In this case, the amplifier is using the inherent characteristics of a coil speaker as a low pass filter? I mean, I understand that if a high enough carrier frequency is used, then it shouldn't bleed out any human hearing component artifact into the final sound. But it's hard to believe that it is completely equivalent to a analog audio signal, the delta-sigma modulated output. Unless this amplifier first probe the speakers characteristics, and then modifies the output parameters.