US2814354A

US2814354A - Loud-speaker assembly and system

Info

Publication number: US2814354A
Application number: US423933A
Authority: US
Inventors: George A Brettell
Original assignee: Ampex Corp
Current assignee: Ampex Corp
Priority date: 1954-04-19
Filing date: 1954-04-19
Publication date: 1957-11-26
Anticipated expiration: 1974-11-26

Description

Nov. ,26, 1957 GA. BRETTELL 2,314,354

LOUD-SPEAKER ASSEMBLY AND SYSTEM Filed April 19, 1954 2 Sheets-Sheet 1 R INVENTOR.

ep George A. fire/f6 Qep. 3 P33 A 770R NEVS 1957 e. A. BRETTELL LOUD-SPEAKER ASSEMBLY AND SYSTEM 2 Shgets-Sheet 2 Filed April 19. 1954 m T m V N I United States Patent LOUD-SPEAKER ASSEMBLY AND SYSTEM George A. Brettell, Redwood City, Calif., assignor to Ampex Corporation, Redwood City, Calif., a corporation of California Application April 19, 1954, Serial No. 423,933

3 Claims. (01. 181-31) This invention relates generally to loud-speakers and systems therefor which are suitable for reproduction of stereophonic sound in outdoor motion picture theaters.

Stereophonic sound systems such as are customarily used in connection with motion picture films employ three magnetic sound tracks, which are reproduced through separate reproducing and amplifier channels at the time the film is projected. The three channels are connected to separate loud-speakers located in spaced relationship in order to afford the desired stereophonic effect. For example the loud-speaker connected to one channel may be near the left end of the viewing screen, the speaker for a second channel near the right-hand end, and the speaker for the third channel near the middle of the screen or directly in front of the audience. Outdoor moving picture theaters have heretofore employed simple portable loud-speakers connected to extension cords, and attached to some convenient part of the car, such as to one of the door windows. Such an arrangement is reasonably satisfactory for reproduction of a simple sound track but cannot be used to obtain stereophonic effects. A plurality of loud-speakers can be located in different parts of the car, and separately connected by extension cords to the channels, but this seriously complicates the equipment required, and necessitates having three separate loud-speaker units.

I am aware of the fact that it has been proposed to obtain a binaural effect by directing sound from several loud-speakers against a reflecting surface, and controlling the direction of the incident and reflected sound to obtain the desired directivity eifect. This principle has been utilized in the present invention.

In general it is an object of the present invention to provide a stereophonic loud-speaker system suitable for drive-in moving picture theaters, and which will aflord a more realistic stereophonic elfect.

Another object of the invention is to provide a novel construction for a loud-speaker assembly which can be used for the purpose described above.

Another object of the invention is to provide a novel means for retaining the loud-speaker assembly in proper position within a car.

Additional objects of the invention will appear from the following description in which the preferred embodiment has been set forth in detail, in conjunction with the accompanying drawings.

Referring to the drawings:

Figure 1 is a plan view illustrating a loud-speaker assembly in accordance with the present invention.

Figure 2 is a side elevational view of the speaker assembly shown in Figure 1.

Figure 3 is a schematic view illustrating how the several loud-speakers are electrically connected to the several reproducing and amplifier channels.

Figure 4 is a side elevational View schematically illustrating how the loud-speaker assembly can be disposed Within an automobile.

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Figure 5 is a plan view of the arrangement shown in Figure 4.

Figure 6 is a schematic perspective view illustrating means for retaining the loud-speaker assembly in proper position.

The assembly illustrated in Figures 1 and 2 consists generally of a housing 10 formed of suitable material such as molded plastic, and which is relatively fiat with respect to its vertical dimensioning. The two side faces 11 and 12 are inclined with respect to the vertical, and they are also at an angle of approximately with respect to each other, as viewed in plan. The rearwardly faced wall 13 is likewise inclined to the vertical as illustrated, and as viewed in plan it extends at angles of substantially 45 with respect to the side walls. The side Walls 11 and 12 have screened or cloth covered

openings

14 and 15, behind which loud-speaker units are mounted. The Wall 13 has a similar screened or cloth covered opening 16. The loud-speaker units 17, 18 and 19 employed are preferably of the elliptical cone type, dimensioned whereby they can be grouped in close proximity substantially in the manner illustrated in Figure 3. The directional axes of each cone is at a right angle to the plane of its associated front covering Wall.

When the loud-speaker assembly described above is placed in a car, it can be placed on the supporting surface 21) which overlies the usual instrument panel, and in alignment with the longitudinal car axis. Because the windshield 21 of most cars is tilted from the vertical as viewed from one side, it is desirable to tilt the assembly in the manner illustrated in Figure 4. Considering Figures 4 and 5 together, it will be seen that the projected

axes

22 and 23 of the loud-speaker units 17 and 18, are divergent, and directed upwardly against the windshield. The incident axes of the directed sound from the loudspeaker units corresponds generally to these axes. The angle reflection is roughly equal to the incident axis, so that as schematically illustrated in Figures 4 and 5, sound is reflected back into the passenger space of the car with directivity corresponding to the two sides of the windshield. The extended axis 24 of the loudspeaker unit 19, and as viewed from the side, extends in the same general direction as the direction with which sound is reflected from the windshield.

It is generally desirable to have all of the units 17, 18 and 19 of the same size and with like characteristics. Therefore if the output from each of the amplifiers were the same for a given track magnetization, the volume level of sound from each of the speakers would be equal. I have found that with such an arrangement the occupants of the car do not obtain the desired directivity effect, and that the directivity from the units 17 and 18 appears to be overshadowed by the sound directly received from the center unit 19. In accordance with the present invention I reduce the volume level of the unit 19, whereby the sound volume from this unit is greatly less than from each of the units 17 and 18, for a given magnetization of the three sound tracks. This can be accomplished by using a suitable volume control of the potentiometer type in the connection from the associated amplifier, or the associated amplifier can be adjusted to produce the desired result.

Figure 3 schematically illustrates the three loudspeaker units 1'7, 18 and 19, connected to separate rcproducing and amplifying channels. The

reproducers

31, 32 and 33 represent magnetic reproducing heads associated with the film projector and which operate in conjunction with each of the sound tracks.

Amplifiers

34, 35 and 36 represent the amplifying equipment connected with the reproducing heads, including pro-amplitiers and power amplifiers. A volume control 37 has been shown connected in the output of the amplifier 35. In a typical instance the power output to the loudspeaker 19 can be reduced to say from ten to twentyfive percent of the power supplied to each of the units '7 and 18, for a given magnetization of the three sound tracks.

As previously explained it is desirable for the loudspeaker assembly 10 to be placed at an optimum angle with respect to the horizontal, and in alignment with the longitudinal center line of the car. The means used for retaining the assembly in its operating position preferably should be adjustable, in order to facilitate placing the assembly in an optimum position, and in addition it should not interfere with normal view through the windshield, or with occupancy of the car. The holding means illustrated in Figures 4, 5 and 6 consists of a U-shaped holder 38 which is applied over the upper edge of the door Window 39, and which is attached to the electrical cord 40 which contains the amplifier cables.

Arms

41, 42 and 43 are linked together to connect the holder 38 to the assembly unit 10. Ball and socket connection 44 can connect arm 41 to the holder, and a similar connection 46 connects arms 41 and 42. These connections can be constructed to provide considerable stiffness in their operation, whereby they tend to remain in a position in which they are placed at the time the loud-speaker assembly is placed in the car by an attendant. A swivel connection 47 connects

arms

42 and 43, and permits arm 44 to rotate about a generally vertical axis. It is desirable for the connection 47 to include spring loading means, tending to rotate the arm 43 in a direction toward the windshield. The free end of arm 43 connects with a fitting 48, which has a ball and socket connection 49 with the housing of the unit 10, and which carries the extensible foot 51': This foot is adapted to rest against the base of the windshield in the manner illustrated in Figure 4. Connection 49 is likewise made to have considerable stiifness so that it is capable of retaining the loud-speaker assembly in a desired position. Both the foot 51 and the bottom side of the assembly are provided with suitable padding to avoid scratching the car finish. All of the arms can be of tubular construction, and may be made to enclose the cord 40. Arm 43 can be made extensible as shown in Figure 5.

It will be evident that the means described above can be adjusted for a wide variety of cars, and when once properly installed by an attendant, the loud-speaker assembly will have a proper operating position with respect to the windshield. The mechanism used for holding the loud-speaker assembly does not interfere with the view through the windshield, and does not obstruct the foot space near the instrument panel. If the door to which the holder 38 is applied should be opened the loud-speaker assembly will remain in substantially its proper position, due to the fact that arm 43 will rotate about a vertical axis by virtue of the swivel connection 47.

I claim:

1. In stereophonic loud-speaker apparatus for installation in automobiles, a housing, three loud-speaker units mounted in the housing, two units being disposed to project sound on divergent axes toward the windshield whereby the sound is reflected from the windshield with stereophonic effect, the third speaker being disposed to direct sound rearwardly into the passenger space of the car, means for supporting the housing and said units at a level corresponding generally to the base of the windshield and spaced rearwardly from the windshield, said means comprising a plurality of arms linked together, and means engaging one door of the automobile and attached to said arms, said means permitting opening of the door Without dislodgement of the housing.

2. In a stereophonic loud-speaker apparatus for installation in automobiles, a housing having two substantially planar side faces and one substantially planar front face, as viewed in plan the faces being disposed at included angles of less than 'with respect to each other and inclined toward the normal vertical axis of the housing, whereby the housing is generally pyramidal in shape, three loud speaker units disposed within the housing, there being a unit disposed behind each face of the housing, the two units associated with the side faces being disposed to project sound on divergent axes toward the windshield of the automobile whereby the sound is reflected from the sides of the windshield with stereophonic effect, the third loud-speaker unit being disposed to direct sound rearwardly into the passenger space of the automobile, and means for adjustably retaining the apparatus in a desired position relative to the windshield.

3. In a stereophonic loud-speaker apparatus for installation in automobiles, a housing having two substantially planar side faces and one substantially planar front face, as viewed in plan the said faces being at the included angles of less than 90 with respect to each other and inclined to the normal vertical axis of the housing whereby the housing is generally pyramidal in shape, three loud speaker units disposed within the housing, there being a unit disposed behind each face of the housing, the two units associated with the side faces being disposed to project sound on divergent axes toward the windshield, whereby the sound is reflected from the sides of the windshield with stereophonic efiect, the third unit asso ciated with the front face being disposed to direct sound rearwardly into the passenger space of the automobile, and means attached to a portion of the housing located intermediate the two side faces thereof for adjustably retaining the assembly in a desired position relative to the windshield of a car.

References Cited in the file of this patent UNITED STATES PATENTS 2,137,032 Snow Nov. 15, 1938 2,179,840 Bucky Nov. 14, 1939 2,544,742 Volf Mar. 13, 1951 2,610,694 De Boer Sept. 16, 1952