Based on the F144 motor, this driver is equipped with a slightly heavier voice coil for higher BL making it suitable for mid-bass applications. Qts can be varied from aprox. 0.4 to 1.2 depending on the desired LF alignment.
With field coil loudspeakers there is always the question of powering it from a constant current supply. It is desirable to keep a steady current through the field coil through the listening session but the power supply must be designed with a low output impedance.
The effect of the induced EMF in the field coil becomes close to zero with a supply that has an output impedance in the miliohm range. A thick copper ring also is beneficial.
Price: 490USD/ per driver.