Fit and Comfort

Seen above is the HIFIMAN HE-R9, both in wired and wireless w/Bluemini R2R configurations, 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 various pivot points, and the height adjustability of the headband and ear cups. This section is mostly a summary of the points expanded upon in more detail on the previous page, but I will point out that the HE-R9 weighs ~330 g by itself and is among the more comfortable headphones to wear as a result of the lower density and the oversized pads. The headband isn't the best for comfort admittedly but it is thick and plush enough to support the HE-R9 on the head easily. Clamping force is on the lower side of average again although not as bad as the Edition XS which sometimes made me question whether I had a good seal at all. Here it may still feel loose although it really is not unless you have a tiny head. In fact, I made sure to have another person use these headphones and I sat next to them only to be pleasantly surprised at the low leakage to where I couldn't really hear what they were playing. By this regard, the HIFIMAN HE-R9 satisfies the basic criterion of being a closed-back set. The headband assembly offers extensive vertical sizing coupled with a small amount of cup swivel and rotation to where the larger pad spacing should still allow for the contoured pads to fit over and around the ears easily enough for most.

Audio Performance

Audio Hardware

HIFIMAN may be most well-known for its planar magnetic headphones but that has not stopped the company from developing dynamic driver headphones and earphones in addition to electrostatic headphones which we will soon examine separately. Indeed, the TWS800 review introduced us to HIFIMAN's so-called topology diaphragms used in its dynamic drivers, of which one such example is used in the HE-R9. HIFIMAN acknowledges that all diaphragm materials flex during operation, so controlling the firmness of the diaphragm can only go so far. What this topology diaphragm does is effectively coat the base material with nano-particles to control the way it will flex as opposed to minimizing it. The company understandably did not reveal more specifics about the coating materials and application process, but confirmed that the coating was done with the target tuning in mind. The diaphragm is paired with a voice coil and rare earth magnets to make for a set of headphones that is relatively easy to drive with a rated impedance of 32 Ω and sensitivity of 100 dB/mW. It makes the HE-R9 a fine choice for portable or desktop sources, and the Bluemini R2R should not be holding things back outside of any Bluetooth-related compression.

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—for measurements in wired mode after confirming it was not a bottleneck in any way. The HIFIMAN HE-R9 was also tested in Bluetooth mode via the provided Bluemini R2R adapter. 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, 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 before, 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. As such, I am opting for the Harman 2018 curve with the bass target from the Harman 2013 curve, which is what is referred to as the "Harman Combined" target. Before we get talking about the sound signature of the HIFIMAN HE-R9, I want to briefly talk about the channel balance achieved here. You will notice how the left and right channels are mostly similar across the entire 20 Hz to 20 kHz range of interest. The areas of discrepancy come in the ear gain region mostly, which I did notice even before measurements were taken. There's also an ear resonance peak at ~8 kHz that I felt closer to 7-7.5 kHz in my ears and that wasn't as different in the ears as the graph suggests. Overall I'd say things could be improved when it comes to driver matching but it wasn't a deal breaker for me.

HIFIMAN doesn't share much on what the goal with the HE-R9 was except in saying it reproduces a natural and detailed sound throughout the rated frequency response range that goes all the way up to 35 kHz. It also claims low end extension under 20 Hz too, although this review will focus on the 20 Hz to 20 kHz range of interest for humans. In that regime I would classify the sound signature of the HE-R9 as being extremely bassy with a tilt towards V-shaped tuning thereafter. I am more accommodating of different tuning styles than most others as long as it's well executed and I have only mixed feelings here. You will notice the HE-R9 has ~9 dB SPL rise peaking at 5-60 Hz relative to the dip at ~400 Hz followed by a further drop in the sub-bass. It makes for a bass shelf that prioritizes mid-bass and the lower mids to where it's not the most ideal set for electronic music but works well enough for house/trance music that isn't all about beats. The mid-bass itself comes off boomy to me without the most detail and yet it works fine with older recordings as well as rock/metal music that aren't the most accurate/detailed in the first place. As with typical closed-back sets, we get a dip in SPL that is effectively a compromise for the design. It has to happen and can be spread out, if you will, and here we see HIFIMAN opt to have it closer to 400 Hz to where I do have issues with a bloated bass that bleeds into the mids affecting both instrumental and vocal clarity.

Layering is not a strong suit here thus and good luck trying to pick out distinct tones for male vocals especially. This makes the HE-R9 a set far down the preference ladder for music monitoring and mastering for me. Imaging could be better too, especially for string instruments and the harmonica/saxophone. On the other hand, the sound stage does come off quite wide to where I suppose the ear cup design has to be complemented. I also did not notice higher order harmonics coming off as strongly as the graphs suggest to where perhaps the ear pads and the foam are indeed helping absorb some resonances inside. Going into the upper mids reveals a HIFIMAN open-back trademark in the form of a dip past 1 kHz which can attribute to a sense of wider and deeper sound stage here too. What it also does is make for a plasticky timbre, but I can't tell you if the tonality itself is the main culprit here or not. Regardless, female vocals can come off slightly hollow or bright depending on your singer of choice but generally I thought the ear gain compensation peaking at 3 kHz wasn't bright for me. The upper mids being prominent over the lower treble also helps prevent sibilance although the overall treble response has some glare to it and the air in the higher frequencies can be a bit much for some. Cymbals in particular can ring in a harsh manner but overall I was pleasantly surprised with how well it handled violins and harps, as well as piano music.



I can think of several headphones that do better wired but the unique selling point of the HE-R9 is its ability to be easily run wirelessly or even as a set of USB headphones thanks to the Bluemini R2R adapter. It offers Bluetooth 5.0 connectivity thanks to the onboard Qualcomm QCC5124 SoC with rich codec support in the form of SBC, AAC, aptX HD, and LDAC. Pairing is simple once you read the manual and I liked how it uses the headphone drivers to effectively have loud and clear voice prompts too! I am not sure why it asks for contact and call history access as it works as expected even without it—could be an Android thing or perhaps HIFIMAN has plans to add in smart assistant support via firmware updates. I got ~6 hours of battery life in LDAC mode at 50-60% volume compared to the rated 6-7 hours that is presumably in SBC codec mode and lower volume. Charging the Bluemini R2R also takes ~2 hours each time and the indicator LED comes in quite handy throughout. You can read my review of the EF400 to see how the Bluemini R2R changes the sound signature generally, and it makes for a slightly warmer set in the mids on top of what is already there. The overall sound doesn't change too much except you potentially have a slightly more balanced bass response and you do lose some more detail in Bluetooth mode. Given the HE-R9 isn't the most resolving set in the first place it's your call as to whether the trade-off is worth it. In my opinion it certainly is given that I wasn't going to use the HE-R9 for critical listening in the first place and this now makes for a wireless set of headphones that can compete with others which also tend to be bassy and generally have a V-shaped sound.


I have tested the HIFIMAN HE-10 Dynamic Version and HE-R10 Planar Version before although I have not yet written reviews for them. In the meantime, I figured you might want to see how the newer HE-R9 fares in comparison to its more expensive siblings. The HE-R10D, if you will, is worse tuned and arguably isn't as technically proficient either to where I can't think of any reason to go with it. It sounds like a set of headphones that is dead inside and EQ doesn't help much either! On the other hand, the HE-R10P may also have a weird tuning out of the box but ends up more balanced, can be easily improved with EQ, and is probably the most detailed closed-back set I have ever heard—the Audeze LCD-XC (2021) might be in the running though. The issue is the HE-R10P costs nearly 20x the cost of the HE-R9 and the recently updated retail version foregoes support for the Bluemini adapter in favor of a more premium look and build. The HE-R9 wins here easily from both value and usability points of view.


On a more relevant comparison, I have here the DCA Aeon Closed X planar magnetic set, the Edifier STAX SPIRIT S3 Bluetooth planar magnetic set, and the Meze 99 Neo dynamic driver set. There are a few other closed-back dynamic driver sets from Sivga that we've covered before but those cost less than the HE-R9 whereas the DCA and Edifier offerings cost more. Clearly I don't have a lot of closed-back headphones in this price range but you will see how all of these have some form of bass shelf that then is either dampened as with the Aeon Closed X, handled via DSP as with the STAX SPIRIT S3, or left unchecked as in the case of the 99 Neo (or Classic). The HE-R9 doesn't look as out of place anymore, at least until you see the weird bumps in the mids that affects clarity more so than the boomy and bloated bass does. I can only wonder if aftermarket pads help the HE-R9 as we saw with the Meze 99 Neo and HarmonicDyne G200, although there are a few 3rd-party modded versions of the HE-R9 that go the dampening route and seemingly make the HE-R9 a far more compelling offering. Overall I'd probably pick the DCA or Edifier offerings for my tastes, with the STAX SPIRIT S3 also having a significantly longer battery life and integrated microphones although at the expense of worse build and comfort compared to the Aeon Closed X and the HE-R9.