Here comes my impressions of the Mest MKii and a comparison with the Mest OG. In the above pic, OG is the one with blue chips in the shell and silver-colored cable. MKii is the one with gold chips and black-colored cable. Like my other review, let me get my conclusion out first.

The Mest MKii is a steady step up from the OG. Put it simply, it addresses a couple of the biggest complaints I have for the OG, which are:

• The number one complaint I had with OG was the fit. It was too big for my ear. Most of the time I need to push it in to get an OK fit, but after hours' long of listening it can still get a bit shaky and I need to readjust the position of it. I tried 5 different kinds of tips and none of them fully solve this issue. MKii is noticeably smaller in size and with a modified form of the shell which achieves a much better fit to my ears. Now, MKii fits my ears like a CIEM. I will share some side-by-side pics below.
• The recessed mids and the edges/harshness in sound I can hear from time to time. That was another big complaint from me as I listen to vocals a lot. I strongly suspect that this is due to my poor fit with OG. With MKii, the recessed mids thing gets significantly improved. The harshness in sound is somewhat improved, but I find that the degree of improvement depends on the source you pair with it.

Mest MKii also comes with a better set of accessories. The cable is now made by PW Audio and is a very nice copper cable. I find it to be more premium and comfortable to have on compared to the cable in OG. MKii also comes with a set of AZLA ear tips which are incredible. In fact, on OG I ended up using the AZLA tips as it gives me the best fit, so I am pleasantly surprised that MKii comes with this as standard in the package.

And, what are the things that MKii keeps from OG? Basically, MKii preserves the strength of OG very well.

• The excellent sound stage. Just incredible.
• A neutral tuning with decent clarity and imaging. The layering and separation between bass, mids, and treble are also quite well-achieved, although some people may think that there is a slight lack of coherence among them. I find the lack of coherence to be less in MKii than in OG. Again, this could be due to the improved fit I get.

My quick suggestion for people who had the OG and are curious about MKii:

• If you are an OG owner and have fit issues, then of course I will recommend moving to the MKii, especially if you are into vocals. The improvement is just so obvious to me.
• If you get a good fit already or if you have a customed version, I don't think you will need to upgrade. For OG, I have seen from several reviewers that the sound is supposed to be smooth if you find the right tips and have the right fit. Hence, if you do not have any real complaints about it, especially about the recessed mids and edges in sound, and you find the OG to be comfortable in long listening sessions, then I think the benefit of upgrading is small. The benefit could be there, but I doubt it will justify the cost of roughly $600 (the difference between buying a new MKii and what you get from selling the OG).
• If you are debating between OG and MKii - MKii is a safe choice to go as it is able to preserve most of the good stuff in OG and comes with an improved fit.

Now, let me dive into and give more details about the FIT and sound signature of Mest MKii. Most of the listening is done with LP's new dongle W2. The test is done with 3.5mm termination for both OG and MKii. A DDHifi 2.5 to 3.5 adapter is used with MKii.

The Fit Comparison between OG and MKii

I think it is most direct for me to use side-by-side pics to demonstrate the size comparisons between OG and MKii. Overall, MKii is smaller. Its shell has more curvatures that should work with your ears better. I also find it to be slightly lighter when wearing it for a long time, but this could be due to the improved fit. The left is MKii and the right is OG.



The Sound Signature of MEST MKii

This section is mostly for the people who are new to Mest. Welcome and I think you are in for a treat.

Mest's biggest strength is its sound stage, which is (at least partially) enabled by its innovative bone-conductor driver. I would describe the sound stage of Mest as wide, deep, and real. From time to time I do not feel that I am listening to an IEM - everything feels so real around me. This is really an experience different from any other IEMs I have tried, except for the Traillii. The benefit of this incredible sound stage is that the music feels real to the listener. You can feel that you are really there, on the performing stage or in the recording room, listening to the artist performing.

Because of the depth Mest is able to achieve in the sound stage, it creates the "room" for Mest to achieve good separation and clarity in the sound. Things are rarely "compressed" together and I rarely feel the sound to be muddled. The imaging you get is also quite good.

Sound Comparison between Mest OG and Mest MKii

Overall, I would say both Mest OG and MKii have a neutral sound signature.

For OG, it has good bass and good treble extensions, but I have found its mids to be quite recessed. This has created difficulties for me to appreciate the emotion the singer tries to deliver, and I don't feel enough of the "impact" from the music. Most of my listening is on female vocals, so this troubles me a lot. In some sense, this is similar to the problem I had with the Sony IER-Z1R, which has excellent soundstage and clarity of music, but the recessed mids made me move away from it.

For MKii, I have found the mids to be significantly better to my ears. It is more forward but not too intimate. Kind of at the perfect balanced position to me. Because of this, the imaging of the mids improved quite a lot for me. Overall, with MKii, I can say that the bass, mids, and treble achieves a good balance.

Regarding the coherence between bass, mids, and treble. In OG I have found them to be pretty "separated". Some people like this and some people don't. In MKii, I have found the coherence among them improves quite a lot, and this is achieved without suppressing them together.

It is also worth noting that I have found both OG and MKii to be quite revealing of the signature of the source, and MKii is the more revealing one of the two.

The Potential of Mest MKii

As I have hinted above, the coherence of Mest MKii can be improved by pairing it with the right source. Because this is a quick impression, I have only been able to do my assessment mostly based on LP's new dongle W2. I managed to spend some time to test its pairing with SP2000 and my "ultimate" IEM machine Cayin N6ii + C9. What I can say is Mest scales up BIG when you find a good source to pair it with. When using Cayin N6ii + C9, I get an incredible experience of the imaging and presence of the music. Everything is vivid and soooo real! I have no more complaints about the harshness of the sound. The sound stage is even better and more extended. WOW. This is possibly the best IEM experience I have had and competes with my experience with Traillii - too bad that I longer have the little bird for a side-by-side comparison. (A side note: Cayin and UM are from the same city and their employees have a very good relationship, so I suspect UM has done quite some tuning test with Cayin's products).

OK let me calm down a bit and stop raving about this pairing. In the coming days, I will spend more time trying out Mest MKii with different sources, including Lotoo S1, Cayin N6ii (E02), SP2000, and of course the N6ii +C9 stack. My initial impression across these pairings is that Mest is quite revealing for the signature of the source. As a result, its performance scales with the source, and it opens up the possibility for you to use an appropriate source to achieve an "optimal" sound to your ears.

Verdict and The Value of Mest

I think Mest is easily my most recommended IEM at the price range of $1000-2000. It can certainly be the BEST choice for a lot of people. I have owned or tried many IEMs that are more expensive than $2000 (check out my signature lol). Now they are all gone and Mest is the one I am keeping as I find it to be of incredible value and also because I have enjoyed its incredible sound stage so much. Although I have had some complaints about the fit of OG, this still does not stop me from keeping it as my daily driver. So, when MKii is announced, I am incredibly excited to get one and I am happy to report that UM listens and is able to deliver an improved version of the Mest that will be a better fit for a group of users. Incredible value from the Mest again and nice job UM!

The Oriolus Traillii is the most expensive, and yet the absolute best IEM I have ever tried. I feel comfortable calling it the Summit-fi in the IEM world. If you do not completely agree with me in its sound, at least you will agree with me for its price - it retails for a shocking $6000. In this impression, I will try to use my own experience with the Traillii to explain what makes it stand out among all the TOTL IEMs. Whether it is worth the price tag? I hope my review can help you draw your own conclusion.

Disclaimer

This is a loaner unit I requested from @MusicTeck.

Packaging and Accessories

The packaging of the Traillii is among the simplest I have ever seen. You get a Van Nuys protective case, a bag of ear tips, a twin-tube double sleeve (in red) to keep the earpieces separated in travel, and the Traillii itself. I was not impressed by its packaging at all, as I was clearly expecting more for an ultra-high-end IEM. However, after using it for a couple of days, I find that these accessories are exactly all I need. The case is large enough to comfortably put the Traillii inside it (my Eletech leather case is in fact not big enough). The case looks and feels very durable and low-profile - perfect for traveling with such an expensive item. The red double sleeve is also very useful in keeping the Trailli protected on the way.

The Build of the IEM and Cable

Traillii is a gorgeous IEM. It has a darker red faceplate (just like the little bird Traillii) and a transparent shell on the other side that allows you to clearly see all the units inside and the internal wires. The Traillii is also very comfortable to have on. It is slightly bigger than my 64 Audio U18t, but smaller than UM MEST. I also don't need to push the Traillii all the way in to get a good seal - it just comfortably sits in my ears and delivers a nice fit. I use the AZLA SednaEarfitLight as recommended by some other Traillii users, but the stock tips work just fine.



The cable is a collaborative one with PW Audio - a custom-made one from PW 1960 4-wired terminated in 4.4mm. The cable is soft, durable, and aesthetically paring very well with the earpieces. Tuning-wise, Oriouls says the cable is specially tuned to optimize its synergy with the Traillii. I did not bother to do cable swapping as I feel that they two work really work together.



General Sound Analysis

The source I have been using the Traillii with is Cayin N6ii (A02) + C9 in tube mode (class A). The sound signature of this source is relatively warm and smooth. I also have an LP P6 Pro coming in a couple of days and will be able to add a quick section to discuss the pairing afterward. 80% of my listening is done with vocals, with the others being some rock and classical music (orchestra).



Traillii is the most balanced and natural IEM I have listened to. When listening to it, you feel the smooth flow of music delivering to you. The bass is tight and fast. The mid is smooth with great textures. The treble has a nice extension. I rarely hear sharpness in any part of the music, and the details and clarity of the music are always there. The soundstage is the highlight of Traillii as it is expansive and well-organized. It surely gives me the feeling of listening to my headphones. Because of its excellent balance in sound, the Traillii is a very non-fatiguing IEM and I can easily enjoy my music with it for hours and hours.

If I want to better explain what "balanced" means for the Traillii, it is that none of the bass, mids, or treble is too forward; nor are they too recessed. And, this is accompanied by an expansive sound stage. From reading this, you may say "Sure! Isn't this what all the (good) IEMs do?" However, this is not the case based on my experience with several TOTL IEMs. For each of the IEM I have experienced, there are always parts of the music that the IEM emphasizes. I tend not to cheat this as deficiencies. Instead, I think these emphases are what give the IEM a characteristic that appeals to a certain group of customers. Just to give a quick example, to me the Sony IER Z1R excels in its expansive sound stage, clarity of the music, and outstanding treble. These characteristics are what keep me engaged when listening to this IEM and drive what I choose to listen to with this IEM. Meanwhile, some of these characteristics come with tradeoffs. Again for the IER-Z1R, some people have found its finds to be a bit recessed, and this is what makes me move away from it eventually.

For the Traillii, I don't find it to put a particular emphasis on any part of the music. However, it is able to deliver different aspects of the music really well and keep me engaged throughout. The soundstage and layering of the music are excellent as I get to enjoy the depth of the music. It is overall a very 3D listening experience with a balanced, natural tuning that I have not experienced in any other IEMs.

Selected Comparisons

I am able to compare the Traillii side-by-side with my two most-used IEMs: 64 Audio U18t and UM Mest. I also had a short demo of the VE Elysium and had some interesting comparison results.

Traillii and U18t (with Eletech Socrates)

Both are quite neutral with respect to the sound. The details and imaging are on the same level. There are two major differences: (1) U18t is a more intimate, or some may say more "engaging" IEM, than the Traillii. The vocals from U18t are noticeably closer to you. This could be very enjoyable when you want to dance to the music, so I like it very much with fast songs. The vocals in Traillii, on the other hand, is further away but without being recessed, so it is more enjoyable for long listening sessions. (2) The soundstage is also better for the Traillii. I can more clearly recognize what is happening in the background, and those information does not distract me away from the vocals I listen to.

Traillii and UM MEST (with Eletech Iliad)

I find both of them to have a similar size in the soundstage. The position of vocals are also similar. The biggest difference between them is the smoothness in sound. N6ii + C9 already helps the MEST to smooth out most of its edges, but the smoothes and rich textures in the sound from Traillii are at the next level, making the vocals truly enjoyable. The details and imaging are also better with the Traiill.

Traillii and VE Elysium

I find the mids and vocals between them to share lots of similarities. The textures and richness in sound are all there and are the best I have ever listened to. However, as has been mentioned by many users, the Ely is a very mid-focused IEM. Threfore, when compared to Traillii, I do not get as much from other parts of the music. The Ely somewhat strikes me as being a not-so-balanced IEM while the Traillii is able to maintain and deliver all the aspects of the music in addition to its intoxicated mids. Overall, if you are a big fan of mid-focused IEMs, you are going to enjoy both of them immensely.




Verdict

Listening to and writing the review of Traillii reminds me of how a reviewer (Josh) describes the TOTL headphone HiFiMan Susvara. The Susvara is able to achieve at least 90% of the very best in the market for every dimension it is evaluated at. However, if you narrow down to a specific angle, you could find a "winner" that slightly outperforms the Susvara in that specific region, such as HD800s's advantage in the soundstage. What makes Susvara a truly summit-fi headphone is that it is able to pack all of these excellencies into one headphone and delivers it to the user. I find this description applies to the Traillii in the IEM world as well.

Would the Traillii be a good fit for your need? I think it really depends on your "habit" in collecting and using IEMs. For some of the users, we would like to have a collection of IEMs and we can enjoy the diversity from these IEMs with different characteristics. For some others, they primarily use 1 IEM to listen to all kinds of music, and it is for this group of listeners that I think the Traillii could be a good fit, especially if you are into vocals like I am. In my own experience, if I can only own one IEM, then Traillii is the one.

This is going to be a long review so I will break it into two parts: The first for C9's functionality and general performance (this post), and the second for its specific pairing with my various gears.

I think it will also be useful that I open this review by giving my conclusion of C9. It is a truly TOTL amplifier for IEMs and headphones. It has the ability to bring any DAPs one or two levels up in their performance. This is true not just for mid-tier DAPs, but even for TOTL DAPs like Lotoo PAW Gold and AK SP2000. The improvement is comprehensive. With it, the sound opens up, the veil is lifted, and the performance of both the DAP and the IEM is brought to their full potentials.

In general, I consider the combo of a decent DAP + C9 to be at least at the level of Hugo 2, which I considered as the king in driving IEMs.



Some Background Info of Portable Amps

If you are quite familiar with portable amplifiers, please feel free to skip this section.

So what is a portable amp, and why do I need it? A portable amp is something that can be connected with your DAP (or any source component) to further enhance its performance. In a super general level, you can consider any DAP as doing two jobs simultaneous: (1) it has the DAC portion that helps to decode the music; (2) it has the Amp portion that takes the input from the DAC portion, amplifiers the input, and then delivers it as the output from the DAP.

Most modern DAPs have the line-out function which, if it works as intended, will bypass the Amp portion of the DAP and only outputs the signals from its DAC. With this function, the DAP can be connected with a dedicated amplifier to achieve a performance upgrade. C9 is such a dedicated amplifier. In principle, an additional, dedicated Amp should do a much better job in taking up the Amp job: It has an independent power supply, better components/circuit design, and potentially better functionalities.

General Introduction of C9

I want to start with a simple personal experience in my journey of DAPs. Back in the days, I got my first DAP from Lotoo: LP6K. I really like its functionality and sound signature. However, I find that it could not really drive my LCD-i4 or IER-Z1R very well. So I thought, OK, let me upgrade the DAP to get better performance out of the two IEMs. I then sold the LP6K and got the LPGT. LPGT did have better performance and I was quite happy with it for a while, but I still have the feeling that there is still room for improvement. I then continue my journal of searching, go through a couple of other DAPs, and eventually come to Hugo 2 which I am finally happy with its performance in driving virtually any IEMs I have.

Does this experience sound familiar to some of you? I think a lot of people have had similar experiences. When C9 came out, I in fact don't really need it as I am quite satisfied with Hugo 2. But I keep thinking this: If C9 were available back in the days when I wanted to upgrade LP6K, maybe all I needed was to buy a C9. No more need for DAPs exploring, and I get to keep my favorite Lotoo sound signature. So, I bought the C9, and I am happy to report that it not only does such a job, but it accomplishes it extremely well.


Functionality

C9 is a tube/solid-state dual-mode portable amplifier. Besides these two modes, it has two classes as well: A and AB. Just from this, you can see that C9 gives you a lot of different sound signatures to explore. It takes both 3.5mm and 4.4mm input and outputs in both 3.5mm and 4.4mm - so again very flexible in how you want to connect your DAPs and IEMs/headphones to it.

An additional interesting point is that, unlike many portable amps that only take line-in signals, C9 can also take pre-amp signals. Its pre-amp mode is designed when your DAP does not really have a line-out function. In that case, you can simply use the regular headphone output and connect that with C9. C9 will then serve as a "power amp" that dramatically increases the power of the signals from your DAP. Unlike the regular line-in mode, where C9 takes up most of the job of delivering the sound signature of the output, in pre-mode the signature of the DAP is mostly preserved. This is ideal for DAPs like WM1Z, which has an excellent sound signature but has been known for its relatively weak output (in today's view). Then, the pre mode of C9 allows you to preserve the sound signature of the 1Z, but gives it a lot of power.

When I say C9 has a lot of power, don't worry, it works very well with sensitive IEMs. In fact, C9 is designed with such a goal in mind. In its low gain mode, C9 works well with virtually any IEMs. In its high gain mode, you get huge power that is enough to drive planars like Abyss Diana V2.


Performance

Here I am going to give an overview of C9's sound performance. Its pairing with my specific gears will be covered in the second part of the review (in a later, separate post). My source gears for this review include Cayin N6ii (E02/A02, both in line-out), Lotoo PAW Gold (line-out), and Hugo 2. My IEMs are Fir M5, UM Mest (with Iliad), and 64 U18t (with Socrates).



In its solid-state mode, I think the best term I can use to describe C9's performance is that it helps to reveal the music. With it, the sound is cleaner, the imaging and placing improve dramatically; you hear ALL the details of the music but in a nice and not "all in your face" manner. I think this is what impresses me the most. Different DAPs/sources I currently own could have different weaknesses in their sound. What C9 does (in line-in mode) is that it "reorganizes" the music and produces a well-rounded, comprehensive presentation of the music. I generally feel like the music coming out of C9 is what the music producers want it to be, and it is no longer limited by my DAPs.

In terms of general IEM pairing, it works really well with the three IEMs I own. I am happy to report that C9 does not work like Hugo 2 in giving a dominant sound signature such that different IEMs sound more or less the same (although in a good way). Instead, it helps to preserve the signature of the IEM rather well but pushes them to their full potential.

Meanwhile, I would say C9 does add some coloring to the music. I would say its signature is between LPG (which is extremely neutral IMO) and Hugo 2 (which adds color to the music and in a very pleasing way). In SS mode it gets closer to the neutral end, and with tube mode, it gets closer to the lush/coloring end. I haven't had the time to compare Class A and Class AB. I mostly just go with Class A because it is my favorite, and it sounds fantastic. I did briefly try Class AB and it sounds almost as good, but it seems a bit softer to my ears than Class A.

Detailed Pairing with DAPs and IEM/Headphone

To be continued in a follow-up review post.

Short Conclusion

In my own experience, C9 is the single biggest improvement I have brought to my system. Before getting C9 I have been listening under the assumption that TOTL DAPs should most likely have competent Amps, at least for IEMs. It was after getting C9 that I realized how much these DAPs are limited by their Amp section. I also want to quote the feedback from @KickAssChewGum which I totally agree with.

"I’m in total agreement with this. I couldn’t believe the improvement with my SP2000 plugged into the C9 and absolutely wasn’t expecting it to be anywhere near as drastic as it is. I’d go as far to say that the C9 is actually the one component that I’ve ever bought that has the most significant effect on sound (for the better). I’m massively impressed by what Cayin have achieved here. The C9 has made me a Cayin devotee for life and it’s literally the first Cayin product I’ve ever bought. I cannot recommend the C9 enough!"

To me, if you are quite happy with your current DAP, but want to upgrade your listening experience, C9 is an excellent choice. You get to keep what you enjoy with your existing DAP, such as its functionality and sound signature; meanwhile, C9 helps you to transform it into a world-class listening system. You also benefit from the great versatility of C9 for its various modes and sound signatures - You can always find one that suits your need, and you will never get bored,



Finally, I am really pleased that Cayin builds C9 with the goal that it is built to last. The VP of Cayin said that Cayin wants C9 to last for 5-10 years. In this process, the technology, especially the functionality of DAPs, will likely evolve quite dramatically. Think about what we had 3 years ago for the Andriod DAPs and the DAPs we have today like DX300, R8 that are at the same level in system functionality as flagship smartphones. So, when you are upgrading your DAPs in the future, with C9 you don't have to go from one flagship to another flagship. You can simply focus on getting the one that has the best functionality and suits your daily needs, and be confident with the fact that when paired with C9, it will always bring you a world-class music experience. C9 has really solid built, removable batteries for easy replacement and future upgrades, and TOTL sound performance. If you have the chance in the coming months, I will strongly recommend to reach out to your local dealers and request a demo unit to try it out yourself. I am sure that a lot of you will be pleasantly surprised by how the C9 can help you bring your current favorite DAPs to the next level.

Edit: For further questions and discussions, please join us in C9's discussion thread.