US3526718A - Portable speaker assembly for large areas - Google Patents

Description

Sept. 1, 1970 D. L. BEATTY 3,526,718

PORTABLE SPEAKER ASSEMBLY FOR LARGE AREAS Filed April 17, 19,67 2 Sheets-Sheet 1 f f 1 M I g y 1 5P6 X t I i l l l l J4 I Jl 4 If 2 INVENTOR. David 1. fleafly BY I E A ffor'ney.

Sept. 1, 1970 D. BEATTY PORTABLE SPEAKER ASSEMBLY FOR LARGE AREAS 2 Sheets-Sheet 2 Filed April 17, 1967 a F i l} INVENTOR. Dar/a L fieafly United States Patent 3,526,718 PORTABLE SPEAKER ASSEMBLY FOR LARGE AREAS David L. Beatty, 10712 E. 84th Terrace, Raytown, Mo. 64138 Filed Apr. 17, 1967, Ser. No. 631,346 Int. Cl. H04r 1/02, 27/00 US. Cl. 1791 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to new and useful improvements in speaker assemblies for public address systems and the like, and has particular reference to speaker systems especially adapted for use in servicing large areas such as auditoriums, field houses, concert halls and similar buildings, as well as outdoor areas such as parking lots, Where public gatherings are often held.

Modern requirements for high-fidelity sound reproduction in systems of this type require the use of separate speakers for high and low sound frequencies, in order that faithfully accurate sounds may be provided throughout the entire sound spectrum. However, the high-intensity sound levels required from the speaker system in order to blanket large areas as described with sounds at an acceptable level create certain problems in that the sound level is often oppressively intense, and even painful, for persons who must be close to the speakers. This undesirable occurrence is particularly noticeable in connection with sounds emanating from the high-frequency speakers, or tweeters, since while the low-frequency sounds tend to be rather non-directional or pervasive, so that to the listener they seem to come from no accurately detectable source but to come from all directions, and further are not particularly oppressive to the ear even when of very high intensities, high-frequency sound has very different characteristics. The sound Waves emanating from highfrequency tweeters or horns tends to be rather highly directional, proceeding from the speaker in a rather tightly restricted conical zone. The sound can be somewhat diffused, and the angle of the conical zone somewhat enlarged, but the speaker must still be aimed or directed much more accurately toward the listeners than is the case with the low-frequency speaker. Moreover, the high-frequency sound at high intensities is much more oppressive to the ear of the listener than low-frequency sound, having a greater apparent loudness, and thus creates discomfort and poor listening for those who must be comparatively close to the speakers. At the same time, the high intensity is necessary if the high-frequency sounds are to carry to the far reaches of large areas. Another comparative characteristic of high and low frequency sounds is that obstructions in the path of high-frequency sounds produce a pronounced shadow effect, tending to create a zone therebehind in which the sound cannot be heard, or can be heard only faintly. This shadow effect, being an inverse function of the wave length of the sound, is much less with low-frequency sound, said low-frequency sound apparently flowing around obstructions, and requiring a much larger obstruction to produce a shadow. While all of the above considerations can of course be 3,526,718 Patented Sept. 1, 1970 taken into account in a carefully designed permanent installation, they heretofore have presented a problem not solved in connection With portable equipment adapted to be transported easily from place to place with a minimum requirement of assembly and disassembly, installation or set-up time, and the like.

Accordingly, the principal object of the present invention is the provision of a portable speaker assembly for large areas which largely overcomes all of the above objectionable features of existing systems, in that it provides adequate coverage of large areas with sound at an acceptable level, without at the same time blasting the ears of listeners who must be relatively close to the speakers. Generally, this object is accomplished by the provision of an assembly including a floor-engaging base cabinet in which the low-frequency speakers are mounted, and a high-frequency speaker mounted in spaced relation above said base cabinet and so directed or aimed that its sound axis is disposed well above the heads of nearby listeners. The base cabinet provides the mass and resonance chamber required for best performance of low-frequency speakers, as well as serving as a supporting base for the highfrequency speaker, and the low elevation of these speakers is acceptable since the low-frequency sound will not be oppressive to nearby listeners, or shadowed by said nearby listeners or other obstructions. Since the high-frequency speaker is directed over the heads of nearby listeners, they hear the high-frequency sound as spillage or diffusion from the main sound cone of the speaker, and thus are not subjected to its full direct force, so that the high-frequency sounds are not oppressive. At greater distances from the speaker, the listeners will be angularly closer to the extended axis of the speaker, so that the high-frequency sound level will tend to be equalized at all distances within range. Both the elevation and vertical angle of inclination of the high-frequency speaker may be adjusted to the size and contour of the area being served, as will be described.

Another object is the provision of a speaker assembly of the character described having structural features contributing substantially to the ease of transportation, handling and use thereof.

With these objects in view, as well as other objects which -will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:

FIG. 1 is a front elevational view of a speaker assembly embodying the present invention, with the cabinet doors closed,

FIG. 2 is a side elevational view of the assembly as shown in FIG. 1, with parts broken away,

FIG. 3 is a fragmentary rear elevational view of the assembly,

FIG. 4 is an enlarged fragmentary sectional view taken on line IVIV of FIG. 3,

FIG. 5 is an enlarged fragmentary sectional view taken on line V-V of FIG. 3,

FIG. 6 is an enlarged fragmentary sectional view taken on line VIVI of FIG. 1,

FIG. 7 is an enlarged fragmentary sectional view taken on line VII-VII of FIG. 1, and

FIG. 8 is a sectional view taken on line VIIIVIII of FIG. 1, with the cabinet doors open.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies generally to a base cabinet normally resting on the floor or ground 4 as shown in FIGS. 1 and 2. Said cabinet is generally rectilinear in form, having side walls 6, top wall 8, bottom wall 10, and back wall 12. The front of said cabinet comprises a speaker face 14 of grill cloth or the like (see FIGS. 6 and 7) behind which, within the cabinet, are mounted one or more low-frequency speakers, or woofers, these speakers being indicated at 16 in FIG. 1. The

speaker face may be covered and protected by a pair of rigid doors 18, each door being secured at its outer vertical edge to the forward edge of the corresponding side wall 6 by means of a piano-type hinge 20. Each door covers half of the cabinet front, said doors being shown closed in FIG. 1 and open in FIG. 8. It will be noted that said doors extend downwardly to floor level, and that each door is provided along its bottom edge with an enlarged foot 22. Thus when the doors are open as shown in FIG. 8, their engagement with the floor causes them to act as stabilizers for steadying the cabinet against vibration or rocking, and to prevent accidental overturning thereof by wind or the jostling of persons thereagainst.

A recess 24 is formed in the cabinet opening outwardly through the upper portion of back wall 12. Mounted in said recess, respectively adjacent opposite sides of the cabinet, are a pair of castered wheels 26, said wheels projecting outwardly from said back wall as best shown in FIG. 4. Back wall 12 overhangs at least the upper edge portion of recess 24, intermediate said wheels, to form a hand hold 28, for a purpose to be described. Terminal posts 30, for making electrical connections to the speakers within the cabinets, may also be positioned in recess 24, for protection thereof against damage from bumping. A pair of recesses 32 are formed in the cabinet at the lower rear portion thereof, said recesses opening through back wall 12 and bottom wall of the cabinet, respectively adjacent opposite sides thereof. Mounted rotatably in each of recesses 32 is a ground-engaging wheel 34, said wheels being coaxial on a horizontal transverse axis. As best shown in FIG. 5, wheels 34 project outwardly from back wall 12, but are spaced slightly above the bottom of the cabinet when said cabinet is upright. When the cabinet is tilted rearwardly, using hand hold 28 as a grip, wheels 34 engage the ground, and the cabinet may be moved or transported in the manner of a wheelbarrow. The juncture between back wall 12 and bottom wall 10 may be rounded as indicated at 36 to facilitate this action. Also, the cabinet may be tilted to lie on its back, all of wheels 26 and 34, then engaging the ground, and the cabinet may then be moved about or transported in the manner of a fourwheeled cart, the castering of wheels 26 permitting steering thereof. In this case, the closed doors 18 serve as a platform for carrying the high-frequency speaker (to be described below) or other supplies.

Extending upwardly from top wall 8 is a standard 38 consisting of a heavy rod or pipe. The lower portion of said standard is carried for longitudinal sliding movement in a tubular guide 40 extending vertically through cabinet 2, centrally thereof, and rigidly mounted therein. This guide will not ordinarily interfere with the placement of bass speakers 16 in the cabinet, since the speakers are mounted in the forward portion thereof, the excess cabinet space providing the resonance chamber required for best performance of said speakers. The cabinet may also be provided with tube vents, not shown, to still further improve the sound quality of the speakers. Standard 38 is vertically adjustable in guide 40, being secured at the desired extension by means of a collar 42 fixed thereon by set screw 44 and resting by gravity on top cabinet wall 8.

A sleeve 46 is mounted slidably on standard 38 adjacent the upper end thereof, and adjustably fixed thereon by set screw 48. Fixed to said sleeve, as by bolts 50, is a horizontally extending arm 52. To the outer end of said horizontal arm an upwardly arm 54 is attached, by means of hinge 56, the axis of said hinge being transverse to standard 38 and offset transversely therefrom. A high-frequency speaker, or tweeter," 58 is attached fixedly to arm 54 as by bolts 60. Usually said speaker is more or less horn-shaped, often being called a horn, and is ordinarily directed or aimed to project sound more or less horizontally. Said horn projects over the upper end of standard 38, which projects above sleeve 46, and rests on said standard by gravity. It will thus be seen that the vertical angle of inclination of the horn can be adjusted by loosening set screw 48 and sliding sleeve 46 up or down on the standard. As previously noted, the sound from such a speaker is highly directional, tending to be confined to a conical zone concentric with the speaker axis. This can be partially corrected, and the sound cone flattened to cover a larger horizontal area, by means of a sound lens 62 comprising, as shown, a series of specially configurated parallel plates attached to the forward end of the horn. This lens, however, forms no essential part of the present invention, and the construction and operation thereof is not detailed herein.

In operation, it will be seen that the structure shown takes advantage of the natural characteristics of the high and low frequency sounds and the requirements for effective distribution thereof. The low-frequency or bass speakers 16 require a massive enclosure and a voluminous resonance chamber for best performance, and cabinet 2 provides this mass and volume. Its considerable mass also provides good support and foundation for the high-frequency speaker 58. Moreover, it is quite satisfactory that the bass speakers be disposed substantially at ear-level of the listeners, even if the low-frequency sound intensity must be at a high level to blanket a large listening area, and even if some listeners must be relatively close to the speakers, since as previously discussed, low-frequency, high-intensity sounds are not offensive to the ear. Furthermore, the nearby listeners themselves, or other obstructions, will not prevent the low-frequency sounds from reaching distant listeners, since obstructions have very little shadow eifect on sounds of long wave length.

On the other hand, the high-frequency sounds emanating from speaker 58 are directed outwardly over the heads of the listeners, as previously described, in a rather highly directional conical zone, or a zone of flattened conical form, concentric with the axis of the speaker. Thus, nearby listeners will be disposed in the lower peripheral portion of the sound cone, or entirely below said sound cone, in which latter case they hear the high-frequency sound as diffusion or spillage from the sound cone. In other words, their angular displacement from the speaker axis is relatively great, and due to the directional nature of this sound, they are subjected only to a fraction of the sound intensity which they would receive if they were positioned directly in the speaker axis. Thus, even nearby listeners are not subjected to the oppressive or even painful effects of high-intensity, high-frequency sound. More distant listeners, however, by virtue of the distance, will be positioned at less angular displacement from the speaker axis, and are hence subjected to a progressively greater proportion of the full sound intensity at that distance. If speaker 58 is properly positioned and directed, the apparent or effective loudness of the high frequency sound will tend to be equalized at all distances from the speaker within the design range of said speaker.

With regard to proper placement of speaker 58, its elevation from base cabinet is a function of the distance to the furthest portion of the listening area, greater required distances requiring speaker 58 to be elevated progressively higher to avoid oppressive loudness to nearby listeners. This elevation can of course be adjusted by loosening set screw 44 and sliding standard 38 up or down in guide 40. If still greater elevations are desired, standard 48 could be formed of multiple telescoped sections, within the scope of the invention. With regard to the angle of inclination of speaker 58, it-has been found in most instances that the speaker axis should be aimed at the ear level of the most distant listeners, and the sound intensity set to deliver sound at an acceptable intensity at that distance to listeners directly in line with the extended axis of the speaker. This may require the speaker to be directed slightly downwardly if the listening area is horizontal or upwardly in varying degrees if the listening area slopes upwardly away from the speakers, as in an amphitheater. The angle of inclination of speaker 58 can of course be adjused in the present structure by loosening set screw 48 and sliding sleeve 46 up or down on the standard.

While I have shown and described a specific embodiment of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention as defined by the scope of the appended claim.

What I claim as new and desire to protect by Letters Patent is:

1. A portable speaker assembly for large areas comprising:

(a) a floor-supported base enclosure comprising a cabinet having a vertical tubular guide mounted therein.

(b) a low-frequency speaker mounted in said base enclosure,

(c) a standard mounted in said base enclosure and projecting upwardly therefrom, said standard being vertically slidable in said tubular guide,

((1) a high-frequency speaker mounted at the upper end of said standard and operable to project sound, which is principally confined to a limited zone coaxial with the extended axis of said speaker,

(e) means for adjusting the degree of vertical projection of said standard above said base enclosure comprising a collar slidably mounted on said standard and resting on the top of said cabinet, and means releasably fixing said collar on said standard, and

(f) means for adjusting the angle of vertical inclination of said high-frequency speaker comprising a sleeve mounted slidably on said standard in spaced relation below the upper end thereof, means releasably fixing said sleeve on said standard, a first arm fixed to said sleeve and projecting horizontally there- UNITED STATES PATENTS 1,782,660 11/1930 Meyer 179-148 X 2,143,175 1/1939 Waite. 2,203,715 6/ 1940 Benecke. 2,288,822 7/1942 McCarron 179l48 3,165,587 1/1965 Alderson. 3,183,305 5/1965 Jespersen. 3,308,237 3/1967 Novak.

OTHER REFERENCES Column Loudspeaker Systems; Augspurger, George L.,

Electronics World, June 1963, pp. 25-26.

KATHLEEN H. CLAFFY, Primary Examiner C. W. JIRAUCH, Assistant Examiner US' Cl. X.R.

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