GB1032540A - A stereophonic sound reproduction system - Google Patents

Abstract

1,032,540. Stereophonic systems; loudspeaker systems. AUTOMATIC CANTEEN CO. OF AMERICA. July 6, 1964, No. 27825/64. Headings H4J and H4R. A pair of identical amplifiers 10, 11 each utilizing push-pull output stages 14, 15 are connected to the opposite ends of centre-tapped primaries 16, 17 of transformers 18, 19. The amplifiers 10, 11 are connected to a stereophonic signal source (e.g. a pick-up cartridge or tape recorder) so that the input signals to the two amplifiers 10, 11 are reversed with respect to one another. The transformers 18, 19 have identical secondaries 27, 28 each made up of three sections, and these secondaries 27, 28 are connected to three loud-speaker systems each comprising at least one loud-speaker. Speaker systems 31 and 41 face away from each other and, as described, each consists of one speaker only. The third loud-speaker system is at right-angles to the other two and consists of a tweeter 52 and a woofer 51. Speaker 31 is connected between one end terminal of secondary 27 through a capacitor 34 and to one end terminal of secondary 28. A choke 36 and capacitor 34 attenuate frequencies below 250 c/s. The circuit is completed by an earthed jumper 38. By this arrangement speaker 31 is primarily energized by winding sections 27A and 27B in series, opposed by winding section 28C. Speaker 41 is similarly connected and is primarily energized by winding sections 28A and 28B in series, opposed by winding section 27C. Speakers 31 and 41 are normally 180 degrees out of phase so that, with identical signals, they move in unison (see arrows 61, 62). The speaker system 51, 52 is energized through the winding sections 27B, 28B, the woofer 51 being connected through a low-pass filter 58, 59 and the tweeter being connected through a highpass filter 57. Speakers 31, 41, 51, 52 are housed within a single cabinet 29 and are mounted with their axes horizontal.