US 2133151 A
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Oct. 11, 1938. P. L. RXTTENHOUSE 2,133,151
RADIO RECEIVING SYSTEM FOR AUTOMOBILES Filed Aug. 6, 1936 B Y 20 30 K I I AA/aaz A? 0/3 P4 4CEME/V7' 590M ATTORN EYS (00051 5441 AXIS Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE RADIO RECEIVING SYSTEM FOR AUTOMOBILES 2 Claims.
This invention relates to improvements in the installation of radio receiving sets in automobiles, particularly in the location and mounting thereof.
An object of the invention is to so mount and locate the loud speaker unit that aural reception will be about the same as to volume and fidelity of acoustical reproduction for all occupants of the car, wherever disposed in one or more seats; and such that the volume-output from the loud speaker unit for a given intensity of aural reception is considerably reduced as compared to that re- .quired under existing practices; while the observed tonal quality and timbre of reproduction at all positions of occupancy will be highlytsuperior to the results heretofore attainable with known types of installations.
A further object of the invention is to so locate and arrange the radio receiver unit as to iii permit any occupant of the car to operate the receiver from his seat of occupancy.
In accordance with the present practice both the radio receiver and loud speaker units are customarily mounted in the forward-most part of 5 the car interior. For example, the receiver unit proper is usually mounted in a compartment just back of the dash-board on which the controls are mounted in front of the driver, the speaker unit being ordinarily mounted just below the dash- 30 board.
This arrangement is defective from the standpoint of manipulating the receiver because it is easily accessible only to the driver. In order to minimize hazards, however, the drivers atten- 5 tion should be concentrated on operating the automobile, from which manipulation of the receiver may divert his attention at critical moments. It is equally unsatisfactoryfor an occupant beside the driver to manipulate the receiver 40 because in so doing the driver is more or less obstructed in his operation of the automobile.
From the standpoint of acoustics the mounting of the speaker unit in the forwardmost part of the car interior, as on or below the dash-board,
45 is unsatisfactory, judged from the standpoints of both volume output efficiency to all points of occupancy and also the fidelity of reproduction thereat. It is a fact well established by numerous investigations and tests that the diaphragms of 50 loud speaker units employed in radio sets, whether of the cone or disk type, and whether actuated by a centrally affixed drive, or driven plungerfashion about the periphery, possess strong beam or directional characteristics tending to concen- 55 trate along the axisof the diaphragm the acous- .tical waves radiated therefrom, this concentration into a beam of increasingly diminishing solid angle becoming increasingly pronounced with in- .crease of frequency. It results from this that any object disposed in the path of the beam which is 5 hi hly absorbent to acoustical waves, produces a selective absorption with frequency, because the waves of lower frequency being radiated through a greater angle pass in large measure around the object; whereas the waves of higher frequency 10 being concentrated within a smaller solid angle, impinge in large measure upon the object and are thus absorbed. As a result of this selective absorption, the higher frequencies which are responsible for the quality, timbre and naturalness yr, in music and intelligibility in speech, are discriminated against, and the fidelity of aural reception is impaired at points outside the path of the direct beam.
This effect occurs in marked degree in present v20 day motor cars equipped with radio sets wherein the speaker element is mounted, as is customary, below the dash-board and in such manner that the speaker is necessarily pointed directly toward the back rest or support of the drivers seat. As is well known, and as appears from numerous tests and scientific papers on the subject, acoustical waves are largely or almost completely absorbed by the materials with which the seat-backs of modern automobiles are covered and backed. Moreover, the absorption is increased when the seats are occupied. It results from these factors and the directional characteristics of the speaker unit, that with the unit mounted in its customary position below the dash-board, the waves radiated directly therefrom are absorbed in large measure by the back of the drivers seat and by the bodies and clothing of occupants thereof, especially at the higher frequencies, so that such acoustical energy as does reach the ears of the listeners is not only greatly reduced in volume but is impaired as to fidelity of reproduction .due to the mentioned selective frequency absorption. The occupants in the rear seat .of a car are of course subjected to these disadvantages to an even greater extent than those of the front seat.
There is a still further serious disadvantage in the customary mounting of the speaker unit on or :below the dash-board, :namely, that but one side of the diaphragm is effective in radiating 5f) waves to the occupants, the other side being directed toward the engine. If therefore the speaker is backed .by medium such as metal, which is highly reflecting acoustically, the waves emanating from the rear of the speaker .dia-
phragm and reflected from the backing material, will combine in varying phase relation with frequency with the waves radiated from the front of the speaker diaphragm with a highly absorbent materiahthe acoustical efficiency of the receiver is approximately halved, with resulting loss of volume necessitating increased amplification of the radio signals.
According to my invention, all of the aforementioned acoustical defects may be overcome by mounting the speaker unit either in the back of the drivers seat about equidistant from the sides of the car and preferably near the top of the seat back with the diaphragm pointing approximately toward the intersection of the windshield and the dash-board, although the exact positioning and direction for best results will depend of course on the interior layout of the car.
In case the drivers seat extends continuously from one side of thecar to the other, the speaker unit may be appropriately mounted in the interior of the seat back, the area occupied by the diaphragm being covered and protected by some strong, substantially non-absorbent and non-refleeting material forming a part of the seat covering, such as a loosely woven textile of the character presently employed for covering the speaker in radio broadcasting receivers for home use. Or, the back of the drivers seat may be centrally partitioned, by a firmly backed and upholstered panel, in which event the speaker may be conveniently mounted in the interior of the back behind this panel. A somewhat similar construction may be employed in the case'of the so-called tudor sedan wherein a pair of separate front seats are provided, at least one of which is foldable. In this case the speaker may be mounted in a housing erected between the seats.
Irrespective of the particular modification employed, the waves emanating from the speaker unit will impinge directly on the windshield and dash-board of the car, which being smooth and polished surfaces of high acoustical reflection efficiency, will reflect the waves in a diverging beam directly toward the ears of all occupants of the car, including those in 'both the front and rear seats.
Also, with the speaker unit mounted as stated, the occupants'in the rear seat of the car will not only receive the reflected'waves thus emanat ing from the front of the speaker diaphragm, but will alsobe in position to receive the waves radiated from the rear of the diaphragm, so that the diaphragm will thus be rendered fully effec-' tive in producing undistorted acoustical energy available to the listeners.
According to a further aspect of the invention the radio receiving unit may likewise be mounted in the interior of the back of the drivers seat, preferably below the loud speaker, with controls for operating the set exposed on both the front and rear sides of the seat back, so that any occupant in either a front or a back seat may operate the set from his seat of occupancy.
Referring now to the drawing for a more detailed explanation of the invention:
Fig. 1 illustrates diagrammatically in side elevation the interior of a passengter or family type of automobile equipped with a radio-receiving set arranged in the forwardmost part of the car in accordance with the present practice;
Fig. 2 is a similar view with the receiving set and loud speaker unit mounted in the interior of the drivers seat back in accordance with the present invention;
Fig. 3 is a View of the drivers seat in front elevation showing the location of the loud speaker and receiver laterally and vertically of the car interior;
Fig. 4 is a section at 4-4 of Fig. 3 showing the installation of the loud speaker and receiver unit more in detail;
Fig. 5 is a perspective view of the interior of a tudor sedan in which a pair of separated front seats are provided, one or both of which are foldable, the receiving apparatus being mounted in accordance with the invention in a housing erected between the seats;
Fig. 6 is a chart illustrating graphically the directional radiating characteristics of a loud speaker unit at various frequencies.
Referring to Fig. 1, the outline of the car body is shown at l, the interior of which contains the drivers seat 2 having a back 3, a rear seat 4, a dash-board 5, housing a radio receiving set 6, the controls 1 of which are exposed through the dashboard, and a loud speaker unit 8 mounted below the dash-board, said unit including a conically shaped diaphragm 9 mounted in a box-like housing I0. A loud speaker so mounted will have directional characteristics somewhat as illustrated by the graphical chart in Fig. 6, the ordinates of which represent acoustical energy output of the speaker at various frequencies and at the angular displacements from the axis thereof plotted as abscissae, the energy output being expressed in each instance in terms of the energy radiated along the axis of the speaker.
It will be observed from this chart that whereas the speaker has very slight directional characteristics at the extremely low audio-frequencies of the order of 300 cycles per second, neverthless as the frequency increases the greater portion of the speaker output is concentrated within a beam of increasingly narrower solid angle. Thus at 4000 cycles per second, about 60% of the output is concentrated within a solid angle of 40 aperture, and about 95% with a solid angle of 60 aperture. For higher audio-frequencies the beam concentration is even more severe.
Reverting to Fig. l, the effect of this is to concentrate the greater portion of the high frequency waves radiated from the speaker 8 within a relatively narrow solid angle having an angular aperture l2 about as outlined by the dotted lines l3, I4. It will thus be observed that with the speaker unit in its customary position below the dash-board in accordance with present practice, the greater portion of the high frequency energy is directed by the speaker toward the back of the drivers seat and the bodies of the front seat 00-- cupants, so that whether the seat is occupied or not this high frequency energy will be immediately absorbedin greater part and will never reach the ears of a listener. For example, tests have shown that the upholstery of the seat back will absorb in excess of 80% of the acoustical energy incident thereon at a frequency of 4000 cycles or higher; while the clothing and bodies of occupants will completely absorb the acoustical energy at such frequencies.
Therefore, with the speaker positioned as in Fig. 1, the high frequency components of speech and music are selectively absorbed, and thus in general never reach the ears of the car occupants, thereby causing the acoustics of the car to have the muffled or barrel effect characteristics so noticeable in the present day operation of automobile radio sets. As has been pointed out, it is the higher frequency components in speech and music, thus selectively absorbed, which impart timbre and naturalness thereto, and by virtue of which the distinctive qualities distinguishing one persons voice or'one musical instrument from another are observed.
Referring now to Figs. 2 to 4 inclusive, the loud speaker I5 is, in accordance with one modification of my invention, mounted in the interior of the back of the drivers seat I6, preferably near the top of the seat back and beside the position l1, occupied by the driver. The speaker is positioned to so direct the acoustical waves toward the windshield l8 and dash-board l9, that said waves will be reflected to the ears of all of the car occupants even at the higher audio-frequencies. Assuming, for example, in accordance with the data of Fig. 6, that waves of 4000 cycles per second and higher will be largely concentrated by the speaker within the angular aperture 20, the waves will be reflected from the windshield and dash-board substantially within the region bounded by lines 2|, 22. It will be thus observed that these waves are directly reflected to the ears of occupants in both the front and rear seats, the ears of whom will normally occupy positions about as indicated by points 23 and 23a respectively. Of course, the waves of frequency lower than 4000 cycles will be spread over a still wider region, so that all car occupants will receive wavelengths of all frequencies emanating from the receiver, in their proper relative amplitudes as determined by the sound impressed on the transmitter at the broadcasting station, the reception therefor constituting a faithful reproduction of sounds transmitted. Moreover, since the sound waves emitted by the speaker do not strike any highly absorbent body before reaching the ears of the occupants, a much lower volume of reproduction will sufiice than otherwise.
If desired the rear side of the speaker unit I5 may be effectively exposed by covering the same with some loosely woven textile material or wire gauze, to permit sound waves produced by the rear surface of the diaphragm to be emitted directly toward the occupants of the rear seat.
Preferably, the radio receiving unit 24 actuating the speaker is installed in the back of the drivers seat beneath the loud speaker. The receiver may be provided with operating controls on the side of the seat back accessible to the driver as is indicated by the control knobs 25, and also on the side of the seat back facing the rear seat, as is indicated by the control knobs 26. Thus any occupant of either the front or rear seat may manipulate the receiver and without in any way obstructing the driver.
Figs. 3 and 4 show in detail a highly effective arrangement for installing the speaker and receiver units in accordance with the invention. The seat back is partitioned by panel 21 comprising a housing 28 for the speaker l5 and receiver 24 units, said housing being of some stiff strong material, such as sheet metal 29, preferably covered by upholstering 30, either with or Without padding as desired.
The speaker um't l5 may be mounted on a metal frame 3| aflixed to the sheet metal 30 comprising housing 28 by screws 32 whereby the assembly is removable from the housing. The housing is provided with an aperture 33 facing toward the front of the car, which aperture is covered by a non-absorbent material 34 such as loosely woven textile or wire mesh. Similarly, if it is desired that the speaker radiate sound waves from the rear of the diaphragm the frame 3| may likewise be apertured as at 35, the aperture being covered with a non-absorbent'material 36 such as loosely woven textile or wire mesh.
The receiver unit 24 is mounted on a frame 38 removably attachable to the housing 30 by means of screws 39. The housing is countersunk at 4|], and the frame at 4|, so that the control knobs 25 and 26 of the receiver will not protrude.
Fig. 5 shows a construction applicable to the so-called tudor type of sedan in which two separate seats 42 and 43 are provided in the front portion of the car, seat 43 being collapsible as shown. In this case the loud speaking unit l5 and the radio receiver unit 24 may be mounted in a housing 44 affixed to a stand 45 erected between the seats.
What I claim is:
1. In a passenger type of automobile in combination: a body containing a windshield and a dash-board contiguous thereto, a drivers seat and a rear seat facing said windshield, said drivers seat having a back, a loud speaker unit of a radio receiver mounted substantially in line with said seat back near the top thereof and beside the position occupied by the driver, said speaker having a vibratile diaphragm positioned to so direct acoustical waves toward said windshield and dash-board that said waves will be reflected to the ears of all car occupants, and said diaphragm being acoustically exposed toward said rear seat.
2. In a passenger type of automobile in combination: a body containing a windshield and a dash-board contiguous thereto, a drivers seat and a rear seat facing said windshield, said drivers seat having a back, a loud speaker unit of a radio receiver mounted substantially in line with said seat back near the top thereof and beside the position occupied by the driver, said speaker being positioned to so direct acoustical waves toward said windshield and dash-board that said waves will be reflected to the ears of all car occupants, and a radio receiver for actuating said speaker mounted below the same, said receiver having operating controls exposed toward said dash-board and similarly functioning operating controls exposed toward said rear seat.
PAUL L. RI'I'IENHOUSE.