US2852089A - Combined loudspeaker diaphragm and horn - Google Patents

Description

Sept. 16, 1958 A. B. COHEN EI'AL COMBINED LOUDSPEAKER DIAPHRAGM AND HORN 4 Sheets-Sheet 1 Filed Jui 2. 195a FICIJQ.

Slum/Mm Sept. 16, 1958 A. B. COHEN ETAL COMBINED LOUDSPEAKER DIAPHRAGM AND HORN Filed July 2. 1956 I 4 Sheets-Sheet 2 Spt.16, 1958 A. B. CQ'HEN ETAL 2,852,089

COMBINED LOUDSPEAKER DIAPHRAGM AND HORN FiledJuly 2, 1956 4 Sheets-Sheet a Sept. 16, 1958 A. B. COHEN ETAL COMBINED LOUDSPEAKER DIAPHRAGM AND HORN 7 4 Sheets-Sheet 4 Filed July 2. 1956 United States Patent COMBINED LOUDSPEAKER DIAPHRAGM HORN Abraham B. Cohen, Bronx, and Sidney Levy, White Plains, N. Y; said -Cohen, assignor, by mesne assignments, to Arthur Blumenfeld, New York, N. Y.

Application July 2, 1956, Serial No. 595,408

' 7 Claims. (Cl. 181-31) This application is a continuation-impart of -,0 ur copending application Serial No. 536,624, filed September 26 1955.

The present invention relates to attachments for loudspeaker diaphragms, and more particularly to a novel attachment which is adapted to be associated with aloudspeaker diaphragm in such a manner and which is so constructed as to improve the mid-frequency and the high frequency response of a loudspeaker embodying the invention.

Heretofore, loudspeaker diaphragrns have been provided with supplemental or auxiliary sound diifusjing attachments which are adapted to increase the spread or dispersion of the mid-frequency sound waves generated by the diaphragm, wherein the attachments are in the form of transversely arched stiffeners of circular form. Such stiffeners are generally provided with apertures therethrough, whereby sounds generated behind thestiifeners are diffused at the apertures and dispersed in all directions, or concentrated and directed towards the axis of the path of sound vtravel, as disclosed in our prior Patent No. 2,641,329, dated June 9, 11953.

In other previous types of loudspeakers, specially designed horns have been developed for producing a more uniform dispersion of sound over the horizontally extended area in front of the speaker, whilelimiting vertical spread or dispersion of the sound waves, as disclosed in Patent No. 2,690,231, dated September 28, 1954.

The present invention contemplates as its primary objective the combining in a sound reproducing structure of the desirable characteristics of a diffuser and a special horn, both as above referred to, whereby the mid-frequency and high frequency responses of the loudspeaker are improved.

Another objective of the present invention is to provide a conventional conical loudspeaker diaphragm having an auxiliary or supplementary sound propagating or diffusing attachment which is so constructed as to either direct the middle or high frequency sound waves generated adjacent to the apex or center of the diaphragm, or generated by the attachment itself, axially with uniform peripheral dispersion; or alternatively, to maintain at a minimum the sound radiation or dispersion in vertical directions, thereby conserving signal energy which is utilized to expand the horizontal sound radiation or dispersion.

The foregoing objectives may be attained by the utilization of a supplementary horn-like attachment which is so formed as to be capable of being attached to a conventional conical diaphragm adjacent to the central axis of the latter, or adjacent to the usual voice coil bobbin with which such loud speaker diaphragms are usually provided, and which may be formed with side walls which flare laterally or horizontally to alarger extent than the top and bottom walls do vertically, while defining a substantially rectangular mouth at the soundoutlet end of the horn-like attachment.

As will hereinafter appear, the supplementary-,horn-like '2 attachment may have any number of difierent forms,.and instead of having a rectangular mouth defined by lateral or vertical walls which are spaced further .apart than the top and bottom horizontal walls, the mouth may be square or even otherwise shaped.

In addition, the flare or expansion of the horn-like attachment may be produced in .various ways, as by the provision of relatively straight diverging walls, or by longitudinally arched walls composed of symmetrically generated surfaces, or by walls having compound angles of divergence. In the latter case, the compound angles of divergence or expansion of the opposed walls of the attachment are preferably such that dispersion of the sound waves is predominant in a vertical direction initially, with subsequent dispersion of the sound waves predominantly in a horizontal direction, and during the subsequent dispersion stage aforementioned, .the opposed top and bottom walls which restrict vertical dispersion serve to build up pressure which increases the signal energy or amplitude in a horizontal direction.

A still further objective of the invention is to provide a sound reproducing assembly comprising a pair of coaxially arranged sound propagating elements adapted to be actuated or vibrated by a common voice coil toproduce sound waves, one of said elements being such that the sounds are generated over a wide angle in one plane, while restricting such sound waves to limit dispersion in a plane normal to the first-mentioned plane.

Other objects and advantages of the invention will be hereinafter described or will become apparent to those skilled in the art, and thenovel features thereof will be defined in the appended claims.

In the drawings:

,Fig. l is a view in perspective, showing a loudspeaker diaphragm having a symmetrically generated conical form of hornlike attachment mounted in assembled relation to the diaphragm in accordance with our invention, with peripheral defraction apertures located at the enlarged boundary of the horn like attachment for purposes of defraction of sound from the areas of themain diaphragm located behind thehorndike attachment;

Fig. 1a is a fragmentary sectional view through the central portion of the diaphragm assembly of Fig. 1;

'Fig. 2 is another view in perspective, showing a loudspeaker diaphragm having .a symmetrically generated curvilinear form of horn-like attachment mounted inassernbled relation to the diaphragm in accordance with our invention, and also with peripheral defraction apertures located at'the enlarged boundary of the horn-likeattachmerit for purposes of defraction of sound from theareas of the main diaphragm located behind the horn-like attachment;

Fig. 2a is a view in side elevation of the horn-like attachment of Fig. 2;

Fig. '3 is a view in perspective, showing .a loudspeaker diaphragm having another modified horn+like attachment which 'is so constructed as to produce minimum sound radiation or dispersion in vertical directions, thereby saving signal energy which is utilized to expand horizontal radiation or dispersion where this form of horn-like attachment is composed of straight-sided boundary walls, with peripheral defraction-apertures located at the enlarged boundary of the horn-like attachment for purposes of defraction-of sound from the areas of the main diaphragm located behind the horn-like attachment;

Fig. 4 is a view in perspective, showing a loudspeaker diaphragm having still another modified form of hornlike attachment which is so constructed as to produce minimumsound radiation or dispersion in vertical directions and thus saving signal energy which is utilized -to expand horizontal radiationor dispersion where this form of horn .is composed :of arched boundary walls-with peripheral defraction apertures located at the enlarged boundary of the horn-like attachment for purposes of defraction of sound from the areas of the main diaphragm located behind the horn-like attachment;

Fig. 5 is a View in section taken on a central plane across a loudspeaker diaphragm having a still further modified form of horn-like attachment mounted in assembled relation with the diaphragm; and

Fig. 6 is a view in section, as taken on the line 6-6 of Fig. 5.

Like reference characters designate corresponding parts in the several figures of the drawings.

Referring first to Figs. 1 to 4, the reference character 1 denotes a conventional cone-type loudspeaker diaphragm having an enlarged mouth bordered by a compliant corrugated marginal flange 2 adapted to be mounted on a suitable support (not shown). The diaphragm 1 tapers towards its end remote from the flange 2 and is provided with a central opening in which is adapted to be disposed the usual cylindrical voice coil support or bobbin 3 on which is disposed a voice coil winding 4. Bridging the forward end of the voice coil bobbin 3 in a conventional manner to provide a dustcap or closure to preclude the passage of dust or other foreign matter through the bobbin into the area behind the diaphragm, is a domed closure 5 which is preferably integrally formed on the bobbin 3.

The various elements described in the foregoing are conventional, and ordinarily, the apex or small end of the diaphragm 1 would be attached, as by cement, to the outer periphery of the bobbin 3, and therefore, the dia phragm is shown as having thereon a short, axially extended flange 6 at its apex end, which enables convenient attachment of the diaphragm 1 to the voice coil bobbin 3. However, in the illustrative embodiments of the present invention, an anchoring tab or flange 7 of a horn-like attachment generally designated 8, is interposed between the bobbin 3 and the diaphragm flange 6, and these elements are preferably secured together in assembled relation as by cementing or the like.

The horn-like attachment 8, is seen in Figs. 1 and 1a, is composed of symmetrically generated side walls which diverge away from the flange 7, and which are straightsided surfaces of revolution, thus defining a symmetrical, conical, horn-like member, the outer or forward end of which is spaced inwardly from the walls of the main diaphragm 1, with the mouth freely suspended in space and preferably within the confines of the main diaphragm 1. At the mouth or forward end of the horn-like attachment 5, the walls thereof are preferably turned radially outward to form an edge-stiffening flange ltl, although it should be understood that this stiffening flange is unes'sential where the horn-like attachment is composed of a material having suflicient inherent stiffness.

A generally similar horn-like attachment is shown in Figs. 2 and 2a, said attachment differing from that shown in Figs. 1 and in by the arched form of the walls of the attachment which define a symmetrical curvilinear horn. In this modification, corresponding parts of the assembly are designated by primed reference characters.

The further modified horn-like attachment in Fig. 3 is designated 8", and is composed of straight-sided walls, with the lateral walls W thereof interconnecting opposed top and bottom walls 11", each of which walls diverges away from the flange '7 (not shown in this view), and terminates in co-planar relation at their forward ends, thereby defining a non-symmetrical pyramidal horn having a rectangular mouth at its forward end. The forward extremity of each of the walls 9", 11 is preferably turned outward and back upon itself to form a reinforcing bead 10".

Fig. 4 shows another modification of the horn-like attachment which generally corresponds to that of Fig. 3, but in which the walls 9" and 11 are arched and define a progressively expanding sound passage within the 4 same, with the walls becoming substantially flat at their forward ends where they terminate in a rectangular month which may have a reinforcing bead 10" extended thereabout. The form of this modified attachment may be characterized as non-symmetrical, curvilinear pyramidal.

It will be understood that in each form of the hornlike attachments described in the foregoing, they have at their so called rear ends a circular opening defined by an anchoring flange or tab 7, as shown in Fig. 1a, and the walls of the attachment diverge away from the opening to form a progressively expanded horn-like member. Preferably, the angle of divergence of the lateral walls 9 in Fig. 3 and 9' in Fig. 4, is larger than the angle of divergence of the opposed top and bottom walls 11" and 11", so that a generally rectangular mouth is provided in these forms of the horn-like attachment, said mouth having a greater lateral extent than vertical extent.

In addition, the angular relation of the walls 9 or 9" and 11" or 11, may be such that they either subtend the solid angle, or such that the progressive internal expansion or flare of each horn-like attachment conforms to one of the conventional exponential rates which may be readily determined by the use of any well-known formula for determining the flare or expansion factor of loudspeaker horns.

As illustrated in Figs. 1 through 4, the forward peripheral margins or boundaries of the horn-like attachments are preferably provided with a plurality of sound defraction apertures or openings designated 14, said openings being disposed in spaced relation to each other in one or more rows or in any other appropriate dispersed relation. When such openings are provided, the sounds generated by the diaphragm 1 behind the horn-like attachments will not be trapped or reflected, but will pass through the respective openings 14 and will be dispersed in wavelets emanating from each opening.

In the circular mouth type of horn attachments shown in Figs. 1 and 2, the middle and high frequency sound waves generated by the attachments and by the diaphragm 1 behind the respective attachments will be radiated in a uniformly solid angle.

On the other hand, in the forms of the horn-like attachments shown in Figs. 3 and 4, the middle and high frequency sound waves generated thereby or at the rear end of the assembly will be directed in a wide horizontal area while limiting vertical spread or dis ersion of such middle and high frequency sounds.

While in each of the specific illustrative embodiments described in the foregoing, the horn-like attachments are shown as being secured to the outer periphery of the voice coil bobbin, it should be understood that the rear end A of each attachment may be secured to the diaphragm at other points, without departing from the invention, as by anchoring the same on the domed cap 5 of the bobbin 3, or on 'the body of the diaphragm l at a position forwardly spaced from the bobbin 3.

In Figs. 5 and 6, there has been shown a diaphragm 1 provided with a compliant marginal flange 2 and a voice coil bobbin 3 having a voice coil winding 4 thereon, said bobbin having a dust cap or closure 5, and the diaphragm being provided with a flange 6 at its small end, all as in the other forms of our invention hereinbefore described. In these views, a still further modified form of horn-like attachment generally designated 18 has been shown, said attachment being so constructed as to provide, in effect, two successive horn sections having similar rates of expansion of their cross-sectional a ca, these sections being respectively designated 19 and 29. The innermost section 19 of the horn-like attachment 1% is composed of 4 walls of which 21, 21 are shown in vertical section in Fig. 5, these walls diverging at a given angle from the 21, 21. Thus, these 4 walls describe a frustrum of a rectangular pyramid, and if successive planes are extended through the horn section 19 perpendicular to the central axis of the assembly, they would intersect the walls on lines embracing areas according to the law of progressional increase of area as a function of the distance of the intersecting plane from the smaller base of the rectangular pyramidal frustrum, and this progressive increase in area would be a direct function of the position of the intersecting plane on the central axis and directly proportional thereto. In like manner, the outer terminal end section 20 of the horn-like member 18 has 2 sets of walls respectively identified as 24, 24 shown in vertical plan in Fig. 5, and 23, 23 shown in horizontal plan in Fig. 6. These latter 4 walls diverge in a vertical plane to a greater degree than the walls in the horizontal plane. Despite the fact that the respective degree of divergence of the walls of section is the reverse of that of the section 19, they may be so proportionately diverged that the progression of area increase in the case of section 20, along the axis, is the same as that of section 19, thereby resulting in two successive horn sections having similar rates of expansion of their cross-sectional areas. Even though the respective horn sections have similar rates of expansion, the fact that the vertical walls 24, 24 diverge away from the axis more than the horizontal walls 23, 23 will help maintain a minimum sound radiation or dispersion in the vertical directions, thereby conserving signal energy which is utilized to expand the horizontal sound radiation or dispersion. The lateral walls 22, 22, from a practical standpoint, may be approximately parallel, but preferably diverge to some extent to facilitate moulding of the attachment. On the other hand, the opposed top and bottom walls 23, 23 of section 20 of the horn-like attachment 18 are slightly divergent, and may, in fact, be approximately parallel except for such slight divergence as may be necessary or desirable to facilitate manufacture of the attachment as aforementioned, while the opposed lateral walls 24, 24 of section 20 diverge at a relatively wide angle, whereby expansion of the sound waves in section 20 is primarily lateral or horizontal, or in other words, is normal or perpendicular to the direction of expansion in section 19.

The mouth of the horn-like attachment 18 may be either square or oblong, as preferred, so long as the expansion of the sound in section 20 is greater in one plane than in a plane at right angles thereto. While no sound detracting or dispersing apertures have been shown in Figs. 5 and 6, it is to be understood that the horn-like attachment of this form of our invention may be similarly provided with such apertures corresponding to those designated 14 in the other forms of the attachment which have been previously described herein.

The respective horn-like attachments herein disclosed are preferably fabricated of paper of a fibrous character capable of being molded, but the attachments may be made of other materials such as thin plastic, aluminum, or the like, which are light in weight and have sufficient rigidity to maintain their form without distortion under vibration.

Other changes and alterations may be made without departing from the spirit of the invention as defined in the appended claims.

We claim:

1. A sound reproducing device, comprising a vibratory diaphragm and an axially extended horn-like attachment mounted co-axially with relation to said diaphragm and connected thereto for vibration therewith, said attachment having a small end operatively secured to said diaphragm and progressively expanding in cross-sectional area from the small end and terminating in a freely suspended large end, said horn-like attachment having a plurality of sound diffusing openings therein adjacent to its large end for liberating and diffusing sound waves generated by the diaphragm behind said attachment.

2. A sound reproducing device as defined in claim 1, wherein said horn-like attachment has a symmetrically generated, conical form and terminates in a circular mouth.

3. A sound reproducing device defined in claim 1, wherein said horn-like attachment has opposed walls diverging in straight lines from the small end to the large end thereof and defining a generally rectangular mouth at the large end of the attachment.

4. A sound reproducing device as defined in claim 1, wherein said horn-like attachment has opposed Walls extending longitudinally of the attachment at compound angles and forming a plurality of expansion sections, with certain of the walls of one section diverging at a greater angle than those of the other section.

5. A sound reproducing device as defined in claim 1, wherein said horn-like attachment comprises a plurality of axially aligned sections having similar expansion factors, said sections expanding predominantly in diflerent directions.

6. A horn-like attachment for vibratory loudspeaker diaphragm assemblies as defined in claim 1, wherein said attachment is composed of a pair of axially aligned sections, with one section expanding predominantly in one plane and the other section expanding predominantly in a plane normal to the first-mentioned plane, and said attachment having a generally rectangular mouth.

7. A horn-like attachment for vibratory loudspeaker diaphragm assemblies as defined in claim 1, wherein said attachment progressively flares towards its freely suspended end and includes a plurality of axially aligned sections respectively flaring at different angles relative to the axis of the attachment.

References Cited in the file of this patent UNITED STATES PATENTS 1,984,542 Olson Dec. 18, 1934 2,565,069 Engholm Aug. 21, 1951 2,685,935 Lenz Aug. 10, 1954 OTHER REFERENCES ArticleAudio Engineering, December 1952, pages 24-25, Wide-Angle Dispersion of High Frequency Sound, by A. B. Cohen.

Article-Radio and T. V. News, November 1953, pages 71-72, Exponential Horn Design, by J. F. Sodaro.

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