Driver Demagnetizer

The permanent magnets in a headphone driver are designed to produce a uniform, static magnetic field across the air gap in which the voice coil or diaphragm operates. Over time, the ferromagnetic components surrounding these magnets — the pole pieces, the yoke, the driver chassis — accumulate residual magnetization from exposure to external fields. This residual magnetization is additive to the permanent magnet’s intended field, creating asymmetries in the air gap that shift the driver’s operating point and introduce distortion. The phenomenon is well-documented in loudspeaker engineering, where it has been addressed by degaussing circuits built into amplifiers since the 1970s. In headphones, where the driver is carried on the listener’s head through a constantly varying magnetic environment, the problem is arguably worse — and yet no manufacturer provides a solution. Until now.

The Driver Demagnetizer generates a controlled, decaying AC magnetic field that progressively reduces the residual magnetization of the headphone driver’s ferromagnetic components to below measurable levels. The process begins with an initial field of 5 millitesla — strong enough to overcome the coercivity of the mild steel used in headphone driver chassis — and decays logarithmically over 90 seconds, with each half-cycle reaching 93% of the amplitude of the previous one. By the end of the cycle, the field amplitude has fallen below 0.001 millitesla, and the driver’s ferromagnetic components have been guided through progressively smaller hysteresis loops until their net magnetization is effectively zero.

The coil is 140mm in diameter, large enough to accommodate any standard over-ear headphone. To use the demagnetizer, place the headphone face-down on the coil so that the driver is centered over the aperture, and press the start button. The LED indicator pulses during the cycle and turns solid green at completion. Do not remove the headphone before the cycle completes — interrupting the decay at a non-zero field will leave the driver magnetized at whatever level the field had reached at the moment of interruption, which may be worse than the condition before treatment.

The demagnetizer is compatible with dynamic and planar magnetic headphones only. Do not use it on electrostatic headphones. Electrostatic drivers do not contain permanent magnets and are not susceptible to residual magnetization, but the demagnetizer’s AC field could induce currents in the stators that damage the diaphragm coating or discharge the bias voltage in an uncontrolled manner. If you own electrostatic headphones and feel compelled to demagnetize something, we suggest the stand or the amplifier chassis, both of which contain ferromagnetic materials that would benefit from the treatment.