Fit and Comfort

Seen above is the HEDDphone TWO placed on a mannequin head, to help show how these headphones would look on the human head. Note that the head is slightly under average sized, so account for the discrepancies accordingly. As with all headphones, getting a good fit and seal is crucial, so make sure to properly use the HEDDband system for both height and clamp force adjustability in addition to the swivel/rotation of the ear cups themselves. This section is mostly a summary of the points expanded upon in more detail on the previous page and I should say right away that the HEDDphone TWO is still bigger than heavier than the average set of headphones. Indeed, it may seem tiny compared to the behemoth HEDDphone ONE at 730 g and its giant ear cups but the HEDDphone TWO weighs in at 550 g and still has relatively big cups. This is because those AMT drivers are still massive compared to, say, a 50 mm dynamic driver and HEDD also wants to give enough room in the ear cups for the drivers. The ~25% mass reduction is handy compared to the previous offering but the biggest improvement has to be the new headband and frame which makes the HEDDphone TWO among the most comfortable set of headphones for people. Whoever came up with the idea to have adjustable clamping force deserves a raise since it allows for everyone to have a reproducible listening experience finally. The suspension band could be slightly stiffer than you'd like, especially if you have the clamping force somewhat high, so the headphones may feel like they are floating on your head at times. If so, reduce the shaping strap by a notch and see if that helps—this should also help distribute the weight much better for longer listening sessions. The ear pads are thick and engulf my ears nicely to add to the overall comfort once everything has been set up. Also, because why not, I also have photos showing the HEDDphone ONE on the same mannequin head so you can visualize further how much things have changed.

Audio Performance

Audio Hardware

This is the first time we are reviewing a set of headphones using air motion transformer drivers, so I'll do a brief primer on how they work. Dynamic drivers, planar magnetic drivers, and electrostatic drivers all operate in a piston-like motion with a single sheet diaphragm moving back and forth in response to the driving force, be it magnetic or in an electrostatic field. This means the amount of air being moved is directly proportional to the size and area of that single sheet itself. With AMT drivers, the diaphragm is instead folded multiple times and each fold opens and closes alternatively to allow air to be squeezed out. As such, for the same unit length of driver, an AMT driver can have far more surface area owing to the folds occupying 3D space and can push out the pressurized air as much as four times as fast as the diaphragm itself moves, hence the name air motion transformer. HEDD's take on the AMT driver uses a Kapton diaphragm with aluminium traces via a printed circuit driven via a Lorentzian force—I am so happy I remember my undergrad electrical engineering lessons—generated by the neodymium magnet associated per driver. The folds and the faster, higher amount of air can be especially helpful for higher frequency reproduction and for instruments with faster transients—strings, cymbals, triangles etc.

It's no surprise then that these AMT drivers were originally employed as tweeters paired with dynamic driver sub-woofers in speaker designs. Making a full-range AMT driver is quite hard for speakers since the lower frequencies would have unacceptably high distortion at typical playing volumes, although HEDD saw a market for headphone drivers where the listening volume is typically far lower. One more trick up HEDD's sleeve was the use of "variable velocity transformation" wherein the folds are of uneven thickness to deliberately have different air velocities and, in turn, different amplitude of the generated sound at various frequencies. This helps put out an even frequency response where, say, the bass isn't a lot quieter than the mids or treble based on HEDD's tuning—at least in theory. The original HEDDphone came out a few years ago and the HEDDphone TWO uses a updated version of the drivers which are smaller but still use the same overall diaphragm length/surface area. The updated drivers are slightly easier to drive than the HEDDphone ONE but a decent amplifier is still recommended owing to the rated impedance of 41 Ω but a relatively low sensitivity of 89 dB/mW. Think more current-driven than voltage and you get the idea. Some powerful tiny DAC/amps such as the FiiO KA13 and Cayin RU7 will do the job well enough, let alone more powerful portable sources such as the FiiO Q7 and xDuoo XD05 Pro, although I expect most people to use the HEDDphone TWO at their home/office with a desktop setup that has plenty of juice. I generally paired it with solid state amplifiers and a good delta-sigma DAC at home.

Frequency Response Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature emphasizing a slightly elevated bass and smooth treble range with detailed mids and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our current headphones test setup uses a set of two custom in-ear microphones for the two channels. These microphones closely adhere to the IEC711 class, but have been tweaked to be more reliable in the >10 kHz frequency range, the precise issue with my previous setup, that is otherwise still very good and will continue to be used for IEMs and earphones. Two soft silicone pinnae are installed on the sides, separated by a distance matching my head, and multiple "height" adapters have been 3D-printed for further customization, based on fit, head size and shape. Each set of microphones has an XLR output I separately adapted to 3.5 mm. I used a transparent source—the JDS Labs Element II—although I also tried the FiiO K9 Pro with the balanced cable to make sure there was no power limitation—for measurements after confirming it was not a bottleneck in any way. This artificial head simulator feeds the microphone lines into a reference USB sound card, which in turn goes to a laptop that has ARTA and REW running. I begin with an impulse measurement to test for signal fidelity, FFT to test for headphone seal, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, netting a good balance of detail and signal to noise ratio. The default tuning was used for testing, and no app or program-based EQ settings were chosen, unless specifically mentioned. Each sample of interest is measured at least thrice with separate mounts to account for any fit issues, and an average is taken of the individual measurements for statistical accuracy.


As per usual, you can find my headphone frequency response measurements on VSG.squig.link, along with all the earphone measurements. Scroll to the bottom and choose different targets there, including two from Harman Kardon, developed after years of R&D. The Harman 2018 over-ear target in particular is a reference curve many headphone makers aim for now, but I find it too bass-boosted—especially for open-back headphones. As such, I am opting for the Harman 2018 curve with the bass target from the Harman 2013 curve, which is what is being referred to as the "Harman Combined" target there. Before we get talking about the sound signature of the HEDDphone TWO, I want to first talk about the channel balance achieved here. You will notice how the left and right channels are extremely close to each other all the way from 20 Hz to 20 kHz, which is the region of interest for human hearing. I did not pick up any channel balance when I first listened to the set before measurements were taken and I still don't perceive anything after seeing the measurements here, which isn't surprising given the slight discrepancies seen in the upper mids/lower treble here are likely measurement artifacts. Keep in mind though that this is a pre-production unit specifically chosen for review, although this one sounded exactly like the demo unit at CanJam London so it feels consistent too. I will also mention that using the headphones for ~75 hours didn't change anything either for those who would undoubtedly be curious about burn-in.

At this point I should mention that HEDD Audio primarily targets professionals in the music industry, be it those looking to mix/master music or those monitoring it. The company is still somewhat new to what audiophiles like and dislike and it shows with the HEDDphone TWO. I remember talking to HEDD's CEO in London about the overall positive impressions for the HEDDphone TWO at the audio show it debuted at and he mentioned being surprised to see so many expensive headphones and IEMs there. Indeed, many headphones in the consumer market are far more expensive than the HEDDphone TWO and this would simply not jive in the pro audio space where most people use $100-200 monitoring headphones. To attract that crowd requires a specific sound signature that doesn't necessarily align with that of audiophiles. In particular, you would notice the HEDDphone TWO goes for a mid-centric, relatively flat tonality. The expectation here is that people using the HEDDphone TWO would thus appreciate the highly resolving and clean sound before they add in EQ themselves. This could come in the form of per-instrument EQ mixed into the final track, in which case having a ruler-flat tuned set of headphones will help make it easy, or specific EQ filters to suit their needs where, once again, a flat frequency response makes it easy to do so. In this regard I would say the HEDDphone TWO does the job quite well. It's the most resolving set of headphones in this price range that I have tried to date and takes EQ like a champ without any perceived distortion. Instrument separation is excellent too and being able to pick out individual notes in a track to then mix/master it would no doubt be easy. The only concern I have from this use case is that the HEDDphone TWO is not as easy to drive as most monitoring headphones so you need to have a capable interface/console or add in a standalone amplifier in the chain which might complicate things.

For audiophiles though, things are not as peachy. The original HEDDphone had people complaining about the lack of bass extension as well as perhaps too much ear gain leading to a darker sound in the higher frequencies. It felt like an AMT tweeter forced into a full-range driver, especially with some minor distortion in the mids as a result of driver modes. The HEDDphone TWO tackles all the distortion issues easily with the newer drivers and does feel far more balanced, yet it might well be more mid-forward and bassy not because it has better bass extension but rather it has less energy in the upper mids and lower treble, thus shifting the frequency response to the lower frequencies indirectly. There's still a slight dip in the sub-bass so electronic music lovers may have already found something to EQ up here, if not dismiss the product entirely if they don't want to play around with equalization. I personally found the bass just right for my library, including for synth and trance music, especially since this is an open-back set and I didn't want bass to overcome the mids that I care more about. You get an excellent sense of contrast between leading and trailing ends of tones which helps appreciate music despite the set not being the most engaging product out there as it ships out of the box. Bass guitars are a noteworthy mention here for how hard they hit without feeling unnatural. This might be a result of the AMT drivers pushing out a lot of air, and fast too.

Perhaps it's also my preference of a warmer tonality that makes the HEDDphone TWO more appealing as the mids overall are the best part here. Precise imaging, excellent resolution, a clean sound with great instrument separation, and add to this a relatively deep soundstage too in addition to fairly average depth and height. It's a set for male vocals and brass instruments in particular—James Brown never sounded so good with the increased body and meat these drivers provide. However, timbre is more likely to be a miss than a hit. There's still a hint of driver modes affecting how accurate drums sound; is it perhaps that dip around 800 Hz? I tried to EQ it out but it never sounded right to me. Likewise, those who prefer less ear gain will probably find the HEDDphone TWO far more appealing for strings and female vocals in addition to piano key harmonics. I do want more ear gain here and, despite the set not sounding anywhere as peaky as the measurements making it seem, this is was the first time I did add a peak filter of ~4 dB centered at 3 kHz. I then immediately followed up with a shelf filter to fill out the lower treble since it came off darker even before I started to EQ. In a weird way, I do feel like the stock tonality makes it harder to fully appreciate the strength of the AMT drivers in the HEDDphone TWO. You may well find the treble to be just right and not bright or fatiguing whereas I want to experience that orchestral recording as if the performers are in front of me. The HEDDphone TWO is capable of delivering that magic and tactility to the notes but not right away. I would certainly encourage HEDD to consider making an audiophile-version of the set, or at least release some recommended EQ profiles.


Given I had specifically borrowed a HEDDphone ONE to add further context to this review, surely that is the first comparison to make! I mentioned before how the HEDDphone TWO improves upon the older model in pretty much every single manner, be it the physical design, the comfort and seal you achieve, or even the improved drivers which sound way cleaner to me. In fact, I even broadly EQ'd the HEDDphone TWO to sound similar to the HEDDphone ONE and definitely appreciated the newer set more. Unless you are absolutely against EQ or simply find something about that big bulky design of the original set more appealing, there is little reason to go for the HEDDphone ONE anymore. HEDD will still continue to make the HEDDphone ONE in smaller amounts for those who prefer that tonality though and I count myself among them. It's more along the warm-neutral route than the HEDDphone TWO although it gets even darker in the higher frequencies to where I do EQ there too. If I had to pick one, there's no doubt I'd go for the HEDDphone TWO.

Funnily enough, the pro market being targeted by HEDD reminded me of other such ventures from the likes of Audeze. In particular, the LCD-X (2021) has similar tonality and weight alike. You do get that typical planar bass extension here but I'd argue the HEDDphone TWO will actually do a better job for monitoring owing to the ease of instrument separation and increased detail retrieval. I'd actually say the flagship Audeze LCD-5 is a closer comparison despite it costing over twice as much, and the tonality is even closer as seen here. There's also the Audeze MM-500 which might be the most direct competitor from Audeze, and perhaps also most other brands, to the HEDDphone TWO but that will have to wait until I get it in for proper testing.

Most other monitoring headphones I have tried/used are way less expensive. Think Sony MDR-7506, beyerdynamic DT 990 etc which were all used before I moved out of the US a few years ago. The only recent such set I've tried is the Moondrop Joker which is, well, not really worth talking about in this context at all since it's got an identity crisis of what it wants to be—more on that another time. As such, and since I unfortunately don't have any dynamic driver or e-stat set in the price range the HEDDphone TWO operates in, I decided to include one of my personal favorites in the form of the HIFIMAN HE1000 Stealth so you get an idea of what I prefer. This used to cost the same as what the HEDDphone TWO goes for now but HIFIMAN has recently given it a substantial price cut to where it will likely win my vote over the HEDD offering. It's not as detailed and I do see a well-rounded soundstage with precise imaging (HEDDphone TWO) being more realistic and handy compared to just a very tall one (HE1000 Stealth) but both trade blows when it comes to comfort and the HE1000 Stealth has a more amenable tonality for my music preference. That said, if you do prioritize build quality a lot then there is no question that HEDD wins out here. I do feel more confident about the HEDDphone TWO lasting longer and the 5-year (extended) warranty along with the extra set of pads will sway some people, as will the better set of accessories.