Patent Publication Number: US-4836326-A

Title: Optimal shadow omniphonic microphone and loudspeaker system

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to new and useful improvements to omniphonic microphone and loud speaker systems illustrated and described in my U.S. Pat. No. 4,122,910 which is hereby incorporated by reference. 
     In this U.S. Patent, a regular tetrahedron construction is used for both the microphone and loud speaker components. However, that particular construction contains some directional ambiguity, which ambiguity is significantly reduced by the improvements described hereafter. 
     A superficial inspection of the enclosed description appears to indicate that the regular tetrahedral basis for the original invention shown in the U.S. Patent, has disappeared. 
     However, as will become apparent, a plane passing through the cylindrical truncations of either the microphone or the loud speaker components once again generates the regular tetrahedral shapes of the original invention. The planes also appear in the modifications made to the baffles of the side speakers. 
     The improvements include the following technical features: 
     (1) All of the transducers are shielded by cylindrical structures with elliptical end faces lying in planes oriented at 1/2 dihedral angle of the regular tetrahedron to the cylinder axis, namely, 35°, 16&#39; and where the long axis of the elliptical end faces are set at 45° to the horizontal. 
     (2) The planes of the elliptical end faces of the shielding cylinders correspond or are isomorphic to the tympanic membrane of the human hearing structure. 
     (3) The shielding cylinders of the optimal shadow omniphonic microphone component and of the isomorphic loud speaker module are isomorphic to the truncated cylinders described in the microphone and loud speaker components of U.S. Pat. No. 4,122,910 and indicated in that patent by reference character 23. 
     (4) The planes of the end faces of a center cylinder located between the shielding cylinders in the optimal shadow omniphonic microphone component correspond to the dihedral planes of the omniphonic microphone of the above U.S. Patent and illustrated in FIG. 8 thereof. 
     (5) The planes of end faces of a center cylinder located between the shielding cylinders in the isomorphic module of the loud speaker component correspond to the dihedral planes of the omniphonic loud speaker illustrated in FIG. 9 of the above U.S. Patent. 
     (6) The long axes of elliptical end faces of shielding cylinders attached to room loudspeaker baffles in the speaker system are set at 45° and incline downwardly to horizontal. The end faces away from the listener. 
     With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the best mode known to the applicant and of the preferred typical embodiment of the principles of the present invention, in which: 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows schematically the geometry of the optimal shadow omniphonic microphone component of the present invention. 
     FIG. 2 is a rear and left hand isometric view of this microphone component with electronic connections being shown schematically. 
     FIG. 3 is a front and right hand isometric view of FIG. 2. 
     FIG. 4 is a schematic end elevation of one of the end faces of a cylinder carrying a microphone. 
     FIG. 5 is a view similar to FIG. 2 and illustrating, schematically, the geometry of a loud speaker module of the present invention. 
     FIG. 6 is a schematic view of the relationship of the isomorphic module and the outer speaker modules. 
     FIG. 7 is an isometric view of FIG. 6 with the electronic connections shown schematically. 
     FIG. 8 is an enlarged front and right end isometric view of the isomorphic module of FIG. 7. 
     FIG. 9 is an enlarged isometric view of one of the shielding cylinders of the outer speaker components. 
     FIG. 10 is a partially schematic front elevation of the left and right baffles of the lefthand speaker module. 
     FIG. 11 is a view similar to FIG. 10 but showing the left and right baffles of the righthand speaker module. 
     FIG. 12 is a fragmentary cross-sectional schematic view of part of one of the outer speaker cabinets showing the relationship between the shielding cylinders and the transducers. 
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION 
     Proceeding to describe the invention in detail, reference should first be made to FIGS. 1 through 4 which which illustrate the Optimal shadow Omniphonic Microphone portion of the invention. 
     FIG. 1 shows partially schematically, a tetrahedron 20 with a geometry like that of the tetrahedron forming the microphone module illustrated and described in U.S. Pat. No. 4,122,910 and specifically FIG. 8 thereof. 
     Reference character 21 illustrates the centre of this tetrahedral structure and points 22 and 23 show the locations where the centres of microphones would be located in the tetrahedron according to FIG. 8 of U.S. Pat. No. 4,122,910. 
     The cylindrical outline 24 shown in phantom in FIG. 1, illustrates a cylindrical core of the tetrahedron, which corresponds to the centre section of a microphone component constructed according to the present invention. Such a microphone component, collectively designated 25 is illustrated in FIGS. 2, 3 and 4 of the enclosed drawings. 
     This microphone component 25 consists of a central cylinder 26, a righthand shielding cylinder 27 and a lefthand shielding cylinder 28, it being understood that FIG. 2 is a rear view of the component whereas FIG. 3 is a front view. 
     The 21 of the cylindrical core 24 of the tetrahedron of FIG. 1 has a corresponding centre point in cylinder 26, as illustrated by reference character 21 of FIG. 2. The cylinders 26, 27 and 28 are formed from a solid material. The ends 26A and 26B of the central section are elliptical and lie in plans oriented at an angle of 35° 16&#39; to the axis x--x of the cylinder, which equals half the dihedral angle of the regular tetrahedron shown in FIG. 1. 
     The corresponding inner ends 27A and 28A of the end shielding cylinders 27 and 28 are also elliptical and lie in planes at a similar angle of 35° 16&#39; to the axis x--x the longitudinal axes of the elliptical end faces are oriented at 45° to a horizontal plane. This is illustrated by comparison of FIGS. 2 and 3 and shown schematically in FIG. 4. 
     Conventional microphone elements 29 open onto the end faces of all four ends 26A, 26B, 27A and 28A and are connected electrically to a conventional microphone mixer 30 and thence to left and right amplifiers all of which is conventional. 
     The confronting ends 26B/27A and 26A/28A are spaced apart from one another thus forming an adjustable gap therebetween which may be in the order of between 1-4 mm as an example and this gap is selected for optimum sound reception with minimal ambiguity. 
     FIGS. 5 through 12 show the isomorphic module and outer speaker modules constituting loudspeaker component of the system and reference should first be made to FIG. 5 which shows a regular tetrahedron 31 similar to the loudspeaker tetrahedron shown in FIG. 9 of U.S. Pat. No. 4,122,910. 
     In this U.S. patent, two transducers are situated on adjacent faces of the tetrahedron where the elipses 32 are shown on faces 33 in FIG. 5. Cylinder 34 shown in phantom in FIG. 5 of the present application to represents, the isomorphic module collectively designated 35 with reference character 36 indicating the theoretical centre of the tetrahedron and of the cylinder 35. 
     The construction shown in detail in FIG. 8, is similar to the module of the microphone component shown in FIG. 3 in that it contains a central section 37 and end sections 38 and 39. These are formed from hollow cylindrical material filled with acoustical insulation material (not illustrated). The outer ends 37A and 37B of the centre section 37 are also elliptical and lie in planes at an angle of 35° 16&#39; longitudinal axis y--y as are the inner ends 38A and 39A. Once again the long axes of the elliptical end faces are oriented at 45° to a horizontal plane as clearly shown by a consideration of FIG. 8 and comparing same with the structure shown in FIGS. 2 and 3. 
     Mid-range transducers 40 are mounted spaced inwardly from the ends 37A/38A and inwardly from the ends 37B and 39A and are connected electrically to the amplifier 41 as shown. 
     Once again the adjacent end faces of the sections 37, 38 and 39 are spaced apart and the gaps therebetween may be adjusted similar to that described for the microphone components. 
     FIG. 6 shows, schematically, the alignment of all of the transducers not only of the isomorphic module but also of outer or side speaker modules collectively designated 42 and 43 with the left and right channel connections controlled by amplitude controls 44 and connected to the amplifier as shown. 
     From this schematic view, it will be seen that the outer speakers 42A and 43A are low-range speakers connected to opposite channels and that the inner speakers 42B and 43B are high-range speakers connected to the opposite channels with the crossover being approximately 700 Hz. The four central speakers 40 are mid-range tweeter type speakers and are also connected to the respective channels as illustrated. The cross-over frequency need not be rigidly fixed but may be in a range between 700-1500 Hz. 
     The speaker modules 42 and 43 may be enclosed in an acoustic suspension or acoustic reflex speaker cabinet 44A of conventional construction with the exception of the speaker baffle panels shown in FIGS. 10 and 11. FIG. 10 shows the left outer baffle panel 45 of the component 42 and the left inner baffle panel 46 also of component 42. 
     FIG. 11 shows the right outer baffle panel 47 and the right inner baffle panel 48 both of the speaker component 43. 
     All of the baffle panels include, adjacent the upper end thereof, a plurality of shielding cylinders collectively designated 49 adjacent the front of the cones of the speakers 42A and 42B and 43A and 43B respectively. Each of these shielding cyinders takes the form of a small cylindrical element having an elliptical outer end 50 oriented at 35° 16&#39;to the axis z--z of the element. They are preferaly provided with a felt outer cover 51 and a felt inner liner 52 and they are mounted in the baffle panels in a symmetrical array as illustrated. Of importance is the fact that the shielding cylinders of the outer panels 45 and 47 are positioned so that their elliptical end faces open downwardly and outwardly from the panel whereas the elliptical end faces of the cylinder on the inner panels 46 and 48 open downwardly and inwardly from the panels as illustrated in FIGS. 10, 11 and 12. 
     All of the surfaces of the optimal shadow microphone/and the isomorphic module are preferably provided with a felt covering. 
     Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.