parallel to a major plane of the panel.

In a preferred embodiment the faces of the panel are segments or chords of a surface of a notional three dimensional shape transposed onto a surface of the panel. The major plane of the panel may be a plane through the notional three dimensional shape.

The three dimensional shape may be a sphere, an asphere or any other suitable regular or irregular three dimensional shape, including tetrahedra, pyramids and the like.

Each face is preferably provided as one side of a groove, which is either circular or linear. The grooves may be of equal width or may subtend the same angle relative to a notional point A particularly preferred panel is based on a notional sphere, in which the panel has a series of faces each defining (in section) an ar or chord of a notional sphere. The term "arc" is intended herein to include not only curved surfaces but also planar surfaces of narrow width so that they appear more or less arcuate.

Each face is preferably provided as one side of a groove, which is either circular or which forms part of a notional circle.

Each face preferably forms a ring or at least part of a notional ring depending upon its position on the panel. Thus, for square panels, faces at or near corners thereof will not form complete rings.

By presenting, in effect, angled faces sound waves striking the faces will be reflected away from incident sound waves so that incidence of standing waves will be reduced.

The term "panel" as used herein is intended to encompass panels used for linings for acoustic enclosures, such as loudspeaker cabinets, recording studios and rooms for listening to live or recorded performances, as well as panels used for constructing walls of such enclosures.

Typically the panels of the inventions will be rectangular, especially square, but may also be of any other desired perimetral shape. Panels of the invention may be made of any suitable material but plastics material, such as, for example, polyurethane is preferred. Panels of the invention may conveniently be moulded of plastics material The use of plastics material which is flexible is preferred especially for panels for lining loudspeaker cabinets, to facilitate fitting of the panels into the cabinets.

The use of panels of the invention in loudspeaker cabinets, especially vented enclosures, may eliminate the need for wadding or the like inside the speaker cabinet and so avoid possible fire risks.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a loudspeaker cabinet; Figure 2 is an isometric view of a panel of the invention; Figure 3 is a side view of the panel of Figure 2 showing sound waves striking the panel; Figure 4 is a partial plan view of a circular panel of the invention Figure 5 is a section through the panel of Figure 4; Figure 6 is a partial side view of another panel according to the invention; Figure 7 is a perspective view of yet another panel according to the invention; Figure 8 is a section through the panel of Figure 7; and Figures 9 to 15 show various three-dimensional shapes from which panels according to the invention may be derived.

Referring to Figure 1 of the accompanying drawings, a typical loudspeaker cabinet 10 is shown in section. The cabinet 10 has a loudspeaker 12 affixed in an opening in front wall 14 of the cabinet The cabinet has planar side walls 16, and rear wall 18. The cabinet top and bottom walls are also planar. Sound waves emitted from the loudspeaker on striking the planar.

walls of the cabinet at 900 to the wall are reflected and the reflected sound waves interact with incidental waves to cause undesired standing waves. However, by presenting faces 20 to the sound waves which faces form part of the surface of a notional sphere, having its centre pre-determined with the inside of the cabinet, sound waves will deflect in a direction away from the incident wave except where the wave strikes the surface at 900, so that less standing waves will occur.

A practical implementation of that theory is shown in Figures 2 and 3 of the accompanying drawings, in which a rectangular panel 30 is shown, which may be used as a lining for a loudspeaker cabinet or forming a wall of a loudspeaker cabinet or for lining or forming a wall of any other acoustic enclosure. The panel 30 has a planar rear face 32 but its front face is formed as a series of grooves 34. Each groove is either in the form of a ring or of part of a notional ring at or near corners of the panel. Each groove has two faces 36, 38, one of which (36) is on a radius of a notional sphere and the other (38) is on a chord of the same notional sphere. Each face 38, therefore, is substantially perpendicular to a radius of the notional sphere, so that sound waves striking the face 38 will deflect in a similar way to striking a notional sphere Figures 4 and 5 of the accompanying drawings show a variation in which a panel 50 is circular but still has the grooves 52 forming two faces 54 and 556 corresponding to the grooves 36, 38 of the panel of Figures 2 and 3 and a planar rear face 58.

Turning to Figure 6 of the accompanying drawings, a panel 60 has a planar rear surface 62 and a front surface formed as a series of concentric grooves 64.

The grooves 64 are in the form of rings of equal width and each groove has two faces 66, 68. The faces 66 are perpendicular to the rear surface of the panel, whereas the faces 68 are chords of a notional sphere transposed from the sphere along the radii shown.

In Figures 7 and 8 panel 80 is shown based on a notional pyramid 90. The panel is rectangular and has a planar rear surface 82 and a front surface formed as a series of grooves 849 Each groove 84 is of equal width and has a pair of faces 86,88. The faces 86 are perpendicular to the rear face 82 of the panel, whereas the faces 88 are segments of the surface of the notional pyramid 90 transposed perpendicularly to the rear surface of the panel.

Figures 9 to 15 of the accompanying drawings show various three-dimensional shapes from which panels according to the invention may be derived by transposing segments or chords of the surface of the shape to form one set of faces of grooves in the panel.

surface either in equi-angular or equi-distant steps.

Claims

1. A panel for improving acoustic performance of an enclosure, the panel being used to line or to form at least part of at least one wall of the enclosure, the panel presenting a series of faces each being other than parallel to a major plane of the panel.

2. A panel as claimed in claims 1, wherein the faces of the panel are segments or chords of a surface of a notional three-dimensional shape transferred onto a surface of the panel.

3. A panel as claimed in claim 2, wherein the major plane of the panel is a plane through the notional three-dimensional shape.

4. A panel as claimed in claim 2 or 3, wherein the notional three-dimensional shape is a sphere.

5. A panel as claimed in any one of claims 1 to 4, wherein each face is provided as one side of a groove, which is either circular or linear.

6. A panel as claimed in claim 5, wherein the grooves are of equal width.

7. A panel as claimed in claim 5, wherein the grooves subtend the same angle relative to a notional point.

8. A panel as claimed in claim 1 having a series of faces each defining in section an arc (as hereinbefore defined) or chord of a notional sphere.

9. A panel as claimed in claim 8, wherein each face is provided as one side of a groove, which is either circular or which forms part of a notional circle.

10. A panel for improving acoustic performance of an enclosure substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings.