A planar magnetic tweeter is a type of loudspeaker driver designed to reproduce high-frequency sounds. It uses a thin, lightweight diaphragm positioned within a magnetic field rather than the dome and voice coil arrangement found in a conventional dome tweeter.

Conductive traces are attached or bonded to the surface of the diaphragm. When an audio signal passes through these conductors, they interact with magnets positioned around the diaphragm. This causes the diaphragm to move backwards and forwards, creating sound waves.

Because the driving force can be distributed across a relatively large area of the diaphragm, planar magnetic tweeters can move in a controlled and uniform manner. The diaphragm is also extremely lightweight, allowing it to respond rapidly to changes in the audio signal.

A loudspeaker crossover determines which frequencies are sent to the planar magnetic tweeter. Lower frequencies are normally handled by a woofer or midrange driver, while the planar magnetic driver reproduces the higher frequencies. The exact crossover frequency varies according to the design of the loudspeaker.

Planar magnetic tweeters are available in different shapes and sizes, and their dimensions can influence how sound is dispersed into the listening room. Manufacturers can design the diaphragm and magnetic structure to achieve particular frequency response, sensitivity and dispersion characteristics.

Planar magnetic tweeters are sometimes confused with ribbon tweeters because both technologies use very thin diaphragms and magnetic fields. The important difference is that a true ribbon tweeter uses the conductive ribbon itself as both the diaphragm and conductor. A planar magnetic driver generally has separate conductive traces attached to a thin diaphragm.

They are also different from Air Motion Transformers. An Air Motion Transformer uses a folded diaphragm that moves air by squeezing it from between its folds, whereas a planar magnetic diaphragm moves more conventionally backwards and forwards.

The purpose of a planar magnetic tweeter is ultimately the same as any other tweeter: to reproduce the high-frequency portion of an audio signal. Its lightweight diaphragm and distributed driving force provide an alternative approach to the conventional dome, ribbon and Air Motion Transformer designs used in modern loudspeakers.