Introduction

Hey guys, this is gonna be my take on S10 Genie model from Fearless Audio. There were some issues initially but all of them were resolved thanks to Lilian from Linsoul.

I have purchased these IEM through Linsoul around mid April and it took some time since it was basically a period when Fearless hype was at it's maximum. First off when I just received them and plugged in into my DAP which was F.Audio FA2 at that time I thought "This is the worst sound I have ever experienced" which was quite quickly replaced with "Something is not right". After about 30 minutes of trying different cables and sources I have figured out that my pair came with "reversed phase" issue. Basically it means that inside one of IEM wires should be soldered vice-versa. Thanks to 2-PIN cable I was able to check it out by simply pluggin in cable in a reversed manner.

I have contacted back Lilian shortly and informed her about this issue. One day later my IEMs were on their way back to Linsoul so Fearless could check and fix them. During that time I have tried to contact HawaiiBadBoy to explain him that his sample was probably with the same issue but he already sent them as part of his giveaway program. That also explains why he did not make a review for them and had a very weird first experience since they probably were the same as mine. Being an owner of S6RUI previously I cannot imagine anyone who would like S6 and dislike S10 because they are like twins with S10 being better in every area compared to S6.

I will leave comparisons for a further part of this review so to cut the long story short. I have received my Fearless back in a month or so and all the issues were fixed. As an apologize for this unpleasant experience both Fearless and Linsoul have sent me their balanced upgrade cables which I will also make a part of this review as a way to say Thank you to them for being so generous but I think it's Lilian whom I should address most of my gratitude since she was very supportive and tried the best she could to resolve this issue for a satisfaction of both parties.




Package

They come with the same package as all other Fearless Audio IEMs. There is a white box which has a serial number and a model number on it. Soft Blue carrying case and a set of grey/green eartips of different sizes.
Default cable is the same as for other Fearless models as well. At least S6RUI and S8F come with the same cable as far as I can tell. It's a pure silver cable according to how it looks. It's nothing special but nothing too bad either. You will be more than fine with it unless you are obsessed with the possibility to push IEMs to their limit.
Another reason why you would want to switch is to use them balanced if your DAP supports that option. I would say that in this situation it's more reasonable to switch even though difference is not night and day.
I won't concentrate much on packaging part since you probably already have an idea how Fearless Audio lineup package looks like. Since there is no difference let's move further.



Comfort & Isolation

They have a little bit bigger shell than S6RUI as far as I remember but it's shape is anatomic and I personally have normal to big ears so I have not had a single issue with how they fit.
Nothing stands out, no harsh edges or any sign of uncomrtable experience even after long listening sessions. I can easily sit with them in my ears for the whole day and won't feel any discomfort about it.
Those of you who have small ears should be a little more careful and I would advice to try before you actually buy them but commonly you won't experience any trouble.
Considering all of the above their isolation is great for me. I would not say that it's better than general competition because it all depends on how good they fit. Most of my recent IEMs isolate about on par with them since I have not had any fit issues with them either. I can comfortably listten to S10 even on low to middle volumes.



Sound Impressions

Here goes the best part. I would say that these are the best IEM both Price/Performance and overall quality wise from my personal taste point of view. At least I have not heard anything which would be significantly better so far.
I have not tried 3000 USD TOTL iem but all IEMs below 1000 USD in my experience sound worse or not to my taste compared to this model. I also think that S10Genie is an easier recommendation than many other IEMs because it is more balanced than some other models which try to emphasize certain regions.

BASS:

Considering that it uses 4 x Sonion BAs for Bass you could think that they would be bass heavy but they are not. Bass is close to linear with good texture and subbass going quite low. It's tight and fast but never lacking. It's not boomy nor loose. I would say if you are a basshead you might want something else since they are close to linear and not bass heavy. It's nothing like Etymotic ER4 style of being linear but still it's not emphasized either.
I personally think that this way it is perfect because it does not drag attention to itself and never bleeds into Mids region. On the other hand I would also understand those who'd prefer to have more bass quantity. Quality wise it's close to perfect though.

MIDS:

Best way to describe them would be - SMOOTH. What always bothered me in my S6RUI is that their high mids / lower treble region is a little emphasized and despite it's being focused somehow it also felt that they are congested and cannot easily reproduce complicated tracks. After a little while my RUI ended up being a little fatiguing while it's never been so with S10.
Genie does not have any sibilance, does not have any extra brightness yet still they can easily reproduce all the detail and even more than some other models with emphasized "details" region. They are tuned almost perfectly in mids region. If you have heard Sony M7 you would know what means totally smooth and S10 are not THAT smooth but somewhere in between M7 smoothness and S8F brightness.
These do not sound thick or warm so if you look for IEM which emphasize lower mids region and if you prefer overall thick & warm tonality then these are not for you. S10 are again close to being neutral in that area with only a little lack of weight which I would personally prefer.

TREBLE:

High region compliments Mids and allows these to have a lot of space and air yet keep being natural and smooth more than anything else.
I perfonally think that Highs are also done right here, there are more high frequencies than in S6RUI but they are never synthetic or overly emphasized.
If you like "crispness" or "refreshing" tonality of highs then you should also skip S10. These do not drag extra attention to detail through highs being boosted. Instead these keep being natural all the way yet still bring out all the detail and air through amount of drivers they have.

If you are interested in Frequency Response and other graphs you may find them here:
https://reference-audio-analyzer.pro/en/report/hp/fearless-audio-s10.php
I won't post images without owner's permission so feel free to use that link.

Comparisons

Fearless Audio S10Genie vs Sony M7:

Sony M7 are more smooth that S10Genie. From sound thickness point of view they are close to being identical. At some situations Sony can sound too smoothed out while S10 sound more balanced overall. S10 also sound wider and more detailed in comparison but that's not night & day difference.
Overall I like both of these models.

Fearless Audio S10Genie vs Fearless Audio S8F:

S8F are more bright while S10 are more smooth. S8F might be fatiguing since it tries to push out more detail into focus. They share an overall Fearless Audio signature but S10 are overall more balanced and more polished. They do cost much more than S8F so I cannot easily recommend one against another. You should listen to both and make a decision personally.

Fearless Audio S10Genie vs Fearless Audio S6Rui:

Even more unfair comparison pricewise. I personally think that sound signature is closer between S10Genie and S6RUI than between S8 and S10 models. S10Genie are better in every area than S6RUI as they share almost identical signature with S10 being a level above and cost 2x times more. Most important fix in my opinion is that high mids focus of S6RUI is redone with smoothness without losing detail.

Fearless Audio S10Genie vs Audiosense T800:

T800 costs less than 2 times of S10 and even though both sound well they are way too different. T800 has more bass quantity wise, even less lower mids and have a boosted high mids & treble region. I can recommend T800 for those who like V shaped sound signature with focus on bass and refreshing feeling in treble. In comparison S10 sounds more wide, more detailed, with better separation and sense of space between instruments. Both male and female vocals are more emphasized and more emotional on S10 than on T800. Money wise I can't recommend one above another. You should listen yourself to judge if paying extra worth it.

DAP compatibility

For most of the time I have listened my S10Genie through 2.5 mm balanced output of Fiio M11 and I am absolutely satisfied with how they pair together. Before I received my Fiio M11 I have listened to S10 through my phone and I also did not have any signfificant issues with that. These IEM are quite easy to drive and are not very source dependant. They preserve their sound character across all of the devices I have heard them with which are - Ibasso DX200, Ibasso DX220, Fiio M11, F. Audio FA2. Even though you can easily notice how they grow together with source if you decide to stop at something like Fiio M11 you will be absolutely fine with it. There is no need to pay extra money for higher quality DAP if you listen to it with S10.

Upgrade cables

Fearless Audio IEM upgrade cable:

Aesthetics: For me it looks better than cable fron Linsoul. It's a black cable with silver parts which visually perfectly pairs with S10 and Fiio M11.

Comfort: I think Linsoul cable is more comfortable than Fearless cable. It has quite stiff area near IEM 2-pin connectors which always reminds me that I wear an IEM.

Sound: I feel that it is more smooth and laidback than cable from Linsoul. It adds a little weight in lower mids region and overall expands sound field a little. However it also may make an effect of "overly smooth sound" so I would not indicate that this cable is better. You should judge according to your own perfonal taste.



Linsoul Supreme 7N OCC Silver Plated Balanced Cable:

Aesthetics: It looks too bright for me personally. Gold yellow color drags a lot of attention but that's just a personal taste thing.

Comfort: Much more comfortable than Fearless upgrade cable. It's connectors are very soft and at some point you may even forget that you wear an IEM.

Sound: It adds more treble and makes overall signature a little more focused and a tad bright. At first I liked Fearless cable more but eventually I prefered Linsoul cable over it. Overall signature being more articulate and precise is what I liked about it.



Conclusion

700 USD region is way too high for blind recommendation of any IEM. You should find a way to evaluate an item before you actually buy it. In my opinion these IEM worth the money. They are balanced, smooth, without any incoherence or peaking regions.For most of the people this level of sound is close to endgame. Is the difference worth it? You have to listen yourself to decide. For me it is. If Fearless have figured out their quality contol problems then this might be the last purchase you make in IEM world. At least for a while

Probably I should say that I have experimented with many Chinese IEMs recently and have auditioned or owned majority of recent hype trains. I do not like fatiguing IEMs, I prefer to enjoy music instead of listening to details and figuring out if something extra is in there so I tend to enjoy an overall picture over small notes. That says that I like balanced, smooth IEM without any noticable peaks.

Purchase story

I have purchased my S6RUI from Linsoul and payed my own money because of snowball effect which was created by one of the famous Youtube IEM reviewers. They took about a week to be made and were shipped out very fast so I received them in about 2 weeks.

I would like to thank Linsoul Audio for great communication and Customer service.

Introduction

S6RUi come in a generic box which has some similaritites with BGVP DMG and BGVP DM6 boxes. If you remember old Xiaomi boxes you would now what I am talking about.There are many different tips mostly with wide nozzle and several types of foam tips. I would rate this package as acceptable / good. Nothing I was surprised with but basically everything you would need.



Comfort & Isolation

These IEM are very comfortable. They have quite a comfortable shell which I personally see for the first time. Nothing hurts my ears and they fit them really great. I would rate their shell as 5 out of 5. I have shared these IEM with several different people and noone experienced any difficulties so it's great.

Considering the text above I have great Isolation with them. Not on the level of Etymotics but quite around maximum level of what you get from Universal IEM.

Sound

Lows:

They focus more on subbass than on midbass and it's quality is around the top levels of what it might be in UIEM. I personally heard only one IEM which I consider to be on another level in terms of subbass quality and they were Sony IER-M9 but they are in a completely different price league so it's not a fair comparison. Additionally their bass can be tuned by using different types of eartips. The smaller the nozzle is the more subbass you get and with wider nozzle focus switches a bit to mid bass. I would say that both for the price and overall these have 9 out of 10 quality bass.

Mids:

They tend to follow modern tendency of Harman like sound as it was mentioned many times. I personally do not really like the way it sounds in implementations I have heard so far (Sony MH755, Dirac HD MK II, S6RUI) so take it into consideration. I have heard that only N5005 have managed to do it right so far but that's just fancy words which are not backed by my own experience.

They lack some weight in lower mids so overall they sound very-very close to natural but still a bit on a thin side. Their high mids bump is done in a very professional way so they manage to be dynamic and focus that region without any weird peaks or cliffs. That makes them quite coherent and sound without any distortions, transparent like a crytal clear mirror.

However to my personal taste I find them being borderline fatiguing. Once you put them in your ears everything sounds great but after a while you find that you feel a bit tired because of their brightness. It is nowhere near something like Andromeda which are like "hearing killers" to me and an absolute fatiguing brightness machine but still If you prefer something smooth or more balanced you should take this into consideration.

Highs:

There is quite a good feeling of air and separation between instruments. In direct comparison with Ibasso IT04 I found S6RUI to have more space and have an overall positioning slightly better even though not a mile ahead.
I would say that there are just enough highs to feel comfortable with them and does not feel that anything is lacking.

Overall sound verdict:

These would be great for people who wants a tad of brightness or sparkle in their sound. I would easily recommend them for people who enjoy subbass + detail retrieval as these IEM do it very good. Soundstrage and separation are also good but not the best I have heard. These sound very close to natural. I would not recommend these for people who are sensitive to brightness or who prefers smooth sound.

Comparisons:

I would not compare these separately with other models but in more of a "free flow of thought" form way. Considering the current market state and fast evolving nature of Asian IEM market every day we get more and more choices. You have probably heard on this forum about some "High Quality 12 BA or FR12" models from China and in direct comparison with them 12BA model does not stand a single chance. I have no idea why this 12BA model has some crazy burn-in recommendation as it is quite broken in a way it is engineered in a first place. However sometimes Chinese OEM make something right and I speak about NK10 here. I have reviewed this model previously(about 6 month ago and my freind still owns a pair). They cost a bit less than S6RUi and in direct comparison I personally would say that they are less fatiguing. NK10 has safer highs mids/highs tuning, sounds more expansive with better separation and more air in sound. It definitely loses in subbass region and sometimes produces more distortions due to 10 BA being in it but eventually I find both models very close to each other. On the other hand something like IT04 costs more and does not stand out in quality over S6RUI. IT04 has more midbass, a bit thicker sound but less air and separation. Considering the price I don't think there is a point to go for IT04.

I would like to thank ElixBerd for making these graphs.

Orange are NK10 and purple are S6RUI, these are very close:



Conclusion:

This model does everything good and "subbass + detail retrieval area" great but it does not impress in "exceptional way". It's not cheap. In 400 USD price region you may get a lot of different IEMs. It is for people who prefers a bit of brightness and sparkle, for smooth sound lovers I would say "try before you buy". It is a very strong model but I personally would go for something like Sony IER- M7 as I prefer smoothness over detail(if we ignore the difference in price).

Introduction:

I have fallen into NiceHCK M6 and BGVP DMG hype train and ordered a pair last year. I have decided to go for NiceHCK M6 solely because of price and experience I have already had with Jim NiceHCK and that I know how things commonly work in "Chi-FI". There was a drama you are probably aware about it and I personally think that these IEM are either identical or share only a minor audible difference.

There are several detailed reviews already available with frequency response measurements and package reviews so I will skip these parts and try to add extra information on top of that. Here are highlights of major parts of my review for your convenience so you won't have to read the same stuff all over again.

Sources:

- M6 pairing with Astell&Kern A&Norma SR15
- M6 pairing with Astell&Kern JR
- M6 pairing with LG G6 (ESS SABRE ES9218)

Comparison:

- Comparison with Kinera Idun Deluxe Limited Edition,
- Comparison with Ibasso IT04
- Comparison with Kinera Odin,
- Comparison with 12 BA iem which cannot be named.

Sound impressions:

Tonality:

The best part about these IEM is that these are absolutely fatigue free and in a very good way. There are many IEMs and DAPs which tend to make their products sound a bit brighter to retrieve more detail out of your sound material but it ends up being a bad scenario when both IEM and DAP are "a bit on a bright side".

M6 is tuned in a way which fits great with most of the modern daps. It does not matter if it is ESS Sabre based devices or Astell&Kern ones M6 sounds comfortable and never fatiguing in any way. There are no signs of sibilance or harshness so I'd say that they are very comfortable for long time listening.

There are several filters available so it might be a little different once you swap default ones. You will find more detail further on

Lows:

There are 2 dynamic drivers and they are decent. If you tried some TOTL IEM then It won't be the best bass you have heard but in it's price range it is good. It has weight and dynamic softness so if you like bass you sure won't miss it in these.

It is not perfect though so it might sound a bit loose or boomy at times but again this comes from a person who used IEMs which cost several times more than M6 and it is not a fair competition.

Also if you are a basshead I recommend you swapping grey filter for gold filter and then you might end up in basshead budget friendly heaven

Mids and Highs:

Considering that you have 4 BA for mid and high regions you get decent amount of detail and separation. Dynamic drivers may sometimes overshadow lower mids region or tend to drag more attention but if you prefer more mids you can either equalize bass a little bit or try a different filter.

Silver filters make high mids / highs to be more prominent but they also can be a little bright with some devices. Personally I prefer them for some intstrumental or classic music.

Also I would like to mention that with bright sounding DAPs like Astell Kern Junior default grey filters still feel the best because it works great with DAP tuning and balances each other just right.

These might lack some air or extra sparkle in high region but there is no magic and you can't have both sparkling and fatigue free comfortable IEM especially in M6 price range. They do not sound dull or boring at all they sound just right to be comfortable and sibilance free.

Comfort, Cable, Filters:

Despite having 6 drivers their shell is not big so they are very comfortable and can be used by people who have small ears. I have read that some other reviewers recommended changing cable for them so I have also tried 2.5mm iBasso balanced cable. Indeed it makes a decent improvement to overall clarity and across whole sound spectrum in terms of separation but I would say that it is a bit of an overkill to use high priced cables. If you manage to find some decent ~30-50 USD cable then I'd say that you should go for it other than that they have quite a decent one bundled with them. It is comfortable and good looking one so I believe it will be more than fine for most of the audience.

I believe that you will get more prominent difference if you swap filters for different sound genres to get the best out of M6. Changeable filters are an extra benefit you may use to your liking in addition to EQ and changeable cables so I recommend you try doing it before any extra upgrades.

Source Pairing:



Astell Kern Junior:

This DAP pairs really well with NiceHCK M6 and I would say that it works best with them across all other models I currently have in my posession. It is a bit bright by it's nature and M6 tuning works in a synergetic way which works well with any genre. AK Jr also a bit bass light by it's sound signature so M6 being a bit bass heavy balance it out good as well.

Astell&Kern A&Norma SR15:

This one feels like an overkill for M6 and in fact it is but I've decided to try it anyway since I have an ability to do so . It brings some extra detail and clarity and almost completely removes a veil M6 have sometimes with default grey filter but it does not worth the price difference in comparison with good mobile devices with DACs or Astell Kern Junior. NiceHCK M6 are a 100 USD region great performer and 700 USD DAP as I said is an overkill.

Mobile devices, Meizu MX4 Pro, LG G6 (ESS SABRE ES9218):

M6 pairs good with mobile devices and in fact I believe that it pairs even better with ESS based ones. Most of ESS 9018K2M / 9218 implementations tend to be a little bright or even harsh with some IEM and they are never harsh with M6. They end up compensating each other in a similair way with AK JR, Bass is tamed a bit by DAP and high mids / highs are tamed by M6.

IEM comparison:



Kinera Idun Deluxe Limited Edition:

If you pay 2x times more and go for Kinera Idun Deluxe LE you will get a different overall signature - less bass, more mids and highs focus. You will lose changeable filters but get some more refinement across whole region. Does it worth 2x times price difference? It is for you to decide. Idun Deluxe LE might occasionally be a little bright here and there while M6 never tend to do so. I have also provided both of these to another person for blind comparison and he told that despite he feels that Idun Deluxe are overall technically better he prefers M6 because they are comforable and free of any harshness.

Ibasso IT04 :

If you pay 5x times more you might end up with Ibasso IT04 which are also a hybrid but provide a different approach. IT04 are more refined and musical but they require a good DAP to shine and are in another league price wise.

Kinera Odin:

If you pay 8x times more you might end up with Kinera Odin which have a similair tuning to Idun Deluxe LE but improved across the whole spectrum. It is absolutely unfair to compare these two but there is still one thing where M6 win - again, harsh free Odins might be bright and fatiguing sometimes while M6 you can use for several hours long without any discomfort.

And last goes an IEM which cannot be named which consists of 12 drivers. I have had only a brief listening experience with them and even though they win in many areas I had a very strong feeling that M6 win in MID region. Either I have not accostumized to them but I feel that M6 sound just fine while this 12 BA model sounds veiled and aritifical in mid region. That's the reason I would like to mention this comparison in a first place.

Conclusion:

I'd say that NiceHCK M6 is a great budget performer and one of the best IEMs in 100 USD price region. They are not perfect, they are not TOTL killers but they sound comfortable, harsh free and even more important customizable to your preference. Sometimes they are sold for even less than 100 USD on quarterly sales and I'd say that these are price / performance champion. I personally have not heard anything better around 100 USD price region and which can give benefits of separation and detail 6 drivers provide. I recommend M6 for entry level DAPs and for Mobile Phones which have separate DACs, I do not have iPhones in my posession but I bet they will end up pairing really well with it's cirrus logic mobile dac implementations as well.

I do not oftenly write reviews on head-fi because English is not my native language and there are many talented members who are well experienced in this area. However from time to time there are some good products which do not get the attention they deserve and in my opinion NiceHCK NK10 is the prime example.

I have purchased these earphones in late August and was one of the first who received them so I have had a lot of time to make my conclusion and in short - these are simply great.

I have had a lot of experience with different IEMs since 2011 and I have owned more than 50 different models already if not more and even though many of them are technologically advanced there are only a little which are done right.

Chinese OEM and Multi BA products

You can skip this part if you want to read directly about NK10 but I would suggest you read it to have a better understanding. I have been into Chinese IEM since their first attempts so I remember how good some of them were into making cheap products which sound right like VE Monk or LZ-A2 being the good examples but once they have moved into mid or even high region I'd say that there were some hickups.

I remember something like Zhiyin QT5 which was an absolute disaster despite having 4 BA + dynamic driver. It was an engineering abomination made by someone who has no idea on how IEMs are made yet it somehow got it's attention by the worst mistake I have ever saw on head-fi. I even ordered one and had to send it back because selling these second hand to someone is a crime. At the same time there were other 6 BA products which used Knowles drivers and they sounded quite allright for the price and still they were lacking something comparing to something like Ultimate Ears, Earsonics, Dunu or Sony hybrids. Also I believe there still are bad products like DZX-1+8. Even though I can't name all of them and they probably have different problems their main issue is despite having many drivers they have a low quality hardware inside made by poor engineering decisions which make them sound like there are a lot of different sounds with unnatural tembre and tonality coming into your face with incorrect positioning and crippled sound scene.

Despite products like this there are of course good examples like Magaosi which make good products over and over again with K1, K3 and K5. Magaosi K5 even was rebranded and sold as many different products like **** or NiceHCK and I won't even name some other brand which sells them for 3x times more than their regular price. To cut the long story short buying IEM from China is a lottery and your chances to lose are high.

NiceHCK NK10 Build Quality, Comfort and Package

Their package is quite default as for any other Chinese IEM. They come in a box which contains plastic case with several different eartips.

Their cable though is quite good. It seems to be made of copper and comfortable to wear. I would even say that it is better than some aftermarket cables which are sold separately so if you are not an absolute perfectionist you would be satisfied with the cable which comes bundled with them.

I am not the one who pays a lot of attention to design but still I'd say that they look stylish and their look is quite good.

Speaking about comfort I'd say that if you find the right tips for them they may be very comfortable to wear. Normally I use middle sized tips but they have quite a wide nozzle so for me the smallest ones made the perfect fit so I used them for several hours straight without having even a little discomfort. I'd say that I have normal to big ears so I can't say anything for someone who have small ones.

They have 2-Pin connector which I personally prefer over MMCX and their connection is tight.

Sound Quality

Sound quality it the best part about these IEM and before I start describing frequencies separately I'd say why.

These are very musical and engaging. They sound emotional and make you feel a lot of satisfaction out of your songs. This is the critical point in every IEM in my point of view because no matter how technically good IEM might be if you do not feel anything while you listen to your songs it makes their technical achievements irrelevant.


For me personally they sound the best either with the small tips + deeper seal because in that way they get a transparency, air and sound stage or with Sony hybrid tips of medium size. Basically tight, deep seal with eartip which has small to mid sized nozzle will sound good with them. Wide nozzle eartip does not work and does not sound well with NK10 in my opinion. Also I feel like deeper seal is the must for them and makes them really stand out of it's competitors.

Bass:

Bass is quite good. Nothing exceptional and at the same time nothing bad. It might be not enough for bass heads or for people who prefer dynamic drivers but for armature there are enough of bass. It is not lacking nor sounds dry. They have sub bass occasionally from time to time but in a very small quanitity so I would say that they can't quite produce sub bass. Also bass texture is not the most detailed compared to something like Earsonics Velvet but Velvets are all about bass and they lack in all areas except it.

Overall I'd say that Bass is not their prime point but is good for armature driver and just enough to make songs sound fun.

Mids:

Mids are the best I have heard in a long time compared to many IEMs I have previously owned. Both male and female vocals sound very forward and in your face but just enough not to sound aritifical or bad.

Sound has enough weight so it does not sound overly thick or thin so it makes them sound natural in tonality. This allows different drivers to produce sound in separate layers without having any cons.

They do not have any peaks or sibilance presense by their own so they won't be uncomfortable for a long listen unless you source tends to do so.

Highs:

I'd say that there are enough highs and their presense is quite obvious. They have a long attenuation so highs are the stars of the show along with mids but not in a bad way when IEM has an artificial bump in higher mids area but their quality makes them stand out on it's own.

Of course there are less highs than in something like Etymotic ER-4P or in some other bright IEMs but I feel that NK10 highs are done just right not having too much or too less but just right to make music sound natural. The word "refreshing" would be the best to describe their highs.

Soundstage, tonality:

Tonality / Tembral characteristics are among the best I have heard. Musical, engaging and very addictive to listen to. It might be very hard to upgrade from something like this because even if you get higher quality in some area there is a big chance that you will lose in musical engagement area.

Soundstage is good both in depth and width and has several layers which makes it sound 3D and detailed so complicated songs don't become messed up and every detail is very well positioned.

I'd say that soundstage and separation are the main beneficiaries of 10 balanced armature drivers done right because it does not lack in coherence.

Source compatibility:

I have listened them with different DAPs both with the ones you can see on the picture above and also with some top tier DAPs I have borrowed. Overall they are not source dependant but they are very resolving so they will sound exactly the way your source makes them sound.

DX200, Fiio X7 MK II: This is the pairing I would not recommend. It might be because I do not like these two on their own but overall it makes them sound a bit too analytical and forces them to lose some sound weight due to Sabre nature in these DAPs.

Meizu MX4 Pro, LG G6, HIBY R3: A good pairing. Despite it also has a Sabre chip I guess Hiby engineers did not try to make it sound too analytical which makes a better pairing. With NK10 you can hear very typical presentation of this DAC and all three of these sound very close to each other. It is nothing overly impressive but quite good.

Also they sound good with Hifiman 650 + Minibox card but I'd personally swap Minibox for something more soft since they could sound too harsh times in terms of energy and attack.

Sony NWZ-ZX300a is a good source for them as well because Sony tends to be more musical and dark so it is also a very good pairing.

Overall I'd say that any DAP which sounds more natural & musical instead of analytical will make a very good pairing. I really liked them with Astell Kern KANN or multibit based deep modification of Hifiman 603.

The only possible CONS I can come with:

Despite all the good things I have wrote there is a con and it is a lottery chance. Even though I have not heard anything bad about NK10 specifically there might be quality control issues when you order from Chinese OEM manufacturers which makes the same model from the same manufacturer sound different. It was the case with **** H5 when two samples sound different with the 3 month difference in production. I hope that NiceHCK NK10 has good quality control for every pair but you have to take it into account.

Conclusion:

These are the best for the price. I won't call it flagship killer because every single IEM is being called the one nowadays but I'd say that it is close to impossible to buy anything better for around 300 USD price point.