Cradeldorf, I have intended to conduct experiments to test for the superior quality of field coil magnetic circuits, but to date I have failed to do so. The prevailing theory is that field coil motors resist flux modulation by voice coil currents better than permanent magnet motors do, providing better fidelity to the driving signal. A permanent magnet structure is provided a magnetic charge from a momentary infusion of energy. This charge can be momentarily or permanantly altered by voice coil currents. An elecromagnet is connected to a DC power supply which is capable of providing current to maintain the magnetic circuit under dynamic conditions. The subjective results of field coil operation are of control of the moving mass, providing great fidelity to the audio signal. The results are similar to a good Alnico motor, but a bit better yet.

This all begins to be a religion after a while, like triodes vs. pentodes, tubes vs. transistors or you-name-it. Most field coil advocates have reached their preference after numerous convincing listening sessions. We are all allowed our preferences, and field coil advocates enjoy the sound of their drivers. A field coil cannot make a flawed speaker great, like a 6" cone trying to operate full range. Electromagnets do seem to provide benefits though, at least to their adherents. "Nuff said.