Abstract: A method for correcting higher order distortion introduced in a complex multifrequency waveform by an element which introduces signal-induced nonlinearities uses a replica of the non-linear element as a part of a high gain electronic feedback circuit between the output and an input of an amplifier. The replica of the non-linear element receives the multifrequency waveform, and is driven to duplicate the non-linear effects, which are used to generate a compensating voltage which is compared to the voltage obtained from the non-linear device. The resultant difference voltage after the comparison and amplification is then closer to the original signal. Thus, in an audio system for example, distortions which are audibly apparent to the human ear but so small they are immeasurable by instrumentation can be eliminated or minimized by employing a number of replicas in the same fashion.

Abstract: The distortion effects introduced in a complex multifrequency wave by parametric variations in individual active elements arising from signal and power supply variations in a circuit, such as an audio amplifier, are compensable through the use of replicas of the active elements, and the generation of a feedback signal incorporating comparable distortion. By high gain amplification of the feedback signal in a differential amplifier receiving an input signal that is not comparably distorted a comparison signal is derived containing distortion components. The comparison signal is used in a feedforward path which includes the circuit that is subjected to parametric variations in a sense to cancel the introduced distortions.

Abstract: In sound generating systems, it has been ascertained that various factors cause spurious, audible emanations when transducers of reasonable size and cost are driven in complex motions characteristic of typical high fidelity audio reproduction. In a typical system in which different transducers are used for different frequency ranges, the spurious emanations are reduced by change of amplitude or frequency or both, without affecting transducer performance, to levels at which they are substantially inaudible. Means are coupled to each speaker in a multispeaker system for compensating for mass, compliance and damping. Further, crossover means are provided for introducing opposing signal components in a crossover range between two adjacent range speakers such that opposing signal components are acoustically cancelled in the composite output.

Abstract: In sound generating systems, it has been ascertained that various factors cause spurious, audible emanations when transducers of reasonable size and cost are driven in complex motions characteristic of typical high fidelity audio reproduction. It is shown that phase effects, unidirectional components, and transient (start-stop) effects give rise to such spurious emanations and that these center about the resonant frequency of the transducer. Means are disclosed which significantly improve the clarity of reproduction by minimizing these spurious emanations. In a typical system in which different transducers are used for different frequency ranges, the spurious emanations are reduced by change of amplitude or frequency or both, without affecting transducer performance, to levels at which they are substantially inaudible. Either or both electronic and acoustic techniques may be used for these purposes.