US2247746A

US2247746A - Cabinet for phonographs

Info

Publication number: US2247746A
Application number: US343107A
Authority: US
Inventors: Alexander D Burt
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1940-06-29
Filing date: 1940-06-29
Publication date: 1941-07-01
Anticipated expiration: 1958-07-01

Description

July 1, 1941. A. D. BURT CABINET FOR PHONOGRAPHS Filed June 29, 1940 (air-r T 63 T I Zinnentor r5510 ttorneg Patented July 2, 1941 J UNITED STATES PATENT ,OFFICE CABINET-FOR. PHONOGRAPHS Alexander D. Burt, Haddon Heights, N. J assignor to Radio Corporation of America, a corporation of Delaware Application June 29, 1940, Serial No. 343,10!v

11 Claims.

This invention relates to cabinets for housing sound-reproducing apparatus, and more particularly to an acoustic filter therein for attenuating sounds of certain frequencies reproduced by phonographs housed therein.

The term phonograph" is usually applied to a system in which a needle follows the undulations fin the groove of a record and transforms the undulations into corresponding acoustical or electrical variations. Where, for example, an

electrical pickup device is employed in conjunc-- tion with the record, the mechanical variations therein due to the motion of the needle are transferred to the mechano-electrical transducer and are transformed into the corresponding electrical variations. The vibration of the various elemerits of the pickup and the vibration of the recrd itself due 'to the interaction between the Y needle and the record results in the production of very high intensity sounds by direct transformation from. mechanical variations into acoustical variations of the air immediately surrounding the pickup. Because of the relatively small sizes of the vibrating elements, most of this energy is confined to the high frequency region,.

and the conditions under which this sound is generated generally leads to considerable distortion-in the sound emanating directly from the pickup and normally reaching'the ear of the listener during operation thereof.

Another object of my present invention is to provide an improved'cabinet as aforesaid which is simple in construction, inexpensive to manufeature, and highly eflicient in use.

In accordance with my-invention, 1* provide either in the upper ends of the walls constituting the body of the cabinet and'against which the cover is adapted to close, or in that portion of the cover itself which overlies; the aforementioned wall ends, one or more grooves or slots running lengthwise of the wall edges or running parallel to the periphery of the cover. Preferably, these groovesshould extend continuously all around the cabinet, the grooves cbnstituting acoustic capacitances which are in shunt relation to the acoustic inertance provided by the. slight space between the walls of the cabinetandthe cover when the cover is closed. If desired, the

space between the cabinet body and the cover may be filled with a material providing an acouspickup and the record. Another objectionable feature found in conventional phonographs of the type under consideration is that the sound of high frequencies due to the mechanical vibration is not in phase with the sound emanating from the loudspeaker connected to the pickup through a suitable amplifier because of the short tic resistance, such asfelt. In any case, the resulting arrangement provides alow pass acoustic filter which is very effective to attenuate the higher frequencies.

. The novel features that I consider character-- istic of my invention are set forth with particularity in the appended claims.- The invention itself, however, both as to its organization and method of operation, as well as additional objects wave-lengths of the higher frequency sounds.

Also, sounds emitted directly into the-atmosphere as a result of the mechanical vibration ofthe pickup device and/or record are not necessarily harmonically related to the sound produced by the loudspeaker, nor can their volume be cone Thus, when the volume of sound emitted by the loudspeaker is low, that emittedibythe pickup and record become even more noticeable and objectionable. For theforegoing reasons, it

I is desirable to suppress the sound which issues directly from the pickup and record system, and the primary object of my present invention is to provide an improved phonograph cabinet which will accomplishthis purpose.

More particularly, it is an object of my present invention to provide, in a cabinet for housing ""solmd-reproducing apparatus such as a phonograph, an acoustic filter which will attenuate sounds emanating directly from the record and and advantages thereof, will best beunderstood from the following description of several embodiments thereof, when read in connection with the accompanying drawing, in which Figure 1 is asectional view of a cabinet according to-one form of my invention;

Figure 2 is a top elevation of the body portion thereof with the cover removed, j

form of my invention,

Figure 4 is a fragmentary section of still an other form of my invention,

Figure 3 is a fragmentary section of another I and a cover B hinged'to one of the walls, such as the wall I, and adapted to overlie the upper ends of the walls when the cover B is in closed relation to the body A. The body A is of hollow construction and is provided with a partition or motor board I upon which is mounted a suitable phonograph which includes a sound-reproducing instrumentality, such as an electrical pickup device I I.

Due to manufacturing inaccuracies, warpage in the wood oi which the cabinet is made, and other similar causes, there is a small space It between the cover and the bodyin practically all cabinets. This space has been somewhat exaggerated in the drawing by having the cover B rest on the hinge II and on a pair of rubber or felt bumpers II.

It is through thisspace that sounds emanatin directly from the pickup device II and a record it due to the mechanical vibration thereof pass out to the exterior of the cabinet and cause considerabie annoyance, especially at the higher frequencies. a

In order to overcome this diiilculty, I provide one or more grooves orv slots II in the upper ends of each of the walls of the body A in accordance with the form of my invention shown in Figs. 1 and 2. The slots 2| runalong the lengths of the upper edges of the walls and continue all the way around the cabinet, as clearly shown in Fig. 2. Any suitable number of slots may be provided and they may be of any desired width and depth.

In any case, the 'slotsll are in shunt relation to the small spaces 23 constituting acoustic inertances for the passage of sound waves from withductances m1, m, m: and mi correspond to the acoustic inertances of the small spaces 23 Just referred to, and 01, ca, correspond to the acoustic capacitances provided by the cavities or grooves II, then the electrical analogue will be as shown in Fig. 5 wherein it will be noted that the capacitances c1, c2, 0: are in shunt'relation to the inertances or inductances mi, 1m, ma, m4, etc. Thus. the acoustic system of Figs. 1 and 2 constitutes a low pass filter which will pass only the lower frequencies but which will attenuate the higher frequencies.

In the form of my invention shown in Fig. 3, I provide the. slots II inthe marginal portion of the cover 3, that is, in the portion thereof which overlaps the body walls. In other respects, the

provided a novel cabinet which will suppress the l. A cabinet for housing sound-reproducing apparatus comprising a body portion and a cover portion movably associated therewith, said parts having portions thereof in overlapping relation when said cover is closed with respect to said v body, and at least certain of said overlapping portwo cabinets are alike, and the operation of the acoustic network in this form of my invention is the same as in that previously described.

If desired, the grooves ll may be formed both in the ends of the cabinet walls and in the cover .-B, as shown in Fig. 4. In this case, the two sets as the felt II shown in mg. 4. In the latter case,-

there will be includedin each branch a resistance n. n, etc., in series-with the inertance mama, etc., as shown in Fig. 6. I

From the foregoing description, it will be apparenttothoseskilledintheartthatIhave'lfi tions being provided with at least one cavity constituting an acoustic capacitance.

2. A cabinet for housing sound-reproducing apparatus comprising a body portion and a cover movably associated therewith, said parts having portions thereof in overlapping and slightly spaced relation when said cover is closed with respect to said body, the space between said cover and saidbody permitting the passage of sound waves emanating from said apparatus out to the exterior of the cabinet and constituting an acoustic inertance therefor, and at least certain of said overlapping portions being provided with one or more cavities constituting acoustic capacitances' adapted to cooperate with said acoustic inertance to attenuate at least a portion of said sound waves.

3. The invention set forth in claim 2 characterized in that said cavities are arranged in shunt relation to saidspace. i

4. The invention set forth in claim 2 characterized in that the end portion of one of said parts is substantially contiguous to the other of said parts and characterized further in that said cavities are constituted by one or more grooves formed in said end portion and extending longitudinally thereof.

5. A cabinet for housing sound-reproducing apparatus comprising a body part constituted by a plurality of interconnected walls and a cover hinged to one of said walls and adapted to overlie the ends of said walls when in closed relation to said body, the ends of said walls adjacent said cover being provided with one or more grooves extending along the lengths-thereof.

6. A cabinet for housing sound-reproducing apparatus comprising a body part constituted by a plurality of interconnected walls and a cover hinged to one of said walls and adapted to overlie the ends of said walls when in closed relation to said body, the portion of said cover which overlies said ends being provided with one .or more grooves extending substantially parallel to the periphery of said cover.v

'7. A cabinet for housing sound-reproducing apparatus comprising a body part constituted by a plurality of interconnected walls and a cover hinged to one' of said walls and adapted to overlie the ends of said walls when in closed relation to said body, the ends of said walls adjacent said cover being provided with one or moregrooves extending along the. lengths thereof, and the portion of said cover which overlies said ends being also provided with one' or more grooves extending around said cover in parallel relation to said first-named grooves.

8. Theinvention set forth in claim 7 characterized in that the grooves in saidwall ends and "the grooves in said cover are arranged in aligned relation.

9. The invention set forth in claim I characterized in that the grooves in said wall ends and the grooves in said cover are arranged in superposed relation, and characterized further in that the pair of grooves of any superposed set of grooves are each of the same width.

10. A cabinet for housing sound-reproducing apparatus comprising a body part and a cover part movably associated therewith, said parts having portions in overlapp n relation when-said cover is closed with respect to said body and be-