Air Motion Transformer

The Air Motion Transformer ( AMT short, also called Jet tweeter ) is a magnetostatic speaker for reproducing high frequencies in the audible sound.

The loudspeaker has been developed by Oskar Heil. On an accordion-like pleated diaphragm meander arranged tracks. When applying a signal they build to an electric field that interacts with that of the permanent magnets in interaction: Open the membrane folds and close, causing air to be sucked in or pushed out. The big advantage over other ribbon tweeters is that with relatively low membrane movement in multiples generated at sound pressure in this way.

The AMT is a classic acoustic dipole. He will also be used in multi- usual loudspeaker designs By rejection and encapsulation of rear sound radiation.

Air Motion Transformer stand out due to the very small moving masses through superior transient response and high efficiency. Another problem was in the first part of popular today AMT embodiments in which ferrite magnets have been used in the solenoid actuator, a generally high overall weight and considerable size, since the magnetic fields in a relatively large air gap require strong permanent magnets, but in more recent designs by using high-coercive magnets ( neodymium ) could be overcome. Although the foil membrane is exposed at high sound pressures strong mechanical and electrical loads, the load capacity of the AMT is not reduced in comparison to other acoustic transducers, if instead of the previously used films made of polyamide or polyester (Mylar ) advanced membrane materials of polyimide (Kapton ) and sophisticated adhesive technologies are used.

Air Motion Transformer are particularly used in hi-fi speakers as tweeters in the frequency range from about 1.5 kHz to a maximum of about 25 kHz.

The Air Motion Transformer is also referred to as a healing or JET tweeter. Speakers on this principle are of the German company ADAM, ELAC, ETON, EVE Audio, MUNDORF, the Swiss company Precide, as well as the company ESS (USA), FAL - manufactured (Japan) - Furuyama Audio Labs.

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