Fit and Comfort

Seen above is the right channel of the MOONDROP Solis 2 placed into an artificial ear mold with the included size M SOFTEARS Ultra Clear silicone ear tip installed. I have average-sized ears, and the ear mold above represents my own experiences well enough as a proxy. Size M silicone tips are my go-to for testing, since foam tips are not included by some brands, and I found these UC tips to work like a charm with the Solis 2's thicker nozzle and insertion angle. The gray flange tips weren't bad either and are less tacky to the touch to where they might be more durable over time too. The Solis 2 is a larger-than-average sized set that will jut out of the ears for pretty much everyone. There is also a decent chance those with smaller ears and/or ear canals won't find the Solis 2 comfortable. Then there's the part where the textured shells can irritate the skin over time. Oh, and did I mention the shells weight ~22.5 g each with the combo of both sides with the cable weighing a flat 100 g? These are the heaviest IEMs I have ever used—quite possibly the heaviest ones ever made too. All of these seem like a disaster in the making and yet somehow I was not only fine with everything, I actually found these to provide a good fit and seal too. Indeed, while not the most comfortable set I've ever used, I actually had no issues using them for my usual 1-2 hour listening sessions thanks to the ergonomic shells with multiple points of contact in the concha as well as the cable providing further support on the back. I feel this will be even more divisive than the debate on the shell design will be though, so I can't tell you my experiences will be valid for everyone despite knowing others who also found the Solis 2 comfortable. There are enough deterrents here to where I have to strongly urge people to demo these before contemplating a purchase, and this is even before we talk about the actual sound experience.

Audio Performance

Audio Hardware

The MOONDROP Solis 2 employs a tribrid driver configuration in that there are three different driver types here for a total of eight drivers per side. The predecessor went with a 4 BA/2 EST configuration and didn't really last the test of time based on how no one really talks about it. With the Solis 2, MOONDROP goes with 2 DD/2 BA/4 EST drivers in a 3-way crossover. The EST drivers continue to be from Sonion as before and handle the higher frequencies, although they are seemingly more consistent and efficient now compared to before. There is no word on the type of balanced armature drivers chosen for the mids and mid-to-treble transition, but presumably these are also reputable units from Sonion or Knowles. Then we get to the dual DD system which appears to be similar, if not the same, as what was used in the Blessing 3 to good effect. MOONDROP refers to this dual 10 mm driver setup as H.O.D.D.D.U.S or Horizontally Opposed Dual Dynamic Drivers Unit System and it is effectively two of the same drivers in a push-pull configuration that come together to provide an output similar to that from a much larger dynamic driver. This in turn should allow for finer tuning for the lower frequencies while maintaining an ultra-low distortion with MOONDROP confirming the drivers handle the lower frequencies. This time we do find out the drivers use a paper dome and a flexible suspension diaphragm, although the composition of said diaphragm remains a mystery. The Solis 2 has a rated impedance of just ~10 Ω and sensitivity of 121 dB/Vrms (101 dB/mW) although these numbers are measured at 1 kHz and may well be different in the bass or treble. This does make it one of the more power and current-hungry IEMs but it's still plenty fine with a decent portable DAC/amp—even more so if you go with the balanced 4.4 mm connector with a compatible 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 that 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 a capable and transparent DAC/amp—I used the MOONDROP MoonRiver 2 here. 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 MOONDROP Solis 2. 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 the two channels are identical across the entire useful 20 Hz to 20 kHz range! In fact, this competes directly with the Blessing 3 for the title of the single best channel-matched set of IEMs I have ever measured to date. Keep in mind also that MOONDROP was, and still is, selling these faster than they can make them owing to the handmade assembly and design, so this is not a deliberately chosen review unit either. Given the price range the Solis 2 operates in, I do expect to see strict QA/QC measures in addition to manual driver matching and I was not left wanting here. Measurements taken after 50 hours of testing, which included these playing a mix of various songs as well as white or pink noise and sine sweeps, showed no difference. There was no perceived burn-in effect thus, and none was measurable, either. The response with the anthropomorphic pinna in place matched the ideal scenario in the coupler extremely well too and this is an indicator of how good the fit and seal was when installed in the artificial ear. But keep in mind that the pinna doesn't care about any comfort issues, so your mileage may vary in your actual ears.



Here is the average frequency response for both channels of the MOONDROP Solis 2 plotted against my personal target taken from VSG.squig.link, which also gives you an idea of my personal preferences to better correlate any possible biases. The tuning of a set of headphones or earphones does not have to match my target as long as it is tuned with some direction, makes sense, and is executed well. After all, no one set will appeal to everyone, and having different options is what makes this hobby so interesting and hard to quantify. This is also why I am debuting the use of a new target that's based on a more scientific methodology involving a -10 dB tilt (-1 dB/octave) applied to the diffuse field target for the newer, more reliable B&K 5128 but then compensated for my exact 711 coupler instead. If this is a lot of gibberish to you, scroll down to the targets in my database linked above and see the new 5128 section to the left where you can click on the yellow question mark for a brief primer. The bottom line is this target is closer to what many people are likely to prefer out of IEMs and headphones alike. This is especially useful for the higher frequencies and ear gain regions where you will notice the biggest changes from my target.

I chose to also measure the Solis 2 with both types of silicone ear tips because the factory curves suggested a non-insignificant difference between the two. As it turns out, that was not the case in practice, with both being close to error margins once you account for a proper fit and seal. I would describe the overall sound signature of the MOONDROP Solis 2 as being warm neutral and one of the smoothest sounding transducers I've heard to date, be it headphones, IEMs, or speakers alike. I will also clarify that the frequency response measurements are somewhat misleading in that the bass feels more in magnitude and quality than the graphs suggest and the treble extension is also further along than you might initially think. Indeed, I was easily able to listen to notes until ~15.5-16 kHz here so please don't compare the Solis 2 to other IEMs that measure dark and sound dark too—LETSHUOER x Gizaudio Galileo, for example. The four EST drivers are implemented to be detailed yet non-fatiguing to allow for excellent reproduction of string instruments, piano keys, triangles, and cymbals to allow for my smooth jazz and orchestral music to be rendered beautifully. The Solis 2 is also fairly resolving here, although I do suspect having some more presence in the higher treble might have helped further with some demanding violin and harp segments in addition to having background instruments in a busy scene stand out more.

I thought the MOONDROP H.O.D.D.D.U.S drivers in the Blessing 3 were exceptional but perhaps held back by the tuning there. It came off leaner than I would have liked, especially with the clean sound and ultra-low distortion on offer allowing for easy EQ to improve the sound so much. With the Solis 2, MOONDROP has decided to go back to its roots and target the VDSF target closer. This works out great with the use of a bass slope that provides a warm sound with good punch in the mid-bass without compromising on detail or making for muddy/boomy mids. Once again the actual bass impact is better than you might expect just comparing graphs courtesy this push-pull dual driver setup, and it also has great dynamic range allowing you to more easily discern quieter and louder sounds, which in turn also helps appreciate both leading and trailing ends of tones. There's no bass tuck here and we end up with kick drums getting their fair dues alongside bass guitars. I can see the Solis 2 potentially working for sub-bass lovers too—especially with some EQ—albeit there are more specifically designed sets for that.

The transition over to the lower mids can be divisive though. I personally prefer a cleaner separation at ~250-350 Hz and you can also see how some might perceive the mids to be slightly recessed based on the other target—plausible for male vocals with baritones arguably playing second fiddle and instruments in rock music overshadowing growly singers such as Lemmy (Motörhead). I didn't find the set lean as much as perhaps not having the depth and range of instrument separation that some other flagships offer, including those that cost slightly less. So here too I can see people having differing opinions based on the fit and seal achieved. What is beyond debate is the impeccable central imaging as well as the relatively wide soundstage you get here; it still feels natural and not overly diffused. I'll also give a special shout out to MOONDROP for achieving the most accurate timbre of any tribrid set I've tested to date, potentially also of any hybrid set too. If you told me this was a single DD set then I might have well believed it. It helps present an extremely coherent and smooth sound that carries on with female vocals too. Some might find it slightly shouty depending on your HRTF but I am confident the vast majority of readers will find this highly agreeable and enjoyable.


I had just got done testing the Campfire Solaris Stellar Horizon when the MOONDROP Solis 2 was announced, so I immediately thought of this given the very similar pricing too and the two having somewhat similar names. The new Solaris is a hybrid driver set that also goes overboard with the unboxing experience, accessories, and IEM design, albeit more with the former two than the latter when compared to the Solis 2. I also appreciated the tonality of the Solaris Stellar Horizon, but would give MOONDROP the win on that front. When it comes to technical performance it's mostly a wash, including on the detail retrieval front. The Solis 2 does better with imaging and has a wider soundstage whereas I found the Solaris Stellar Horizon to handle layering and air better. The Solis is also more dynamic whereas the Solaris Stellar Horizon has better slam. Campfire Audio certainly gets the win for comfort in terms of being more likely to work for the general populace but the Solis 2 can be more comfortable with a better seal for those who can work with the potential issues mentioned at the top of the page. I'll also give MOONDROP the win for the cable and ear tips so ultimately I'd personally go with the Solis 2 given I did not have comfort issues.

The tougher competition to MOONDROP comes from China itself with more local brands now finding themselves mature enough to compete in the >$1000 market. There are options from the likes of Kinera, ThieAudio, Unique Melody, to name a few, but I'll bring up the LETSHUOER Cadenza 12 here (review in the works). This is a 1 DD/11 BA set in a titanium chassis that is the new LETSHUUOER flagship and is arguably tuned to play to the driver strengths even better. It's a highly energetic set compared to the smoother Solis 2, perhaps overly so since it was irksome in the upper mids for me, and I found it more resolving than any of the other sets being discussed here. It's also a chunky set with some specific usability issues though—the shells are a dust magnet and can scratch up over time. I'd say LETSHUOER has a better unboxing experience and accessory collection too, although unfortunately it does feel like the Cadenza 12 has already been mostly forgotten about. MOONDROP enjoys a much larger brand presence and I am confident that the Solis 2 will retain its value more too. While my heart says Cadenza 12, I have a feeling my brain will go the MOONDROP way. Still, do check out the Cadenza 12 and my review when done because there is a good chance it will be on sale to be far more competitive. Even if not, there are enough strengths there to where it can be a legitimate end game for many and with fewer comfort niggles too.

I've not covered a lot of IEMs in the price range the MOONDROP Solis 2 finds itself in, but 64 Audio came to mind as well. There's of course the famous U12t, especially with the new m12 module that launched with the U4s. The modules do allow for different sound signatures on the U12t but overall I'd say the technicalities are in favor of the Solis 2 easily to make this more an enjoyable colored tuning (U12t) vs. a competently tuned and technical flagship in the Solis 2. Instead, the 64 Audio U18t comes in closer from a price point as well as resolution. I would still give MOONDROP the edge here but will note that the U18t is a much older set that is far more comfortable and intended for professional use. The Solis 2 would not be used on stage easily given the design! It's more designated to be the Ferrari of the IEM world where you leave it home and use in private sessions more often than not. Perhaps the newer U18s would be a more comparable test, or even the Tia Trio, but I have not reviewed them. Likewise, I will also mention that the Solis 2 handles itself competently against the likes of the Lime Ears Pneuma and Noble Audio Viking Ragnar, beating the former almost every which way and taking the tuning win over the Viking Ragnar but losing out when it comes to detail retrieval and instrument separation.