Rotatable tremulant sound producer

Nov. 18, 1952

2,618,352

D. J. LESLIE

ROTATABLE TREMULANT SOUND PRODUCER

Filed June 13, 1949

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DMding Network

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INVENTOR.

Patented Nov. 18, 1952

2,618,352

UNITED STATES PATENT OFFICE

2,618,352

ROTATABLE TREMULANT SOUND PRODUCER

Donald J. Leslie, Application June 13,1

Claims. (( 1

The present invention relates to the production of musical tones, and is more particularly directed to apparatus or devices for imposing pitch tremolo or vibrato on musical tones.

This application is a continuation-in-part of ⁵an application filed in the name of Donald J. Leslie, Serial No. 603,850, filed July 9, 1945, for “Acoustic Apparatus,” now Patent No. 2,489,653, which application is a continuation-in-part of an abandoned application filed in the name of Donald J. Leslie, Serial No. 369,413, filed December 10, 1940, for “Acoustic Device.”

The foregoing applications disclose the production of musical tones by electrical means, including a low frequency sound translating device and a high frequency sound translating device. A sound transmitting channel is associated with each device and vibrato effects are obtained by causing the mouths of these channels to rotate. During such rotation, the mouths move alternately toward and away from the listener or sound source at a frequency corresponding to the vibrato. In this maimer, the pitch of the sounds heard by the listener is alternately increased and decreased.

As set forth in the foregoing applications, proper vibrato effects are obtainable by moving each sound channel through which the sound passes cyclically between five and eight cycles per second, or at a speed of rotation of between about 300 and 480 revolutions per minute.

An object of the present invention is to provide an apparatus for imposing vibrato on sound, embodying rotatable and separate high frequency and low frequency sound translating devices and associated sound channels that are compactly arranged and occupy much less space than was heretofore necessary.

Another object of this invention is to provide an apparatus for imposing pitch tremolo or vibrato on sound, embodying separate rotating or movable low frequency and relatively high frequency sound channels, in which the sound is transmitted simultaneously through the channels in the same direction.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and 5' forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, 5

Wilmar, Calif.

&gt;49, Serial No. 98,815 &gt;1. 181—27) since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a vertical section through a portion of an apparatus embodying the invention;

Fig. 2 is a cross-section taken along the line 2—2 on Fig. 1; and

Fig. 3 is an enlarged vertical section through part of the high frequency speaker and horn portion of the apparatus.

As disclosed in the drawings, a base or low frequency speaker or sound generator 10, and a treble or high frequency speaker or sound generator II are housed within a cabinet 12. A ’ directional horn (3 is associated with the low frequency speaker 10, and another directional horn 14 is operatively associated with the high frequency speaker 11. These horns form sound channels 15, 16 having mouth or sound emitting ¹ openings 17, 18 spaced from their common axis of rotation 19. The sound inay pass from the horns 13, 14 outwardly of the cabinet through a number of openings 20 that may be covered by . louvers, grilles, or with a light fabric material 21. ' In the form of invention disclosed in the drawings, the speakers 10, II and horns 13, 14 are coaxially arranged. The low frequency speaker is disposed upon a low frequency cone 22, including the diaphragm 22 a, that is suitably ) fastened to a platform or shelf 23 extending across the cabinet 12 above the cabinet openings 20. The high frequency speaker II, which is coaxial of the low frequency speaker, is suitably supported in a transverse bar 24 extending across &gt; a central opening 25 in the platform or shelf 23, through which the sound from the low frequency speaker and cone may pass.

The cabinet 12 is of such design as to prevent radiation from the back of the speaker cone 22a ) into the room. Thus, the cabinet can have a top or transverse partition 12a forming a complete enclosure 12b with the cabinet side walls 12c, or it may be of the bass reflex design, with relief ports which radiate at low frequencies only. The 5 purpose of the enclosure is to restrict radiated sounds to the front surface of the cone only, as this is the portion of the speaker radiation that is directed through the rotary horn 13.

The sound from the low frequency cone 22a ) passes through the opening 25 and through the throat 26 of the rotatable low frequency horn 13, which has its mouth or sound emitting opening spaced from the axis of rotation 19 of the horn. This horn defines the elbow-like sound channel 15 extending between its throat 26 and

2,618,352 mouth IT, to enable its direction of sound outwardly through the cabinet openings 20.

The sound from the high frequency speaker II passes into the throat or hub portion 27 of the rotatable high frequency horn (4. The high frequency horn is suitably secured in a hub member 28 fixed to and supported coaxially of the low frequency horn 13 by a plurality of radial spokes 29. extending, across the low frequency, horn throat 26 to its outer portion. Thus, the 1 high frequency horn 14 is fixed to, and coaxially of, the low frequency horn S3, with its mouth 18 facing in the same direction as the mouth 17 of the low frequency horn 13. This latter mouth may be suitably covered by cloth 39 to reduce 1 the effects of windage during rotation of the horn 13. If desired, a conical deflector 31 may be secured at the mouth portion 18 of the high frequency horn 14; so as to broaden the radiation pattern of the high frequency sounds emanating 2 from the sound channel 16.

As was noted above, the desired pitch tremolo or vibrato can be obtained by rotating the horns 13, 14 at from about 300 to 480 revolutions per minute. To enable such rotation to occur, the 2 lower portion of the low frequency horn 13, which is in the form of a drum shaped rotor, is fixed to a shaft 32 rotatably supported in. a suitable bearing 33 mounted on the base 34 of the cabinet. The upper end of the rotor 13 and the high fre- 3 quency horn 14 are rotatably supported by causing the throat 27 of the high frequency horn to rotate within a ball bearing 35. The inner race 36 of the bearing is secured on the throat 27, the bearing load being transmitted through 3 suitable balls 38 to an outer race 39 mounted in a plate 49 that is suitably attached to the supporting bar 24, as by means of bolts 41. The sound emanating from the high frequency speaker 11 can pass through a central aperture .4 42 in the plate 40 into the throat 27 of the inner horn 14.

The bearings 33, 35 are coaxial and also coaxial with the speakers 10, 11 and throats 26, 27 of the horns 13, 14. Accordingly, rotation of the 4 low frequency horn 13 about the axis 19 will also effect rotation of the high frequency horn 14 about the axis. Such rotation may be provided by a suitable electric motor 43 attached to the cabinet 12 and having a drive pulley 44 5 for moving a belt 45 disposed over a driven pulley 46 mounted on the horn shaft 32. The motor speed and diameters of the pulleys are so chosen as to rotate both horns 13, 14 at the desired speed to impose pitch tremolo on the musical tones 5 emanating from the speakers 10, 11.

The apparatus is intended for use in connection with an electronic device, such as an electric organ (not shown). The final amplifier stages of such a device may be connected with 6 the speakers 10, it by suitable cables 47, in, a conventional manner, through a suitable dividing network 48, which will limit the frequencies., supplied to the respective speakers. Such dividing network 48 and the connections 47 be- 6 tween the amplifier and high and low frequency speakers are. well understood by those skilled in . the art, and need not be detailed in this specification.

The horns 13, 14 are rotated simultaneously 7 by the electric motor 43 at the appropriate tremolo or vibrato speed, the sound from the low frequency. speaker 19 and cone 22 passing through the low frequency sound, channel 15 and, outwardly through its opening 17.- Similarly, the: 7 sound is passing from the high frequency speaker 11, and through the mouth 18 of its sound channel 16, which faces in the same direction as the mouth 17 of the other channel 15. By dispos&gt; ing one horn (4 within the other 13, a compact arrangement is provided, necessitating only a single operating mechanism, such as the motor 43, for effecting simultaneous rotation of the horns at the appropriate speed. At the same 0 time, the high and low frequency notes are transmitted simultaneously in the same direction at any instant of time, the high frequency notes being appropriately superposed upon the low frequency notes, as well as the vibrato effects from 5 both notes.

Although the invention has been particularly described with respect to sound channels for directing sound from high and low frequency speakers, it is quite apparent that a similar ar0 rangement may be used' for transmitting sound from a source into high and low frequency microphones, that would be located at the same positions as the speakers are located in the drawings. By rotating the horns at the appropriate: 5 speed of from about 300 to 480 revolutions per minute, or from about five to eight cycles per second, the vibrato or tremolo effect will be imposed upon the several tones entering the sound channels 15, 16.