US3388218A - Random directivity loudspeaker - Google Patents

Description

June l1, 1968 H. HURvrrz 3,388,218

RANDOM DRECTI V ITY LOUDSPEAKER Filed Aug. 13, 1964 P1 G. l

Z2 "i1" Musm souRcE xii 24 -J- INVENTOR HYMAN Hmzvrrz AITORNEY5 United States Patent ABSTRACT QF THE DISCLOSURE A loudspeaker which is mounted as a pendulum and which is subjected to forced vibrations as a pendulum.

The present invention relates generally to a system for introducing random variations of frequency and direction into radiated sound.

It is well known that music radiated by a stationary loudspeaker can be aesthetically improved by diusing the sound by means ot a rotating horn, rellector, or the like. Such systems normally provide a regular rotation of the directivity of the radiator over 360, coupled with provision for introducing a Doppler frequency shift into the radiated sound. The Leslie speaker is typical. Such systems require a stationary speaker, and a rotating sound diverter, i.e. a horn or a reilector, coupled with a driving motor, which must beit drive the diverter. The total of the technical requirements involves considerable cost. Moreover, the regular or periodic movement of the deflector may cause unpleasant variations in amplitude of the radiated sound, except perhaps in a highly reflective room, wherein patterns of sound waves which are randomly changing can occur. However, in all devices of this type it is not practical to rotate the speaker, because this imposes difculty in coupling electrical signal energy thereto.

It is a function of the present invention to provide a moving loudspeaker, the movements of which are random, both in the directivity of sound and its angular rate, the movement being accomplished by means of a solenoid impulse motor instead of a rotating motor.

It is another object of the invention to provide a swinging speaker, hung as a pendulum capable of oscillation both in translation and in torsion, or in one of these alone.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specitic embodiment thereof, especially when takeny in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a view in perspective of a sound system according to the invention, and

FIGURE 2 is a view in plan of the system of FIG- URE l.

In the system of the invention, is a loudspeaker, encased in an enclosure 11. The enclosure 11 is hung by a steel wire 12 (about l long) from a rigid support 13, so that it normally faces outward, i.e. toward the listener, when stationary. Signals are brought to the speaker 10 by leads 14, extending from music source 15. Leads 14 may loosely extend parallel to, or be entwined with, wire 12, so that swinging or rotatory oscillation of the enclosure 11 will not tense the leads 14 and b eak their connections to speaker 10.

Near the support point 16 for wire 12 is located an impulse motor, including a solenoid 20, the armature 21'v of which terminates in a V-shaped impulser 22, having its apex pointed toward the listener and also at the wire when the latter is vertical. Two contacts 23, 24 are arranged behind the impulser 22, normally closed by the back surface of the impulser when enclosure 11 hangs free and stationary.

The contacts 23, 24 complete a circuit 25 for solenoid 3,388,218 Patented June 11, 1968 "ice 20, when closed, from source 26, which may be AC or DC. A switch 27 can interrupt the circuit.

In operation, closure of switch 27, enclosure 11 being assumed stationary and contacts 23, 24 closed, energizes solenoid 20. The armature 21 moves forward and impulser 22 pushes wire 12 causing the enclosure 11 to swing and break the contacts 23, 24. The enclosure sways as a pendulum, reclosing the contacts 23, 24 on each swing back-thus causing impulser 22 to apply successive impulses to the wire 12. The wire 12 does not, at each return, fall symmetrically of the impulser 22, nor is the wire 12 attached perfectly at the center of mass of enclosure 11. This effect can be readily enhanced to eifect considerable unbalance and the impulser can be slightly or sharply V-shaped. The result, in any case, is that the enclosure 11 swings as a pendulum, both in translation and torsion, but only seldom directly forwardly. The rotation of the enclosure causes the wire 12 to move as a whole about its axis, in orbiting motion. Each impulse then occurs at random, since impulser 22 is impacted at random locations and the enclosure 12 moves in a random direction, and the enclosure moves, rotates, and orbits, all at once. The translatory motion of the speaker produces Doppler shifts, and changes in vertical directivity, while its rotations and orbitings produce azimuthal directivity variations. The motions of the pendulum are random periodic since the period of a pendulum depends on its dimensions and not on its motions. The natural period of the pendulum in `translation and in torsion are not the same, and the times of the impulses are not regular so that the natural periods merely represent an average or a tendency.

The total range of motion required of the impulser is about l/s" so that a small, inexpensive solenoid suffices. The total swing of the pendulum may be 2" or 3", and 15 to 60. This implies that rate of change of phase is different for different audio frequencies, and that absolute changes in phase are constantly occurring. For example, at i000 c.p.s. one wave length is about 1 foot, whereas at 5000 c.p.s. it is little over 2". A two inch swing in one second results in roughly a 30 phase shift at 1000 c.p.s. almost zero phase shift at c.p.s. and 360 phase shift at 5000 c.p.s. A complex tone, with fundamental at 440 c.p.s. (middle C) but with tenL effective harmonics, is subjected by the motion of the speaker to different and continuously varying phase shifts at the listener, for the several tone partials. This shift in phase patterns is quite desirable in music, per se. Changes of directivity provide changes of standing wave patterns due to reflections from an enclosed listening space, such as a room or hall, and since where q'n is phase and f is frequency, Doppler shifts different for different partials also occur. The effect is particularly pronounced if two spaced speakers are employed,` both according to the invention, even for -monaural sound, but particularly for stereo music.

While l have described and illustrated one specic embodiment of the present invention, it will become apparent that variations of the specific details of construction may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. 1n combination, a loudspeaker, means suspending said loudspeaker, and impulsing means for swinging said loudspeaker in both translation and rotation.

2. A music enhancing system, comprising a pendulum having as its mass a loudspeaker enclosure, a loudspeaker in said enclosure, said pendulum including a wire suspension for said enclosure, and motor means coupled to said pendulum for moving said pendulum as a pendulum.

3. A music enhancing system, comprising a pendulum having as its mass a loudspeaker enclosure, a loudspeaker in said enclosure, said pendulum including a wire suspension for said enclosure, wherein is provided an impulse motor for effecting oscillation of said pendulum.

4. A music enhancing system, comprising a pendulum having as its mass a loudspeaker enclosure, a loudspeaker in said enclosure, said pendulum including a wire suspension for said enclosure, wherein is provided an impulse motor for effecting oscillation of said pendulum, and wherein is provided switch means responsive to each return of said wire suspension to near a predetermined location for energizing said impulse motor.

5. In combination,

a loudspeaker,

a torsional suspension for said loudspeaker, and

means causing said loudspeaker to oscillate on said suspension as a torsional pendulum.

6. A loudspeaker system, comprising a loudspeaker,

a torsional pendulum having said loudspeaker as its primary mass, and

means causing said pendulum to oscillate continuously in torsion.

References Cited UNITED STATES PATENTS 1,819,721 8/1931 Stone ISI-31.1 1,943,499 1/ 1934 Williams 81-31.1 2,629,044 2/1953 Marsi 181-3 1.1

15 KATHLEEN H. CLAFFY, Primary Examiner.

H. ZELLER, Assistant Examiner.

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