Oskar Heil protegé. Ongoing AMT developer at first ADAM now HEDD – for studio/home speakers and headphones¹. For that CV, we call on Klaus Heinz and his Heinz Electrodynamic Designs. When he first bowed the original HEDDphone, it was a clunker of a 730g heavyweight. No matter the theoretical appeal of a wideband air-motion transformer, such a skull load hit an instant 'delete' on my personal lust meter. Now the 2 successor beckons at 550g; and promises much superior comfort from twin-strap adjustments for height and clamping force that seem inspired by Raal-Requisite's SR1a ribbons. As an owner of those, I imagined raw transducer speed as more potential overlap. The pleated makeup of an AMT gives it a 4:1 velocity advantage over a dynamic driver's 1:1 ratio between membrane and displaced air. Air isn't set in pistonic push/pull motion like dynamic and planar drivers but squeezed and sucked from accordion folds. A true ribbon's speed advantage implies negligible energy storage from minimal membrane mass without need for a separate voice-coil layer. It also eliminates motor reflections when its magnets position at the diaphragm's top and bottom not across. That translates into wicked dynamic responsiveness and supremely lucid transient fidelity.
¹ "In the development phase of the HEDDphone it became necessary to rethink one of the key properties of the original AMT driver geometry, namely that its folds are all exactly the same shape. A new diaphragm with folds which vary in both width and depth had to be engineered to reproduce the full spectrum from 10Hz-40kHz. We call this evolutionary step VVT for Variable Velocity Transform."
On paper, the HEDDphone 2 suggested potential for very similar reflexes; without requiring a special amplifier or impedance interface like the ribbons' virtual dead short does. Where the original HEDD's sheer weight had passed me by like a bullet train in the night, the successor's clever skull suspension and lighter construction now rang all of my bells. Could this be a direct Raal-Requisite competitor? Whilst flagship headphones have climbed up the pricing ladder, it's still far more within reach to assemble a top headfi collection—and certainly takes up far less room—than homing multiple speaker pairs of equivalent sonic ambitions. A premium drive-all headphone amp from Burson, Cen.Grand or Enleum will accommodate the lot except for electrostats. Already a €699 FiiO R7's extreme gain mode covers most all ground and includes a complete server/streamer and DAC. Next see how HEDD manufacture one of their AMT tweeters. Unlike a conductive true ribbon's, an AMT's membrane requires the adhesion of voice coil traces which in its pre-folded state we can clearly see here.
Having already digested the opening photos, it goes without saying. Just like wearing an SR1a or Jecklin Float outs us as nerds, today's AMT proposition isn't the last word in stylish sex either. That's due to its cup depth and sizeable head-band array. This is still a big rig not slinky Abyss Diana. But who'd wear the 2 out in the first place? Within the confines of our own crib, anything goes. If you're self-conscious, simply don't look in the mirror.
Instead focus on wear comfort by making your ideal strap adjustments…
… and then delve into in-head sonics. For a look behind the scenes of HEDD's early digs², see the below video from Berlin colleague John Darko. We appreciate HEDD's focus on science; and their decades-long experience working with professionals in the recording sector. We also learn of Klaus Heinz's eventual falling out with Oskar Heil who apparently wasn't amused at all that someone had different ideas on how to take his original air-motion transformer concept to the next level. Once the Heil patent expired, the invention was open to all and today we see AMT manufacture from Dayton to Dynavox, Mark & Daniel to Monacor, Mundorf to SB Acoustics. Applying the operational principle across the full audible bandwidth when used in ultra-close proximity like a headphone now becomes the next challenge which to my knowledge only HEDD have tackled. oBravo from the UK combine a small AMT tweeter with a standard dynamic driver for a hybrid. That's not the same as using one ATM for the entire bandwidth. As Raal-Requisite is for ribbons and Stax for electrostats, HEDD would seem to be the godfather for AMT headphones. Just as today we have estat options beyond Stax, competitors will eventually reverse-engineer a HEDDphone 2 for their own wrinkle in this genre. Regardless, the HEDDphone remains the original which commercialized the concept and now birthed this NextGen rethink based on much feedback from owners of the first.
² As John explains, "that was filmed at their old place in a light industrial area near Tempelhoferfeld. Now their factory is closer to me, just on the other side of the Tiergarten in Moabit. Back then Klaus Heinz was very much still in charge and very concerned with what I filmed of the driver folding process. Since then Herr Heinz has stepped back and his son Freddy is the new boss. I think his protectivity over IP is a little less strict now than it was back then."
As to early feedback I found on the Second, "it lacks sub bass" is a common thread. One reviewer returned his sample unreviewed because he couldn't square the lack of bottom octave with a €2K ask when a ~€300 headphone he had in simultaneously suffered no such issues. Such observations would seem to mirror why AMT speaker tech never appears for bass duties? At this juncture my HEDD factory contact failed to answer emails so I cancelled my planned review for lack of interest. I understand 'no'. The above now serves as a basic 'it exists' feature.