US3627948A

US3627948A - Stereo loudspeaker system

Info

Publication number: US3627948A
Application number: US850949A
Authority: US
Inventors: Frederick W Nichols
Original assignee: Electro Voice Inc
Current assignee: MARINE MIDLAND BANK NA A NATIONAL BANKING ASSOCIATION AS AGENT
Priority date: 1969-08-18
Filing date: 1969-08-18
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

A stereo loudspeaker system with right-hand and left-hand loudspeaker sections each having forwardly and rearwardly directed loudspeaker means fed with middle and high-frequency signals of the associated stereo channel, the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to a horizontal plane and a vertical plane extending transversely to the vertical sound reflecting wall in a room in front of which the loudspeaker system is placed. Means are provided for selectively orienting the asymmetric pattern of the rearwardly directed loudspeaker means so the pattern is directed principally laterally inwardly or principally outwardly of said vertical plane.

Description

Unite States Patent Frederick W. Nichols [72] lnventor South Bend, 1nd. [21] AppLNo. 850,949

[22] Filed [45 1 Patented [73 Assignee Aug. 18, 1969 Dec.'l4, 1971 Electra-Voice, Inc. Buchanan, Mich.

54 1 STEREO LOUDSPEAKER SYSTEM 24 Claims, 30 Drawing Figs.

s21 u.s.c1 179/1011, l79/lE,l8l/31B s11 1m.c1 ..G10kl1/00 501 Field at Search 179 1 E, 1

G, 1 GA, 1 AT; 181/31 B [56] References Cited UNITED STATES PATENTS 10/1934 Goshaw 2,710,662 6/1955 Camras.... 2,921,135 1/1960 Hoodwin Primary Examiner -Kathleen l-l. Claffy Assistant Examiner-Douglas W. Olms AttorneyWallenstein, Spangenberg, Hattis & Strampel ABSTRACT: A stereo loudspeaker system with right-hand and left-hand loudspeaker sections each having forwardly and rearwardly directed loudspeaker means fed with middle and high-frequency signals of the associated stereo channel, the I rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to a horizontal plane and a vertical plane extending transversely to the vertical sound reflecting wall in a room in front of which the loudspeaker system is placed. Means are provided for selectively orienting the asymmetric pattern of the rearwardly directed loudspeaker means so the pattern is directed principally laterally inwardly or principally outwardly of said vertical plane.

PATENTEDUEBMISYI 352194 sum 2 [IF 5 JIIIIIIIIIIIII :mIIII'IIIIIIIm PATENTEDBECMISII 3527,945

saw 3 nr 5 PATENIEU DEC I 4 I971 ALL FREQ 6455 dlvLy liuenz fi' ALL ,ji edem/ MJVM wZJ STEREO LOUDSPEAKER SYSTEM This invention relates to stereo loudspeaker systems and particularly to such systems which have their primary utility for home entertainment applications.

lt has been, heretofore, recognized that dispersion and/or reflection of at least a portion of the directive middle and high frequencies of a stereo system, can under certain conditions, provide an enhanced, more desirable effect in comparison to a stereo system which directs sound only forwardly into the room. Accordingly, some stereo loudspeaker systems have, heretofore, directed middle and high-frequency signals against the vertical wall in front of which the loudspeaker system is positioned. Most of these systems provide an overall rearwardly directed sound pattern which is symmetrical with respect to a vertical plane extending transversely of the sound reflecting wall so that sound is directed rearwardly in all directions. Since such a sound pattern distributes sound in such a way that the sound from each stereo channel reaches the observer from all directions, the stereo effect is diminished.

In some stereo loudspeaker systems the directive middle and high frequencies are directed rearwardly and laterally outwardly in a pattern symmetrical with respect to a horizontal plane. However, when sound is directed rearwardly against a vertical sound reflecting wall only symmetrically with respect to a horizontal plane, the spacing of the speaker units from the wall' generally must be substantial to avoid sound interference problems and the propagation of sound laterally outwardly near the sidewalls of a room can frequently cause undesirable resonance effects, depending upon the geometry of the room and the relationship of the loudspeaker system thereto.

Thus, a given loudspeaker system may produce highly effective results under one set of room geometry and loudspeaker placement conditions and be completely unsatisfactory with another room geometry or loudspeaker placement condition. Also, a given desired furniture arrangement may limit the physical separation of stereo loudspeaker units to a point where such spacing is too far apart or too close for the proper stereo effect. In this connection also, it has been discovered that orchestral recordings sound more like live performances when a wide lateral outward angle of dispersion of the sound is effected and small ensemble recordings sound more like a live performance when a narrow angle of dispersion of the sound is effected.

Accordingly, uncontrolled dispersion and/or reflection of sound within the listening environment often creates unsatisfactory sound reproduction for a given recording due to effects from geometry and constraints on the placement of the loudspeakers due to furniture arrangement problems in the room involved.

Accordingly, the objects of the invention involve the provision of a stereo loudspeaker system which overcomes one or more of the various problems referred to above. More specifically, an object of the invention is to provide an improved stereo loudspeaker system which can easily and readily be adapted to a wide variety of room geometry, music recording type, loudspeaker placement limitations and other variable conditions. A related object of the invention is to provide a loudspeaker system which can provide a desired stereo effect whether near normally obstructing pieces of furniture or where the loudspeaker units involved must be spaced abnormally close together or far apart or close to the sidewalls of a room.

Another object of the invention is to provide a stereo loudspeaker system as described which can be manufactured at a relatively low cost. A related object of the invention is to provide a stereo loudspeaker system as described which includes relatively small and lightweight speaker units which can be placed on tables and bookshelves as well as on the floor.

Still another object of the invention is to provide a stereo loudspeaker system as described utilizing cone loudspeaker units and where a maximum total loudspeaker cone area operative at low frequencies is achieved while accomplishing the other objectives of the invention described.

In accordance with one of the aspects of the invention, each of the mirror-image loudspeaker sections of a stereo loudspeaker system includes loudspeaker means for radiating directive middleand high-frequency sounds preferably symmetrically forwardly into the listening area, and loudspeaker means for directing these frequencies rearwardly against a vertical sound reflecting wall of a room in a rearwardly directed sound pattern which extends principally laterally outwardly or principally laterally inwardly of a vertical plane passing through the sound pattern extending transversely to the sound reflecting wall. Where, in a given room-arrangement, it is most effective to place the directive stereo loudspeaker sections involved abnormally close together, the rearwardly directed overall asymmetric sound pattern described is oriented principally laterally outwardly, and, where it is most effective to place the stereo loudspeaker sections abnormally far apart or near the sidewalls of a room, the rearwardly directed overall asymmetric sound pattern is oriented principally laterally inward. I

A further advantageous feature of the invention is in arranging the rearwardly directed loudspeaker sections so that the overall directive sound patterns thereof are asymmetric both with respect to the said transverse vertical plane and a horizontal plane passing through each overall directive sound pattern so that, for example, when the speaker sections are supported on the floor, a table or a low portion of a bookshelf, the asymmetric sound pattern inclines upwardly as well as laterally outwardly or inwardly as the case may be. In such case, the loudspeaker sections may be placed much closer to the sound reflecting wall in comparison, for example, to an orientation where the rearwardly radiated sound is directed in a horizontal direction or plane.

In accordance with the most advantageous form of the invention, where it is desirable to minimize the cost and the size of the stereo loudspeaker system, all of the forwardly and rearwardly directed middleand high-frequency loudspeaker means of each stereo loudspeaker section are contained within a relatively small common enclosure which is portable and lightweight, so that it can be readily supported on a table or bookshelf and be moved about with ease. in its most preferred form, the common enclosure for each loudspeaker section has a truncated cubic shape with a front baffle-forming wall with an opening therein behind which a cone loudspeaker is mounted for directing sound forwardly into the listening area, and a pair of rearwardly facing, truncating, baffle-forming walls at the rear thereof in at least two planes which make an obtuse angle with respect to one another. The truncating bafile-forming walls have openings behind which cone loudspeakers are mounted for directing sound along axes which make an acute angle with respect to one another.

The loudspeaker units now being described for the two stereo channels are mirror images of one another relative to a centered vertical plane extending transverse to the sound reflecting wall of the room involved midway between the loudspeaker sections. The cone loudspeakers mounted behind the truncating baffle-forming walls form overlapping directive sound patterns which, in one orientation of the enclosure, are principally horizontally spaced to provide an overall fanshaped sound pattern facing generally horizontally and, in another orientation of the enclosure, are principally vertically spaced to form an overall fan-shaped pattern facing generally vertically. These overall fan-shaped sound patterns are rearwardly and laterally inwardly or rearwardly and laterally outwardly directed depending upon whether each enclosure is used as a right-hand or a left-hand enclosure for the stereo sound system involved. There are thus provided four different possible sound pattern configurations to adapt the loudspeaker system to a variety of different environmental conditions.

In a more sophisticated form of the invention which provides a better low'frequency response and a selection of different directive sound patterns electrically without moving the loudspeaker enclosures around, each of the loudspeaker enclosures preferably has one or more loudspeakers mounted on a front vertical baffle-forming wall for directing sound forwardly directly into the listening area, a first pair of mirrorimage related, rearwardly and upwardly facing baffle-forming walls facing in opposite lateral directions at the right-hand and left-hand ends of the loudspeaker enclosures and a central rearwardly and upwardly facing baffle-forming wall interconnecting the above-mentioned mirror-image related baffleforming walls. Most advantageously, the first pair of mirrorimage related baffle-forming walls are intersected at the bottom thereof by a second pair of'mirror-image related, rearwardly facing walls formed in general vertical planes facing in opposite lateral directions. Cone loudspeakers are mounted on all the aforementioned rearwardly facing baffle-forming walls to direct sound through openings therein. The low frequencies of the stereo channel involved are fed at all times to all of the loudspeakers in each enclosure so maximum lowfrequency response, which is partly a function of the total cone area of the various loudspeakers, is achieved. The selection in the directivity pattern is achieved by the use of lowpass filters which are connected selectively to various ones of the rearwardly directed cone loudspeakers. The loudspeakers which have no low-pass filters connected thereto will generate directive middleand high-frequency sound patterns along their axes.

The above-mentioned and other features and advantages of the invention will become apparent upon making reference to the specification to follow, theclaims and the drawings wherein:

FIG. 1 is a view of the end of a room with a pair of stereo loudspeaker units constituting the most preferred form of the invention positioned relatively close together;

FIG. 2A and 2B are respectively rear perspective views of the two loudspeaker units shown in FIG. 1;

FIG. 3 is a transverse sectional view through the loudspeaker unit shown in FIG. 2B, taken along section line 3-3 thereof;

FIG. 4 is a side elevational view of the stereo loudspeaker system shown in FIG. 1;

FIG. 5 is a view of a different room arrangement than that shown in FIG. 1 where the loudspeaker units are relatively widely spaced apart near the sidewalls of the room;

FIG. 6A and 6B are respectively rear perspective views of the loudspeaker units shown in FIG. 5;

FIG. 7A is a plan view of the loudspeaker units shown in FIG. 1 with the individual sound directivity patterns of each cone loudspeaker therein diagrammatically indicated, the loudspeaker units being oriented in such a way that the rearwardly directed cone loudspeakers are spaced apart principally in a horizontal direction to provide an overall horizontally broadened directive sound pattern directed principally laterally, outwardly and upwardly of the speaker units;

FIG. 7B is a side elevational view of the left-hand loudspeaker unit of FIG. 7A with the individual directive sound patterns of the cone loudspeakers diagrammatically indicated;

FIG. 8A is a plan view of the loudspeaker units of FIG. 1 reoriented so that the left-hand and right-hand loudspeaker units of FIG. 7A are the right-hand and left-hand loudspeaker units in FIG. 8A and diagrammatically showing the individual directive sound pattern of each cone loudspeaker thereof, the rearwardly directed ones jointly providing an overall horizontally broadened sound pattern for each loudspeaker unit directed principally laterally inwardly and upwardly of the loudspeaker unit;

FIG. 8B is a side elevational view of the left-hand loudspeaker unit of FIG. 8A with the individual directive sound patterns of the cone loudspeakers diagrammatically indicated;

FIG. 9A shows the loudspeaker units of FIG. 7A reoriented by tilting the right-hand and left-hand loudspeaker units 90 laterally inwardly so that the rearwardly directed cone loudspeakers and the individual sound directivity patterns thereof diagrammatically indicated are principally vertically spaced to provide an overall vertically broadened sound pattern for each loudspeaker unit directed principally laterally inwardly and upwardly of the loudspeaker unit;

FIG. 9B is a side elevational view of the left-hand loudspeaker unit of FIG. 9A with the individual directive sound patterns of the cone loudspeakers diagrammatically indicated;

FIG. 10A is a plan view of the loudspeaker units shown in FIG. 9A reoriented so that the left-hand and right-hand loudspeaker units of FIG. 9A are the right-hand and left-hand loudspeaker units in FIG. 10A and diagrammatically showing the individual directive sound pattern of each cone loudspeaker thereof, the rearwardly directive ones jointly providing an overall vertically broadened sound pattern for each loudspeaker unit directed principally laterally outwardly and upwardly of the loudspeaker unit;

FIG. 10B is a side elevational view of the left-hand loudspeaker unit of FIG. 10A with the individual directive sound patterns of the cone loudspeakers diagrammatically indicated;

FIG. 11 is a sectional of a room with a furniture and loudspeaker taken arrangement utilizing a more sophisticated and expensive form of the present invention;

FIG. 12 is a rear perspective view of one of the identical loudspeaker units shown in FIG. 11;

FIG. 13 is a sectional view of the loudspeaker unit of FIG. 12 taken along section line 13-43 thereof;

FIG. 14A is a front elevational view of the loudspeaker units shown in FIG. 11 and diagrammatically showing the individual directive sound patterns of the cone loudspeakers thereof when the rearwardly facing middle and outermost cone loudspeakers are energized with the middle and high frequencies;

FIG. 14B is a side elevational view of the left-hand loudspeaker unit of FIG. 13A with the individual directive sound patterns of the cone loudspeakers diagrammatically indicated;

FIG. 15A is a front elevational view of the loudspeaker units shown in FIG. 11 and diagrammatically showing the individual directive sound patterns of the cone loudspeakers thereof when the rearwardly facing middle and innermost cone loudspeakers are energized with middle and high frequencies;

FIG. 15B is a side elevational view of the left-hand loudspeaker unit of FIG. 13A with the individual directive sound patterns of the cone loudspeakers diagrammatically indicated;

FIG. 16A, 16B, 16C, 16D and 16E respectively show five different energizing circuit arrangements for the cone loudspeakers used in each of the loudspeaker enclosures shown in FIGS. 14A and 15A to provide a choice of five different rearwardly directed sound patterns thereof;

FIG. 17 illustrates a switching system and a pair of capacitors constituting low-pass filters which provide the five different energizing circuit arrangements shown in FIGS. I6A-l6E;

FIG. 18 is a chart illustrating the various frequencies generated by the cone loudspeakers shown in FIGS. l6A-l6E.

Referring now to FIG. 1, a room furniture arrangement as illustrated wherein it is convenient to locate a pair of

stereo loudspeaker units

2A and 2B constituting a preferred form of the invention on tables 4 and 6 located on opposite sides of an armchair 8. Normally, such close spacing of stereo loudspeaker units is highly unsatisfactory because of inadequate separation between the stereo channels acoustically radiated by the loudspeaker units. However, because of the features of the present invention, this close spacing does not become a problem.

Although, as above indicated, the present invention may take a variety of forms, as illustrated in FIG. I the stereo loudspeaker system there shown comprises a pair of loudspeaker sections for the two stereo channels involved including relatively closely spaced, small, lightweight, mirror-

image loudspeaker units

2A and 2B having

loudspeaker enclosures

10a and 10b. The

loudspeaker enclosures

10a and 10b include forwardly and rearwardly directed cone loudspeakers to be described and, in the closely spaced arrangement shown in FIG. 1, the

enclosures

10a and 10b are oriented so that the rearwardly directed cone loudspeakers therein radiate directive middleand high-frequency sounds principally laterally outwardly and also most advantageously upwardly against a vertical sound reflecting wall 11 in front of which the furniture and loudspeaker units illustrated are placed, so that a listener sitting across the room will receive directly and by reflection off of the sound reflecting wall 11 directively radiated middleand high-frequency stereo sound over wide angles with good stereo separation.

FIGS. 2A and 2B show a rear perspective view of the

loudspeaker units

2A and 2B. The details of the right-hand loudspeaker unit 28 'will now be described, it being understood that the other loudspeaker unit 2A is the mirror image of the same, and so corresponding portions of the

loudspeaker unit

2A and 2B will be given similar reference numbers except that a prime has been used with reference numbers for loudspeaker unit 2A. As best shown in FIGS. 23 and 3, the loudspeaker enclosure b is a cube-shaped enclosure having a square vertical front baffle-forming wall 12 and a square bottom wall 14. The front baffle-forming wall 12 has an opening 16 therein behind which is mounted a cone loudspeaker 18 which directs sound forwardly through the opening 16. An attractive sound transparent cloth 20 covers the front surface of the baffle-forming wall 12.

The loudspeaker enclosure 10b has truncated

vertical sidewalls

22 and 24 and a truncated vertical rear wall 26 which define, with a truncated horizontal top wall 32, the margins of cube truncating horizontally spaced baffle-forming

walls

28 and 30 which respectively intersect one another and form an obtuse angle preferably of about 145 therebetween. The loudspeaker enclosure 10b thus resembles an unsymmetrically truncated cube.

The baffle-forming

walls

28 and 30 incline in an upward direction in the orientation shown in the drawing, the baffleforming wall 28 extending in a plane transverse to the

vertical sidewalls

22 and 24 and extending at about a 45 angle to two reference transverse vertical planes PLl and Pl .2 respectively extending transversely and parallel to the front vertical wall 12 of the speaker enclosure 10a. The other baffle-forming wall 30 extends at an angle of about 35 with respect to the baffleforming wall 28. i

The baffle-forming wall 28 has an opening 33 therein behind which is supported a'cone loudspeaker 35 which directs sound through the opening 33. The other baffle-forming wall 30 has an opening 39 therein behind which is supported a cone loudspeaker 37 which directs sound through the opening 39. A suitable covering of sound transparent cloth 20 is placed over the baffle-forming

walls

28 and 30 to improve the appearance of the enclosure.

The

cone loudspeakers

35 and 37 radiate at the middle and high frequencies (that is frequencies of approximately 300 Hertz and higher) directive sound patterns resembling the diagrammatic representations of the sound patterns P2 and P3 shown in FIGS. 7A and 7B representing the relative sound intensities at various angles extending from a point at the base of each sound pattern, as is well known in the art. (Actually, the sound patterns illustrated represent an average directivity pattern of these frequencies since the directivity pattern of the middle frequencies is generally much wider than that illustrated and that of most of the high frequencies is narrower than that illustrated.) The axes of these directive sound patterns incline rearwardly between about 35-45 asymmetrically to a horizontal line parallel to the front enclosure wall I2 and to a vertical line. The sound patterns from the

cone loudspeakers

35 and 37 overlap to provide an overall horizontally broadened (i.e., a vertically facing fan-shaped) sound pattern directed upwardly and principally laterally outwardly of the loudspeaker enclosure 10b.

As previously indicated, the low-frequency response of a loudspeaker system is a function of a number of variables including the total cone loudspeaker area efiective in generating low frequencies and the amount of enclosure volume per loudspeaker. The

loudspeaker enclosures

10a and 10b are sealed enclosures and the cone loudspeakers l8, 18', 35, 35', 37 and 37' may be, for example, 4" cone loudspeakers which are fed with all of the frequencies of the associated stereo channel. However, with three such small-sized enclosures per stereo loudspeaker section, it is not feasible to obtain a very good low-frequency response down, for example, to 30 to 40 Hertz. However, a good low-frequency response in the 30- to 40- Hertz range can be electrically achieved by using a suitable circuit in the amplifier system involved, as is well known in the art.

One of the main advantages of the

stereo loudspeaker units

2A and 2B just described is that they provide, in addition to the desirable overall rearwardly, horizontally broadened, principally upwardly and laterally outwardly directed sound pattern referred to, three other rearwardly directed sound pattern configurations to adapt the loudspeaker system illustrated to a variety of different room geometries and loudspeaker unit placement limitations. Referring, for example, to FIG. 5, there is shown a furniture and loudspeaker unit arrangement wherein the

loudspeaker unit

2A and 2B are mounted on tables 4 and 6 positioned at the opposite ends of a long sofa 40 adjacent to the sidewall 42-42 ofthe room involved. For this arrangement,

loudspeaker unit

2A and 2B are rotated inwardly from the position shown in FIG. 1 as indicated by the change in direction of arrows 43a and 43b positioned adjacent to the

reference characters

2A and 2B in FIGS. 1 and 5. In such case, it will be apparent that the axes of the rearwardly facing

cone loudspeakers

35 and 37 and the directive sound patterns P2 and P3 are vertically spaced and are directed rearwardly and laterally inwardly of the enclosure 10b (FIGS. 9A and 9B) to provide an overall vertically broadened sound pattern inclining principally laterally inwardly of the enclosure 10a.

An overall principally laterally inwardly and upwardly directed horizontally broadened sound pattern can be achieved by interchanging the positions of the

loudspeaker units

2A and 28 shown in FIG. 7A, so that the left-hand and right-hand loudspeaker units therein become the right-hand and left-hand loudspeaker units as illustrated in FIGS. 8A and 8B. (A generally horizontal broadened sound pattern configuration shown in FIGS. 7A or 8A is especially useful, for example, where cone loudspeakers are directed against horizontally broken up reflecting wall surfaces, as in the case of shelving and the like supported upon the sound reflected wall 11.)

An overall principally laterally outwardly and upwardly directed vertically broadened (i.e. a horizontally facing fanshaped) sound pattern can be achieved by interchanging the left-hand and right-

hand loudspeaker units

2A and 2B in FIG. 9A to provide the loudspeaker unit arrangement illustrated in FIG. 10A and 10B. 7

Although in the embodiment of the invention just described all of the cone loudspeakers radiate both low, middle and high frequencies, the

loudspeaker units

2A and 2B are adaptable to loudspeaker systems wherein the low nondirective frequencies are generated by special low-frequency loudspeakers or woofers which may be positioned below, above or to one side of the

loudspeaker units

2A and 2B.

To obtain an even better low-frequency response and to provide adjustability of the directive sound patterns of the loudspeaker units electrically, a more sophisticated and expensive loudspeaker system of the present invention may be provided as illustrated in FIGS. ll through 15. As in the case of the

loudspeaker units

2A and 2B, the stereo loudspeaker units now to be described and identified by

reference characters

2C and 2D are most advantageously made sufficiently compact that they may be readily placed upon end tables, bookshelves or the like or even in the open rear portion of a large console cabinet. Physically, the

loudspeaker units

2C and 2D are identical (identical elements, however, can also be considered mirror images of one another). However, as will appear electrically and acoustically they are not identical since the sound patterns generated by the

loudspeaker units

2C and 2D will generally provide overall mirror'image, asymmetric, rearwardly directed sound patterns at the middle and high frequencies extending principally upwardly and laterally outwardly or upwardly and laterally inwardly of the loudspeaker system. Also, the

loudspeaker units

2C and 2D directively radiate middle and high frequencies forwardly of the

loudspeaker units

2C and 2D. The selection of different rearwardly directed sound patterns is accomplished by the use of switches and filters contained in a separate switch housing 41 (FIG. 11) which may rest on one of the end tables 4 or some other suitable support surface. The housing will contain a multiposition switch with a control knob 41a or the like for selecting one of a number of sound patterns.

Refer now to FIGS. 12 and 13 which best illustrate the construction of the left-hand loudspeaker unit 2C, it being understood that

loudspeaker units

2C and 2D are physically identical and so corresponding parts thereof will be identically numbered. (The corresponding parts will be related and numbered in a mirror-image sense so that the confronting or facing parts thereof will be considered corresponding parts, etc.) Consequently, loudspeaker unit 2D will not be separately described. As shown in FIGS. 12 and 13, loudspeaker unit 2C includes an enclosure 43 having a front baffle-forming wall 45 with one or more cone loudspeaker-receiving openings 47 (only one being shown). Cone loudspeaker 49 is mounted behind the opening 47. The bafile-forming wall 45 joins at the right-hand and left-hand margins thereof vertical sidewalls 51-51" and at the top and bottom margins thereof a horizontal top wall 53 and a horizontal bottom wall 55. (Primed numbers are used for parts of the loudspeaker unit which are positioned on the laterally outwardly facing sides thereof.)

A centered rearwardly and upwardly facing rectangular baffie-forming wall 57 making an angle of about 45 to a horizontal plane intersects the rear margin of the top wall 53 along a portion of the length thereof, the baffle-forming wall 57 being connected to the bottom wall 55 of the enclosure 43 by a rectangular vertical rear wall 61. The side margins of the upwardly and rearwardly facing baffle-forming wall 57 are connected to the vertical side walls 51-51 respectively by upwardly facing mirror-image related baffle-forming walls 63-63. As illustrated, the baffle-forming walls 63-63 extend at about a 35 angle with respect to the adjacent baffle-forming walls. It should be apparent that the angular relationship between each of the baffle-forming walls 63 and 63' and the center baffle-fonning wall 57 is similar to the angular relationship between the baffle-forming

walls

30 and 28 in the embodiment of the invention shown in FIGS. 1 through 10. The mirror-image related baffle-forming walls 63-63 are connected to the bottom wall 55 through vertical lower mirrorimage related baffle-forming walls 65-65.

Centered within the central rearwardly and upwardly facing baffle-forming wall 57 is a cone loudspeaker-receiving opening 67 behind which is mounted a cone loudspeaker 69. The first mentioned mirror-image related baffle-forming walls 63-63 are provided with cone loudspeaker-receiving openings 71-71 behind which are mounted cone loudspeakers 73-73. The lower mirror-image related baffle-fonning walls 65-65 are provided with cone loudspeaker-receiving openings 75-75 behind which are mounted cone loudspeakers 77-77.

The various cone loudspeakers 49, 73-73 and 77-77' may be identical cone loudspeakers, such as 4" cone loudspeakers mounted within a common sealed enclosure space 79. The various bafile-forming

walls

45, 57, 63-63 and 65-65 may be covered by suitable sound transparent cloth as indicated by reference numeral 8].

Particularly in the embodiment of the invention now being described, it is highly desirable that all of the loudspeakers receive the nondirective low frequencies of the associated stereo channel so that advantage can be taken of the increased low-frequency response when the total cone area of the low frequency radiating loudspeakers is a maximum.

Two possible directive middleand high-frequency sound patterns generated by the various loudspeakers 49, 73-73 and 77-77 are illustrated in FIGS. 14A, 1413, A and 158. As indicated by these figures, directive middle and high frequencies are fed, in addition to the forwardly directed loudspeaker 49 and centered rearwardly directed loudspeaker 69, selectively to either the

outer loudspeakers

73 and 77 or the

inner loudspeakers

73 and 77 so that, in addition to a for-- wardly radiated directive sound pattern at these frequencies, there is provided either an overall principally rearwardly, upwardly and outwardly, or rearwardly, upwardly and inwardly directed sound pattern which, unlike the embodiment of FIGS. l-l0 has both horizontally and vertically spaced components. These overall rearwardly directed sound patterns are, as in the case of the other embodiment of the invention described, a result of the overlapping and reinforcement of individual directive sound patterns P2, P3, and P4 of the

cone loudspeakers

73, 69 and 77 in the case of FIG. 14A, and individual directive sound patterns P2, P3 and P4 of

cone loudspeakers

73, 69 and 77 in the case of FIG. 15A. The individual directive sound patterns P2 and P3 in FIG. 14A and P2 and P3 in FIG. 15A are horizontally spaced to provide a horizontally broadened sound pattern component and the directive sound patterns P2 and P4 in FIG. 14A and P2 and P4 in FIG. 15A provide a vertically broadened sound pattern component.

In addition to the sound patterns shown in FIG. 14A and 15A, several other sound patterns can be obtained by applying directive middle and high frequencies selectively to other combinations of the rearwardly directed loudspeakers. One way in which a total of five different sound pattern configurations, including those shown in FIG. 14A and 15A, can be simply and inexpensively achieved is illustrated in FIGS. l6A-16E, FIG. 17 and FIG. 18 to which reference should now be made.

The voice coils of the various cone loudspeakers described of each loudspeaker unit may be connected across a pair of stereo input terminals 80-82 containing the low, middle and high frequencies of the associated stereo channel in a variety of ways. To simplify the switching circuitry, the voice coils of the six cone loudspeakers described may be connected in series connected pairs across the stereo

channel input terminals

80 and 82 as illustrated in FIGS. l6A-I6E. Accordingly, the

voice coils

49a and 69a of the centered forwardly and rearwardly facing cone loudspeakers149 and 69 are connected in series across the

input terminals

80 and 82, the

voice coils

73a and 73a of the mirror-image related loudspeakers 73' and 73 are connected in series across the

input terminals

80 and 82, and the

voice coils

77a and 77a of the mirror-image related loudspeakers 77' and 77 are connected in series across the

input terminals

80 and 82.

A suitable low-pass filter, which may be

capacitors

84 and 84, are connected across various ones of the voice coils of the mirror-image related loudspeakers as indicated in FIG. 16A, 16B, 16C and 16D by means of the switching network shown in FIG. 17. (FIG. 17 shows the switching network for one of the loudspeaker units 2C, it being understood that an identical switching network is used and ganged therewith for the other loudspeaker unit 2D.) The switching network shown in FIG. 17 includes two ganged switch sections 85 and 85' including movable wipers 85a and 850' which respectively make selective contact with stationary contacts 85-1 through 85-5 and 85-1 through 85-5', respectively. The movable wiper 85a is connected through the low-pass filter capacitor 84 to the juncture 89 between the

voice coils

73a and 73a. The movable wiper 85a is connected through the low-pass filter capacitor 84' to the juncture 89' of the

voice coils

77a and 77a. The stereo channel input terminal 80 is shown connected to the stationary contacts 854 of the switch section 85 and the stationary contact 85-3 and 85-4' of the switch section 85. The stereo channel input terminal 82 is shown connected to the stationary contact 85-1 of the switch Section 85 and stationary contacts 85-1 and 85-2' of the switch section 85. When the

wipers

85a and 85a are sequentially connected to the various similarly numbered associated stationary contacts, the four difierent capacitor circuit connections shown in FIG. 16A, 16B, 16C and 16D are achieved. In FIGS. 16A, the low-pass filter capacitors 84 and 84' are respectively connected in parallel with the

voice coils

73a and 77a so that the

cone loudspeakers

73 and 77 do not receive any significant amount of middle and high frequencies, thereby producing individual overlapping directive sound patterns from the forwardly directed loudspeaker 49, the center rearwardly directed speaker 69 and the laterally outwardly facing loudspeakers 73' and 77'.

FlG. 16D shows the low-pass filter capacitors 84 and 84' coupled across only the

voice coils

73a and 77a of the

loudspeakers

73 and 77 to produce individual overlapping sound patterns which are the mirror-image of that just described in connection with FIG. 16A.

In FIG. 16B only voice coil 77a of loudspeaker 77 has a lowpass fllter capacitor 84' connected thereacross so that the overall sound pattern achieved by the individual overlapping sound patterns has both laterally inwardly and laterally outwardly components (but of different configuration) which, although normally not preferred, can be desirable under certain circumstances. Similarly in FIG. 16C, only the voice coil 77a has a low-pass filter capacitor 84 connected thereacross to provide a sound pattern which is the mirror-image of that just described in connection with FIG. 168.

FIG. 16E shows a circuit arrangement where none of the voice coils are bypassed by low-pass filter capacitors. in such case there are directive components generated by all of the loudspeakers which may be desirable for monaural recordings.

it should be apparent that other switching arrangements may be made to provide for other selective connections of low-pass filter capacitors to the loudspeakers. For example, a different switching network could provide for connection of the low-pass filters across

voice coils

73a, 69a and 77a to duplicate the sound pattern provided by the loudspeaker unit arrangement of FIG. A where a vertically broadened (i.e., horizontally facing fan-shaped) sound pattern extends laterally outwardly, Similarly, another switching arrangement could produce the mirror image of the sound pattern just described to duplicate the sound pattern provided by the loudspeaker arrangement of FIG. 9A.

It is apparent that the present invention provides an extremely adaptable stereo loudspeaker system which, unlike the loudspeaker systems of the prior art, can be adapted to a maximum number of roomgeometry and loudspeaker unit placement conditions.

It should be understood that various modifications may be made in the most preferred form of the invention just described without deviating from the broader aspects of the invention.

lclaim: I

l. in a room havingan upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having housing means resting on a horizontal support surface in a predetermined position and containing right-hand and left'hand loudspeaker sections including rearwardly directed loudspeaker means respectively connected to said first and second sources of electrical signals, the rearwardly directed loudspeaker means of each section producing an overall directive sound pattern of the associated middleand high-frequency signals which is the mirror-image of the rearwardly directed loudspeaker means of the other section with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections and which overall directive sound. pattern is asymmetrically directed toward said upstanding sound reflecting wall so the overall directive sound pattern is directed mainly in a direction making a substantial angle with both the associated horizontal and vertical planes extending at right angles to said sound reflecting wall and passing through the rearwardly directed loudspeaker means producing the overall directive sound pattern involved, and said housing means further including for each loudspeaker section a forwardly directed loudspeaker means also connected to the associated source of electrical signals of the associated stereo channel and providing a forwardly directive sound pattern of said middle and high frequencies whose axis is directed forwardly in a direction generally parallel to said centered vertical plane.

2. The stereo loudspeaker system of claim 1 wherein said right-hand and left-hand loudspeaker sections are relatively closely spaced so that they are remote from the sidewalls of said room which extends traversely of said upstanding sound reflecting wall of the room, and said rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections respectively producing respective overall rearwardly directed sound patterns which'are directed principally outwardly of the loudspeaker system.

3. The stereo loudspeaker system' of claim 1 wherein said right-hand and left-hand loudspeaker sections are positioned a substantial distance apart where they are closer to said sidewalls of the room than the center of said wall, and the rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections producing respective overall rearwardly directed sound patterns which are directed principally inwardly of the loudspeaker system.

4. The stereo loudspeaker system of claim 1 wherein the overall rearwardly directed sound pattern produced by the rearwardly directed loudspeaker means of each loudspeaker section is fan-shaped so as to have a cross section much greater in one direction transversely through the sound pattern than in the other direction transversely through the sound pattern.

5. The stereo loudspeaker system of claim 1 wherein there is provided means for selectively positioning the overall directive sound pattern produced by said rearwardly directed loudspeaker means of each loudspeaker section so it is directed selectively principally laterally outwardly or inwardly of the loudspeaker system.

6. In a room having an upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having right-hand and left-hand loudspeaker sections each including a separate loudspeaker enclosure having rearwardly directed loudspeaker means connected to a different one of said sources of electrical signals and providing an overall sound pattern directed rearwardly against said sound reflecting wall, said loudspeaker enclosure of each loudspeaker section being readily supportable on a horizontal support surface in two different orthogonally related positions where said overall sound pattern of said rearwardly directed loudspeaker means is directed respectively principally laterally outwardly and principally laterally inwardly of a vertical plane extending transversely to said sound reflecting wall and passing through the walls of the rearwardly directed loudspeaker means producing the overall sound pattern involved.

7. In a room having an upstanding sound reflecting wall, a

first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having housing means resting on a horizontal support surface in a predetermined position and containing right-hand and left-hand loudspeaker sections each including first and second rearwardly directed loudspeaker means, each of said first and second rearwardly directed loudspeaker means producing an overall directive sound pattern directed asymmetrically rearwardly towards said sound reflecting wall in the opposite lateral direction from the other of same so the overall directive sound patterns produced by each of said first and second rearwardly directed loudspeaker means is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and means for selectively coupling the middle and high frequencies of said signal sources to the first or second rearwardly directed loudspeaker means of each loudspeaker section.

8. In a room having an upstanding sound reflecting wall, a first and second source of electrical signals of two stereo channels encompassing at least the middleand high-frequency range where acoustically directed sound signals. are directive, a stereo loudspeaker system mounted in front of an upstanding sound reflecting wall in spaced relation thereto, said loudspeaker system having a right-hand and a left-hand loudspeaker section with rearwardly directed loudspeaker means respectively connected to said first and second sources of electrical signals, said rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections being positioned near the sidewalls of said room, and the rearwardly directed loudspeaker means of each section providing an overall directive sound pattern which is the mirror image of the loudspeaker means of the other section and is directed 7 only inwardly toward said upstanding wall to reflect off the central portion of said wall into the listening area.

9. In combination, first and second source of electrical signals constituting the two channels of a stereo system and encompassing at least the middle and high frequencies of the signal channels involved, a loudspeaker system spaced adjacent but in spaced relation to an upstanding sound reflecting wall of a room and comprising right-hand and left-hand stereo loudspeaker sections respectively for directively radiating signals of said stereo channels and which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section having a separate housing resting on a horizontal support surface which housing includes both forwardly and rearwardly directed loudspeaker means all connected to the said associated source of electrical signals, the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane extending transversely to said upstanding wall so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, wherein directive signals for each stereophonic channel are directed both forwardly into the room and rearwardly mainly either laterally inwardly or outwardly of said associated vertical plane, where they reflect off of said upstanding wall.

10. The combination of claim 9 wherein said first and second sources of electrical signals include low frequencies as well as middle and high frequencies, wherein the forwardly and rearwardly directed loudspeaker means act as full-range sound radiating means.

11. In combination, first and second sources of electrical signals constituting the two channels of a stereo system and encompassing at least the middle and high frequencies of the signal channels involved, a loudspeaker system spaced adjacent but in spaced relation to an upstanding sound reflecting wall of a room and comprising right-hand and lefthand stereo loudspeaker sections respectively for directively radiating Y signals signal channels including signals in at least the middle and high frequencies which are directively acoustically radiated thereby, all of the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane which is to extend at right angles to said vertical wall and passing through the overall directive sound pattern involved so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and said forwardly directed loudspeaker means having directive sound patterns which are generally parallel to one another and to said centered vertical plane, so directive signals for each stereo channel are directed both forwardly into the room and rearwardly either inwardly or outwardly of said associated vertical plane.

12. A stereo loudspeaker system to be positioned adjacent but in spaced relationship to a vertical sound reflecting wall of a room, said loudspeaker system having housing means adapted to be supported on a horizontal support surface and containing right-hand and left-hand loudspeaker sections which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section having forwardly and rearwardly directed loudspeaker means to be connected to one of two stereo signal channels including signals in at least the middle and high frequencies which are directively acoustically radiated thereby, all of the rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane which is to extend at right angles to said vertical wall and passing through the overall directive sound pattern involved so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and said forwardly directed loudspeaker means having directive sound patterns which are generally parallel to one another and to said centered vertical plane, so directive signals for each stereo channel are directed both forwardly into the room and rearwardly either inwardly or outwardly of said associated vertical plane.

13. The stereo loudspeaker system of claim 12 wherein all of said loudspeaker means of each loudspeaker section being mounted in a separate portable enclosure of a size and weight readily to be placed upon a table, bookshelf or the like.

14. The stereo loudspeaker system of claim 13 wherein the common enclosure of each loudspeaker section can be supported in either one of two orthogonally related positions wherein the axis of the overall rearwardly directive sound pattern thereof extends substantially at an angle either outwardly or inwardly of said associated vertical plane.

15. A stereo loudspeaker system to be placed in adjacent spaced relation to a vertical sound reflecting wall, said loudspeaker system comprising: housing means placeable on a horizontal support surface and containing a right-hand and left-hand stereo loudspeaker section for receiving respectively at least the middle and high frequency electrical signals of two stereo channels and which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section when said housing means is supported on said horizontal support surface in front of said sound reflecting wall having forwardly and rearwardly directed loudspeaker means to be respectively connected to a source of stereo signals including said middle and high frequencies which are to be directively acoustically radiated thereby, said rearwardly directed loudspeaker means of each loudspeaker section providing'an overall directive sound pattern which is asymmetrically related to both a horizontal plane and a vertical plane which extends between the front and rear of said housing means, so the overall rearwardly directed sound pattern of each loudspeaker section is directed rearwardly principally in a direction inclining substantially in an upward or downward direction extending either substantially laterally outwardly or inwardly of said associated vertical plane.

16. The stereo loudspeaker system of claim 15 wherein said rearwardly directed loudspeaker means of each loudspeaker section comprises at least two loudspeaker units having overlapping directive patterns forming an overall directive sound pattern which is fan-shaped so as to have a cross section much greater in one direction transversely through the sound pattern than in the other direction transversely through the sound pattern.

17. The stereo loudspeaker system of claim 16 wherein the axes of said overlapping directive sound patterns of the loudspeaker units of each loudspeaker section form an acute angle.

18. A stereo loudspeaker system to be placed near a vertical sound reflecting wall in a room, said stereo loudspeaker system comp-rising a right-hand and a left-hand loudspeaker sections which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections; each loudspeaker section including a common speaker enclosure having a bottom portion to be placed upon a floor, table or the like, the enclosure having outer enclosure-forming walls defining a sealed enclosure space, said enclosure-forming walls including at the rear end portion thereof a first upwardly rearwardly and laterally facing baffle-forming wall with a cone loudspeaker-receiving opening therein and a second rearwardly facing baffle-forming wall with a cone speaker-receiving opening therein and making an obtuse angle with respect to said first baffle-forming wall, and cone loudspeakers mounted within a said sealed enclosure space behind said one loudspeaker-receiving openings of said first and second baffleforming walls.

19. The stereo loudspeaker system of claim 18 wherein said common enclosure of each loudspeaker section is portable and easy to manipulate and has a pair of outer support walls substantially right angles to one another upon which the enclosure may be selectively supported in two different positions where said first and second laterally facing baffle-forming walls then respectively face in opposite rearwardly and laterally facing directions.

20. The stereo loudspeaker system of claim 18 wherein said first and second baffle-forming walls of each enclosure are horizontally spaced from one another, said common enclosure of each loudspeaker section has a support wall upon which the enclosure may be supported when the enclosure is turned about a horizontal axis extending between the front and rear of the enclosure where said first laterally facing baffle-forming wall then faces rearwardly in the opposite lateral direction and said first and second baffle-forming walls are substantially vertically spaced fromone another.

21. The stereo loudspeaker system of claim 18 wherein said first and second baffle-forming walls of each enclosure are horizontally spaced from one another, said first baffle-forming wall makes a substantial angle to mutually perpendicular vertical planes extending respectively laterally and from the front to the rear of the enclosure, and said second baffle-forming wall extends substantially transverse to the latter plane and at a substantial angle to the former plane.

22. The stereo loudspeaker system of claim 21 wherein said first and second baffle-forming walls of the enclosure of each loudspeaker section intersect one another.

23. The stereo loudspeaker system of claim 21 wherein each speaker enclosure has a front vertical baffle-forming wall with a cone loudspeaker receiving opening therein and a cone loudspeaker mounted behind the same for directing middle and high frequencies forwardly into the room.

24. A stereo loudspeaker system to be placed in front of a vertical sound reflecting wall of a room, said loudspeaker system comprising: a right-hand and a left-hand loudspeaker section which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section comprising a common speaker enclosure having a bottom wall which establishes two orthogonal reference vertical planes which are to extend respectively parallel and transversely to said vertical sound reflecting wall, said enclosure having a first pair of corresponding mirrorimage related rearwardly and upwardly facing baffle-forming walls which face in opposite lateral directions, a centered rearwardly and upwardly facing baffle-forming wall ositioned between said irst pair of mirror-image related ba e-forming

Claims

1. In a room having an upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having housing means resting on a horizontal support surface in a predetermined position and containing right-hand and left-hand loudspeaker sections including rearwardly directed loudspeaker means respectively connected to said first and second sources of electrical signals, the rearwardly directed loudspeaker means of each section producing an overall directive sound pattern of the associated middle- and high-frequency signals which is the mirror-image of the rearwardly directed loudspeaker means of the other section with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections and which overall directive sound pattern is asymmetrically directed toward said upstanding sound reflecting wall so the overall directive sound pattern is directed mainly in a direction making a substantial angle with both the associated horizontal and vertical planes extending at right angles to said sound reflecting wall and passing through the rearwarDly directed loudspeaker means producing the overall directive sound pattern involved, and said housing means further including for each loudspeaker section a forwardly directed loudspeaker means also connected to the associated source of electrical signals of the associated stereo channel and providing a forwardly directive sound pattern of said middle and high frequencies whose axis is directed forwardly in a direction generally parallel to said centered vertical plane.

2. The stereo loudspeaker system of claim 1 wherein said right-hand and left-hand loudspeaker sections are relatively closely spaced so that they are remote from the sidewalls of said room which extends traversely of said upstanding sound reflecting wall of the room, and said rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections respectively producing respective overall rearwardly directed sound patterns which are directed principally outwardly of the loudspeaker system.

3. The stereo loudspeaker system of claim 1 wherein said right-hand and left-hand loudspeaker sections are positioned a substantial distance apart where they are closer to said sidewalls of the room than the center of said wall, and the rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections producing respective overall rearwardly directed sound patterns which are directed principally inwardly of the loudspeaker system.

7. In a room having an upstanding sound reflecting wall, a first source of electrical signals of at least middle and high frequencies for a first stereo channel, and a second source of electrical signals of at least middle and high frequencies for a second stereo channel, the improvement comprising a stereo loudspeaker system mounted in front of said wall in spaced relation thereto, said loudspeaker system having housing means resting on a horizontal support surface in a predetermined position and containing right-hand and left-hand loudspeaker sections each including first and second rearwardly directed loudspeaker means, each of said First and second rearwardly directed loudspeaker means producing an overall directive sound pattern directed asymmetrically rearwardly towards said sound reflecting wall in the opposite lateral direction from the other of same so the overall directive sound patterns produced by each of said first and second rearwardly directed loudspeaker means is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and means for selectively coupling the middle and high frequencies of said signal sources to the first or second rearwardly directed loudspeaker means of each loudspeaker section.

8. In a room having an upstanding sound reflecting wall, a first and second source of electrical signals of two stereo channels encompassing at least the middle- and high-frequency range where acoustically directed sound signals are directive, a stereo loudspeaker system mounted in front of an upstanding sound reflecting wall in spaced relation thereto, said loudspeaker system having a right-hand and a left-hand loudspeaker section with rearwardly directed loudspeaker means respectively connected to said first and second sources of electrical signals, said rearwardly directed loudspeaker means of said right-hand and left-hand loudspeaker sections being positioned near the sidewalls of said room, and the rearwardly directed loudspeaker means of each section providing an overall directive sound pattern which is the mirror image of the loudspeaker means of the other section and is directed only inwardly toward said upstanding wall to reflect off the central portion of said wall into the listening area.

11. In combination, first and second sources of electrical signals constituting the two channels of a stereo system and encompassing at least the middle and high frequencies of the signal channels involved, a loudspeaker system spaced adjacent but in spaced relation to an upstanding sound reflecting wall of a room and comprising right-hand and left-hand stereo loudspeaker sections respectively for directively radiating signals signal channels including signals in at least the middle and high frequencies which are directively acoustically radiated thereby, all of the rEarwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to an associated vertical plane which is to extend at right angles to said vertical wall and passing through the overall directive sound pattern involved so the overall directive sound pattern thereof is directed mainly in directions making a substantial angle with the associated vertical plane passing through the sound pattern involved, and said forwardly directed loudspeaker means having directive sound patterns which are generally parallel to one another and to said centered vertical plane, so directive signals for each stereo channel are directed both forwardly into the room and rearwardly either inwardly or outwardly of said associated vertical plane.

15. A stereo loudspeaker system to be placed in adjacent spaced relation to a vertical sound reflecting wall, said loudspeaker system comprising: housing means placeable on a horizontal support surface and containing a right-hand and left-hand stereo loudspeaker section for receiving respectively at least the middle and high frequency electrical signals of two stereo channels and which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section when said housing means is supported on said horizontal support surface in front of said sound reflecting wall having forwardly and rearwardly directed loudspeaker means to be respectively connected to a source of stereo signals including said middle and high frequencies which are to be directively acoustically radiated thereby, said rearwardly directed loudspeaker means of each loudspeaker section providing an overall directive sound pattern which is asymmetrically related to both a horizontal plane and a vertical plane wHich extends between the front and rear of said housing means, so the overall rearwardly directed sound pattern of each loudspeaker section is directed rearwardly principally in a direction inclining substantially in an upward or downward direction extending either substantially laterally outwardly or inwardly of said associated vertical plane.

18. A stereo loudspeaker system to be placed near a vertical sound reflecting wall in a room, said stereo loudspeaker system comprising a right-hand and a left-hand loudspeaker sections which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections; each loudspeaker section including a common speaker enclosure having a bottom portion to be placed upon a floor, table or the like, the enclosure having outer enclosure-forming walls defining a sealed enclosure space, said enclosure-forming walls including at the rear end portion thereof a first upwardly rearwardly and laterally facing baffle-forming wall with a cone loudspeaker-receiving opening therein and a second rearwardly facing baffle-forming wall with a cone speaker-receiving opening therein and making an obtuse angle with respect to said first baffle-forming wall, and cone loudspeakers mounted within a said sealed enclosure space behind said one loudspeaker-receiving openings of said first and second baffle-forming walls.

20. The stereo loudspeaker system of claim 18 wherein said first and second baffle-forming walls of each enclosure are horizontally spaced from one another, said common enclosure of each loudspeaker section has a support wall upon which the enclosure may be supported when the enclosure is turned about a horizontal axis extending between the front and rear of the enclosure where said first laterally facing baffle-forming wall then faces rearwardly in the opposite lateral direction and said first and second baffle-forming walls are substantially vertically spaced from one another.

24. A stereo loudspeaker system to be placed in front of a vertical sound reflecting wall of a room, said loudspeaker system comprising: a right-hand and a left-hand loudspeaker section which are mirror images of one another with respect to a centered vertical plane extending transverse to said sound reflecting wall midway between the loudspeaker sections, each loudspeaker section comprising a common speaker enclosure having a bottom wall which establishes two orthogonal reference vertical planes which are to extend respectively parallel and transversely to said vertical sound reflecting wall, said enclosure having a first pair of corresponding mirror-image related rearwardly and upwardly facing baffle-forming walls which face in opposite lateral directions, a centered rearwardly and upwardly facing baffle-forming wall positioned between said first pair of mirror-image related baffle-forming walls, cone speaker-receiving openings in the aforementioned baffle-forming walls, cone speakers mounted within said enclosure behind said cone speaker-receiving openings for directing sound through said openings, and means for feeding low nondirective frequencies to all of said cone speakers in each enclosure but selectively feeding the middle and high directive frequencies to various ones of the cone speakers of each enclosure to obtain a selection of directive sound patterns from the enclosure.