The Air Motion Transformer (AMT) is a type of electroacoustic transducer or loudspeaker, also called Air Velocity Transformer (AVT) or JET transducer. Invented by Dr. Oskar Heil, it operates on a different transduction principle than other loudspeaker designs, such as moving coil, planar magnetic or electrostatically driven loudspeakers, and should not be confused with planar or true ribbon loudspeakers. In contrast to a planar ribbon loudspeaker the diaphragm of the AMT is of pleated shape similar to a bellows. The AMT moves air in an augmented, semi-perpendicular motion using a folded sheet (made of polyethylene, polyester or polyimide), structured around a series of aluminum struts positioned in a high-intensity magnetic field. The diaphragm pushes back and forward from itself in a physical motion similar to that observed when an accordion is pushed in and pulled out to pump air though the reed chambers, albeit over an exceedingly smaller motion range.
The result is a dipole driver with an extraordinarily rapid response rate, enabled by the extremely low mass of the polyester driver and the far smaller distance it travels on each “swing” compared to a dynamic driver. In this technical respect, it shares characteristics with the electrostatic driver.
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. As a matter of surface comparison, a standard 1-inch-wide (25 mm) AMT strip has a functional driver area comparable to an 8-inch-diameter (200 mm) circular dynamic cone. The folded driver design, combined with the small motion range, means the AMT acts like a point source version of a larger driver, inherently resulting in lower sound reproduction distortion. As a result of its motion pattern, the AMT "spits" the air out in a way similar to the action of shooting a watermelon seed from your hand by squeezing it between thumb and forefinger. The speed of the air as it leaves the diaphragm is approximately five times faster than the speed of the actual driver structure, hence the name, Air Motion Transformer.
Although it is possible to operate the diaphragm without the magnetic field, using piezoelectric technology, this method has been used only by TakeT for their headphone and tweeter products.
There are a couple of companies producing Heil AMTs:
Dayton Audio (USA)
EmotivaPro (USA) under the name Airmotiv
MartinLogan (USA) under the name Folded Motion Tweeter[3]
Precide (Switzerland) who calls their version the AVT (Air Velocity Transformer). Precide uses an AMT driver for their top of the line headphones.
ELAC (Germany) who calls their version of the transducer JET
ADAM (Germany), under the name Accelerating Ribbon Technology[4]
ETON (Germany)
Beyma (Spain)
Furuyama Audio Labs - FAL (Japan)
SoundTouch (China)国内有厂在做（嘉兴的）
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Post By：2015-10-31 20:40:38 [显示全部帖子]
