US 3842203 A
Loudspeakers and associated horns of the low-frequency portion of a system are arranged to face inward towards a common point or axis around which they are arrayed. The speakers are driven in phase and create a pulsating core mass of air from which energy radiates through spaces between and around the horns and speakers and into surrounding space. Guide surfaces and interposed bodies may be used to shape channels around the other elements through which waves travel from the pulsating core to surrounding space. A plug body may be centered in the core to raise the crossover frequency between the low and medium frequency portions of the system.
Description (OCR text may contain errors)
United States Patent 1191 Weisberg Oct. 15, 1974 PUBLIC ADDRESS SYSTEM WITH HORN 898,445 6/1962 Great Britain 179/1 GA SPEAKERS ARRAYED AROUND AND FACING INWARD TOWARD A COMMON POINT  Inventor: Jack Weisberg, 450 Broome St.,
New York, NY. 10013  Filed: June 30, 1972  Appl. No.: 268,032
 US. Cl. 179/1 AT, 179/1 E  Int. Cl H04r 27/00  Field of Search 179/1 E, 1 M, 1 G, 1 AT, 179/1 GA; 181/30, 31 A, 27 D, 31 B  References Cited UNITED STATES PATENTS 1,943,499 1/1934 Williams 181/31 A 2,124,575 7/1938 Kames 181/30 2,138,717 11/1938 Volk ..181/31A 2,194,664 3/1940 McDonald 181/31 A 3,157,247 11/1964 Ishimura 181/31 B FOREIGN PATENTS OR APPLICATIONS 461,106 2/1937 Great Britain 181/27 D L F AUDIO CURRENTS Primary Examiner-Kathleen H. Claffy Assistant Examiner-Jon Bradford Leaheey Attorney, Agent, or Firm-Flynn & Frishauf [5 7 ABSTRACT Loudspeakers and associated horns of the lowfrequency portion of a system are arranged to face inward towards a common point or axis around which they are arrayed. The speakers are driven in phase and create a pulsating core mass of air from which energy radiates through spaces between and around the horns and speakers and into surrounding space. Guide surfaces and interposed bodies may be used to shape channels around the other elements through which waves travel from the pulsating core to surrounding space. A plug body may be centered in the core to raise the crossover frequency between the low and medium frequency portions of the system.
25 Claims, 9 Drawing Figures LOW FREQUENCY AUDIO TRANSDUCER mm m 1 5 SHEET 1 0f 4 FIG. 1
LF TR 45 I LOW FREQUENCY AUDIO TRANSDUCER LF TR "4 H SOURCE OF L F AUDIO CURRENTS Y 3.842.203 sumsora PMENIED BUT I 51974 PAIEmmww m' v 3.842.203
PUBLIC ADDRESS SYSTEM WITH HORN SPEAKERS ARRAYED AROUND AND FACING INWARD TOWARD A COMMON POINT This invention relates to speaker systems for public address systems, or stated in more general terms, compressional wave radiating generators effective at wave lengths of the order of magnitude of the over-all dimensions of the apparatus. The invention is particularly applicable for the lowest frequency elements of high power loudspeaker systems of large sports arenas, convention halls and similar places as well as for high quality outdoor loudspeaker systems for bandstands or for music festival set-ups.
In public address systems for large audiences, whether indoor or outdoor, it has not been possible heretoforeto provide loudspeaker equipment for the lower audible frequences from about 150 to 200 herz down to the neighborhood of the threshold of audibility, or about 30 herz, with anywhere near the same effectiveness and quality as is done for sounds in the middle and higher register. This deficiency has been tolerated in sports arenas and convention halls where the systems were used primarily for transmission of speech. In recent years musical events have come to outgrow in scale the concert halls that make little or no use of electrical amplification and popular music audiences have become more critical of the quality of the electrical amplification equipment used at recitals, music festivals, outdoor performances and even some large theaters. Finally, the incidental presentation of music at conventions, sports events and similar occasions so obviously exposed the deficiencies of large public address systems that the audience begins to notice a synthetic quality in the sound of speakers and announcers and tends to get a general sense of annoyance whenever the speaker system is in use. The public becomes frustrated about such events when a recording of the event played on a reasonably good home system sounds more natural than actually being there in the audience.
In order to avoid dead spots and resonances for particular frequencies at particular places, there has been a preference for concentrating the speakers of a high powe'r'speaker system at a particular point at the center of'an arena or above a stage or bandstand, rather than to provide speakers or collections of speakers at various points in the space to be served, although in connection with a stage, a cluster of speakers on either side of the stage has been found suitable to many halls and theaters. it is conventional in a cluster of speakers diffusing sound to an audience to use speakers with horns directed outward from a common axis or point so that the sound will diffuse evenly to the audience. At the higher frequencies the wave lengths are short and the horns may be short and relatively wide flaring. At the very highest frequencies the mouth of the horn may be one or many wave lengths across and the horn may be sectored to avoid excessive directivity. At the lower frequencies directivity is no problem because the structures are not large in comparison with the wave length. This has the advantage that supporting struts and other incidental structures do not interfere with the even diffusion of the sound when they are in its path. A serious problem exists, however, for coupling the speaker with the air well enough for sufficient energy radiation at these low frequencies (long wave lengths) to balance the sound output available in other frequency ranges with known types of equipment. The coupling problem, as it is well known, can be regarded as a problem of matching the motional impedance of the transducer constituted by the speaker to the characteristic imped-- ance of the unconfined medium of transmission. For this purpose it is common to use long horns coupling the movement of air at the throat of the horn, where the speaker is located, to a much smaller but evenly distributed in-phase motion of air across a very large area at the mouth of the horn.
In systems heretofore used, when two or mroe such horns were clustered to serve a large space, these horns, like those used for a medium and higher frequency, have been directed outward from the center of the cluster. The flare of these horns, that is, the rate of increase of cross-sectional area with respect to distance from the throat of the horn, determines the lowest frequency that is transmitted with reasonable efficiency. it is common to use an exponential flare, in which the area increases exponentially with successive equal increments of length, but some other variants are used, such as hyperbolic horns. Furthermore, in order to couple the compressional waves in the horn to the unconfined medium, the horn opening must have a minimum area that depends on the longest wave length (lowest frequency) to be transmitted. This area is of the order of 1/ 10th of the square of the wave length and this has given rise to the rule that if the opening of the horn is circular the diameter should be approximately a third of the maximum wave length (area equal to 8.7% of the square of the maximum wave length) and if the opening is square, it should be approximately a third of the maximum wave length on a side (area l/9th of the square of the maximum wave length).
The foregoing considerations have generally discouraged the provision of equipment for effectively diffusing sounds of frequencies as low as or lower than to 200 herz in sports arenas and convention halls. Where any equipment for this low frequency range has been provided, only one or very few horns have been provided at a central cluster and the horns have rarely been designed for a maximum wave length approaching the threshold of audibility.
it is an object of this invention to provide a speaker system capable of diffusing sound waves in air efficiently at the lower range of frequencies, down to 50 herz or even lower, from a unified cluster of apparatus at a power level suitable for large spaces, whether indoor or outdoor. More generally, it is an object of the invention to provide apparatus for the generation and radiation of compressional waves in a fluid medium from a central point or axis efficiently with equipment of over-all dimensions substantially less than the maximum wave length, whether at low or moderate frequency.
It is a further object of the invention to provide means for effectively combining the outputs of a multiplicity of transducer means into a single effective source from which compressional wave energy may be diffused with wave lengths including some of the order of magnitude of the over-all dimensions of the equipment. it is a still further object of the invention to provide a system of clustering a multiplicity of transducers for difiusing waves of relatively long wave length either without individual horns or with individual horns that are shorter or have orifices of lesser area than those heretofore used or coupling with an unconfined medium.
The invention is realized by arranging transducer means so as to direct their energy, with or without the aid of a horn, inwardly towards a central point or axis, from the neighborhood of which the energy travels around the transducers and any associated horn structures outwardly into the unconfined medium of transmission.
SUBJECT MATTER OF THE INVENTION Briefly, the apparatus of the invention comprises a multiplicity of transducer means arranged to respond in phase to a common exciting signal to produce compression variations in the transmission medium, in phase, at the respective outputs of a corresponding multiplicity of horns the mouth areas of which are orthogonal to radii from a common point or axis, in such a way that initial propagation of compressional waves is towards the aforesaid point or axis in other words, the waves are launched inwardly to the point or axis. The result of this arrangement is to form a pulsating core in the medium in the space in which the waves from the various transducers converge, which may completely surround the aforesaid central point or axis or may surround it over a smaller arc, for example, 180 if a structure is against a wall of a hall, or for even less, to about 90, if the structure is in an angle of a wall or even a corner. Channel means are provided either by the spaces between the speakers and their associated horn structures, or by the spaces above and below them, or, more commonly, both, for evenly diffusing compressional waves from the pulsating core just described, around the transducer means, and radiating them into the surrounding medium outside. Additional bodies may be provided between the speakers or between their associated horn structures to modify the transmission characteristics of the channel means so as to pro vide a more gradual expansion of the cross sectional area traversed by the travelling waves being radiated into the unconfined medium. Furthermore, a solid body may be provided in the middle of what has just beendescribed as the pulsation center, in order to extend the high frequency limits of the system by preventing destructive interference between transducer outputs where their effective output surfaces are separated by a distance of a half wave length or more for the frequency. The central .body or phasing plug" provides isolation at the higher frequencies between oppositely disposed elements of the system in a 360 installation and may also be useful, for example in'a 180 installation, to prevent similar undesirable interference between elements by way of reflection from the wall of such an installation.
It is possible to create a pulsation center according to the invention by clustering transducer means directed inwardly toward the point or axis equipped with somewhat short horns, that is, horns that do not fully reach the output area needed for coupling the energy to the unconfined medium at the lowest frequency. Particularly, when no horns are used at all, it is desirable to fashion the channel means to provide a gradual and smooth increase of cross sectional area in the medium through which the waves diffuse as they proceed outward from the pulsation center. The converging short horn arrangements are adapted to provide an effective low frequency component for a wide range public address speaker system of high power, with a structure surprisingly compact.
Illustrative embodiments of the invention are described below with reference to the annexed drawing in which:
FIG. 1 is an elevation view of an apparatus cluster for omnidirectional diffusion of sound with a number of the radially disposed elements of the cluster omitted;
FIG. 2 is a plan view as seen from the top, of the apparatus cluster shown in FIG. 1;
FIG. 3 is a partial vertical median section of another form of apparatus cluster emboding the invention;
FIG. 4 is a partial horizontal median section of the form of apparatus cluster shown in FIG. 3:
FIGS. 5 and 6 are diagrammatic partial median sections of still other forms of apparatus cluster in accordance with the invention;
FIG. 7 is a partial median section of a form of apparatus cluster according to the invention taken on the median plane of a pair of bodies inserted between horn units, instead of on the median plane of an opposed pair of horn units as in the case of FIGS. 3, 5 and 6; and
FIGS. 8 and 9 are a diagrammatic vertical median sections of embodiments of the invention utilizing stacked apparatus clusters.
FIGS. 1 and 2 show in simplified form apparatus for radiating sound from a central location into a large hall or arena, or outdoors. The sound radiated is the low frequency range output of an amplifying system, sounds of other frequency ranges from the same amplifying system being radiated from the same neighborhood by means of other speaker systems, such as one or more outwardly directed horn clusters (not shown) mounted above or below, or both, above and below the equipment shown in FIGS. 1 and 2.
In this embodiment of the invention twelve loud speakers are mounted in the enclosures l l2 and are excited in phase by an electric signal in the low frequency audio range supplied by a source 15, which may be an amplifier or a frequency dividing network. These respectively transmit sound into the throats of the horns 31, 32 42. The horns are exponential horns with parallel sides, the necessary increase in crosssectional area with length being provided by the increase in vertical dimension of each horn. This type of horn permits a large number of speakers, which may also be referred to as drivers or transducers, to be coupled to a core of air in the center of the array, while providing also exit channels 45 leading from the gaps 46 between the horn mouths 47 for spreading the sound energy from the pressure pulsations of the central cylindrical core out to the unconfined air outside the array.
The sound may also spread to the outside over the top and bottom of the horns and speakers.
In order to show an unobstructed side view of the horn 37 and the speaker enclosure 7, the speaker units 5 and 6 and horns 35 and 36 have been omitted in FIG. 1, a portion of their outlines only being shown in dotted lines to indicate their presence. The supporting and p0- sitioning structure for the array of speakers and horns, which is symbolized by the struts 45 and 46 in FIG. 2 and may include additional cross bracing not shown, is also omitted in FIG. 1 in order to simplify the illustration. A lattice or cage of tubular members, including the members 45 and 46 of FIG. 1, is suitable for holding the illustrated structures in the proper relative position, for the presence of such structural members in the central cylindrical volume and in the spaces between the horns does not disturb the diffusion of the sound without undesired resonances because the diameter of the necessary tubular members is so very small compared with the wave lengths of the sounds diffused by this apparatus.
The speaker units are distributed around circle, for example down circle 47 drawn through the throats of the respective horns, of which the center is a point of convergence P at which the median lines of the horns, for example the lines 48 drawn in FIG. 2 for a few of .the horns, meet. The whole structure may be mounted on a platform above the center of the space to be served, such as above a speakers platform or bandstand, or may be suspended from a ceiling or roof, or from cables running between towers outside an arena space. A system of this type can give good transmission doen to 40 herz even though the horns 31, 32 42 individually have a mouth area of only 2 square feet. In the system which gavesuch results, there were 9 rather than 12 speakers and horns. The horn mouths were 6 inches wide and 4 feet high and the flare was designed for 32 herz cut-off frequency. If the throat of the horn is 6by 12 inches then for a lower cut-off frequency of 32 herz the horn must be 4 feet long in this case. The wave length corresponding to 32 herz for sound waves in air is slightly over 35 feet. The ordinary outwardly directed exponential horn for effectively transmitting at such a frequency to unconfined air would have to have a mouth with an area of 113 square feet and a length of over 8 feet from a throat having a cross section 6 X 12 inches.
In the example cited of 9 speakers and horns arranged in a manner of the 12 shown in FIGS. 1 and 2,
the total 'mouth area of the horns was 18 square feet, which suggests that for a cut-off frequency of 32 herz it would be desirable to approximate an exponential increase in cross-sectional area of the channel through which the sound proceeds from the central cylindrical core (which may be regarded as a center of pulsation) between and around the horns at least until that crosssectional area has tripled. The usual presence of other structures immediately above and'below the array cooperates in the usual case with the shape of the horns so that the outwardly proceeding waves do expand in such as way as to couple effectively with the unconfined space, but as explained further below, it is possible to add refinement to the structure in order to assure this transition. Of course the greater the mouth area of each individual horn, the shorter the distance over which it is necessary to control the shape of the channels leading outward around the horns from the central cylindrical pulsating air mass.
If it is desired to provide a speaker system radiating from a position in the middle of a large wall of only one side of which the audience is located, the same principle may be applied. With reference to FIG. 2, for example, the dashed line 50 could represent the surface of the wall and either half of the cluster of speakers and horns shown could then be used mounted in the relation shown to the wall surface. If it is desired to diffuse sound from a wall-mounted structure with its axis in a concave angle of the wall a still smaller sector of the array shown in FIGS. 1 and 2 could similarly be used.
The speakers mounted in the enclosures shown may be of any-of the various commonly used types. Indeed, each of the enclosures l, 2 12 may house two or more driver units feeding the throat of the same horn. If acoustic suspension speakers are used a confined space will be provided at the back of each speaker. It is not necessary, however, to provide an enclosed space in the back of each speaker and if speakers of types generally used in vented enclosures are used, the enclosures 1, 2, 3 12 may be open at'the bottom, for example, because in this arrangement the back of the speaker is not coupled efficiently to the surrounding air and makes only an utterly negligible contribution to the radiated sound.
In the type of system shown in FIGS. 1 and 2, the maximum frequency tends to be limited by the diameter of the cylindrical volume into which the horns open out, because if the diameter exceeds about-one-third of the wave length, valleys and peaks in the transmission characteristic of the system begin to appear as frequency increases. The upper frequency threshold of the system, and hence the cross-over frequency of the dividing networks used between the amplifier and the various output systems, can be increased by the provision of a central phasing plug as shown in the system of FIGS. 3 and 4 and also, more diagrammatically, in FIGS. 5, 6 and 7.
FIG. 3, is a vertical median section of a system embodying the invention with the throat ends of the horn and the speakers and speaker enclosures broken away. The section is taken on the median plane of a pair of diametrically opposed horns, this plane being indicated by the line 3-3 in FIG. 4. FIG. 4 is a horizontal median section, its plane being shown by the line 4-4 in FIG. 3.
As shown in FIGS. 3 and 4 the central phasing plug is cylindrical and consists of an outer portion which should be made of a sound reflecting material, such as rigid glass fiber laminate, which is a suitable material also for the horns and speaker enclosures, and a filling 62 of a lighter material such as cellular polyethelene, polystyrene or polyurethane. The center portion could be left hollow, if desired, or the entire plug might be made of this same material. The axis 55 is both thecentral axis of the plug 60 and the central axis of the horn array.
In the systems shown in FIGS. 3 and 4 flaring dished surfaces 65 and 66, which may likewise be provided out of sheets of glass fiber laminate, serve to assure that the expanding path of the diffused sound waves will follow a suitable progression in cross-section area, until the area becomes sufficient for coupling to unconfined space at the lowest frequency of operation. In the system of FIGS. 3 and 4 this progression in the crosssectional area of the channels leading outward from the pulsating air mass surrounding phasing plug 60, is modified by contoured vanes 70. In a system in which dished surfaces 65 and 66 are used above and below the array of horns, it is convenient to provide the contoured vanes in a form extending from the surface 65 to the surface 66, as shown, and in that case they can serve as structural members on which the horns can be mounted by rods or tubular members extending between the vanes, as shown at 72 in FIG. 3.
In the form of system shown in FIG. 3 but omitted in FIG. 4 for simplicity of illustration, eyes are mounted where the mechanically strong parts of the plug 60 and at least some of the vanes 70 meet the surface elements 65 and 66. The eyes 75 at the top of the structure are designed for suspending the system from above'and the eyes 76 at the bottom are for suspending speaker and horn arrays for higher frequencies beneath the structure shown.
It is, of course, by no means necessary that the horns of a system according to the invention should be of rectangular cross section or that the phasing plug should be cylindrical. Indeed, the objectives of the system as described above may sometimes be particularly well realized and the appearance of the system improved so that it does not need to be dissimulated behind a grill (such as indicated by the dashed line 80 in FIG. 2) if the components of the system are moulded in curved shapes. For instance the horn cross sections may conveniently be elliptical and their mouth profiles may also be curved as shown in FIGS. 1, 3, 6 and 7.
As shown diagrammatically in FIG. the central phasing plug may be spindle shaped or, as shown in FIG. 6 it may be in the shape of a spool that gradually merges into upper and lower surfaces confining the radiation path for the sound at top and bottom. The spindle shape is particularly useful when the horn length is sufficient so that open space at the top and bottom of the pulsating air mass does not provide too sudden a transition to unconfined surrounding space.
FIG. 7 illustrates the fact that the vane 70 described in connection with FIGS. 3 and 4 may be contoured verticallyas well as horizontally. FIG. 7 is a vertical median section in a plane which bisects diametrically opposed vanes 85. These vanes may have various shapes according to the conditions imposed by the surrounding structures. In the case illustrated in FIG. 7 they are kidney shaped fish interposed between the horns, this shape, somewhat exaggerated in the drawing, being intended to compensate for the bulk of the speaker housings, it being assumed that these speaker housings in this particular case are still close enough to the center of diffusion, as well as big enough in bulk, (which is unlikely) to affect the smoothness of expansion to the channels leading from the central pulsating air core surrounding the phasing plug '86, out towards the substantially unconfined space around the structure. Likewise, external horn walls could be contoured in thickness.
FIG. 8 shows a system in which two concentric arrays of horns feeding a common cylindrical pulsation center are provided. An elongated phasing plug 90 stands at the center of the array. FIG. 9 shows another form of stacking".
FIGS. 8 and 9 are highly daigrammatic, for the purpose of illustrating different types of stacking of arrays of horns, each array with its transducers disposed at uniform intervals around the axis 55, which corresponds to the axis 55 of FIG. 3 (and of FIGS. 5, 6 and 7). Only the two horns of the array that are disposed broadside to the direction of view are shown in FIGS. 8 and 9 since that is all that is necessary to show the manner of stacking. It is to be understood that structural members as mentioned in connection with FIG. 2 and FIG. 3 and additional bodies as described in connection with FIGS. 4 and 7 may also be provided. In FIG. 8, the horns 91 of the upper array are disposed with their median lines lying in a plane intersecting on the axis 55, as in the case of FIGS. 1 and 2, and the same is true of the horns 92 of the lower array. In the arrangement of FIG. 9 it is evident that the median lines and the horns of the upper array, of which two are shown at 93, will not lie in the same plane and, actually, they will lie on a cone with the vertex on the axis 55 at 97. The same is true for the median lines 96 of the horns of the lower array of which two are shown at 94 except that the cone, the vertex of which is at 98 on the axis 55, will be dished downwards, rather than upwards as in the case of the upper array.
In designing systems of this type account must be taken of the fact that the lowest frequency of satisfactory transmission of an exponential horn is about 20% higher than the theoretical cut-off frequency. This is illustrated by the example previously cited, in which the cut-off frequency of the horns was 32 herz but the lowest frequency satisfactorily transmitted was actually slightly under 39 herz.
The invention has been described in connection with its principal application at the present time, that is, bass range high power loudspeakers for arenas, convention halls and outdoor installations.
A single opposed pair of speaker-driven horns may be used to form, according to the invention, a rudimentary omnidirectional radiator. Generally, of course, a larger number of such elements is desirable, both for even distribution of the sound and for attaining high power levels. In general, therefore, the invention is characterized by the use of a multiplicity of convergingly directed horn and speaker (or transducer) units, but the term multiplicity is to be understood with the foregoing remarks in mind.
In the-case of a system that is omnidirectional in three dimensions the provision of a spherical phasing plug is appropriate instead of one of the various elongated shapes shown in the drawings. In such a system horns flared in two dimensions could have appropriately been used and if round horns rather than square ones are used, spindle shaped bodies rather than vanes might appropriately be used to modify the channels between the horns. Other variations of the invention to suit particular conditions or purposes will be apparent from s study of the foregoing description.
What is claimed is:
l. A loudspeaker system for evenly distributing sound over a wide angle, outdoors or in a large hall, and with a frequency transmission band including sound of wave lengths greater than the overall apparatus dimensions, comprising:
a multiplicity of speaker transducer units each equipped with a horn flared in at least one dimension and connected to respond to a common electrical exciting signal and arranged to direct their principal sound output towards a common point around which they are disposed in a substantially horizontal arc, of at least sufficiently surrounding said point to produce a pulsating sound core in the space between themouths of said horns and said point; and
channel means between and around said speaker transducer units and their horns, constituted by means providing spaces therebetween and therearound, for evenly spreading out sound waves over a wide angle in a large volume of space to the rear of said speaker transducer units.
2. A loudspeaker system as defined in claim I in which each of said horns has a median which is a straight line directed towards said common point, and
in which saidchannel means includes passages between adjacent horns.
3. A loudspeaker system as defined in claim I in which said horns are flared predominantly in the vertical direction.
4. A loudspeaker system as defined in claim 1 in which the throats of the respective horns of said speaker units are spaced at regular intervals around a circle of which said common point is the center.
5. A loudspeaker system as defined in claim 3 in which the throats of the respective horns of said speaker units are spaced at regular intervals around a circle of which said common point is the center.
6. A loudspeaker system as defined in claim 1 in which a plug body is disposed around said common point, said plug body having a surface in the shape of a surface of revolution, said surface being located between said common point and the mouths of said horns, said surface of revolution having an axis passing through said common point.
7. A loudspeaker system as defined in claim 3 in which a vertically elongated plug body is disposed around said common point, having a surface in the shape of a surface of revolution located between said common point and the mouths of said horns, said surface of revolution having a vertical axis passing through said common point.
8. A loudspeaker system as defined in claim 3 in which bodies of contoured cross-section are provided between said horns to modify the configuration of said channel means. 9. Aloudspeaker system as defined in claim 6 in which bodies of contoured cross-section are provided between said horns to modify the configuration of said channel means.
10. A loudspeaker system as defined in claim 7 in which vertical radially disposed vanes of contoured cross-section are provided between said horns to modify the configuration of said channel means.
11. A loudspeaker system as defined in claim 6 in which upper and lower guiding surfaces are provided adjoining the ends of said plug body, and extending radially outward from the axis of the surface of revolution of said plug body, and having at least their outer portions divergingly dished.
12. A loudspeaker system as defined in claim in which the-aggregate mouth area of said horns is less than 2% of the square of the maximum wave length of the sound waves the system is adapted to excite.
13. A loudspeaker system as defined in claim 5 in which the aggregate mouth area of said horns is less than 2% of the square of the maximum wave lengths of the sound waves the system is adapted to excite.
14. A loudspeaker system for evenly distributing sound over a wide angle, outdoors or in a large hall, and with a frequency transmission band including sound of wave lengths greater than the overall apparatus dimensions, comprising:
a plurality of arrays of speaker transducer units each equipped with a horn flared in at least one dimension and connected to respond to a common electric exciting signal. each array consisting of a multiplicity of said speaker units having the throats of their respective horns distributed on a substantially horizontal arc of at least l50 about a convergence point external to the horns. so that the principal sound output of the units of the array is directed towards said convergencepoint, the said arrays being vertically stacked so that their respective convergence points lie on a substantially vertical line thus defined as the axis of the system; and
channel means between and around said speaker transducer units and their horns, constituted by means providing spaces therebetween and therearound, for evenly spreading out sound waves over a wide angle in a large volume of space to the rear of said speaker transducer units.
15. A loudspeaker system as defined in claim 14 in which each of said horns has a median which is a straight line directed to the convergence point of the array of which said speaker transducer unit is a member.
16. A loudspeaker system as defined in claim 14 in which said horns are flared predominantly in the vertical direction.
17. A loudspeaker system as defined in claim 16 in which a plug body is provided centered on the axis passing through said convergence points, and having an outer surface in the shape of a surface of revolution about said axis, located between said axis and the mouths of the horns of said speaker units.
18. A loudspeaker system as defined in claim 17 in which vertical radially disposed vanes of contoured cross-section are provided between laterally adjacent horns to modify the configuration of said channel means.
19. A loudspeaker system as defined in claim 17 in which upper and lower guiding surfaces are provided adjoining the ends of said plug body and extending radially outward from the axis of said plug body, at least the outer portions of said guiding surfaces being divergingly dished.
20. A horizontally omnidirectional loudspeaker system with a frequency transmission band including sound of wave lengths greater than the overall apparatus dimensions, comprising:
a plurality of arrays of speaker transducer units each equipped with a horn flared in at least one dimension and all connected to respond to a common electrical exciting signal each of said arrays being a horizontal array in which the horns of the speaker units of the array are directed towards a central point and are distributed substantially evenly around said central point, the arrays being stacked vertically and their central points lying in a vertical line thus defined as the axis of the system; and
channel means between and around said speaker transducer units and their horns, constituted by means providing spaces therebetween and therearound, for evenly spreading out sound waves in a large volume of space to the rear of said speaker transducer units.
21. A loudspeaker system as defined in claim 20 in which each of the horns of said speaker transducer units has a median which is a straight line directed towards the central point of the array of which the unit is a member, all the said medians of one array lying in the same plane.
22. A loudspeaker system as defined in claim 20 in which said horns are flared predominantly in the vertical direction.
23. A loudspeaker system as defined in claim 22 in which a plug body coaxial with the axis of the system, and having an outer surface in the form of a surface of said channel means.
25. A loudspeaker system as defined in claim 24 in which upper and lower guiding surfaces are provided adjoining the ends of said plug body and extending radially outward from said axis, at least the outer portions of said guiding surfaces being divergingly dished.