HEDDphone One: a gentle giant

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This week we reviewed the HEDDphone One open-back hi-fi headphones. This model from the young German brand is particularly innovative as it features AMT (Air Motion Transformer) electrodynamic transducers, which are usually found in high-end speakers such as the Elipson Legacy, paired with VVT (Variable Velocity Transform) technology. This technological feat allows the headphones to offer an extended frequency response from 10Hz to 40kHz with great fidelity. Priced at €1,700, the HEDDphone One hi-fi headphones promise a powerful and reliable solution for professional use. Will it be the same for everyday use?

The HEDDphone One features AMT transducers, derived from the tweeters found on some high-end speakers.

HEDD HEDDphone One: the brand

Founded in 2015 by physician Klaus Heinz and his son Frederik Knop, a mastering engineer, HEDD Audio is a German brand offering high-end audio solutions that are made by hand in Berlin. The manufacturer is notable for its adoption of proprietary AMT (Air Motion Transformer) technology for its HEDDphone One headphones.

HEDD HEDDphone One: packaging and accessories

The HEDDphone One hi-fi headphones are delivered in an elegant black box that comes in a cardboard sleeve with a photo of the headphones as well as its name, logo and origin printed in white letters on the front. On the back is a table summarizing the technical specifications and included accessories. Once the sleeve is removed, there is a simple black box on which “HEDDphone One” is written.

The HEDDphone One headphones come with a detachable 2x mini-XLR to 6.35mm jack cable.

Inside the box is a glossy paper sheet summarizing some characteristics and directions for use. The headphones are in a first compartment, securely wedged into a thick piece of packing foam, and the 2x mini-XLR to 6.35mm jack cable is packed in an elegant box inside the second compartment.

HEDD HEDDphone One: presentation

The only model currently offered by the brand, the HEDDphone One open-back electrodynamic headphones are a genuine revolution in terms of individual hi-fi listening. The design of the HEDDphone One is based on the AMT (Air Motion Transformer) principle usually used for the tweeters in high-end speakers to accurately reproduce all audible frequencies and beyond. Here, the AMT principle is paired with VVT (Variable Velocity Transform) technology. This design allows the headphones to provide an extended frequency response from 10Hz to 40kHz, compatible with Hi-Res music. Lastly, despite their relatively low impedance of 42 ohms, their low sensitivity of 87dB means they have to be paired with a source that has a hefty power reserve.

AMT transducers and VVT technology

The HEDDphone One are the first ever consumer headphones that use AMT technology and can be associated with several sources (unlike the Ergo AMT headphones, designed to work only with their dedicated amplifier). The HEDDphone One studio headphones use a wideband electrodynamic AMT transducer. This technology uses a pleated diaphragm, a design that has two advantages: it increases the diaphragm’s contact area with the air and provides higher velocity at the reproduced frequencies. By pinching the air in between its folds, the AMT transducer optimizes the speed of the expelled air compared to a conventional driver. The HEDDphone One headphones’ AMT transducer also benefits from VVT technology for an optimal reproduction from 10Hz to 40kHz. These frequencies are then more rapid and clear with an improved transient response.

AMT principle

The Air Motion Transformer is an electromagnetic driver based on the Lorentz force. This force moves the air in the single folds of the diaphragm, which has an aluminum circuit printed on it (violet arrows). It is also surrounded by a strong magnetic field. Thanks to this accordion-like design, the air flow (blue arrows) is four times faster than the speed in which the individual folds move, which is a big advantage when it comes to reproducing music signals with fast transients (cymbals, etc.).

Open-back headphones

The HEDDphone One headphones have an open-back design. Sound is therefore diffused towards the listener’s ears but also out of the earpieces.

The open-back design of the HEDDphone One headphones provides a particularly wide soundstage.

The advantage of open-back headphones is that you can enjoy your music with a wonderful spaciousness similar to the sound offered by a real hi-fi system (amp + speakers), but with less clutter. Note that to take full advantage of their performance, open-back hi-fi headphones must be used in a quiet environment. If you are not alone in the room, those around you will hear your music, even at low volume, and you will also be able to hear all surrounding noises.

Design and comfort

The HEDDphone One open-back hi-fi headphones have an over-ear design. The wide earpads therefore surround the listener’s ears without resting on them. Although their thick and soft design adds to the bulky aspect of the headphones, they also guarantee great comfort.

Although the earpads are quite bulky, the HEDDphone One’s earpieces can be folded for easy storage.

For easy storage, the earpieces of the HEDDphone One can be folded towards the headband. Their height can also be adjusted to provide a better fit. The headband, however, could have been a little wider in order for these huge 718kg headphones to have been worn for longer. Consequently, they won’t suit everyone.

Detachable cable

The Y-cable included with the HEDDphone One features locking 4-pin mini-XLR balanced connectors. Conveniently, the right connector is marked with a red ring.

For ease of use, the detachable cable measures approximately 2 meters long and is equipped with a 6.35mm jack connector. It can therefore be easily connected to a wide range of headphone amplifiers.

HEDD HEDDphone One: key specifications

Type: open-back, over-ear
AMT electrodynamic transducers
VVT technology
Frequency response: 10Hz – 40kHz
Impedance: 42 ohms
Sensitivity: 87dB
Detachable Y-cable, mini-XLR to 6.35mm
Weight: 718g

HEDD HEDDphone One: listening conditions

For our review, we paired the HEDDphone One hi-fi headphones with the Naim Uniti Atom Headphone Edition headphone amplifier (read our review of the Naim Uniti Atom Headphone Edition) to enjoy our Qobuz playlists (24-bit/192kHz) as well as FLAC files stored on a USB stick.

HEDD HEDDphone One: listening impressions

Simply Red – If You Don’t Know Me By Now

The HEDDphone One whisked us away on this lovely journey and handled the cymbals brilliantly. The drum hits were crisp and reproduced with authority thanks to the dynamic qualities of the AMT transducers.

2CELLOS – Eye of the Tiger

This cello cover of Eye of the Tiger was masterful. We simply had to close our eyes to feel each note pierce us with the energy that characterizes this duo so well. During our listening session we enjoyed an exceptional feeling of spaciousness, both in terms of depth and width, and perfect stereo. Every instrument, played by the duo or the accompanying orchestra, was perfectly positioned. It was as if we were right beside them. What a magical moment!

Pedro Abrunhosa – Se Eu Fosse Um Dia O Teu Olhar

This beautiful love song was once again enhanced by our headphones! The synth notes were wonderfully clear, the drums and the electric guitar excellently sustained, and Pedro Abrunhosa’s smooth voice was reproduced with precision, softness and naturalness.

Kofs – Bande Organisée

We were very pleasantly surprised with this rap track. Once again, the HEDDphone Ones perfectly reproduced every frequency. The lows were impactful, the highs sustained without becoming sibilant. It was a pleasure to listen to!

HEDD HEDDphone One: compared to…

Focal Clear MG: sold for €200 less, the Focal Clear MGs are more comfortable and offer slightly deeper lows. However, the HEDDphone Ones come out on top in terms of details and openness of the soundstage.

Sennheiser HD 800S: available for around 100 euros less, the Sennheiser HD 800S have a wider frequency response and reproduce more details than the HEDDphone Ones. The HD800S also come with a balanced cable as well as a 6.36mm cable. However, the HEDDphone Ones are easier to power, with an impedance of 42 ohms compared to the Sennheiser headphones’ 300 ohms.

HEDD HEDDphone One: who are they for?

The HEDDphone One hi-fi headphones are designed for anyone looking for a powerful, open-back model. Their incredibly spacious sound suits most musical styles, except perhaps rock or electronic tracks.

HEDD HEDDphone One: conclusion

The HEDDphone One headphones are rather bulky. Weighing 718g, they can feel quite heavy after about thirty minutes. The headband could have been wider to distribute the weight of the headphones more evenly across the head. Although it is not suitable for all head shapes, those who are lucky enough will enjoy a high-caliber performance. Throughout this test, we enjoyed every track we listened to, with a level of detail and openness we had rarely experienced before. The advantages of the AMT transducers are clearly audible, with high frequencies that are both precise and pleasant. To get the best musical performance with these headphones, it is best to pair them with a powerful headphone amp such as the Naim Uniti Atom Headphone Edition (used for this test), the iFi Audio iDSD Diablo (read our review of the iFi Audio iDSD Diablo) or, for a warmer sound, the McIntosh MHA200.

We liked:

The magnitude of the soundstage
The level of details
The natural reproduction
The precise and pleasant highs
The powerful lows

We would have liked:

For the headband to have been wider
For them to have been lighter
A balanced cable 


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