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Publication numberUS3370125 A
Publication typeGrant
Publication dateFeb 20, 1968
Filing dateMay 26, 1964
Priority dateMay 26, 1964
Publication numberUS 3370125 A, US 3370125A, US-A-3370125, US3370125 A, US3370125A
InventorsGamble Howard C, Shaw Henry W
Original AssigneeSound Craft Systems Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Auxiliary loud-speaker system
US 3370125 A
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Description  (OCR text may contain errors)

Feb. 20, 1968 H. w. SHAW ETAL 3,370,125

AUXILIARY LOUD-SPEAKER SYSTEM Filed May 26, 1964 INVENTORS Henry W. Show 8" Howard C. Gamble ABSTRAQT OF THE DISCLOSURE An auxiliary loud speaker system wherein multiple locally powered units can be coupled to a main speaker unit.

The input to each is taken from the output of the preceding unit. A by-pass connection employing a drop-out relay enables any speaker unit to be turned off or to malfunction with no effect upon those that follow it and further enables the entire system to be turned off from the main speaker unit.

This invention relates to a system utilizing auxiliary loud speaker units which are powered and connected to a powered main sound reproducing unit such as a portable lectern for speakers at indoor and/or outdoor exercises. More particularly, this invention pertains to such a system in which any desired number of units may be added to a main unit and each other to accommodate audiences of different sizes and/or auditoriums or fields, so that the person speaking or other sound, such as music, for example, may be heard clearly without distortion, differences in phasing between the respective auxiliary loudspeaker units, and at comfortable volume levels throughout the sound broadcast area.

One common practice heretofore in the use of a public address system for speech or other sound, whether portable or fixed, involved the use of a single main unit usually with a high powered amplifier so that if a larger audience were present the volume control could be turned up to increase the output resulting, however, in overloudness for auditors nearer the main unit and a tendency to distortion. On the other hand, when additional loud speakers were connected to the audio output of the main unit, problems arose in matters of energy distribution to the supplemental speakers, line losses, impedance matching, and, phasing of the supplemental speakers relative to the output of any speaker in the main unit. While such problems could be taken care of beforehand in a public address system with relatively previously predetermined components including supplemental loud-speakers, the use of supplemental speakers in varying numbers at varying distances under varying circumstances, deriving their power from a main unit, whether portable or fixed, resulted in such problems remaining relatively unsolved, even when last minute adjustments were attempted.

In a powered auxiliary loud-speaker system of this invention, such shortcomings and deficiencies are overcome whether the main unit and auxiliary loud speakers are portable, or fixed, in Whole or in part. Under this invention, any selected number of powered auxiliary loud speaker units may be added to the main unit, within the capacity of the system, to reach audiences of any size even as determined at the last moment without requiring computation and adjustment to compensate for problems of line loss, impedance matching, speaker phasing, or other distorting factors. For example, a portable powered lectern such as that illustrated in Patent No. 3,023,274, in common ownership with this invention, may be used conveniently to address an audience of from 50 to 1000 people. The addition of powered auxiliary loud speakers of this invention may be done quickly and conviently simply by plugging them into the main unit and/or one States Patent another in serial and/ or parallel arrangement, as may be desired, to reach audiences of up to 20,000 people and over, even in the open air, without distress of those in the audience nearer the main unit, or loss of quality and clarity of sound to those on the fringes of the group. Under this invention, each powered auxiliary loud speaker is self-contained and normally provides its own power; in case of failure of power in a particular auxiliary unit, it is arranged in such wise that it does not cut off those auxiliary units which are farther away and connected through it to the main unit. On the other hand, when the amplified sound output is shut off at the main unit, the entire system will become silent.

Other objects, features and advantages of this invention will be apparent from the following description and the accompanying drawings, which are illustrative of one embodiment only, in which FIGURE 1 is a schematic view of one embodiment of this invention with powered auxiliary loud-speakers in series connection to a main unit;

FIGURE 2 is a perspective view of two powered auxiliary units which when fastened together comprise a single carrying set;

FIGURE 3 is a view of the two auxiliary speaker units shown in FIGURE 2 after they have been fastened together and are ready for such carrying; and

FIGURE 4 is a circuit diagram of one powered auxiliary speaker unit for purposes of illustrating one mode of functioning of the system of this invention.

Referring to the drawings, a portable powered lectern 10 comprising a main unit is shown in opened operative condition for a person to speak into a microphone 11 connected to a suitable transducer-amplifier in lectern 10 to actuate one or more loud-speakers located in the lectern behind a cloth screen or grill 12 so as to face an audience. Microphone 11 is mounted on a boom arm adjacent a lectern surface 13 on which the speaker may place his notes or other material for the talk to be given. While main unit 10 is illustrated in the form of a powered speakers lectern which is portable, it will be understood that it may be fixed; it may be understood, further that such main unit 10 may comprise other kinds of main units with an audio output circuit for the transmission of reproduced and amplified sound audible to human beings. Or, such main unit 10 may provide an amplified audio signal output at some remote location, for example, to supply powered auxiliary loudspeakers. In the illustrated embodiment of this invention using lectern 10, a string of such self-contained powered auxiliary speaker units is represented by identical auxiliary units bearing numerals 14 to 17, inclusive and respectively, to be placed at spaced intervals among the audience. Further, although auxiliary speakers 14 to 17, inclusive, are illustrated in series connection beginning at output panel 18 on main unit 10, forming an extended trunk of such auxiliary speakers, either the main unit 10, or any of the auxiliary speakers may have parallel branches of auxiliary speakers leading therefrom in a tree and branch arrangement, if desired, by the use of sockets, plugs or adapters which allow more than one of such auxiliary speakers to be connected to a powered main or auxiliary speaker unit, to cover any arrangement of an audience, whether fanshaped, columnar, or bent as in the case of a meeting hall having bays to each side in which an embodiment of this invention is used.

As shown, each powered auxiliary speaker unit of this invention is in a case 19 the back of which is an open recess and extends inwardly to a partition 20 having a volume control 21, a switch 22 and an output socket 23 mounted on the partition and facing rearwardly. A long length of lamp cord 24 connects each of the auxiliary speakers to an immediately preceding unit; when not in use, such lamp cord 24 may be coiled and fitted into the aforesaid recess of its unit where it may be held by a strap or clip secured to partition 20. The front side of each auxiliary speaker may be provided with a combination fabric and grill screen 25 overlying one or more auxiliary speaker horns 26. In the auxiliary speaker units shown in the illustrated embodiment, three relatively uniform diameter horns are arranged in a vertical column between partition 20 and screen 25 together with most of the circuit components shown in FIGURE 4. At the bottom of the aforesaid recess in the back of each speaker unit may be positioned dry cell batteries 27 for the amplifier therein. If desired, a battery meter may also be mounted on panel 20 to shown when such batteries have to be replaced.

Each case 19 is provided with four cushion feet 28 at the corners and along the bottom rear edge there is a spaced pair of the same leaf of a pair of separable hinges 29. Thereby, when two cases 19 having opposite hinge leaves thereon are placed back-to-back, a carrying set 195 is formed comprising a pair of auxiliary speaker units, as shown in FIGURE 4. The upper rear edge of each case 19 in a set is attached to an appropriate half of a separable toggle clasp 30, which is closed to complete the fastening together of two cases 19 hinged to each other to form set 198. Each case 19 also has a half handle 31 so that when two cases are formed into a set, both such half handles form a full diameter carrying handle as illustrated in FIGURE 3. Since each auxiliary speaker unit is powered, although such may be used in a series arrangement with an alternately positioned unpowered auxiliary speaker on some occasions, no ditficulty is encountered in quickly setting up to address an audience of virtually any size, either under a roof, or in the open air. The rest of the cord 24, which may be fifty feet long or more, for each auxiliary unit, enables them to be placed where they best will serve and they may 'be faced in any direction relative to the main unit and the other auxiliary units, depending upon the location of the audience, and any wind conditions or other factors that have to be taken into account at the time of setting up. All of the powered auxiliary speakers of this invention are connected in proper polarity so that the sound uttered by them at a given instant will be the same and also the same as the sound uttered by the main unit. Moreover, the power output of the main unit is not relied upon to reach part of a larger audience beyond the normal and intended number within the capacity of that main unit inasmuch as each of the auxiliary loud-speaker units in a system of this invention takes care of its own sound reproduction and amplification by means of its own amplifier, thereby eliminating need for concern about impedance matching relative to the main unit, auxiliary unit and lines losses between units and other distortion elements. Still further, if an amplifier in one of the powered auxiliary speaker units of this invention should fail, it will not cut out or adversely effect other such units which may be farther out or away from the main unit. At the same time, when the main unit is shut off it will automatically silence the auxiliary speaker units and open the respective battery circuits in them. Although the description herein has to do with a portable auxiliary loudspeaker system to be used with a main speaker or audio sound output signal unit, it will be recognized that systems which are permanently fixed in place, or semi-permanently fixed in place, may be provided which embody teachings of this invention.

In operation, when the main unit is turned on, an electrical switch 52 is closed and the circuit in unit 10 is energized to produce an amplified output audio signal across the secondary 50 of an output audio transformer therein. Such drives the speaker or speakers 51 in unit 10 and imposes such audio signal across the polarity terminals 53 and 54 of a receptacle socket 55 mounted on or adjacent the surface of unit 10 in a position accessible from the outside. Socket 55 is adapted to be bridged by the respective prong terminals 56 and 57 of a polarity plug 58 at the far end of a cord 24 leading to a powered auxiliary speaker of a system of this invention, which in the illustrated embodiment is speaker 14. Because of the respectively different sizes of the prong terminals of socket 55 and plug 58, there can be no reversal of polarity in the feeding of the audio signal to the next succeeding unit and such polarity oriented socket and plug connection continue in each succeeding connection. Jacktype plugs and sockets may also be used.

In auxiliary speaker unit 14, the closing of On-Off" switch 22 and the insertion of plug 58 into socket 55 energizes a relay 59 by means of batteries 27 for D.C. current flow through a portion of the audio output circuit of the preceding unit via conductor 60, coupled terminal 57-54, coil 50, closed switch 52 to the coupled terminal 55-56, a blocking condenser 61 preventing D.C. current from passing through the speaker 51; thence back through On switch 22 to the battery in unit 14, or other auxiliary unit as the case might be. Such energization of relay 59 closes a normally open gang switch 62, raising its three movable switch arms into contact with their respective, closedposition terminals to which such switch arms are shown extending in full line position in FIGURE 4. As a consequence, the wave form of the audio input signal is impressed across a potentiometer resistance 63 through the middle gang switch arm, such resistance with a selector element 64 comprising volume control 21 and feeding the primary side of an input transformer 65 in a transistorized push-pull amplifier 66. The D.C. supply for the transistors 67 and 68 is supplied by D.C. current from the battery 27 flowing through a subcircuit completed by the uppermost switch arm of gang switch 62, through resistances 69 and 70 and conductor 71. Hence, the impressed audio signal through the secondary of transformer 65 respectively modulates the flow of current through the respective transistors 67 and 68 to supply an amplified audio signal to the primary 72 of amplifier output audio trans former 73, thereby embodying within the powered auxiliary speaker selected amplification in situ for that portion of the audience comfortably and conveniently reached by its speakers 26.

The amplified audio output subcircuit of the auxiliary speaker 14 whose full circuit is shown in FIGURE 4, is completed by the raising of the lowermost switch arm 76 of gang switch 62 to the full line position shown in FIG- URE 4, thereby placing the secondary 74 of transformer 73 in a subcircuit which proceeds through conductor 75, switch arm 76, conductor 77, the switch arm of switch 22 in its On" position, speakers 26 and conductor 78 back to the other side of secondary 74. A capacitor 79 blocks off any D.C. current to the speakers 26. A resistance-capacitor feedback connection 74a is provided between the secondary of the output transformer 73 and an earlier stage of audio amplifier 66 to inhibit distortion of the output audio signal from such auxiliary unit.

A branch subscript across secondary coil 74 leads to the respective polarity terminals 80 and 81 of socket 23, adapted, when needed, to be engaged in one position only by a plug 82 of the next succeeding speaker, such as speaker 15; plug 82 being identical to plug 58 and connected by a lamp cord 83 identical to lamp cord 24, just as the circuit in powered auxiliary speaker 15 is identical, for the illustrated embodiment, to the circuit of speaker 14 shown in FIGURE 4. When plug 82 is inserted in socket 23, the battery circuit of speaker 15 for the actuation of its relay corresponding to relay 59, is completed by the audio output portion of the circuit of speaker 14. Thus, upon such insertion, current flows from one terminal in socket 23 through closed (On) arm of switch 22, conductor 77, raised switch arm 76, conductor 75, the coil 74 and conductor 78 to the other terminal of socket 23. It is clear also that When switch 62 is opened by turning off main unit 10, all of the powered auxiliary loudspeaker units of this invention will fall silent inasmuch as the gang switches in each of them will drop out automatically by virtue of the deenergization of relay 59 and those corresponding thereto in the other speakers, namely, 15 to 17 in the illustrated embodiment.

Further, in the event that in one of the auxiliary speakers, such as speaker 14, battery 27 should become too weak to energize relay 59 sufiiciently to hold gang switch 62 in closed (raised) position, the gang switch will drop out shutting off the amplifier 66 in that speaker. A lamp circuit may be installed, if desired, to show any dropping out of gang switch 62 when switch 22 is still in its On position; or a battery meter may be mounted on partition 20 to indicate when the battery drops so much in strength as to be unable to energize the relay sufiiciently to hold the gang switch in operative position to provide auxiliary amplification therein. When gang switch 62 opens due to insufiicient battery strength, the uppermost switch arm will fall down into contact with rest 84, the middle switch arm will move downwardly into engagement with terminal 85 and the lowermost switch arm will move downwardly into engagement with terminal 86. Terminals 85 and 86 are connected by a lead 87 with the consequence that the audio signal impressed across the terminals of plug 58 will be impressed across the terminals of socket 23 in correct polarity relation without, however, amplification thereof in unit 14. Speakers 26 will receive energy at the level supplied by main unit 10, or a prior auxiliary speaker unit if the one cutting out follows an earlier auxiliary unit in the string leading back tothe main unit. The unamplified audio signal thus received across the terminals of plug 58 will be conducted through the one side of cord 24, switch-22, conductor 88, the middle contact movable arm of gang switch 62, jumper 87, the lowermost movable arm of switch '62, conductor 77, the movable arm of switch 22 to terminal 80 of socket 23. Such audio signal will then pass through the still completed audio input portion of the circuit in the next succeeding auxiliary speaker leading to terminal 81, terminal 81 and from thence through conductors 78, 71 and 60, back to terminal 57 of plug 58. Or, if switch 22 of one of the auxiliary speakers such as speaker 14 should be turned Off, .the audio input signal impressed across the terminals of the input plug 58, or identical input plug of any other of such auxiliary speakers, will then pass without amplification through the movable arm of switch 22 in Off position leading to one terminal of socket 23, a jumper 89 shown in the circuit diagram being shown simply for ease of illustration, since the 01f position of switch 22 in the two positions shown in the circuit diagram may be one and the same. The other terminal on the output socket 23 completes the subcircuit to such terminals of socket 23 through conductors 78, '71 and 60 to the corresponding input plug terminal 57. Hence, when switch 22 is turned Off while a powered auxiliary speaker of this invention is in connection with the main unit or the main unit and other powered auxiliary speakers of this invention, while there will be no amplification in that turned-off auxiliary speaker, it will bypass the audio signal to the next succeeding unit and the speaker means 26 of the turned off auxiliary speaker will receive signal impulses at the energy level of the immediately preceding unit turned-on unit when the main unit is On, which may be suflicient for some operation thereof such speaker means 26 at lowered volume. Or, turning switch 22 to Ofi position may be used to cut-off any amplification in that unit and any bypassing of the audio signal to a succeeding unit, by a single circuit change breaking conductor 60 when switch 22 is Off.

From the foregoing, it will also be clear that the auxiliary loud-speaker system of this invention may be readily set up and as quickly taken down for the service of audiences of any size, even if such is determined at a late moment. And, the illustrated embodiment is wholly portable, or may be fixed, inasmuch as each pair of auxiliary speaker units can be quickly fastened together into a set for convenience in carrying as portrayed in FIGURE 3, either to storage, for movement to the next place of use. And in some situations, rectified current may be used as a DC. source in powered auxiliary unit.

Various changes may be made in details and circuit portions of the illustrated powered auxiliary speaker embodiment and other embodiments provided without departing from the spirit of this invention or the scope of the appended claims.

What is claimed is:

1. An auxiliary loud-speaker unit comprising an amplifying circuit having polarized audio input means and polarized output means, at least one loud-speaker coupled across said audio output means, a supply circuit for supplying energizing otential to said amplifying circuit, a circuit path connecting said input means and said output means in polarized relation, said circuit path by-passing said amplifying circuit, and switch means in said by-passing circuit path and in said supply circuit for completing said by-passing circuit only when said supply circuit is disconnected from said amplifying circuit.

2. The combination according to claim 1 wherein switch means include a relay switch having a coil energizable by said supply circuit, said relay switch having normally closed contact means coupled to said input and said output means in by-passing relation to said amplifying circuit and having normally open contact means in said supply circuit. 7

3. In an auxiliary loud-speaker system, the combination comprising a plurality of self-powered auxiliary speaker units, each auxiliary unit having audio input means and audio output means, circuit means for coupling said input means to the output of a similar adjacent unit and for coupling said output means to the input of a different adjacent unit, each of said auxiliary units including a local audio amplifying circuit, circuit means for coupling said amplifying circuit to the associated input means and output means and to a source of energizing potential therefor, each of said auxiliary units having at least one loud-speaker coupled across'its audio output means, and switching means in each of said auxiliary units for directly interconnecting the input means and output means thereof in by-passing relation to the amplifying circuit when the latter is de-energized so that said adjacent units remain electrically interconnected through said de-energized unit.

4. The combination according to claim 3 wherein switch means are in series with said main unit output means for controlling the audio energization of said main unit output means and for simultaneously controlling the audio energization of said auxiliary units.

5. In an auxiliary loud-speaker system in combination, a main loud speaker unit having audio signal output means, polarized main unit output terminals connected in parallel with said output means, an on-olf switch in the circuit of said main unit terminals, a loud-speaker in said main unit connected across said output means, at least one locally powered auxiliary speaker unit having audio signal input means including polarized input terminals connectable with said m'ain unit output terminals, said auxiliary unit further having an audio signal amplifying circuit therein connected to said signal input means, said amplifying circuit including a transistorized push-pull amplifier coupled to an audio output transformer and to local audio signal output means including polarized output terminals for connection to similarly polarized audio input terminals of another auxiliary speaker unit, said first-mentioned auxiliary unit having at least one loud-speaker connected across the secondary of said audio transformer, a local source of DC. potential coupled to said amplifying circuit through a relay switch having a coil connected to said source for energization thereby, said relay switch having normally open contacts coupling said source and said auxiliary unit speaker to said amplifying circuit and normally closed contacts coupled in circuit means connecting the input and output terminals of said auxiliary unit in by-passing relation to its amplifying circuit, manually operable switch means having first contact means for coupling the coil of said relay switch to said source and alternative second contact means for coupling said auxiliary unit output terminals in polarized relation to the input terminals thereof and in by-passing relation to said amplifying circuit when said relay switch coil is de-energized.

6. In an auxiliary loud-speaker system, in combination, a first speaker unit having audio signal output means, polarized audio output terminals connected across said output means, at least one loud-speaker in said first unit connected across said output means, at least one auxiliary speaker unit having similarly polarized audio input terminals, means for electrically connecting said input and said output terminals, an audio signal amplifying circuit in said auxiliary unit coupled to said input terminals, a supply circuit in said auxiliary unit for connecting said amplifying circuit to a source of DC. potential, a relay switch in said supply circuit having a coil energizable by said source, said amplifying circuit including an audio output transformer, said auxiliary unit having at least one loud-speaker and polarized output terminal means connected across the secondary of said output transformer, said relay switch having normally open contacts coupling said DC. source and said auxiliary unit speaker to said amplifying circuit and normally closed contacts by-passing said amplifying circuit when said relay switch coil is de-energized, and manually operable switch means having first contact means in series with the coil of said relay switch and alternative second contact means for coupling said auxiliary unit output terminals in polarized relation to the input terminals thereof and in by-passing relation to said amplifying circuit.

7. In an auxiliary loud-speaker system, in combination, a first unit having audio signal output means and polarized terminals connected thereacross, at least one auxiliary speaker unit having audio signal input means and polarized terminals connected thereacross, means for connecting the input terminals of said auxiliary unit to the output terminals of said first unit, an audio signal amplifying circuit in said auxiliary unit coupled to said audio signal input means, a supply circuit for coupling said amplifying circuit to a source of electric potential,

said amplifying circuit having audio signal output means, said auxiliary unit having at least one loud-speaker and polarized output terminals connected across said audio signal output means associated with said amplifying circuit, means for connecting the output terminals of said auxiliary unit to polarized input terminals of a similar auxiliary unit, and switch means on said auxiliary unit having first contact means in series with said supply circuit and alternative second contact means for coupling said auxiliary unit output terminals in polarized relation to the input terminals thereof and in by-passing relation to said amplifying circuit so that upon de-energizing of said amplifying circuit second contact means couple said similar auxiliary unit in polarized relation to said first unit through said auxiliary unit.

8. In an auxiliary loud-speaker system having a main speaker unit, the combination comprising a plurality of self-contained power auxiliary speaker units coupled to said main speaker unit, each of said auxiliary speaker units having an audio amplifying circuit therein including audio signal input means coupled to audio signal output means of an adjacent one of said units, the amplifying circuit of each of said auxiliary units having audio output means, at least one loud-speaker connected across each of said amplifying circuit output means, each of said auxiliary units including a supply circuit for supplying a DC. potential to the associated amplifying circuit and to the coil of a relay switch, said relay switch having normally open contacts coupling said supply circuit and said auxiliary unit speaker and said auxiliary unit output means to said amplifying circuit, said relay switch having normally closed contacts coupling said auxiliary unit audio signal input means directly to the audio signal output means of said auxiliary unit in bypassing relation to the amplifying circuit thereof, and manually operable switch means having first contact means for coupling said relay switch coil to said supply circuit and alternative second contact means for coupling said auxiliary unit input means to the output means thereof in by-passing relation to the amplifying circuit thereof.

References Cited UNITED STATES PATENTS 3,023,274 2/1962 Shaw 179--1 3,167,314 1/1965 Bentsen. 181-3 1.1 3,183,305 5/1965 Jespersen 179l KATHLEEN H. CLAFFY, Primary Examiner.

R. P. TAYLOR, Alrsistant Examiner.

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Referenced by
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Classifications
U.S. Classification381/120, 381/76, 381/123, 381/77
International ClassificationH04R1/02
Cooperative ClassificationH04R1/02
European ClassificationH04R1/02