Test ESS AMT-1

Oskar Heil was a German physicist and inventor (1908–1994) who became famous for developing the Air Motion Transformer (AMT). The US company ESS was the first manufacturer to commercially utilize Heil's invention. A patent was filed in 1972, which expired in 2004. Among hi-fi and DIY enthusiasts, the original ESS AMT-1 is considered a classic. The large "Great Heil" driver is regarded as one of the most natural and dynamic tweeters. Consequently, the ESS AMT-1 is highly sought after and frequently used. This AMT was tested in Hobby HiFi, issue 2-3/2024. However, since the manufacturer is constantly making improvements, our test is intended to reflect the current state of the technology. The certificate for our driver is dated December 2025 with serial number 7109. The drivers are available for purchase from hifisound.