US1844803A

US1844803A - Acoustic device

Info

Publication number: US1844803A
Application number: US503999A
Authority: US
Inventors: John D Seabert
Original assignee: GEN MOTORS RADIO CORP
Current assignee: GEN MOTORS RADIO CORP; GENERAL MOTORS RADIO Corp
Priority date: 1930-12-22
Filing date: 1930-12-22
Publication date: 1932-02-09
Anticipated expiration: 1949-02-09

Description

Feb. '9, 1932. J. D. SEABERT 1,344,803

ACOUSTIC DEVICE Filed Dec. 22, 1930 INVENTOR 4,44; ATTORNEYS Patented Feb. 9, 1932 UNITED STATES FATE QFFFIQE JOHN D; snannnr, OF DAYTON, ox qnssmnon r o GENERAL morons nemooow- Tron; A conPoRATIoN oFoHIp aoonsvnc DEVICE This invention relates to an acoustic device and more particularly to acoustic devices such as loud speakers for mounting in the dome of automobiles.

In the conventional speakers or reproducers that are used for reproducing signals from radio receivers, phonographs and the like it is customary to provide a baflle, a sound chamber, or the. like which greatly improves the acoustic pro erties of the reproducer.

When repro ucers are mounted in the dome of automobiles the spaceavailable for a bafile or for a sound chamber is so, limited that a baflie extending, radiallyfrom the peripheryv of the diaphra in cannotver ,well be used and due to the s fallownessoft 1e top ofa car a suitable sound chamber cannot be provided. If either a baflle or a sound chamber were to be used the reproducer due to the shallowness of the top wouldextend down so as. to interfere with the comfort of the passengers.

An object of this invention is to eliminate the conventional sound chamberand the conventional battle that extends radially from the periphery of the diaphragm. This, has been accomplished by providing an internal baflie so OOIlSjtIllQlZfidilIid arranged, as to increasethe length of the pathof'thesound waves especially the low frequency notes and so as to dampen the flow of air from oneside of the diaphragm to the other thereby accomplishing the same results Or substantially the same results as though a sound chamber were used or a battle extending radially from thediaphragm were used.

Another object of this invention isto provide a reproducer that is very shallow in comparison with its width. This has been accomplished by providing a reentrant die phragm soas to reduce the altitude of the diaph m Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodimentof one form oi the present invention is clearly shown.

In the drawings: a

'1 represents a front view of an acoustic device part .ofwhich is shown-in takenon the line 1-1 ofFigliz.

Fig. 2 representsasection taken line 2.2 of Fig. 1

Referring-tome drawings p rticularlyto Fig. 2, a supporting or plate 20 has attach d thereto a cupshaped held housing 22, a center pole piece E l e Rd a reenforcing ple eze apted t i e fi i t permeability jofthe base 28 ofthe heldhdqsl s A adl al re -fl w sithefi hte P lQ. pi 24 Pres t eve .a enrtut of h aid. 1 s i g. 2,2 h ure r e P at 20. and the reenf cmg Plate 2 nd is riveted thereto, thus securingfthe housing 22 eenter pole piece 24 and plate 26 to the sup prtingplate ZO. Th s could beaccomplisliefin any other suitable and. well. .known A nnul P p e 3 r ttaehe m t field hous ng 22 by snotwelding or ne other su table manner, carries areentorcing ferric-magnetic ring .34, whi h is welded to pr otherwise secured to the annular pole .32, The reenforoing ring 34. decreases flux density, reu h the {ai ,gap

Amagnetic c0il; having two terminals-38 and 40, connected-to either. a source ofdirect Ql llent .or to a source of rectified current so as to excite the magnetic field,- links the center pole piece 24. Inter osed between the uppermost layers of the eldv coil 36 and the an- Pal Pieee 13 i a sewe of any; e rac ma r tha p ventsaxia movement of the fieldccoil 36.

p A reentrant .diaphragrn42 that, includesa pair of frustoeconicalsurfaces is hel. in pbsi ie ya 0v r n .T ed th r entrant diaphragm {iZ-isattached to the ring y ce e .0 any othe u b b nd n material, cloth ring 44 has r r p ryelamp d between a ine d er ainping member 48 of suitableshapeand the e d r Provided by the la vr' p ate baffle 2; y reW i h 5 i ppor e v pqn. ehoflw a ing mem rs 56 through which extend the screws .58, threade y en aein ih rba fi 5 se 0- Th b fl p ourse ca hamp redd properly positiol fid by any other suitah e eans A l a nul p01 p t -'32 y swi e.

closely located to the baflle 52 as its inside diameter is only slightly larger than the outside diameter of the annular pole piece 32, it is The baffle 52 also increases the length of the V path of the air from the inside of the diaphragm to the outside. This increase in the 'air path improves the acoustic properties of the reproducer. The restricted opening found between the bafie 52 and the annular pole piece 32 probably tends to reduce undesired reverberations, caused by the'rather shallow type of reproducer.

The diaphragm 42 also carries a speech 1 coil 62, wound upon'a cylindricalsupport 64,

which is cemented to or otherwise secured to the inner inclination of the diaphragm 42 as at 66; I V

In order to properly centerthe cylindrical support 64 with respect to the center pole piece 24'and the air gap 33 between the center pole piece 24 and the annular pole piece 32 and the reenforcing plate 34, a spider 68 is cemented toor'otherw-ise secured to the inner inclination of the'diaphragm '42 as at 7 and fastened to a reduced portion 7 2 of the center pole piece 24 by a screw. 74'. The spider '68 allows axial play of the cylindrical support 64 with the speech coil 62, but prevents any radial deflection thereof. The spider 68 and the flexible ring 44 exert a restoring force upon the diaphragm whenever the diaphragm is displaced. I 7

A cover plate or grille 76 of suitable design,

provided with several openings 78 to allow suflicient air to flow through is supported by the studs 80, riveted at 82 to the supporting plate and located by the screws 84, threaded 7 into the'studs 80. f

Operation Whenever the diaphragm of a reproducer. is displaced due to the'flow of signal current through the speech coil unequal air pressure I will result on opposite sides of the diaphragm.

If'no baffle or the like is used the air tends to flow around theedge of the diaphragm from the high pressure to the low pressure side,- thereby equalizing the pressure without any substantial displacement of the air away from the diaphragm, thereby greatly reducing the efficiency of the reproducer. Unless the displacement is extremely large the in- V ternal baflle plate 52'prevents a free flow of air from the high pressure side to the low pressure side of the diaphragm, thereby preventing a too sudden equalization of the unequal air pressure on the opposite sides of a the diaphragm, but at the same time permitting a suflicient flow of air either into or out of the cavity found intermediatethe baffle 52 and the diaphragm 42. It has been found that the baflle 52 accomplishes the same result as though either a sound chamber or an external bafie extending outwardly'from the diaphragm were used.

The leakage effect of the bafiie 52 may be further controlled by suitable perforations, not shown, if this is found desirable.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all comingwithin the scope of the claims whlch follow. I

What is claimed is as follows:

LA reproducer for automobile use, comprising a supporting disc, a reentrant dlaphragm, supports for supporting the reentrant diaphragm'in spaced relation wlth respect to said disc, a movement mounted 1ntermediate said disc and said diaphragm, and an internal batfle extending from the outer periphery of the diaphragm inwardly towards saidmovement whereby the free flow of air from one side of the diaphragm to the other is limited.

, '2. A reproducer for reproducing sound in response to electrical impulses, a diaphragm, a'movement for actuating said diaphragm, a disc-like frame for supporting said diaphragm and said movement in spaced rela-' tion, and an internal baflie extendinginwardly from the outer periphery of the diaphragm, soas to increase the length of the path of the air from one side of the diaphragm to the other. 7 V

3. An acoustic device, comprising, a diaphragm, a baffleextending radially from the outer periphery of said diaphragm, said baffle having an annular flange, and an annular clamping member cooperating with the flange to clamp the edge of the diaphragm.

4. An acoustic device, comprising in combination, a diaphragm, a battle extending inwardly from the edge of the diaphragm, said baflie having an annular flange at the outer periphery, an annular clamping member having a flange, the outer edge of the'diaphragm being clamped between the flange of said baffle and the flange of said clamping member.

5. An acoustic. device, comprising in combination, a housing including a disc shaped member, a diaphragm, supporting members attached to said housing for supporting said diaphragm, and a grille mounted opposite said housing for protecting the diaphragm, supports for said grille, said supports for the grille being independent of the supports carrying the diaphragm.. 5 V

6. An acoustic device, comprising in combination, a disc-shaped housing, a plurality of rows of concentric rows of supports carried by said housing, a diaphragm, and an inwardly extending baflle support on one row of supports and a grille protecting said diaphragm supported on another row of supports.

7. An acoustic device, comprising in combination, a disc-shaped frame, a movement mounted in the center of said frame, a plurality of concentric rows of sup orts carried by said frame, an annular ba e carried by one of said rows, a diaphragm mounted on an edge of said bafile, said diaphragm being actuated by said movement, and a grille for protecting said diaphragm mounted on another row of said concentric supports.

8. In an acoustic device, a frame, a driving movement mounted on said frame, a diaphragm, a grille, and a plurality of rows of supports, one of said rows of supports supporting the diaphragm and another row the grille whereby the ille and the diaphragm are mounted on in ependent supports.

In testimony whereof I hereto afiix my signature.

JOHN D. SEABERT.