What is an AMT Tweeter?
An AMT tweeter is a specific sort of tweeter. AMT stands for Air Motion Transformer and was invented by scientist and physicist Dr. Oskar Heil in the 20th century and differs from other loudspeaker designs like moving coil, planar magnetic, or electrostatically-driven loudspeakers in that it uses a different transduction principle. An ATM tweeters should also not be confused with a planar tweeter or true ribbon tweeters. In contrast to a planar ribbon loudspeaker, the AMT's diaphragm has a bellows-like pleated shape. Using a folded sheet of polyethylene terephthalate (PET) film with metal etching, the AMT moves air laterally in a perpendicular direction. An AMT tweeter can reproduce sound down to 650 Hz and is particularly well-suited for high frequencies. The midrange-tweeter or tweeter in high-end multi-driver speakers, occasionally paired with horns.
How does an AMT Tweeter work?
To pump air through the reed chambers, the diaphragm physically moves back and forth from itself in a motion resembling that seen when an accordion is pushed in and pulled out, albeit over a much smaller motion range. Due to the extremely low mass of the polyethylene substrate and the significantly shorter distance it travels on each "swing" compared to a dynamic driver, the result is a dipole driver with an incredibly quick response rate. It has traits in common with an electrostatic driver in this technical sense. Here at SoundImports, you can buy premium AMT tweeters from our well-known brandsDayton Audio, Monacor, Mundorf, and SB Acoustics!
Each diaphragm flexure moves very little air, but because of the folded structure, more air is moved than it would by an electrostatic or conventional cone driver with the same plotted surface area. In terms of surface comparison, an 8-inch (200 mm) circular dynamic cone's functional driver area is comparable to a standard 1-inch (25 mm) wide AMT strip. The AMT behaves like a point source version of a larger driver due to the folded driver design and the small motion range, which naturally leads to lower sound reproduction distortion. The name "Air Motion Transformer" comes from the fact that the speed of the air as it exits the diaphragm is roughly five times that of the driver structure.