A Planar Magnetic driver, has coined a few other terms such as “orthodynamic” or “Isodynamic”, all of which mean the same thing (in regards to headphones). They can be described as the child of a dynamic and electrostatic driver, sort of… The best of both worlds, at least.
Like the dynamic driver, it requires a magnetic field around a conductor with a current flowing thought it to drive the diaphragm. And like the electrostatic driver, it contains a thin sheet of flexible film. The key difference that coined the term “planar” refers to the planar magnetic field that has a printed circuit spread across the surface of the thin film in the same parallel plane as the diaphragm. In other words the planar magnetic driver contains a charged flat wire or voice coil unwound on the thin, flat film. The diaphragm is “sandwiched” with magnets on either side of the diaphragm, and when charged the magnetic field pulls on either side of the diaphragm pulling it one way or the other causing the air to move, creating sound waves.
Planar magnetic drivers are beneficial because they offer better bass response than other headphones because of the large surface area of the membrane producing the sound waves. Additionally, they have a wider sound range, low distortion levels, are amplifier friendly and are more durable without loosing their sound quality. The large surface area of the diaphragm allows the heat generated by the currant passing through it to pass or dissipate.