THE SURPRISING ANTIQUITY OF THE AIR MOTION TRANSFORMER SPEAKER DESIGN PRINCIPLE OF THE AEMPYREAN REF
Most audiophiles associate the AIR MOTION TRANSFORMER loudspeaker design
with ELECTROSTATIC SOUND SYSTEMS, INC, known as ESS. As I write this discussion I’m referencing the much distributed eight page color brochure from around 1973, which discusses the operational details of the transducer, and lists the product range available then: beginning with the now collectable AMT-1, on through the AMT TOWER, the AMT 3 ROCK MONITOR, the AMT 4 and 5, on to the AMT 6 PROFESSIONAL. Over the production years, until ESS was sold, many other model iterations evolved also.
The sonic performance of the AMT line is well described by the advertising phrase,
SOUND AS CLEAR AS LIGHT. In the product line, the AMT 1 TOWER with an
Arthur Bailey type transmission line, hearkens back to my design of the TRANS-STATIC I,
which was the first ESS product.
Now within inventive reality, the ESS AIR MOTION TRANSFORMER as created by Oskar Heil, and patented by him several times in the Seventies, was not quite the unexampled first revelation of the design principle ever, a unique in all the world device, as then often believed.
For the actual history of the AIR MOTION TRANSFORMER principle, basically inhaling and exhaling, while accelerating, or TRANSFORMING the direction and velocity, of a partially confined volume of air; we turn to a superlative and exhaustive text by Justus Verhagen, PhD: RIBBON LOUDSPEAKERS THEORY AND CONSTRUCTION. ISBN Number 1-882580-24-X.
The Heil AMT design is a subset of ribbon transducers generally: or more specifically
folded ribbon transducers in general. The book referenced above carefully and thoroughly explicates the early days of ribbon transducer development in Germany in the period just subsequent to the First World War. This well written and well-documented section reveals a surprising progenitor of the AIR MOTION
TRANSFORMER: the patented Erwin Gerlach ZIG-ZAG TRANSDUCER, discussed and described in 1924.
This transducer meets all of the AMT criteria stated above with respect to transforming
the direction and velocity of a partially confined volume of air.
Now historical detail minded people will recall that eventually the mid and high
frequency response of the ESS AMT was extended on down in frequency in an iteration
named the TRANSAR, carefully described in patent detail, but largely unsuccessful,
perhaps because of excessive complexity. However, much truly excellent patent research
and product development has followed the Oskar Heil ESS work, so that now extremely
high -quality AMT mid-high drivers are quite reasonable in price.
Thus far the Gerlach-Heil AMT principle has not produced a successful full range
loudspeaker system, although the related thin film planar magnetic and electrostatics
technologies certainly have: these speakers are among the very best in the world.
We have a patented, extended deep bass, in fact, capable to pulsed DC AMT technology as embodied, and described in granted US Patent 5,872,853. We’re working now on building a full range AIR MOTION TRANSFORMER transducer system, which should fully establish the Gerlach-Heil principles as capable of the absolute highest full range and beyond musical fidelity.
