US3500953A - Loudspeaker system - Google Patents

Description

March 17, 1970 u. L. LAHTI LOUD-SPEAKER SYSTEM Filed Dec. 4, 1968 INVENTOR UDLEVI L. LAHTl ATTORNEKS United States Patent 3,500,953 LOUDSPEAKER SYSTEM Uolevi L. Lahti, 909 Sunset Road,

Ann Arbor, Mich. 48103 Filed Dec. 4, 1968, Ser. No. 781,133 Int. 'Cl. Gk 13/00; H04r 7/16 U.S. Cl. 18131 2 Claims ABSTRACT OF THE DISCLOSURE A loudspeaker system including an enclosure containmg a downwardly directed low frequency loudspeaker provided with an inverted exponential horn, and an upwardly directed high frequency loudspeaker provided with a convex reflector which is adjustable in both height and angle of tilt, and which may include a pre-stressed soft reflecting surface.

BACKGROUND OF THE INVENTION The problem of providing a high fidelity loudspeaker system which occupies small space, yet which can if called on to do so, provide 360 coverage, is a perennial one, as is the problem of providing low frequency response in a small volume speaker. It is this problem to which the present invention addresses itself.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a view in front elevation of a preferred embodiment of the invention;

FIGURE 2, is a view in section taken on the line 2-2 of FIGURE 1;

FIGURE 3 is a view in section taken on the line 3--3 of FIGURE 2; and

FIGURE 4 is a view in section of a modification of the system of FIGURES 1-3, employing a cylindrical in place of a spherical enclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGURES 1-3 is illustrated a spherical enclosure 10 preferably fabricated of flexible resinous sheet material. Enclosure 10 is mounted on a standard 11, which includes a circularly arcuate support 12 which faces concavely upward for less than 180, and which contains pivotal supports 13, 14, adjacent its ends. Enclosure 10 is pivotally mounted on the supports 13, 14 so that it is susceptible of tilting. Mounted internally of enclosure 10 and normally directed downwardly is a low frequency loudspeaker or woofer 15. The back of the speaker is air loaded in the usual manner, as by glass wool or cotton 16. The front end of the speaker, 17, is provided with an inverted exponential horn 18, which proceeds to an opening 19 in enclosure 10.

The effect of the horn is known. It loads the front end of the speaker, thereby improving and extending low frequency response, provides an improved acoustic load and matching, and spreads the acoustic radiation pattern.

The loading appears to remove resonances, so that very low frequency high fidelity response is achieved, despite use of a small enclosure. In the present invention the sound is downwardly directed toward a floor, which may be carpeted. Nevertheless, good azimuthal spread of the acoustic pattern is achieved, and can be achieved over 360. Should it be desired that radiation be directional, the sphere 10 can be tilted to direct horn 15 generally horizontally, or at any angle intermediate vertical and horizontal, or above horizontal, there being no restriction provided to tilt by the pivots 13, 14.

Normally directed vertically is a tweeter 20, and loaded in the enclosure 10, but not provided with a horn. The permanent magnet 21 of the tweeter 20 is divided vertically to slidably accept a rod 22. Enough friction is provided to maintain the rod 22 in any adjusted position. Atop the rod 22 is secured a ball 24 and to the ball is secured a convex reflector, 25, tiltable about the ball 24 in a wide range of degrees and directions. The reflector 25 is fabricated of two discs of resilient plastic sheet, 26 and 27, joined at their edges 28. A small guide cylinder 29 joins the centers of the discs and contains a compression spring 30 and into which and against spring 30, protrudes the major part of ball 24, a minor part extending beyond the disc 27 via a tight opening 32. The spring acts to prevent flopping and assures smooth movement of the reflector 25 on the ball by providing friction and also maintains the convexity of the discs 26, 27 by tending to spread them. If the edge 28 is horizontal the disc 27 spreads sound in all directions azimuthally. But, by tilting reflector 25 and adjustin its height, directivity may be achieved, or enhanced directivity in preferred directions.

In FIGURE 4 is illustrated a modification of the invention employing a cylindrical enclosure on a vertical axis. This lacks the element of positional adjustability of the woofer and tweeter, but all other features of the system of FIGURES 1-3 are present, which are not further described since to do so would be superfluous.

What I claim is:

1. A loudspeaker system including an enclosure having a normally vertical axis, a low frequency loudspeaker mounted in said enclosure and directed downwardly,

an inverted exponential horn coupling said loudspeaker to atmosphere,

at high frequency loudspeaker mounted in said enclosure and directed upwardly, a convex reflector mounted above said high frequency loudspeaker, and means mounting said reflector for vertical adjustment and for angular tilt adjustment with respect to said loudspeaker, said reflector including a convex surface as seen from said high frequency loudspeaker of approximately the transverse dimensions of said high frequency loudspeaker.

2. The combination according to claim 1, wherein said high frequency loudspeaker includes an axial permanent magnet, and means mounting said reflector is a said rod extending through said magnet and slidable therein, and wherein a ball is mounted atop said rod, said reflector being tiltably mounted on said ball.

References Cited UNITED STATES PATENTS 2,065,367 12/1936 Evans 18l31 3,329,235 7/1967 Shaper .18l3l FOREIGN PATENTS 700,630 12/1964 Canada.

STEPHEN J. TOMSKY, Primary Examiner

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