Loudspeakers

Although ELAC did not invent the AMT (Air Motion Transformer) driver – the concept was patented by German engineer Dr Oskar Heil in 1973 – its loudspeakers have long been associated with the technology, now increasingly popular as an alternative to more traditional dome tweeters. The AMT uses a pleated, accordion-like substrate onto which is bonded an aluminium foil ‘voice coil’. The polymer/alloy strip is bathed in a magnetic field so the applied signal current causes it to compress and expand along its length, squeezing the air out from its folds and, thus, launching the soundwave(s).

Typically, AMT drivers offer a resistive impedance, the promise of low distortion and potentially better power handling than an ‘equivalent’ dome tweeter, but engineering an AMT driver to achieve a uniform on- and off-axis output is not trivial [see PM's Lab Report]. Also, the clamping of the AMT strip within its frame is critical in tackling resonances within the ‘squeezebox’, an issue addressed in ELAC’s latest 6th-gen driver by employing ‘unequal moving masses’ to distribute modes over the AMT’s radiating surface.

While Burmester employs the ELAC JET tweeter [HFN Jun ’24], as does Neat [HFN Jul ’18], other AMT-style tweeters are employed in the FinkTeam KIM [HFN Feb ’21], Kroma Atelier Stella Xtreme [HFN Feb ’23], MartinLogan Motion XT F200 and B10 [HFN Jul ’23 & Oct ’23], and Monitor Audio Gold 300 6G. PM