Brand: PRECIDE Dr. Oskar Heil, noted physicist and inventor of the Field Effect Transistor, began his research into loudspeaker design, not with abstract theory of how a loudspeaker should work, but with a study of the peculiarities of the human listening aparatus. The result of this intensive year-long research program led to his discovery of the principle on which the Oskar Air Velocity Transformer (AVT) is based. By applying this principle to the design of a loudspeaker diaphragm, he was able to achieve a revolutionary breakthrough in solving the fundamental problems of diaphragm mass, inertia and self resonance which led to the development of the Heil Air Motion Transformer (AMT) speaker.