Quadraphonic reproducing system

Claim 1

Apparatus for reproducing on four loudspeakers four audio information signals respectively designated Lf, Rf, Lb and Rb contained in first and second composite signals respectively containing dominant signals Lf and Rf and each including subdominant signal components Lb and Rb and wherein said signal components Lb and Rb in one of said composite signals are in substantially quadrature relationship with said signal components Lb and Rb, respectively, in the other of said composite signals, with the Lb component leading the Rb component in one of said composite signals and with the Lb component lagging the Rb component in the other of said composite signals, said apparatus comprising: first and second input circuits for respectively receiving said first and second composite signals, said input circuits including means for shifting the phase of one of said composite signals relative to the other by substantially 90* to thereby position said Lb and Rb signals components in one of said composite signals either in phase coincidence or in phase opposition with the Lb and Rb signal components, respectively, in the other of said composite signals, first and second amplifiers each having first and second input terminals and an output terminal, the Second input terminal of each of which is connected to a point of reference potential, means for coupling the relatively phase-shifted composite signals from said first and second input circuits to the first input terminal of said first and second amplifiers, respectively, first, second, third and fourth output circuits each including a respective one of said loudspeakers for respectively displaying composite signals containing said Lf, Rf, Lb and Rb signals are predominant components, each of said loudspeakers having first and second terminals, means connecting the output terminals of said first and second amplifiers to one terminal of said first and second loudspeakers, respectively, means connecting said third loudspeaker in circuit between the output terminals of said first and second amplifiers and operative to couple to said third loudspeaker a signal proportional to the sum of said relatively phase-shifted first and second composite signals and containing said Lb signal as its predominant component, and means connecting said fourth loudspeaker in circuit between the output terminals of said first and second amplifiers and operative to couple to said fourth loudspeaker a signal proportional to the difference of said relatively phase-shifted first and second composite signals and containing said Rb signal as its predominant component.