The Heil Air Motion Transformer (AMT) uses a folded pleated Mylar Diaphragm of a mere 0.0005” thickness! The voice coil is a serpentine pattern of precision etched aluminum chosen for light weight and high power handling. Unlike a normal piston loudspeaker which excites the air by alternately pushing and pulling the diaphragm, the AMT displaces the air by alternately squeezing and expanding the pleats, moving the air at a very high velocity. Because the moving mass of the AMT is extremely low, and the magnetic structure very powerful, this combination results in extremely high acceleration yielding amazing transients. The AMT's low mass and high output allow for a unusually high combination of efficiency and bandwidth to be attained in a single loudspeaker. The AMT is a dipolar transducer, meaning like a real musical instrument, it creates as much sound to the front as it does to the rear, allowing for a more natural and musical ambiance to be heard in your listening room. The shape of this diaphragm allows for wide dispersion in the horizontal axis, but tightly controlled vertical dispersion. This creates a wide sound-stage while simultaneously minimizing unwanted reflections from floor and ceiling. Ess is the manufacturer of the original and still best Air Motion Transformer invented by Dr. Oskar Heil over 30 years ago. The AMT is able to efficiently reproduce frequencies over the very wide range of 500 to 20,000 Hz. The minimum recommended crossover frequency is 800 Hz at 12db/octave or more. Impedance is 4 ohms nominal, 3.5 ohms minimum. Maximum sustained RMS power is 400 watts RMS band limited pink noise, 160 watts maximum peak. Sensitivity is 92db for 1Watt @ 1 Meter.