ABSTRACT
The use of motional feedback (MFB) to improve loudspeaker operation is closely related to active crossover technology. Only one company – Yamaha – has released stand-alone amplifiers with a MFB capability. The amplifier is usually physically part of the loudspeaker because it is even more closely coupled than an active crossover system. Russel Breden's MFB was accomplished by using dual-coil drivers, one coil being driven by amplifier and the other giving velocity feedback. Consensus of any kind in the audio business is extremely rare, but there seems to be agreement that the Philips MFB loudspeakers gave unusually deep and clean bass from boxes that were apparently impossibly small. One of the main challenges of MFB is sensing the motion of the drive unit cone without putting any restraint on its movement. The Philips numbering system is somewhat opaque. For example AH468 and AH483 sound like they might be in same MFB product series, but actually both were passive crossover loudspeakers.
