Air Motion Transformer

The AMT moves air laterally in a perpendicular motion using a metal-etched folded sheet made of polyethylene terephthalate (PET) film.

The diaphragm (now, as a unit) is then housed between 4 stacks of steel pole-plate pieces positioned at 45° within a high-intensity, quadratic, opposing magnetic field.

The air motion transformer with its sheet film equally exposed at 180° behaves as a dipole speaker, exciting front and rear sonic waves simultaneously.

The discernible motion of each diaphragm flexure is very small, but because of the folded structure, more air is moved than would be by a conventional cone or electrostatic driver of the same plotted surface area.

Crossover points are design decisions (depending on the model application, using a cut-off frequency of 18 dB at 800 Hz, or 1 kHz).

This technique called Variable Velocity Transform [1] allows the AMT drivers to extend down to 10 Hz and function as full range headphones.

From 2006 to 2008, air motion transformers were made available directly to the European consumer as the company closed its doors in California and relocated to Germany.

Polyester film is purported to be of greater longevity, while the original polyethylene remains popular due to critical acclaim of its response characteristics.