AUSTRALIA Patents Act, 1990 COMPLETE SPECIFICATION STANDARD PATENT A Loudspeaker Enclosure Bass Reflex and High Frequency Venturi Unit The following statement is a full description of this invention, including the best method of performing it known to me: Title A Loudspeaker Enclosure Bass Reflex and High Frequency Venturi Unit Technical Field [0011 This invention relates to and for the improved efficiency and propagation of sound waves from bass reflex loudspeaker enclosure cabinets incorporating a high audio frequency range loudspeaker driver, and to provide for a compact front baffle board surface area for small loudspeaker enclosure cabinet design and construction. Background to the Invention [002] It has long been difficult to effectively incorporate high audio frequency range loudspeaker drivers or tweeters with other necessary low audio frequency range loudspeaker drivers, requiring a vent or port necessary for the effective propagation of low audio frequencies generated from within a loudspeaker bass reflex enclosure cabinet and into the ambient atmosphere and listening environment, from the front baffle board surface area of small compact loudspeaker enclosure cabinets. [003] In an attempt to reduce loudspeaker enclosure cabinet size it has long been common practice, particularly with smaller scale bass reflex loudspeaker enclosure cabinets, to locate the bass reflex port orifice on either the base, rear or side external panel surface of the enclosure cabinet. However, such location of the port orifice requires the enclosure to be in some way elevated at its base should the port be so situated, or otherwise positioned at a sufficient distance from any opposing surface to the external port orifice of the enclosure cabinet, to provide for adequate ambient atmosphere for the unrestricted propagation of the lower frequency sound waves from the port. Such necessary positioning of the loudspeaker enclosure cabinet in effect increases the actual operating area required for any proper performance of the enclosure to be somewhat greater than the actual overall physical size of the enclosure cabinet, and to such extent effectively defeating the objective of endeavouring to effectively reduce or compact the actual loudspeaker enclosure cabinet size and its operating area and encroachment into the listening and living environment. [004] It is also a common associated problem with the port orifice being located on the base, rear or side panel of such conventional loudspeaker enclosure cabinet designs, that there is a substantial loss of efficiency in the propagation of the sound waves being at any incident conjointly produced from the port and the respective loudspeaker drivers mounted on the front baffle board of the enclosure cabinet, as such sound waves will inevitably as a consequence of the different travelling distances to the listener, together with further common frequency sound wave reflections and absorption of their energy from the surrounding room surfaces associated therewith, be to such relevant extent out of phase with each other and subsequently produce a relevant level of distortion and loss of efficiency of such frequencies of sound presented to the listener.
Z [0051 In an effort to facilitate and improve the efficient propagation of high audio frequency sound waves generated by high audio frequency loudspeaker drivers it has been a conventional and current state of the art design practice for such drivers to be provided with a large faceplate area about the perimeter of the active diaphragm of such drivers to assist with the necessary deflection, reinforcement and direction of the high frequency sound waves generated by the diaphragm of the high frequency driver into and about the ambient atmosphere and listening environment. However such a conventional practice of high frequency driver design and application for smaller loudspeaker enclosure cabinets further increases and determines the necessary overall area and size of the front baffle board for any particular loudspeaker enclosure cabinet design concerned. Summary of the Invention [006] The difficulties outlined above are somewhat overcome by this invention which provides for and applies the principles of physics relating to and for the operation of a venturi, with the application of a combined Loudspeaker Enclosure Bass Reflex and High Frequency Venturi Unit ('the unit') which is mounted on and secured to the external front baffle board of a bass reflex loudspeaker enclosure cabinet, which in application also provides for an improvement in the efficiency and dynamic range and transient response capacity of the loudspeaker enclosure. The unit consists of an independently enclosed active high audio frequency range loudspeaker driver without an outer surround faceplate or a tweeter module, securely suspended and enclosed within a main tubular body section of uniform cross-section ambient atmospheric area of sufficient internal dimension to accommodate the high frequency driver to effectively form a venturi of and for the unit, by and with a uniform reduction of displacement of ambient atmosphere in and about the perimeter of the active radiating diaphragm surround frame area and body of the high frequency driver which is securely suspended and centrally mounted there within. The high frequency driver is mounted and positioned within the main tubular body section to form the throat of and the venturi of the unit with the active radiating diaphragm and outer surround frame of the driver centrally suspended within and aligned with the most forward facing end of the tubular body section of the unit, from which point and in common axis thereto the body of the unit is further extended in overall length by an integrated or attached flared section thereof having an outer orifice and perimeter rim affixed to and supported by the external front baffle board surface of the loudspeaker enclosure cabinet, and there aligned together with a low audio frequency range loudspeaker driver or drivers employed within and or mounted on or from the front baffle board of the loudspeaker enclosure cabinet, with the overall internal body displacement of ambient atmosphere and orifices of the unit conjointly operating as a bass reflex port in tuned compliance with the internal loudspeaker enclosure volume and respective low audio frequency range driver or drivers mounted and engaged within the bass reflex chamber of the loudspeaker enclosure cabinet. The high audio frequency range driver is supported and centrally suspended within the main tubular body section of the unit to form the venturi and throat thereof by a suitable bracket or arm attached thereto, and may be so attached and secured by and with slotted screw holes to provide for any necessary adjustment or tuning of the venturi of the unit; or the supporting arm or bracket may be fitted with a friction ball-and-socket type joint to provide for any manual directional adjustment of the active radiating surface area of the diaphragm of the high frequency driver into any preferred area of the listening environment. L007] In a preferred embodiment of the invention the cross-section area of ambient atmosphere within and about the inner wall of the main uniform tubular body section of the unit at and about the area forming the throat of the venturi, immediately adjacent to the outer surround frame of and for the active diaphragm of the high frequency driver when mounted there within, should be uniform in displacement about the outer surround frame perimeter of the driver and preferably represent no less than about one-third of the total internal cross-section area provided for the main tubular body section of and for the venturi of the unit; with the overall length of the main tubular body section to form the venturi of the unit preferably being no less than the internal diameter thereof; with the cross-section area of ambient atmosphere at the perimeter of the front flared orifice of the unit being no less in total cross-section area as the internal main tubular body section of and for the venturi of the unit excluding the high frequency driver, plus the total overall front facial area of the high frequency driver suspended and engaged there within. The cross-section area of the orifice of the body of the unit extending into and exposed within the bass reflex chamber of the loudspeaker enclosure cabinet should preferably be no less in total cross-section area than the cross-section area of the internal main tubular body section of and for the venturi of the unit excluding the high frequency driver. The overall length of the flared forward facing section and outer orifice of the unit, measured in common axis with and from the most forward point of the active diaphragm of the high frequency driver mounted within and situated at the most forward point of the main tubular body section to form the throat and venturi of the unit, to the very outer flared front orifice at the perimeter rim of the unit, where mounted on and secured to the front baffle board of the loudspeaker enclosure cabinet, should preferably be no less than half the length of the main tubular body section provided for the venturi of the unit. [008] The central positioning of the high audio frequency range driver engaged within and forming the venturi of the unit as described will in operation as a combined bass reflex port effectively provide for the maximum possible pressure from sound wave activity within the main throat area of the venturi at and about the perimeter and to the central axis point of the active diaphragm of the high frequency driver mounted therein, thereby assisting with the extraction and propagation of the high audio frequency sound waves generated by the diaphragm of the high frequency driver into the ambient atmosphere and listening environment, at incidences of sufficient amplitude levels of combined low and high audio frequency sound waves when generated by the respective drivers activating and operating within the venturi of the unit, and in consequence thereof effectively increasing the overall dynamic range capacity of the particular loudspeaker drivers and enclosure cabinet design concerned. In addition thereto the high degree of sound wave activity and movement within the body of the venturi and unit in and about the body of the high frequency driver will further assist to maintain a more constant and stable operating temperature for the high frequency driver with improved efficiency thereof The high audio frequency range driver being recessed within the body of and to form the venturi of the unit allows for the unit to be specifically designed to provide for the active radiating diaphragm surface area of the high frequency driver engaged therein, to be situated at a calculated distance from the front orifice of the unit to ensure that the active radiating surface area of the high 14 frequency driver is in a complimentary or common axis alignment with the active radiating diaphragm surface area of the low audio frequency range driver or drivers; and or within a central point between the active diaphragms of a push-pull configuration of such drivers; or diaphragms of a dual-cone tympanic loudspeaker driver or drivers mounted within a tympanic, isobaric or other front chamber of a dual-chamber loudspeaker enclosure cabinet; with such axis alignment of the respective active diaphragms of the drivers so employed and mounted within the loudspeaker enclosure cabinet assisting to provide for and improve the harmonic integration and propagation of common sound wave frequencies when generated conjointly within the crossover band of audio frequencies by the respective drivers from the enclosure and into the ambient atmosphere and listening environment. With the overall application of the preferred embodiment of the unit of the invention as outlined and described above assisting to provide for the improved efficiency and dynamic range and transient response capacity for any given loudspeaker drivers and enclosure cabinet design concerned. [009] The overall length of the main tubular body section of and for the venturi of the unit extending into the loudspeaker enclosure cabinet may also be further extended to any necessary length to tune the overall body of the unit as an effective bass reflex port to an appropriate frequency or band width of frequencies to comply with the internal volume of the particular enclosure dimensions and the respective low frequency loudspeaker driver or drivers employed and exposed within the bass reflex chamber of the loudspeaker enclosure cabinet, with any such extension preferably being no less in cross-section area of ambient atmosphere than the internal cross-section area of the main uniform tubular body section of and for the venturi of the unit excluding the high frequency driver. [0101 The high audio frequency range loudspeaker driver employed and mounted within the main tubular body section of and to form the venturi of the unit may be constructed or fitted with a frustum, conical or pyramidal shaped fin at and from the very rear of the driver, diminishingly extending there from into the rear portion of the main tubular body section of the venturi of the unit, to aerodynamically improve the efficiency and operation of the venturi of the unit and to prevent or limit the possibility of sound wave turbulence and any associated distortion being generated there from within and about the main tubular body section and throat of the venturi when the unit is operating as a tuned resonate low audio frequency bass reflex port for the loudspeaker enclosure cabinet. The aerodynamic fin should be constructed with a smooth outer surface and of non-resonate solid material or an outer shell casing sealed from the ambient atmosphere. [0111 The body of the unit or any part or section thereof should be constructed from any material of sufficient density to provide for a smooth internal surface finish, and be of such sufficient strength to securely support the mounted high audio frequency range loudspeaker driver within and to form the throat of and the venturi of the unit, and to minimize or eliminate any possible acoustic resonance of any material of or the unit during any operation thereof when securely mounted to and supported by the flared front section of the unit to the front baffle board of the loudspeaker enclosure cabinet. [012] The unit in combining the high audio frequency range driver and bass retlex port function will reduce the total area necessary for the front baffle board of any given bass reflex loudspeaker enclosure cabinet design, and improve the overall efficiency and fidelity of the particular design in comparison to the more conventional and current state of the art of construction and design with the respective installation of a high audio frequency range loudspeaker driver requiring a faceplate of large surface area in addition to the vent or port area required for any given bass reflex loudspeaker enclosure cabinet design. Description of the Drawings [013] To assist with an understanding of the invention example drawings of the unit are provided herewith and described with reference to the accompanying respective figures of common constituent part reference numbers thereto: [014] With reference to Figure 1 this drawing illustrates a cross-section view of the main tubular body of and for the venturi section and the extended forward flared body section of the unit (1), and a view of the independently enclosed and active high audio frequency range loudspeaker driver (2) and radiating diaphragm thereof (2A), with connecting electrical wires thereto (3), and associated supporting bracket (4), with an optional adjustable slot and screw (5), to suspend and adjust the high frequency driver within the main uniform tubular body section of the unit to form the venturi and throat thereof (6), with the radiating diaphragm of the high frequency driver situated near the point of commencement of the forward facing flared orifice (7), with the outer flared frame of the unit body (8) attached to and supported by the outer surface of the front baffle board (9), with an optional internal extension fitted to the rear main tubular body section of the unit (10) for tuning the resonate low audio frequency range of the enclosure with the respective low frequency range loudspeaker driver or drivers employed within the enclosure in compliance with the internal volume of the bass reflex chamber of the loudspeaker enclosure cabinet (11). [0151 With reference to Figure 2 this drawing illustrates a modified form of the arrangement shown in Figure 1, without the optional internal extension (10) shown therein, but with an optional aerodynamic frustum conical fin (4A) fitted to the very rear of the high audio frequency range loudspeaker driver (2) secured and centrally suspended within the main uniform tubular body section of the unit to form the venturi and throat thereof (6).