IE904125A1 - Improvements in or relating to audio loudspeakers - Google Patents

Abstract

An audio loudspeaker includes a baffle board (18) with one or more drive units (24, 26) mounted therein and a moulded plastics cover (42) member fitted to the front of the baffle board (18) defining a space therebetween. The cover (42) is formed with apertures (46, 48) corresponding in size and number to the drive units and enables the cosmetic and technical advantages of using moulded plastics, while retaining the strength of a wooden baffle board.

Description

Improvements in or Relating to Audio Loudspeakers The present invention relates to audio loudspeakers, and is particularly concerned with the construction of loudspeaker enclosures and the mounting of driver units therein.

The baffle board of a loudspeaker enclosure supports the drive units, which are mounted in apertures formed therein and forms the front surface of the enclosure.

Thus, it must have sufficient structural strength to retain the drive units rigidly in place, so as to avoid distortions arising from vibration or deformation, and must also be finished to an aesthetically acceptable standard. Conventionally, materials such as fibre boards or chipboard have been used for loudspeaker baffle boards, which have the reguired strength, are relatively cheap, and may be finished with wood or artificial veneer, or other suitable coatings or coverings. Such materials are, however, difficult to machine accurately, which presents problems in the mounting of the drive units. This is the case with treble units in particular, which often have to be mounted to a shoulder formed around the periphery of a circular aperture formed in the baffle board in order IE 904126 to align the forward surface of the driver with the front surface of the board. The difficulties in machining such a shoulder to accurate dimensions mean that the forward surface of the driver is not always perfectly flush with the board, which is undesirable both acoustically and cosmetically. The need to apply a cosmetic finish to the board at some stage in the manufacturing process creates further problems.

More recently, baffle boards have been moulded from plastics material, such as polypropylene. Such moulded boards may be manufactured to close tolerances, and require no further finishing, however the weight of plastic required to give the necessary structural strength means that they are very expensive compared with conventional baffle boards.

It is an object of the present invention to obviate or mitigate these disadvantages.

Accordingly, the invention provides an audio loudspeaker comprising an enclosure including a baffle board, and at least one drive unit located in an aperture formed in said baffle board, said loudspeaker further including a cover member of moulded plastics material, having apertures formed therein corresponding in size and number to said at least one drive unit, and being fitted to the front of said baffle board with a predetermined space defined therebetween.

The loudspeaker, preferably includes at least one drive unit having a front surface projecting forwardly of the baffle board, the spacing of the cover member from the baffle board corresponding to the forward projection of said first drive unit such that the front surface of the unit is substantially flush with the front surface of the cover member. This first drive unit would normally be a treble unit.

The loudspeaker, preferably also, includes at least one drive unit having a peripheral flange by means of which it is affixed to the front surface of the baffle board, and having a conical diaphragm extending rearwardly into the interior of the enclosure, and the peripheral portion of the cover member surrounding the corresponding aperture formed in the cover member is frusto-conical, extending rearwardly to abut said flange adjacent the periphery of the diaphragm.

Preferably, the surface of the frusto-conical portion is substantially contiguous with the surface of the conical diaphragm. In this case the drive unit would normally be a mid-range and/or bass driver.

Preferably also, means for affixing the cover member to the loudspeaker enclosure comprise a plurality of pegs extending rearwardly from the cover member to engage a corresponding plurality of holes formed in the baffle board.

Preferably, the pegs include radially extending webs having top surfaces which define the spacing of the cover from the baffle board.

The cover preferably further includes a peripheral skirt extending rearwardly towards the edges of the enclosure.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a sectional side view of an enclosure of an audio loudspeaker embodying the invention, wherein the mounting of a treble unit and a bass unit is illustrated schematically; Fig. 2 is a front view of a cover member forming part of the enclosure of Fig. 1; Fig. 3 is a sectional side view, on line A-A, of the cover member of Fig. 2; and Fig. 4 is a fragmentary rear view of one corner of the cover member of Fig. 2, showing one of a plurality of fixing members.

The illustrated example is of a two-way speaker, having a treble unit and a bass unit, however it will be appreciated that the invention is equally applicable to other single- or multi-way speakers.

Referring now to the drawings, the enclosure of an audio loudspeaker is generally rectangular, comprising top, bottom, rear and side walls 10, 12, 14 and 16 respectively, typically of chipboard, and a baffle board 18, typically of medium density fibre board, closing the front thereof.

The baffle board 18 is provided with first and second vertically-spaced, circular apertures 20 and 22, a treble (high frequency) drive unit 24 being mounted in the first, upper aperture 20 and a bass (low frequency) drive unit 26 being mounted in the second, lower aperture 22. The drive units 24 and 26 are affixed to the front surface of the baffle board 18 by means of circumferential flanges 28 and 30 respectively and suitable fixing means such as screws, bolts or the like. Rubber gaskets or the like (not shown) would normally be interposed between the flanges 28 and 30 and the baffle board 18.

The loudspeaker would also include suitable wiring, crossover circuitry, acoustic wadding, connection terminals etc, however these are all conventional and well known in the art and have been omitted for the sake of clarity. As indicated schematically in Fig. 1, the treble unit 24 further includes a forwardly projecting portion 32 having a generally planar front surface 34, and the bass unit includes a transducer 36, a conical diaphragm 38 connected at its centre to the transducer 36 and at its periphery to the mounting flange 30, and support members 40 interconnecting the transducer 36 and flange 30 rearwardly of the diaphragm 38.

Affixed to the front of the loudspeaker is a cover member 42, of moulded plastics material such as polypropylene or polystyrene (see also Figs. 2, 3 and 4). The cover 42 has a generally planar front surface 44 disposed parallel to the baffle board and spaced therefrom and is generally rectangular and of a size corresponding to the front of the loudspeaker enclosure. First and second circular apertures 46 and 48 are also provided, having positions and dimensions corresponding to those of the baffle board apertures 20 and 22 and drive units 24 and 26.

The spacing of the front surface 44 of cover 48 from the baffle board 18 is selected such that the forward surface 34 of the treble unit 24 is flush with the front surface 44. These surfaces can be aligned to a high degree of accuracy since the treble unit is mounted directly to the front of the baffle board 18, and the cover 42 can be moulded to relatively close tolerances.

The periphery of the lower cover aperture 48 is angled rearwardly towards the baffle board to define a frusto-conical portion 50, the innermost edge whereof abuts the flange 30 of the bass unit 26 adjacent the periphery of the diaphragm 38. The dimensions of the frusto-conical portion 50 are preferably selected such that its surface is substantially contiguous with that of the diaphragm 38.

The cover 42 may be affixed to and spaced from the baffle board 18 by any suitable means. In the present example, the cover 42 is provided with six identical mounting pegs 52, extending from the rear surface of the cover 42 at positions indicated by the crosses 54 in Fig. 2. The pegs 52 each include a central, hollow dowel portion 56, which, in use, engage corresponding holes (not shown) formed in the baffle board 18. The pegs 52 also incorporate spacing means comprising four rectangular webs 58 extending radially outward from the dowel 56, whose top edges abut the baffle board 18 when the cover 42 is in position. The cover 42 is preferably retained in position by means of a friction fit between the dowels 56 and rubber inserts (not shown) located in the holes formed in the baffle board 18, or, alternatively, by means of screws or bolts (not shown).

The cover 42 further includes a peripheral skirt 60 extending rearwardly towards the edges of the enclosure. In the present example, a gap 62 is left between the skirt 60 and the enclosure, which might suitably receive the edges of an elasticated speaker cloth (not shown), as described in GB-A-2205213 (Linn Products Limited). In the illustrated example, the front surface 44 of the cover 42 is divided into upper and lower portions by a transverse groove 64, the lower portion providing a suitable surface for trade marks, logos or other insignia.

The invention thus provides an improved loudspeaker construction, which exploits the cosmetic and technical advantages of moulded plastics baffle boards, without the expense of producing heavy, structural plastic mouldings, and the shape and configuration of the cover may be varied to suit all types of loudspeaker. The structure of the cover and the method of fixing it to the enclosure may likewise be varied widely, however the arrangement should be sufficiently strong and rigid to resist excessive vibration in use.

Claims (13)

1. CLAIMS 3 1. An audio loudspeaker comprising an enclosure 4 including a baffle board, and at least one drive unit 5 located in an aperture formed in said baffle board, 6 said loudspeaker further including a cover member of 7 moulded plastics material having apertures formed 8 therein corresponding in size and number to said at 9 least one drive unit, and being fitted to the front of 10 said baffle board with a predetermined space defined 11 therebetween. 13 2. A loudspeaker as claimed in Claim 1, including at 14 least one drive unit having a front surface projecting 15 forwardly of the baffle board, the spacing of the cover 16 member from the baffle board corresponding to the 17 forward projection of said first drive unit such that 18 the front surface of the drive unit is substantially 19 flush with the front surface of the cover member. 21 3. A loudspeaker as claimed in Claim 1 or Claim 2, 22 including at least one drive unit having a peripheral 23 flange by means of which it is affixed to the front 24 surface of the baffle board, and having a conical 25 diaphragm extending rearwardly into the interior of the 26 enclosure, and the peripheral portion of the cover 27 member surrounding the corresponding aperture formed in 28 the cover member is frusto-conical, extending 29 rearwardly to abut said flange adjacent the periphery 30 of the diaphragm. 32 4. A loudspeaker as claimed in Claim 3, wherein the 33 surface of the frusto-conical portion is substantially 34 contiguous with the surface of the conical diaphragm. 1 5. A loudspeaker as claimed in any preceding Claim,

2. Further including means for affixing the cover member

3. To the loudspeaker enclosure, comprising a plurality of

4. Pegs extending rearwardly from the cover member to

5. Engage a corresponding plurality of holes formed in the

6. Baffle board.

7. 8 6. A loudspeaker as claimed in Claim 5, wherein said

8. 9 pegs include a plurality of radially extending webs

9. 10 having top surfaces which define the spacing of the

10. 11 cover from the baffle board.

11. 13 7. A loudspeaker as claimed in any preceding Claim,

12. 14 further including a peripheral skirt extending

13. 15 rearwardly towards the edges of the enclosure. 16 8. A loudspeaker substantially as hereinbefore described with 1 7 reference to the accompanying drawings.