We are now fully open, but due to Covid 19, we are taking the precaution of asking for demos by appointment only, to arrange your appointment please call us 01592 859163 or email

We are maintaining social distance and the premises and equipment is cleaned regularly and between appointments.

Hedd HeddPhone


Interested? Contact Us


HEDDphone®. A New Chapter in Headphone Technology

HEDD the first full range Air Motion Transformer headphones to audiophiles and recording artists worldwide. The Air Motion Transformer (AMT) is an electrodynamic transducer that allows to move air significantly faster than common voice coil, planar, or electrostatic systems. Their traditional piston-like movement is overcome by a folded diaphragm that squeezes out air four times faster: A breakthrough for capturing more details in a musical recording.

30 years ago HEDD founder and CTO Klaus Heinz designed the first compact and marketable AMT tweeter based on American-German Physicist Oskar Heil’s original Air Motion Transformerinvention. Since then, Heinz has increased its sonic quality in several fundamental revisions for his loudspeaker tweeter designs at ADAM Audio and HEDD.

In 2019 Heinz has started developing a full range Air Motion Transformer to break new grounds for this superior transducer principle. In order to reproduce the complete audible frequency band (and beyond), the HEDDphone® incorporates VVT® technology (Variable Velocity Transform). It introduces a new, variable diaphragm geometry that expands the AMT principle to a linear full range (10Hz–40kHz) headphone transducer.

The HEDDphone® brings the enormous dynamic capabilities and the superior sonic resolution of the AMT principle to the world of top-end headphones. HEDDphone® excels where it really matters: in accurate, untamed, and touching music reproduction.

» If Mercedes made a headphone this would be it «
Steve Guttenberg The Audiophiliac

» This changes everything «
Resolve Reviews

»The sound great, in a way that’s actually useful for mixing & mastering «
Sound On Sound Magazine

The HEDD Air Motion Transformer by Klaus Heinz

Of the many ideas on how to build a loudspeaker transducer, Oskar Heil’s (1908–1994) Air Motion Transformer is unique in its way of making the air move. In the course of the history of loudspeakers, many different transducer designs have been introduced. All of them feature piston-like diaphragms that move the air in a 1:1 ratio so that the diaphragm velocity equals the air velocity. Whether we talk about electrostatic and magneto-static speakers, ribbons, voice coil based dome and cone speakers or even a Blatthaller design – they all follow this particular design approach.

It was not until the early 1960s that German-American physicist Oskar Heil came up with a new idea and proposed a folded elastic diaphragm, where single folds open and close in an alternating pattern and thus „breathe“ air in and out, with the special charm that the air driven through the folds is accelerated to a ratio four times as fast as the diaphragm itself. In the early 1990s, Klaus Heinz was so intrigued by Heil’s idea that he used it to build a compact, reliable, and superior sounding tweeter.

Heinz later went on to found ADAM Audio in Berlin, a company that manufactures loudspeakers based on Heil’s invention. The X-ART tweeter designed by Heinz during his time at ADAM was widely praised and gradually revolutionized the speaker landscape, as similar designs emerged on both the HiFi and the studio monitor market. In 2020 HEDD has introduced another evolutionary step in the development of the AMT: The HEDDphone® is not just the first full-range AMT headphone, it also incorporates VVT® technology. This means that the HEDDphone® is based on a new diaphragm geometry that expands the AMT principle to a linear full range (10Hz–40kHz) headphone transducer. It replaces the fixed geometric structure of conventional AMT drivers as the folds vary both in width and depth.

Open over ear headphone with Air Motion Transformer
87 dB SPL for 1 mW
42 Ω
718 g
Mini XLR

Klaus Heinz’ early encounters with Oskar Heil in Silicon Valley

Klaus Heinz and Oskar Heil’s first meeting took place in the 1980s. It is a moment that Klaus Heinz remembers vividly:

“It was back in 1985 when I got to know the Air Motion Transformer and its inventor Oskar Heil. I was intrigued by the idea and the sonic results of Heil`s ESS loudspeakers, which used the Air Motion Transformer in a rather quirky way and definitely included some questionable details. And yet, the accurate and brilliant sound removed a heavy curtain from all the recordings I liked and had previously listened to in what I had until then considered a rather decent quality. I was curious enough to visit Heil in his home in San Mateo, south of San Francisco, an area known as the Silicon Valley. I listened to his life story, we discussed electrons (his favorite „animals“) and, of course, loudspeakers. I was very impressed when granted the chance to visit his laboratory in Belmont. Here, I found myself in the most disorderly, chaotic room I had ever been in, and yet Heil definitively knew where to find what. He showed me quite a number of new transducer approaches that were different from the boring voicecoil/piston-like diaphragm combinations that we were, at the time, familiar with, be it in the form of cones or domes.”

Klaus Heinz recalls how Heil presented some of his highly original and often quirky inventions to him – and how fascinated he was by the physicist’s imaginary reservoirs:

“What fascinated me most when discussing loudspeakers with him was the fact that he really thought originally. He constantly looked for new ways to create sound out of alternating current. He did not first ask which voice coil parameter or which resonance frequency would play what role, as a typical engineer in the Research&Development community would have done, but rather focused on the physical interdependencies between current and force in magnetic or electrical fields. Heil also constantly thought about ways to develop a better flaming ionic tweeter than Alan Hill’s Plasma driver, a fascinating device that excited air molecules electrically in order to reproduce frequencies between around 700hz and the ultrasonic range. While Hill’s invention was probably great for listening to single songs, a Mahler Symphony would probably have caused lethal lung cancer or similar illnesses with all the ozone produced by the music.”

During one of their first meetings, Oskar Heil surprised Klaus Heinz by telling him that it had actually been him who invented the dome back in the 1930s.

“How was that possible? From everything I knew, Wolfgang Seikritt invented domes in the 1960s, and in Germany. Yet here was Oskar Heil who led me through the almost absurd process of his invention: “What I did,” he explained, “was that I took my mother’s silk stockings, then added a darning mushroom, drew the stocking over the mushroom, applied egg white as a thin coating, let it dry out, glued it to a voice coil – and there it was: the first dome tweeter made of wood, stockings, and eggs.”

Although quite a few other audio-related inventions can be traced back to Heil’s ideas (such as the ‘traveling tube,’ the so-called ‘Wanderfeldröhre,’ which sensationally allowed to amplify frequencies up to above 1 GHz), Klaus Heinz’ favorite discovery in Heil’s lab was the Air Motion Transformer, which should later become the signature design of the many loudspeakers that Heinz developed from the 1990s onwards and that he remains dedicated to until this very day.


Subscribe to our newsletter

Contact us about the


Thank you

Thank you for contacting The Hi-Fi Gallery. We will respond to your enquiry as soon as possible.