Loudspeaker enclosure

Abstract: The enclosure comprises inner (2) and outer (6) wall members with a vacuum space (5) there between. The space (5) is sealed by an O-ring 4 and a flange (7) of a loudspeaker at the mouth of the enclosure. The enclosure has the form of a vacuum-flask. It reduces unwanted propagation of sound by the enclosure.

Description: The present invention relates to a loudspeaker enclosure. A loudspeaker is normally supported by an enclosure. Some sound energy from the loudspeaker is propagated by the enclosure resulting in undesired distortion of sound reproduced by the speaker. See for example Chapter 7 of "High Performance Loudspeakers" 3rd Edition, Martin Colloms, Pentech Press. DE-C-923 070 discloses a loudspeaker mounted on a housing, which forms a gas-tight chamber. Gas is pumped out of the chamber so that the gas pressure in the chamber is below atmospheric pressure. According to the invention there is provided a loudspeaker enclosure comprising a wall structure defining an opening in which a loudspeaker can be arranged, characterised in that the wall structure comprises spaced-apart inner and outer wall members defining a vacuum space therebetween. The enclosure may have a structure like that of a vacuum flask to minimise the sound propagated by the enclosure. For a better understanding of the present invention, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a top plan view in cross-section of a loudspeaker enclosure incorporating a loudspeaker according to the present invention, and Figure 2 is an end view of the enclosure of Figure 1. The enclosure comprises a wall structure having an inner wall 2 spaced from an outer wall 6 to define there between a vacuum space 5. The wall structure together with the loudspeaker at the mouth of the enclosure defines an internal space 3 which contains air and/or sound damping material. The vacuum space 5 between the inner and outer walls 2 and 6 is closed by a flange 7 on the loudspeaker and an O-ring 4, the flange and O-ring being held in place by the external air pressure, once the vacuum space 5 is pumped out via port 8. Port 8 is sealed after pumping out. The O-ring acts as a sound damper to reduce the transfer of sound energy from the speaker 1 to the wall structure. Because of the vacuum space 5, sound propagation by the structure of the enclosure is reduced. The inner and outer walls may be of metal, glass or plastics. Plastics such as methyl methacrylate, polycarbonate, or polystyrene, may be useful. In addition, fibre reinforced plastics such as polyester could be useful. The materials used must be sufficiently strong and air tight. Various changes and modifications may be made to the enclosure shown in Figures 1 and 2. Instead of the O-ring some other seal could be used. In addition to, or instead of the seal providing damping, other damping means could be provided. Further mechanical support for the loudspeaker and between the inner and outer walls may be provided. However, excessive support will bridge sound propagation between the walls. The material of the mechanical support should provide good damping. Lead, bitumen or polyurethane may be useful. The space between the inner and outer walls may be permanently sealed by a seal integral with the wall members. For example, the inner and outer walls may be sealed together (like a vacuum flask) at the mouth of the enclosure. In the event that it is difficult to maintain a high degree of vacuum, the sealed port 8 may be replaced by a valve for connection to a vacuum pump. The pump would be operated only when the loudspeaker is not in use to avoid interfering with sound reproduction. A sensor for sensing the degree of vacuum may be used. In addition, a controller for automatically turning on the pump in response to the sensor when the speaker is not in use may be used. The enclosure may be of any suitable shape. A spherical or cylindrical shape would be appropriate. The inner wall 2 may be formed of a single piece. The outer wall 6 may be formed of two pieces. There may be multiple internal walls one within another. Several loudspeakers may be isolated from one another using enclosures as described above. The present invention may be applied to the loudspeaker systems described and claimed in our copending British Patent Application GB-A-2188811.

Claims: A loudspeaker enclosure comprising a wall structure defining an opening in which a loudspeaker (1) can be arranged, characterised in that the wall structure comprises spaced-apart inner and outer wall members (2,6) defining a vacuum space (5) therebetween. An enclosure according to claim 1, wherein the inner and outer wall members (2,6) are joined by a sealing member (4). An enclosure according to claim 2, wherein the sealing member (4) is integral with the inner and outer walls (2,6). An enclosure according to claim 2 or 3, wherein in use the said sealing member (4) co-operates with a flange (7) on the loudspeaker (1). An enclosure according to any preceding claim, comprising at least one damping member (4) for coupling the loudspeaker (1) to the enclosure. An enclosure according to claim 5 when dependant on claims 2, 3 or 4, wherein the said sealing member (4) comprises the damping member. An enclosure according to any preceding claim, wherein the vacuum space (5) is permanently closed. An enclosure according to any one of claims 1 to 6 comprising a valve for coupling the vacuum space (5) to a vacuum pump. An enclosure according to any preceding claim, wherein the wall structure is of plastics material. An enclosure according to any preceding claim, wherein the wall members define an opening for the propogation of sound from the enclosure. An enclosure according to any preceding claim, further comprising a loudspeaker (1) supported by the enclosure. An enclosure according to claims 2, 3 or 4, wherein said sealing member comprises an O-ring. An enclosure according to claim 5 or 6, wherein said damping member (4) comprises an O-ring.

Inventors: NEGISHI HIROKAZU, NEGISHI, HIROKAZU
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1989
Main classification: H04R1
IPC codes: H04R1