AMT Driver Principle

From Wikiphonia

1 Air Motion Transformer (AMT) Driver Principle
2 Brochures
3 Pictures of drivers
4 Articles of interest

Air Motion Transformer (AMT) Driver Principle

The first thing to be understood about the Heil AMT (Air Motion Transformer) is that it does NOT operate like an accordion. In other words, the animated gif you see plastered all over the internet, this[1] one, ..is wrong.

The truth, as those of us who've seen political ads on TV know, is more complex. It always is.

This[2] one, from the Precide SA website, is correct. Alternate pleats move toward one magnet, the others move toward the other magnet. You could say the diaphragm "claps" (blows, squeezes the air out) in one direction while it simultaneously "spalc" (unclaps, sucks) in the other, giving a dipole radiation pattern-- the front wave is 180 degrees out of phase with the rear wave.

The fact that a sound wave is being launched by two surfaces rushing toward one another rather than simply flopping about in space gives the Heil its fast rise time.

The fact that the pleats don't contain very much air is the limiting factor in the understandable ambition to coax the Heil to produce usable output below 500 Hz as a tweeter. The problem isn't as severe, but remains, in a headphone application. Compare the TAKET piezoelectric modified Heil AMT.

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