Fit and Comfort

Seen above is the HEDDphone TWO GT 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 GT is still larger and heavier than the average set of headphones, weighing ~550 g with its relatively bulky ear cups. This is primarily a result of the air motion transformer (AMT) drivers used here, which in turn are massive in all dimensions compared to typical dynamic drivers and thicker than many planar magnetic drivers too. That said, the HEDDband and lighter metals used in the frame help make the HEDDphone TWO GT more comfortable than you might think. Take your time to set up the headband system properly, and don't take the adjustable clamping force feature lightly either. This helps people have a more reproducible fit, comfort, and listening experience with these headphones, which in turn makes it easier to compare the sound signature with other users. The suspension band and the fabric straps are stiffer than I'd like though, especially if you have the clamping force somewhat high to where the suspension band has less contact area with the top of your head. If you feel as much, then try lowering the shaping strap by a notch on either side 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, and I personally preferred the leather pads over the velour ones in the UK winter time I am testing these headphones—your mileage may vary. Despite being an open-back set, the HEDDphone TWO GT is more isolating than you might expect too, with less leakage to the external environment too.

Audio Performance

Audio Hardware

As with the HEDDphone ONE and TWO before, the HEDDphone TWO GT uses air motion transformer drivers, which are quite rare in headphones—I can only think of three other brands that have done it (Goldplanar, oBravo, and Monoproce) to varying degrees of success/discontinuation thereafter. 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. With the HEDDphone TWO GT, HEDD Audio is using a new multi-layered Kapton polyimide film diaphragm with aluminium traces via a printed circuit driven via a Lorentzian force 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.

A full-range AMT driver driven to typical listening volumes for headphones can still present some distortion, and HEDD Audio says the latest drivers have even lower distortion than the ones used in the HEDDphone TWO and ONE before. These drivers also use "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 the brand's desired tonality. The HEDDphone TWO GT has a rated impedance of 41 Ω and a rated sensitivity of 88 dB/mW, making it ever-so-slightly harder to drive than the HEDDphone TWO, although not enough to where both would be equally demanding on your chain and benefit from a capable amplifier—think more current-driven than voltage and you get the idea. Some powerful portable DAC/amps such as the FiiO BTR17 and Cayin RU7 will do the job well enough, but I've found the HEDDphone TWO GT to scale well with more powerful desktop sources that you are likely to use with these headphones anyway. 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 my Squig Link database, 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 GT, I want to first talk about the channel balance achieved here with the pre-installed leather pads, although the velour pads didn't change anything in this metric. 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 either, and this is a randomly chosen retail unit which makes it all the more impressive. HEDD Audio having stringent quality assurance and control checks during the various stages of its in-house assembly is paying dividends here. I will also mention that using the headphones for >100 hours didn't change anything either for those who would undoubtedly be curious about burn-in.


HEDD Audio mentions on the product page that the HEDDphone TWO comes with "new velour and leather ear pad options, which can be switched at your leisure." Headphones coming with multiple ear pads is not a new thing in itself, some brands such as ZMF Headphones even makes it a selling point to have multiple different ear pads for you to try and achieve a different, more amenable tuning of the headphones with. The HEDDphone TWO is not going for different tonalities though, with the pre-installed sheepskin leather and the optional velour pads sounding and measuring basically the same. There are subtle differences when you dig in further, such as the leather pads offering a snappier and punchier bass, and the velour pads giving some more reverb and air to my ears. But overall I'd say it's not really worth the time to treat these as a tuning kit as much as simply choosing what works better for you in terms of fit and comfort. I can see some using the leather pads in the winter and the velour pads in the summer, for example. Achieving a near-identical tonality from two very different ear pad materials is quite difficult to do, so I'll give props to HEDD Audio for managing this.

While the HEDDphone TWO seems to have been targeting professionals in the music industry, be it those looking to mix/master music or those monitoring it, the newer HEDDphone TWO GT is going for a decidedly warmer tuning. In fact, I'd go as far as to say the HEDDphone TWO GT probably has the one of the most appealing—for audiophiles—tonality for a premium set of headphones out of the box, which is more a statement on how poorly many flagship/premium set of headphones are tuned. There are a few places where my experience differs from the measurements seen above though, and some of this could well be from the unique headband system which makes it harder for me to tell whether the HEDDphone TWO GT on my measurement rig is positioned exactly as it is on my head. There is a more noticeable sub-bass dip in my ears, for example, starting at ~80 Hz and dipping 4–5 dB by the time you get to 20 Hz. This is not very noticeable with music given there is very little information recorded in this frequency range, yet there's an aftereffect in terms of how hard EDM tracks might resonate for you. I personally found the bass to work fine and, if anything, the HEDDphone TWO GT arguably has too much mid-bass for me. Keep in mind that these AMT drivers add a lot of heft to tones in the first place, and this warmer tuning, that also results in the lower mids being slightly elevated, makes for an excessively rich sound—almost like adding bone marrow on top of A5 Wagyu. I already know a lot of people will adore this though, especially as the HEDDphone TWO GT still manages to sound engaging and dynamic, with good contrast between leading and trailing ends of tones. Yet, you lose some of the snappiness that AMT drivers are associated for with this tuning.

The good news is the rest of the frequency response is nailed in tight. The same precise imaging and detail retrieval from the HEDDphone TWO help the GT stand out among its peers too, and most instruments still benefit from the clean sound and excellent separation + layering. Soundstage feels taller than it is deeper though, giving me more of a cathedral-style feeling than a concert hall atmosphere. Vocals are quite forward, be it male or female, with the former working nicely in most genres and the latter maybe affected by your HRTF. Here is where the second point of difference compared to the measurements come in. I found the 4-5 kHz region to be more elevated in my ears, and this in turn caused slight sibilance for female vocals—this seems to be highly dependent on the person though. The ear gain is also leaning towards being excessive, which can also cause some vocals to sound hot, yet it helps balance out the richer bass earlier. Timbre is again dependent on the instrument class, with brass instruments sounding natural to me, strings leaning a touch metallic, and drums potentially being affected by driver modes in the midrange. The elevated upper mids and ear gain also meant the treble came off slightly dark to me. This is where we get back to HEDD Audio's core business, and how its long-lasting target audience has come to expect a product that is mostly flat/neutral to then EQ to their desire. The HEDDphone TWO GT is a set that doesn't need EQ out of the box, in a welcome change to audiophiles, and still provides a sense of tactility that you won't easily get from other driver types. It's not a perfect set though, as I did EQ the 4-5 kHz region down slightly before upping the mid-high treble slightly to add some sparkle and air to my orchestral music collection in particular. This is why you might need a more powerful amplifier, even beyond the relatively lower sensitivity of these drivers, to allow for headroom with a negative preamp for the EQ filters.


The obvious comparisons to make would be the HEDDphone TWO, with the older HEDDphone ONE making a showing too. The older HEDDphone ONE was special in introducing AMT drivers to headphones for the first time, albeit it had quite a few fit and comfort challenges even before we get to the sound. There was more noticeable bass roll-off, the driver modes were prevalent in the mids and distortion was higher than I'd like. The HEDDphone TWO improved in nearly every single manner when it comes to the design, comfort, fit/seal, and newer, cleaner-sounding drivers too. The HEDDphone TWO GT further builds upon this with even newer drivers that have lower distortion, and of course the tuning is going to be more pleasing to the average audiophile out of the box. If anything, the HEDDphone TWO GT might have a bit too much going on in the mid-bass and lower treble as previously mentioned, yet it is easily the set I would recommend of the three out of the box. The HEDDphone TWO feels more detailed to me though, if only from its more analytical tuning. It's the set to go if you do EQ, as the treble feels smoother and more relaxed compared to the HEDDphone TWO GT and it is fairly easy to just add some peak filters where you need them. However, many audiophiles are not keen on EQ and may well find the HEDDphone TWO to be bass light, which in turn could tempt them to simply increase the volume to up the bass level. Of course, this also just raises the volume in the mids and highs too, making it a more fatiguing set in no time. So if you don't want to EQ and wanted a bassier, warmer, more musical tuning, then just get the HEDDphone TWO GT and call it a day.


Stepping outside HEDD Audio, most of the headphones I have here in this price range use planar magnetic drivers. This includes the MM-500 from Audeze, which actually tries to target the same studio and pro music market as HEDD. The MM-500 is a collaboration with renowned mixing engineer Manny Marroquin, and benefits from the R&D exercises that went into the making of the Audeze LCD-5 flagship headphones. The MM-500 is built nicely, albeit the clamp force is honestly too much for even average-sized heads unless you carefully bend the steel headband. Larger heads are prone to get headaches over time if you don't address this issue, and clearly Audeze has not done anything to remedy this. It's unfortunate, because the MM-500 is one of the best tuned headphones if you prioritize a neutral and highly resolving sound signature. It's a touch darker in the treble and is another set that benefits highly from EQ, but it's a true contender to the HEDDphone TWO when it comes to music monitoring, although I do feel the HEDDphone TWO still handles instrument separation and layering better. The HEDDphone TWO GT offers a warmer tuning that deliberately deviates from neutral to be more musical, and this lends favorably to audiophile use at home instead. It bests the MM-500 again for layering and has a larger soundstage too, although it's mostly a wash in terms of resolution, dynamic range, and imaging in my books.

Go to the other side of the world and HIFIMAN greets you with the HE1000se and HE1000 Unveiled, the former being HIFIMAN's first flagship released years ago at $3500 before being discounted to be lower than what the HEDDphone TWO GT costs. The set I reviewed was fairly typical of HIFIMAN at the time, with a large oval-shaped ear cup and an excellent headband system ensuring great comfort and a reliable fit for many, yet looking nearly as weird as the HEDDphone TWO GT to the average layperson. It goes for a neutral-bright tonality with a dip in the upper mids, further emphasizing the ear gain and treble thereafter to where it's too bright for even my more accommodating ears. While you do get very good bass quality—not quantity, at least without EQ—and detail retrieval on par with many flagship sets costing more, the tuning is just too fatiguing. I've heard rumors of newer batches being more relaxed in the treble though, but nothing confirmed on that end yet. This is where the recently released HE1000 Unveiled comes in, with no grilles on the outside for a more transparent sound at the risk of having exposed drivers. The HE1000 Unveiled is more neutral than the HE1000se and the HEDDphone TWO GT, has better vocal timbre and a wider + taller soundstage too, albeit I do think the bass quality and quantity are both superior on the HEDD Audio offering, and the treble is also more likely to appeal to the average audiophile compared to the increased upper treble in the HE1000 Unveiled. This is what I meant when I said the HEDDphone TWO GT arguably has one of the best out-of-the-box tonality in this price range.