ATC Multichannel Concept 7 Collection powered surround speaker system Hysteresis
Hysteresis is a term that's been bandied about by some US audio manufacturers for years, but few people understand that it refers to a discrepancy between the amount of magnetic energy applied to a block of steel (by current passing through a coil, for example) and the degree to which the steel is magnetized by that energy. Normally, the degree of magnetism lags significantly behind the magnetizing force, both when the force is magnetizing and then when it is de-magnetizing the steel. A plot of the relationship produces a parallelogram, called a hysteresis box.
In a dynamic loudspeaker, hysteresis acts to change the relationship between applied signal voltage and voice-coil displacement, which by definition causes unwanted distortion. I didn't understand ATC's explanation of how their "Super-Linear" system counters the effect, but the C7 system sounded so much better than I'm accustomed to that I am prepared to believe that it works.—JGH