HEDD Audio HEDDphone: AMT Driver Headphone Review

By Andrew Park (@Resolve)

Introduction

The review unit was provided on loan from headphones.com for evaluation. Read more about this product on the HEDDphone thread in the HEADPHONE Community Forum.

Every once in a while something comes along that completely changes the landscape for high-end flagship headphones. We can think of headphones like the HD800, Focal Utopia, or perhaps a planar magnetic headphone like the LCD4, where the experience of using them definitively provides the listener with the recognition that something new is possible - that there's more to be experienced than previously thought possible with headphones. Revolutionary products like these have also typically commanded wallet-shattering price tags, and with each new benchmark often comes a new upper limit for how much it costs to have these amazing new experiences. HEDD Audio have now entered the arena, and their first release takes aim at precisely this issue. They're a company that's so far been known for revolutionary tweeter and speaker designs, however they've now implemented their design ideas into a flagship headphone, the appropriately named "HEDDphone".

The HEDDphone's introduction to audiophiles and enthusiasts over the past year has generated rumors and rumblings about how much of a game changer this could be. It uses a new transducer type - one that HEDD has successfully demonstrated in the speaker world, using what's called 'Air Motion Transformer' technology - and this has sparked a substantial amount of interest among seasoned audiophiles with insights into up and coming technological advancements in the headphone world. Now that the HEDDphone is commercially available, I'm left with the following questions: Is the HEDDphone one of these revolutionary new experiences? Is this a new benchmark for audio fidelity, and is it able to deliver at less than half the price of existing flagships? If the answer to these questions is 'yes', the HEDDphone has the potential to completely change the landscape for high performance headphones, because anyone coming out with a new flagship at $1899 and above needs to make sure it's at least as good.

Specs

  • Type - Over Ear Open-back headphone
  • Driver - Air Motion Transformer
  • Efficiency - 87 dB SPL for 1 mW
  • Impedance - 42 Ω
  • Weight - 718 g
  • Connector - Mini XLR
  • Price - $1899 USD

Source

Build, Design & Comfort

As mentioned, the HEDDphone uses a unique transducer type called a full range 'Air Motion Transformer' (AMT). You may be familiar with dynamic, planar magnetic, or even electrostatic driver types, but AMT is something completely different. The basic design principle is that instead of a diaphragm that creates air speed consistent with the velocity of the material being moved, the AMT transducer is able to increase air speed to four times that of its diaphragm velocity. The AMT diaphragm uses a series of folds, which open and close in an alternating pattern, effectively squeezing the air, rather than behaving in a traditional piston-like fashion found in other common transducer types. This extra pressure creates increased air velocity, similar to the way bellows work for stoking a flame.

It should be mentioned that AMT has been tried before in headphones to limited success, but what's unique about HEDD Audio's implementation here is that they use folds that vary in both width and depth. Through the HEDDphone's development, the geometry of the sound-producing folds was altered and optimized in order to improve the frequency response curve, ultimately leading to the tonality that it now has. Without the geometry optimization, the tonality would not have been as linear.

The implementation of this design has also unfortunately meant that the HEDDphone is quite heavy at around 700g. I'm told that the air gap necessary for AMT needs to be larger than that of traditional transducer designs, and so the increased size and weight are a necessary trade-off. 700 grams puts the HEDDphone right in line with the weight of some flagship planars from Audeze. I was critical of Audeze for the weight, and so I have to remain consistent and be critical of the HEDDphone for its weight as well. The important difference, however, is that the HEDDphone doesn't weigh down on my neck nearly as much. My guess is that this has to do with the weight distribution and the clamp force for the cups.

The top headband piece has a notch in the middle, and the two side pieces take the bulk of the weight where the surface area comes into contact with the top of my head. This means that there's no hot spot in the middle after a few hours, thankfully, and the weight is instead distributed to a more variable surface area laterally on the sides of my head, rather than pressing down on the middle part. The cups also clamp inward more substantially than the LCD4, and this helps alleviate some of the weight at the top. This idea was also effective for the Rosson Audio RAD-0, however I found that headphone to clamp a bit too hard, where as the HEDDphone gets the balance just right. Moreover, the pads soften much of the clamp so it doesn't press in on my jaw all that much either. In fact, after a few hours, I don't have any problems for my neck, jaw or the weight on my head. My one criticism apart from the weight has to be the fit for larger heads. I have a slightly larger than average head, and I have to extend the arms where they attach to the yokes as far as they go, meaning for those with larger heads, this may be a problem. But the way it fits also means you can kind of push it down onto your head even if the arms seem initially too short. Thankfully, there's also a bit of cup swivel meaning it's not too difficult to get a decent fit.

For build quality, the HEDDphone feels solid, but it doesn't feel quite as premium as some of the other flagships out there like the Focal Utopia or LCD4. It should also be mentioned that this is an extremely open headphone, so it doesn't block any sound in or out.

Score - 8.5/10

Performance

The theory behind the AMT driver is interesting, but none of that matters if it can't deliver the promised performance benefits. Thankfully, it does - emphatically so. The HEDDphone delivers the kind of performance one might expect from a nano-scale planar flagship, or electrostatic headphone, and this already answers one of my initial questions at the beginning of this review.

Detail Retrieval

In order to demarcate this performant category from perceived detail that's conferred by tonality or frequency response optimization, I have to stress that this refers to how a headphone sounds for individual representations in the mix, clarity and structural definition for the images, and textural nuances for instruments being played. It's the reason why an Audeze LCD4 is easily discernible as highly detailed for all different parts of its frequency range, in spite of its less than ideal tonal balance. And to that end, the HEDDphone is right up there with the LCD4 in terms of its strict detail capability as identified by the definition above. This is one of the most detailed headphones available, similar in capability to many of the nano-cale planars like the LCD4 or HiFiMAN HE1000se.

Score - 9.8

Speed & Dynamics

Just like with detail, this is also one of the fastest headphones available for the initial leading edge, along with a clean decay. These are more matters of taste and preference, but I love that tight and snappy quality to the presentation. Interestingly, I find that I notice this just as strongly for the treble and midrange as I do for bass hits - and I'm not normally used to hearing this quality as clearly or immediately for higher frequency ranges. Usually it's how tight and well-controlled the bass is first, and then the evaluation focuses up from there. For dynamics, the HEDDphone's technical capability is a bit less obvious. Due to the tonality, the bass isn't elevated for extra perceived punch, so the 'slam' quality can be difficult to evaluate (similar to the Utopia). But occasionally for tracks that make use of the full frequency range, it hits with impact and authority. However when I did increase the bass energy by a few dB, it should come as no surprise that I could feel the impact quite a bit more strongly. When listening to tracks like Why So Serious from Hans Zimmer, you physically feel the air being moved for sub-bass frequencies. Throughout the rest of the frequency range, everything feels like it has solid impact as well. So while it might not slam as hard in the bass as high excursion dynamic driver bass cannons, its dynamic presentation is reminiscent of flagship planar headphones like HiFiMAN's HE1000 series - if not slightly more impactful overall.

Score - 9.5/10

Stage & Imaging

Stage and imaging are the HEDDphone's shining characteristics. Someone who heard the HEDDphone at a show recently described the stage as "endless", and I can certainly see the inspiration for this description. Not only does it have a large presentation, with superb lateral and forward definition, It's able to represent instruments with a range of depth that goes from inside my head to way out in front of me, again similar to the space representation of the HiFiMAN flagship planars. If any headphone has a 'speaker-like' presentation, in my mind the HEDDphone earns that classification above all others. Moreover, its image distinction and distribution are flawless. To be more specific, some recordings have actually made me jump at how realistic the stage presentation is.

Score - 9.8/10

Timbre

If there's a shortcoming to the HEDDphone's technical performance, it may be in its timbre. This isn't the most 'natural' sounding headphone like a ZMF or the HD6XX. There's a kind of sharpness that comes with the exceptional detail retrieval, and it comes across with an almost planar-like character to it. This is something that I find is easy enough to identify, but I'm not personally bothered by it in the slightest. Moreover, it's not as noticeable as many planars (remember this isn't technically a planar), but those who are specifically sensitive to that quality, it may be worth keeping in mind.

Score - 8.5/10

Tonality

I've found that for many of technically capable high performance headphones like the nano-scale planars, there's often something to criticize with their tonal balance or frequency response. It's as if some tonal imperfection is the price to pay for the crazy technical performance we all want. The HEDDphone is perhaps the closest I've yet heard to getting tonality right - for certain genres.

For the most part, the tonality is similar to that of the Focal Utopia, meaning that the frequency response emphasizes clarity, adding to increased perception of detail in the process. The HEDDphone does this, however, with better sub-bass extension as well. For many, the Utopia is a bit lean in the bass, with a bit of roll-off below 60hz. The HEDDphone on the other hand has bass that sits at a similar level, but doesn't roll off. So you get full extension into the sub-bass, similar to what's achieved by many planar magnetic headphones. The downside is that this is still a few dB below the traditional consumer curve. I find this is actually agreeable for music with instruments, like Jazz, classical or acoustic music. But for modern genres, it may lack a bit of that bass emphasis that a lot of people like (as it's reflected by the consumer target). Thankfully, for those of us looking for that, the HEDDphone does respond well to EQ, and for anyone who prefers the Harman bass emphasis, it's easy to achieve by adding a 2.5 dB shelf to around 80hz and below. Doing so also adds the perception of increased dynamic impact in the bass.

Measurement taken from the MiniDSP EARS rig with the HEQ compensation (closer to Harman target - not an industry standard measurement system (and there is a rig artifact between 4-5khz)

For the rest of the frequency response, I wouldn't change anything. The treble is exceptionally well-extended with lots of air up top, while not going overboard to incur tonal imbalances to the rest of the frequency response. This means cymbal hits resolve with perfect clarity and don't sound unfocused like is often the case when treble extension is cranked up too high above 12khz. Moreover, there's absolutely no aggressiveness or unnecessary emphasis to the consonant range around 8.5khz, so the 'S' and 'F' sounds aren't overly sharp or piercing.

But perhaps my favorite part of the HEDDphone's tonality is the midrange. I'm finding it more and more common for flagship headphones to exhibit a recession in the upper mids and lower treble. This is likely done because an elevation in that region can be particularly annoying for modern genres - it has a tendency to make electric guitars or more moderns sounds a bit shrill and shouty, and can even introduce resonant ringing if overdone. So manufacturers take the lesser of two evils and subdue that region so as not to run the risk of shrillness creeping in. For the HEDDphone, it's thankfully not withdrawn - at least not to the same degree. This is important because it means good tonal balance for certain types of music. For piano hits in particular, the resonant trail that occurs after the primary hit retains its clarity - just like it would in real life - rather than being slightly muted or muffled by any recession in that frequency range. Importantly, it's also not overemphasized, and it feels like HEDD Audio got the region between 3-5khz just right. So it's acceptable for modern genres, but then also shines for acoustic music.

Measurement with the HPN compensation.

The bottom line for tonality is that it's very agreeable, but for those looking for that 'fun', bassy sound, this is not that headphone without EQ. Instead, it's a more traditionally 'audiophile' tuning, and of course by that I mean one that excels at what Metal571 calls "serious audiophile music" - and that happens to be the kind of music I enjoy! So it gets good marks from me.

Score - 9/10

Comparisons

ZMF Vérité

This is my current go-to flagship headphone. It has some of the best performance for a dynamic driver headphone, second perhaps only to that of the Focal Utopia. To my ear, the HEDDphone does beat the Vérité in terms of detail retrieval, speed, stage and tonality. The Vérité still wins in the dynamics and slam department, as well as that natural ZMF timbre we all love. Of course, the Vérité is also considerably lighter and so it's much more comfortable for longer listening sessions. For those who already own a ZMF Vérité, the HEDDphone would make an excellent companion headphone as it's able to do certain things the Vérité can't - and it's also got a tonality that excels with genres that the Vérité might not be as good for.

Audeze LCD4

At the moment, I'm unable to say conclusively whether the HEDDphone or the LCD4 has better detail retrieval. It's close enough to the point where I'd need to have them side by side to make definitive statement. But if I had to give an answer, from memory I'd say the LCD4 may just barely edge out the HEDDphone - or maybe just in the bass. I can say more confidently, however, that the LCD4 hits harder in the bass, but the HEDDphone is at least as fast, it has a much bigger and more precise stage (similar to that of the HE1000se), and a much better tonal balance for the upper mids/lower treble as well as the treble above 10khz. I also find the HEDDphone to be noticeably more comfortable as I'm able to actually wear it for a good 4-6 hours, while I struggled to get through an hour at a time with the LCD4.

For me, it really just comes down to which performant categories you value more, because again, a lot of people are comfortable adjusting the LCD4's tonality with EQ or the 'Reveal' plugin. If you care most about slam, the LCD4 is the better choice, but if you care more about stage and imaging, the HEDDphone is much better. In my mind the other categories are close enough. Keep in mind though that the LCD4 is more than twice the price of the HEDDphone - and so the fact that it's able to keep up, and beat the LCD4 in some categories is remarkable.

Focal Utopia

I love the Utopia, but for detail retrieval I have to give the edge to the HEDDphone slightly. For speed again, the HEDDphone feels tighter and more intense for its leading edge, and it has a much more speaker-like presentation for its stage. The Utopia wins when it comes to macrodynamics and punch, even though it has a slight bass roll-off that makes the perception of its capability somewhat hard to follow, and that's also where the HEDDphone does a better job once again with better bass extension. The Focal Utopia is considerably more comfortable for long listening sessions, weighing substantially less than the Headphone, and on the whole it's a much more 'normal' and manageable headphone. But for those looking for similar if not superior performance, with a similar slightly counter-clockwise tilted tonality, at half the price, the HEDDphone is a bit of a flagship killer.

Conclusion

I'm thrilled to report that the HEDDphone does live up to the hype. More importantly, this release changes the landscape for high performance headphones. I can't think of anything else that performs as well in as many categories at the sub $2000 price point, and in my mind it's therefore a new benchmark for flagship headphones at this range. Up until now, end-game flagship headphones have had a lot of flexibility with regards to pricing. But now that the HEDDphone exists, anything that's intended to come out at a similar or higher price tag needs to be at least as good. For me, very few headphones are able to do that, and the ones that do currently cost over twice as much - many of them also have other serious downsides that the HEDDphone doesn't have. So in many ways it comes down to weight and comfort more than price. If you're okay with a headphone that's a bit on the heavy side, I can't think of anything I'd recommend over the HEDDphone at this price.

Score - 9.2

You can also check out my video review here: 

- Andrew Park (@Resolve)

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