A sound projection system comprising means defining a longitudinally extending acoustic channel which is acoustically open at a front end of the channel and acoustically closed at a rear end and at sides of the channel, a loudspeaker having a cone diaphragm operating into the channel at the rear end of the channel, and a longitudinally extending member mounted within the channel directly in front of, and in alignment with, the loudspeaker so as to restrict the free space within the channel, the cross-sectional area of said member varying along its length.
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1. A sound projection system comprising a housing having a means defining a longitudinally extending acoustic channel, said channel having an acoustically opened front end and an acoustically closed rear end and acoustically closed sides; a loudspeaker carried at the rear of said housing, said loudspeaker having a cone diaphragm defining a part frusto-conical volume and operating into the channel at the rear end of the channel, said diaphragm having a maximum longitudinal displacement at a center of said diaphragm in response to an audio electrical signal; and a longitudinally extending member mounted within the channel directly in front of, and in alignment with, the loudspeaker to restrict the free space within the channel, said member having a front portion, which is tapered towards the front of said channel, and a rear portion, which is tapered abruptly towards said loudspeaker and projects into said part frusto-conical volume, terminating with a flat end facing the loudspeaker, said member being supported by a strut fixedly attached at one end to the inner wall of said housing extending radially inward and attached fixedly to said member at the other end ., said rear portion of said member being spaced away from said diaphragm substantially in excess of the maximum longitudinal displacement of the center of said diaphragm.
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1. Field of the Invention
This invention relates to a sound projection system. One aplication of the invention is to a sound projection system which is particularly suitable for use outdoors, and in other environments where it is necessary to transmit sound over relatively long distances, in the form of a fairly narrow beam.
2. Description of the Prior Art
A large number of special types of transducers, and enclosures for transducers have been proposed, which variously aim to provide improved directional characteristics, efficiency, and/or band width of response, and one of the more successful types of system is the well known horn-loaded type. In this type of system, the transducer feeds into the rear of a flared horn, the characteristics of which are such that very efficient conversion of electrical energy into acoustic energy can be obtained, as compared to a loudspeaker without such a horn.
Such horns do however suffer from a number of disadvantages in practice, in that in most cases they need to be rather large and of special shape, so that they are difficult to fabricate; and furthermore they are not easily adaptable for different environments, since the ideal shape for the horn varies with the environment, e.g. the size of room, in which it is being used. Further such horns are not as directional as may be desired in some instances.
According to the invention there is provided a sound projection system comprising means defining a longitudinally extending acoustic channel which is acoustically open at a front end of the channel and acoustically closed at a rear end and at sides of the channel, a loudspeaker having a cone diaphragm operating into the channel at the rear end of the channel, and a longitudinallly extending member mounted within the channel directly in front of, and in alignment with, the loudspeaker so as to restrict the free space within the channel, the cross-sectional area of said member varying along its length.
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Further, the distance between the loudspeaker diaphragm and the surface of the rear portion of the restrictor member may increase in the direction parallel to the longitudinally extending restrictor member along the free space defined by the diaphragm and the rear portion of the longitudinally extending restrictor member. This is shown, for example, in both FIGS. 1 and 3. Additionally, the sound projection system may be constructed such that the point where the rear portion of the member becomes abruptly tapered toward the loudspeaker is substantially forward of the forward edge defined by the part frusto-conical volume. This is shown, for example, in both FIGS. 1 and 3.
Furthermore, the free space between the housing and the longitudinally extending restrictor member may have a substantially constant cross-sectional area between the points where the rear portion becomes abruptly tapered and where the front portion becomes tapered. For example, this is shown most clearly in FIG. 3.
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Aug 02 1983 | Turbosound Group Ltd. | (assignment on the face of the patent) | / | |||
| Feb 05 1987 | TURBOSOUND GROUP LIMITED, THE | Turbosound Limited | CHANGE OF NAME SEE DOCUMENT FOR DETAILS EFFECTIVE DATE: FEBRUARY 5, 1987 LONDON | 004966 | /0075 |
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