US2440078A - Radio cabinet and speaker mounting - Google Patents

Description

April 6, 1948. I G. F. DEVINE 2,440,078

RADIO CABINET AND SPEAKER MOUNTING Filed March 17, 1943 Inventor: George F Devine,

I by .Z -T W l-hs Attorney.

Patented Apr. 20, 1948 RADIO CABINET AND SPEAKER MOUNTING George F. Devine, Easton, Conn., assignor to General Electric Company, a corporation of New York Appli ation March 17, 1943, Serial No. 479,523

3 filairns. 1

My invention relates to cabinets for radio receivers and in particular to the mounting of loud speakers within such cabinets. It is an object of my invention to-provide a new and improved loud speaker mounting for a radio cabinet to permit the use of larger speakers in such cabinets.

Another object of my invention is to provide an improved radio cabinet in which the speaker is inclined at an angle to the front of the cabinet, thereby permitting the use of a larger speaker in a cabinet of a given size.

A further object of my invention is to provide an improved speaker mounting for a radio cabinet in order to effect certain improvements in the low frequency sound response thereof.

Still a further object of my invention is to effect certain improvements in the technique of manufacturing radios by permitting the use of speakers of difierent sizes with a single design of chassis.

An important feature of my invention is the mounting of the loud speaker in a radio cabinet at an angle to the front surface of the cabinet, thereby permitting the use of a larger speaker for a given frontal surface area.

Another feature of my invention is the provision of a specially developed reflecting surface for use with an inclined speaker in order to prevent multiple reflections, between the walls enclosing the space between the speaker and the reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 is a front elevational view, partly broken away, illustrating a radio cabinet of the table model type embodying my invention, and Fig. 2 is an enlarged side View, partly in section and, partly broken away, of a portion of the cabinet of Fig. 1.

In Fig. 1, I have shown a domestic radio receiver of the familiar table model type, the cabinet thereof having a front surface [El and a top surface H. The front surface H) has the usual tuning dial I12 disposed thereon, over which moves an index l3 controlled by the usually manually operated knob I4 which also, in the usual manner, controls the tuning adjustment of the conventional unicontrolled tuning condensers or other tuning device. The receiver also includes the-usual volume adjuster l5 and a switch l6 for selecting any one of a plurality of radio frequency bands. The knobs I l-l6 are supported by shafts which extend directly into the usual radio chassis (not shown) located in the bottom portion of the cabinet.

In order to provide a compact receiver unit, the tuning dial I2 is disposed directly above the control knobs M-l5 and the loud speaker I7 is placed directly above this tuning dial for purposes which are explained in detail later.

In order to provide a radiocabinet in which both length and height are kept to minimum dimensions, while a large speaker is utliized to provide an improved sound output, in the embodiment of my invention shown the speaker I7 is located above the tuning dial l2 and is inclined at an angle to the front surface It, the angle of inclination being determined by the frontal surface area available for the mounting of the speaker and the'size-of the speaker which it is desired to use. The geometry of the speak er cone determines the limit of the angleof inclination, it being undesirable generally to tilt the speaker backwardly so far that any portion of the cone radiates sound at an angle greater than with the opening in the front of the cabinet. Other factors which enter into the angle of tilt of the speaker are pointed out later.

One manner of mounting the speaker in such a position is best seen in Fig. 2 in which the specially shaped speaker supporting member 253 is attached in any suitable manner, such as by gluing, to the top surface ll of the cabinet. The speaker I! has a metal mounting ring 24 which is secured to the member 20 at the upper end of the speaker by screw 25 and at the lower end by means of bolt 2'6 and nut 21. The speaker I! is preferably of the typeusually used in radio receivers and, supported bythe ring 24, is the usual cone or diaphragm 28 and field structure 29 including a voice coil, not shown, to which are supplied audio frequency voltages from the output of the receiver circuit. The-construction of the speaker per se forms no part of my invention and the details thereof, other than those already pointed out, are not shown.

A decorative cloth or grille 36- of the usual type is provided over the speaker opening in the front surface ll] of the cabinet. Alternatively, louvers or any other desired type of grille work may be used for this purpose. A transparent member, such as the glass [8, is provided as means to protect the dial l2 and is supported on the front panel of the receiver by means of clamp l9.

In the conventional type of receiver mounting, the loud speaker usually is attached directly to th front panel of the receiver so that the effective diaphragm diameter of the speaker is limited to the available frontal surface area which, in the case of Fig. 2, is indicated by the dimension A. By supporting the speaker at an angle to the front surface of the cabinet, however, the effective diaphragm diameter of the speaker is increased to the dimension B. By varyin the angle between the front surface H] of the receiver cabinet and the inclined surface 3| of the member 20, the diameter 13 of the speaker may be made considerably greater than the height A of the frontal space usually available for mounting the speaker so that the dimension B may be as much as '75 to 100 per cent greater than the dimension A. Such a construction, therefore, permits the use of a larger speaker in a small cabinet and effects a considerable and desirable improvement in the sound output of the receiver.

When the speaker is tilted back in the manner illustrated, some of the sound waves emanating from diaphragm 28 strike against the top or opposite wall of the cabinet and are directed toward the grille 30, the angle of reflection of the sound waves being equal to the angle of incidence with the opposing surface. As the angle between the surface 3| and the front surface I is increased, ultimately the higher audio frequencies, When reflected from the opposing surfaces of the cabinet, do not pass directly through grille 30 but instead reflect back upon the cone and upon other surfaces within the cabinet, thus causing multiple reflections of the wave within the cabinet and producing an undesirable sound quality which may be likened to sea shell effect and which is caused by interference of sound waves within the boundaries of the cabinet.

In order that full advantage may be obtained from my improved speaker mounting, the speaker supporting member 2i! is provided with a special sound reflecting surface 32 in opposition to the cone or diaphragm 28, the purpose of the surface 32 being to direct sound Waves emanating from the diaphragm 23 directly to the exterior of the receiver through the cloth or grille 35 without permitting any multiple reflections of the sound waves'within the cavity or enclosure formed by the speaker I1, the surfaces of supporting member 28, and the grille 30. The special shape of the sound reflecting surface 32 is developed by tracing the path of sound waves emanating from the diaphragm 28 to the surface 32 and the exterior of the receiver cabinet, the shape of surface 32 being such that these sound waves are reflected within the above-mentioned cavity only by the surface 32, and are directed by that surface through the grille 33 to the exterior of the cabinet with substantially no further reflection from any of the 7 tion within the above-mentioned cavity. By tracing in this manner the paths of waves from all points along the cone 28 to the inner surface of the member 20 and by adjusting the reflection angle of these waves from this irmer surface so that all of these waves are directed through grille 30 without further reflections within the cavity, the shape of the surface 32 required to give the desired results is readily obtained.

As stated previously, generally it is undesirable to tilt the speaker I! backwardly with respect to the front panel ID to such an extent that any portion of the cone diaphragm radiates sound at an angle greater than with respect to the opening in front of the cabinet. If this angle is made greater than 90", it becomes difiicult properly to shape surface 32, so that this surface possesses good sound reflecting qualities, without the member 20 itself becoming so large as to consume a portion of the available frontal area. For economy of construction and greatest space saving, the maximum angle of inclination of speaker I! with respect to the front panel l0 should be approximately 90 minus the angle indicated at C on the drawing.

The side surfaces 40 of the speaker supporting member 29 may be developed in a manner similar to that explained in connection with the surface 32 so that substantially all sound emanating from the diaphragm 28 is directed through the available frontal opening in the front surface Iii without multiple reflections within the cavity or semi-confined space formed by the member 28 and the speaker I? with the grille 38. With this construction of the upper surface 32, side wall surfaces 40 and inclined surfaces 3| of the member 29, the dimensions of the above-mentioned cavity or semi-confined space are kept as small as possible and effect an improvement in the sound output of the speaker I! at the bass end of the audio range which results apparently from a better loading of the diaphragm 28 by the column of air in this semi-confined space in front of the speaker. Such a result is commonly attributed only to a horn type of speaker and not hitherto achieved with the type of speaker usually employed in the conventional domestic radio re ceiver.

The member 20 may be formed from any suit- I able material, such as wood, or may be molded from a plastic material of the synthetic resin type. With any given radio chassis, by the use of different dimensions for the member 20, various sizes of speakers may be used for an available amount of frontal surface area in a particular cabinet. Thus, in a cabinet formerly limited to a speaker having a maximum dimension of 5 inches, by the use of different sizes of supporting members 20, speakers ranging up to 10 inches in diameter may be employed. Such an arrangement not only effects improvements in the output sound characteristics of the receiver, but permits an over-all design of a radio receiver with reduced dimensions for a given speaker size.

Preferably, the dimensions of the sound reflecting'member both laterally, i. e. between the side wall portions 49, and rearwardly, i. e. the farthest point of member 20 from grille 3e, are kept as small as possible in order that the space within the cabinet and behind the speaker remain as great as possible as well as to form the previously mentioned cavity to give the effect of a horn type of speaker. In some instances, where other factors permit, these dimensions may be increased to obtain the effect of a larger cavity in front of the speaker. Likewise, in order to obtain optimum bass response from the construction, the side wall surfaces 49 are fitted tightly to the inclined surface 3|, the upper surface 32, and the top surface I I.

It is thus seen that my invention provides means for improving the audio characteristics of a radio receiver by permitting the use of a larger speaker in a relatively small cabinet. By using a specially shaped reflecting surface developed in the manner disclosed above and forming a semiconfined cavity between the speaker and the front opening in the cabinet, an improved low frequency response is obtained for all sizes of speakers.

While I have shown the speaker I! as mounted above the tuning dial and chassis, it is apparent that it may be placed below the chassis without increasing the over-all height of the cabinet. Likewise, the arrangement of my invention may be employed to mount a speaker along one side of a cabinet so that a large speaker may be used with only a small amount of available frontal area.

Hence, while I have shown particular embodiments of my invention, it will of course be understood that I do not wish to be limited thereto since various modifications may be made, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by I Letters Patent of the United States is:

1. In combination, a radio cabinet having an opening therein, a cone-shaped sound emitting diaphragm of dimensions substantially larger than one dimension of said opening and supported within said cabinet at an angle to said opening, a sound wave reflector supported within said cabinet, said reflector having a pair of angularly related surfaces, said reflector being arranged at such an angle to said diaphragm that lines perpendicular to the respective sides of said diaphragm and forming equal angles of incidence and reflection with a corresponding one of said surfaces are directed through said opening.

2. A radio cabinet having a front wall having an opening therein, a cone-shaped sound emitting diaphragm having a diameter substantially larger than one dimension of said opening and supported within said cabinet at an angle to said wall, a sound reflector within said cabinet arranged at an angle with both said wall and said diaphragm, said diaphragm and said reflector having their adjacent edges arranged substantially opposite the middle of said opening and the remote edges supported respectively adjacent opposite edges of said opening, said reflector comprising a pair of angularly related surfaces arranged respectively to direct sound emitted by opposite sides of said diaphragm through said opening.

3. The combination of a cabinet having a wall with an elongated opening therein, a cone-shaped sound emitting diaphragm having a periphery whose diameter is substantially larger than the small dimension of said opening being supported within said cabinet, the periphery of said diaphragm being located in a plane which intersects the plane of said opening substantially adjacent one side of said opening, a sound reflector having an edge positioned adjacent the side of said opening opposite to said one side across the small dimension of said opening and including a pair of angularly related surfaces, one of said surfaces lying in a plane which intersects the plane of said Iperiphery at the side of said diaphragm opposite said opening and the junction of said surfaces being located substantially opposite the middle of said diaphragm, the angular relationship between said reflector surfaces and said diaphragm being such that lines perpendicular to the respective sides of said diaphragm and forming equal angles of incidence and reflection with a corresponding one of said surfaces are directed through said opening.

GEORGE F. DEVINE.

REFERENCES CITED UNITED STATES PATENTS Name Date Brown Oct. 27, 1936 Number

Images