Fit and Comfort

The subtle fit differences between the different included ear tips of the same size with the XENNS UP are hard to see on the camera front-on since the larger shells cover the actual section that fits into the concha and ear canal. As such, I am only showing one such example of a size-M ear tip (silicone) on the right ear bud, inserted into an artificial ear mold. I have average-sized ears, and the ear mold above represents my own experiences well enough. Size M silicone tips are my go-to for testing since foam tips are not included by some. You should try out the various tips on offer, including the foam tips which seal better but can potentially dampen the treble response. I mentioned on the previous page that there are several factors that can affect the fit and comfort with the XENNS UP, including the size and shape of the shells and nozzle. This ear tip will be too large for many with smaller conchas and ear canals, so take that into account before considering getting the XENNS UP. On the plus side, if they do fit, it will be a secure, comfortable fit since they weigh slightly over 7 g each, and the cable adds a further point of contact on top of the general ergonomic design for the shells, as seen above with an example fit into an Asian female's ears courtesy Linsoul. Passive isolation is fairly decent depending on the fit since the IEMs of course take up more room in the concha than most.

Audio Performance

Audio Hardware

The XENNS UP is a tribrid with a total of seven drivers per IEM channel, so there understandibly is no first-party internal layout diagram. Even with the IEMs themselves, shining a light through the resin shell reveals some of the drivers placed by the exterior, but then there is plenty more wiring inside to where assembling this must be a real nightmare. Kudos to the assembly and QC team thus, as they are the unsung heroes here. XENNS is using a single dynamic driver for the bass response, which is a 10 mm beryllium-coated diaphragm driver for added stiffness. There is then a crossover to two Sonion 2300-series balanced armature drivers for the mids and upper mids transitioning to the highs, with XENNS not mentioning which ones specifically. This is already different from what we saw with the ThieAudio Monarch that had a couple of BA drivers assisting the DD for the bass response, and XENNS is instead focusing on the treble response, where we get the other two BA drivers—custom Sonion ones at that—as well as the Sonion EST65DA01 dual-unit electrostatic (electret) tweeter handling the highs. This makes for a 1+2+2+2 driver configuration for the XENNS UP that is very easily driven with an impedance of just 20 Ω and a high sensitivity of 110 dB/mW, at least presumably since XENNS omits the full unit details as many others, which I dislike. The XENNS UP is just fine with mobile devices thus, and a portable DAC/amp will suit your needs perfectly for when you find yourself without an available 3.5 mm audio jack on the go, and this is before the 2.5 to 3.5 mm adapter. If not, the shorter cable included with IEMs might be a potential handicap if connecting to a PC as the audio source.

Frequency Measurement and Listening

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


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear IEMs can feed into enough for decent isolation. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through the sound card. 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, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the appropriate ear mold fitted to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry instead of just the audio coupler. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the XENNS UP, or at least the useful part. The left channel was separately tested from the right one, and colored differently for contrast. I did my best to ensure an identical fit for both inside the IEC711 orifice, so note how there's obviously something wrong here. Listening to these, I immediately realized that the right channel barely had any bass response. Noting that it is handled by a single DD, it was logical to assume something was wrong with the dynamic driver, and Linsoul and XENNS confirmed it was likely a sealing issue on the unit. This is how I ended up with a second set of the XENNS UP, and the first one is on its way back to XENNS for diagnosis.


Ah, that's much better. I have no reason to believe this second sample is cherry-picked since Linsoul currently has a 2–3 week lead time for the XENNS UP, which boasts individual channel matching and hand-painted face plate and assembly, so this is more representative of the current product. The first one, measured and tested with the older silicone tips, also had a slightly different response even across both channels. The newer tips on the second sample seem to balance out the treble response further, which is a good thing, but I also got slightly more sub-bass extension from more than just the tips. Regardless, the two channels are nearly identical throughout the 20 Hz to 20 kHz range, with slight deviations past the coupler resonance, following which you need to take things with a grain of salt anyway. There was no perceived channel imbalance in my ears, and the consistency continued with the artificial ear and cheek simulator set up showing minimal resonance shifts as expected. There was no burn-in effect, with it unboxed what you get even after 50 hours of music and a mix of white/pink noise going through the IEMs. So with the new sample, everything is excellent.


Knowing thus that the old sample was a one-off, I used the frequency response measurements of the new sample in my measurements database found on VSG.squig.link as the default, with the old sample retained for the records as "sample 2." As before, I urge you to play around with these since it is quite a handy tool to inspect and compare various headphones and earphones I have measured to date. Seen above is the average frequency response of the newer XENNS UP sample plotted against my personal target for some additional context on my individual preferences, and of course deviation from the target is not a fault in itself. In the company's own words, the XENNS UP features an "airy smooth high frequency, especially when play instruments and vocals, the detailed changes of emotions is so thrilling and moving." With its bass response, XENNS goes on to claim the IEMs are "flexible, powerful and dynamic," and that the three regions of the frequency response are "divided clear but precise, full of atmosphere and broad soundstage. It could be one of the most appropriate IEMs for rock and roll, popular music or vocals."

This is certainly a mouthful, but it does present a few expectations the XENNS UP has to live up to. Interestingly, if treated purely as a tribrid, I would perhaps find all that treble-focus for the driver configuration somewhat disappointing. The XENNS UP gets dark in the highs no different from many non-EST tweeter IEMs, and in fact more so than a few DD/BA IEMs. Some ungainly peaks can also come off bright, and potentially a touch sibilant. I've seen many describe the XENNS UP as a dark set of IEMs, and I wasn't sure why, but it does apply in the ultra highs, where the Sonion ESTs don't get airtime in more ways than one. Piano keys in particular struggle with resonances, and string instruments don't shine much. On the flip side, some piano keys are more emphasized than others, and if considering the XENNS UP for classical music, this alone does clash with other instrument classes.

I started with the treble section because all the marketing talk made it seem the center of attention, which unfortunately is not the case in practice. The real reason to consider the XENNS UP is its excellent bass response. I mentioned how the newer sample had slightly more sub-bass extension, which I do hope is more indicative of the norm as it is so well-rounded that it will appeal to many lovers of not just head-thumping EDM and house music, but old school rock n' roll music. If this is from a single dynamic driver, maybe the XENNS UP would have been better served with a simpler driver configuration after all. There is plenty of detail to accompany the energy, making for a set many a V-shaped tuning fan will appreciate. The crossover to the first set of two Sonion BA drivers is also extremely well handled to where I couldn't really tell where it happens, and this lends itself favorably to male vocals that present themselves more forward-facing than instruments.

Channel separation is a high point in the mids too, which tracks that make use of good imaging will once again benefit from. Soul/funk music, and even the likes of jazz rap are great with the XENNS UP. The soundstage is wider than I originally thought, and while we are talking about the technical performance, let me again say that microdynamics were more impressive on the second sample. I can't rule it out on sub-bass extension itself, but both sets had plenty of slam. The mids proper is also good for what the XENNS UP is about—it would not be my choice for an analytical/reference set, but is clearly tuned with audiophiles in mind. It is fun without going overboard on presence with vocals, be it male or female. The transition into the upper mids is similarly well done, which makes going back to where the ESTs are a bit of a let down that much harder.

Comparisons

There are some obvious comparisons that come to mind, and the first set would be in the form of two other tribrid IEMs I have here. The ThieAudio Monarch costs slightly more than the XENNS UP, but is a very different set. It is more technically competent and detailed, and ends up being a reference set with glorious room for instruments in the mids and highs alike, as well as a sub-bass emphasis that leaves little appreciation for the likes of rock and metal music, which the XENNS UP does much better. I can see them complementing each other, so it's not really a case of one over the other. The newer Monarch MK.2, of which a review sample is coming, may be a much closer alternative for the XENNS UP, but let's discuss that in due course of time. I also have here the LETSHUOER EJ07M, whose review will be coming up shortly. It is another tribrid that costs less and uses four EST tweeters. It shows too, as it ends up having the most treble extension of the trio. The XENNS UP manages to be the only one with the 10 kHz peak, which wouldn't be as bad were it not for the steep drop right after that emphasizing it further. Based on my current testing, I might well go with the EJ07M over the XENNS UP.


The second set is not with direct competitors as much as other IEMs you may have or are considering the XENNS UP as an upgrade path from. The XENNS Mangird Tea comes to mind first, but it is another case of a different tuning to where I feel it does better for its price point and tuning than the XENNS UP. Both are dark IEMs, though, so I suppose by comparison, the XENNS UP does have slightly more treble. The other two are extremely popular new releases in the $100 and $200 range, and while the MOONDROP Aria (2021) and 7Hz Timeless are tuned similarly, both lack an extended treble presence, too. The XENNS UP will be an upgrade from the Aria in particular, with the latter lacking in technicalities and having a generally worse treble response even for those who like it bright. The 7Hz Timeless, on the other hand, might be worth sticking with for the money. There is little to gain in imaging and soundstage by going to the XENNS UP.