Patent GB-1056541-A (GB)
Title: Speaker system
IPC: G10K15/10
Filed: 1964-04-24
Abstract: 1,056,541. Reverberation systems. MOTOROLA Inc. April 24, 1964 [May 13, 1963], No, 17097/64. Heading H4R. [Also in Division H1]  An automobile includes an audio signal source, first and second loud-speakers mounted respectively in the front and rear interior portions of the automobile and a circuit connected to a reverberation device and including switches providing a plurality of circuit configurations, whereby the sound reproduction system may be operated in various different ways. As described (Fig. 1, not shown) the automobile carries a radio receiver 17 mounted in a dashboard 13 so that controls 19 and a dial 21 are visible. A front loud-speaker 23 is mounted in the dashboard 13 and a component enclosure 25 is mounted adjacent receiver 17, A rear loudspeaker 31 is mounted in a rear shelf 15 and a component enclosure 33 in the boot is connected by cable 29 to the front of the automobile. In one circuit arrangement (see Fig. 2) receiver 17 is coupled to front speaker 23 through a transformer 37. A resistor 39 and potentiometer 41 are connected across the secondary of transformer 37. In the rear of the automobile there is a reverberation unit 45 having a drive transducer 47 and a pick-up transducer 49. The pick-up transducer 49 is coupled by a transistor amplifier 54 and a transformer 57 to rear speaker 31. Ganged switches 44, 61, 63, 65 are provided. In position B of switch 63 signals are applied to the reverberation unit 45 and to a by-pass circuit including resistor 59 and the pick-up transducer 49 so that reverberated and unreverberated signals reach speaker 31. Switch 65 in position B applies positive D.C. from receiver 17 to energize amplifier 54. With switch 44 in its B position, speaker 23 is connected across resistor in series with the upper tapped portion of potentiometer 41. In the A position, speaker 23 is connected across that portion of the potentiometer 41 above the tap 43, and speaker 31 is fed directly through switch 63 and transformer 57, In another circuit (Fig. 3, not shown), the amplifier 54 is used in both positions A, B of two switches 69, 71. In position A, speakers 23 and 31 are connected across respective portions of potentiometer 41, with variable tap 43 regulating the amount of signal applied to speaker 23 and the amount of unreverberatod signal by-passing reverberation unit 45 to drive amplifier 54 and speaker 31. Resistor 59 substantially prevents coupling to the reverberation unit 45. In position B, speaker 23 is in parallel with potentiometer 41. Tap 43 feeds speaker 31 through reverberation unit 45 and through by-pass resistor 59. The amount of sound at speaker 31 is controlled by tap 43. In a third circuit (Fig. 7, not shown) a potentiometer 105 is centre-tapped to earth and is provided with a variable tap 109. Ganged switches 111, 113 and 115 provide two circuit configurations and are linked with the variable tap 109. When the tap 109 is in its upper position, switches 111, 113, 115 are in the A position and unreverberated sound will issue from both speakers 23, 31. The volume from speaker 23 will increase and the volume from speaker 31 will decrease as tap 109 moves towards the centre of potentiometer 105. Upon tap 109 passing the earthed centre tap switches 111, 113, 115 assume the B position. Signals are applied to the speaker 31 through the reverberation unit 45. Continued downward movement of tap 109 decreases the volume from speaker 23 and increases the signal applied through reverberation unit 49 to speaker 31. Reference has been directed by the Comptroller to Specification 983,636.