Fearless S6 Rui: Ultimo!


Today we’re checking out one of the mid-range models in the Fearless lineup, the S6 Rui.

The last few years have seen Chinese audio manufacturers really take off, and they’re not slowing down. With brands like Knowledge Zenith absolutely dominating the budget sector, it was only natural for other markets to see massive growth too. For 150 bucks you can get a feature rich and very impressive sounding earphone that makes you question why you’d ever considering spending the same amount or more on something from a mainstream brand. Fearless Audio, established in 2012, seems to be taking the same approach but with the mid-tier market. For the sub-500 USD price tag the S6 Rui commands, you are getting a whole heap of performance and quality for not a lot of money… to some.

Let’s take a closer look at why this earphone should be high up on your list of gear to get in 2019.


Thanks to Lillian with Linsoul Audio for arranging a complimentary sample of the S6 Rui for the purposes of review. All thoughts within are my own opinion based on time listening to the S6 Rui and do not represent Fearless, Linsoul, or any other entity. At the time of writing, the S6 Rui retailed for 389 USD. Note that the S6 Rui can be heavily customized (for an additional fee) so if you’re not a fan of the design seen here, you can easily swap to something more your style. Check it out here: https://www.linsoul.com/product-page/fearless-audio-s6rui-IEM


The S6 Rui was paired primarily with my TEAC HA-501 desktop amp with either a ZiShan DSD or HiFi E.T. MA8 providing source duty. I find a lot of BA-only iems a poor pairing with my HA-501 due to their high sensitivity causing an intrusive background hiss. That is not an issue with the S6 unless you crank the damping factor all the way up. For mobile use my Shanling M0 was recruited for source duty and proved a fantastic pairing. Note that while I listen most of the time at quite low volumes, the S6 Rui really comes alive at moderate to high volumes. Those of you who tend to listen loud will get more out of this earphone than those than listen quietly.

Personal Preferences:

I listen primarily to various EDM sub-genres (liquid drum and bass, breakbeat, drumstep, etc.), hip hop, and classic rock. My preferences for earphone tuning are quite relaxed and as such their is no one signature I look for. The HiFiMAN RE800 Silver, Brainwavz B400, and Massdrop x MeeAudio Planamic are examples of earphones with wildly varied signatures that are enjoyable for different reasons. I generally listen at very low volumes, so keep this in mind when perusing my thoughts on how an earphone sounds.


  • Driver: 6 balanced armatures (Sonion bass x2, Knowles mids x2, Knowles treble x2)
  • Frequency Response: 15Hz – 20Hz
  • Sensitivity: 113dB/mW
  • Impedance: 20ohms
  • Isolation: 26dB

Packaging and Accessories:

The S6 Rui arrives in a very downplayed cardboard box with little in the way of flourishes. The lid contains a simple outline of face plate with the Fearless logo in the top left corner while the side contain nothing. Flipping to the pack you find some specifications and a QR code. Lifting off the lid you’re greeted to a long plastic protected by a flexible cardboard insert. Inside the case are the earphones and accessories. In all you get:

  • S6 Rui earphones
  • 8-core 0.78mm 2-pin braided cable
  • Hard plastic carrying case
  • Shirt clip
  • Velcro cable tie
  • Whirlwind tips (s/m/l)
  • Single flange silicone tips (s/m/l)
  • Foam tips (white, blue, and red)
  • Cleaning brush
  • Aluminum information plaque

While the unboxing experience is very basic, the accessory kit is not. I was truly surprised to see a set of medium Whirlwind tips preinstalled since I had only ever seen them included with KZ products in the past. Even more shocking was that paired with the S6 Rui, they actually sealed! This is the first earphone I can use them on. The shirt clip is nicely built but on the chunky side. Also, it can only be clipped above the y-split due to the thickness of the wire. It works well though. The information plaque is a really nice touch since it gives you the exact model designation (S6-2133) who made it and when (Yoyo on Feb 28, 2019), and where. That extra bit of personalization helps make a purchase feel special. Let’s not forget that excellent case. The plastics are tough and textured making it scratch resistant. The interior is lined with foam to protect the contents. Unlike most cases, the hinge is is one one of the short ends with a thick clasp at the other keeping it securely shut. Waterproofing is about the only thing missing.

Build, Comfort, and Isolation:

The S6 Rui doesn’t do anything particularly new and special with their materials and body style, and that’s a good thing. The acrylics feel amazing with that telltale softness to the touch that is typical of quality plastics. Since it is clear, you can see the layout of the drivers, the painfully accurate soldering job, the compact 3-way crossovers, as well as the sound guides and Knowles-style filters within them. There are no bubbles, or imperfections to be found anywhere. This particular example of the S6 Rui has a silver tinsel/wire face plate and visually it is quite stunning, especially when looking at it up close. The way the Fearless brand name and logo float above it is sweet too, and it does float as evident by the short shadows cast when tilting it in the light. It all looks extremely clean, tidy, and frankly quite impressive. Fearless has done an amazing job with the construction and visual style of the S6 Rui. My only concern is the lack of a nozzle lip which makes pairing tips very important. The shape of the nozzle makes the wrong tip subject to slipping off, more so than other earphones I’ve used. The stock tips are fine but when you start moving into third party alternatives be careful.

The cable impresses too with it’s eight core, braided design and attention grabbing silver colouring. The sheath feels fairly tough but still retains good flexibility, though sharp bends do reveal some memory in the form of kinks that remain. They can easily be straightened out though. Another nice plus is that the sheath is not at all sticky so the cable doesn’t catch on your clothes or skin, sliding smoothly over it instead. All of the hardware shares a consistent polished steel design which is refreshing. Other cables seems to pull from a generic parts pins and lack a cohesive look. The 90 degree angled jack is fairly beefy but has a 3mm extension to accommodate cases, and a stubby, strain relief that won’t really do anything, not that a cable like this really needs it anyway. The tubular y-split tapers in at the edges drawing focus to the laser etched Fearless “W” logo imprinted on it. There is no strain relief entering or exiting here. Fearless thankfully eschewed memory wire for preformed ear guides which look to be made from heat shrink. The curvature is natural and it is just stiff enough to keep the cable in place during activity without causing issues with friction around the top of the ear. The 2-pin plugs are the only area I can draw criticism. The plugs are longer than the recession in the ear pieces so they stick out a bit leaving them susceptible to damage from bending. The blue ringed metal sheath surrounding the left plug is also screwed further down the plug leaving the cable looking a touch lopsided when installed. 99% of people wouldn’t notice this, nor would they care if they saw it, but for someone like myself that like things to be uniformly mirrored, it is a little irritating. Now that I’ve noticed it, I can’t unsee it. Also, while the pins fits in tightly, the right ear piece is prone to detaching unexpectedly. I have no idea why because it feels very secure, but it’s happened a handful of times over my month or so of testing so it must be mentioned. Thankfully the ear piece has only ever fallen onto carpet so there has been no damage, as evidenced by my images which are almost always taken shortly before the review is written and posted. Nice to show any wear and tear a unit could pick up during testing since I try to use stuff as a daily whenever possible.

Thanks to a very ergonomic design, likely crafted from overlaying hundreds of ear impressions like many other brands have been doing as of late, the S6 Rui is a very comfortable earphone. However, as is usually the case with this style of shell this earphone is on the large side. It does contain 6 drivers per side and the accompanying crossovers, hardware for the 2-pin cables, and some filters after all. Still, as long as your ears aren’t too small the S6 Rui is probably going to fit you like a dream, locking naturally into the outer ear to provide a stable, ear hugging fit. Another plus is that despite being a sealed design, the feeling of pressure you often get with sealed designs is absent, for me at least.

With 26dB of isolation, the sealed S6 Rui should be completely suitable for use in noisy areas. Using it in the local coffee shop was wonderful since I didn’t have to increase the volume to drown out the chaos around me. The same could be said on a recent trip I took to a nearby city as a passenger in a noisy truck. Tossing on a set of the included foam tips makes things even better. Those who like to take their premium gear with them into the outside world will find the S6 Rui a solid companion.


You’re sitting on a beach in the middle of the ocean. The sun bathes you in it’s rays of glorious life giving vitamin D. A salty, calm ocean breeze washes over you. This really is utter bliss. And the Fearless S6 is right there with you, caressing your ear holes to the soothing sounds of Dragonforce. What does this have to do with anything? Nothing really.

The S6 Rui has a mild u-shaped signature to my ears. Treble sees a meager bit of elevation with a refreshingly even balance of presence and brilliance regions. Lower treble finds itself in a classy place, like Jim Douglas in “Herbie Goes to Monte Carlo”, with there being enough emphasis to provide a detailed sound that falls just short of being analytic all while avoiding the pitfalls and potential for harshness that go along with exaggerated boosting. Upper treble is much the same. It provides a grounded but airy note presentation with a silvery sparkly and shimmer to relevant notes. There is no harshness or anything overly aggressive going on with the S6 Rui’s treble. It’s easy on the ears but still very technically competent and with the snappy decay you expect from a balanced armature.

The midrange is full and engaging with strong vocals that peer through the mix despite not being jacked up and shoved forward as other earphones try to do. The clarity is stellar with a fair amount of micro-detail cutting through and pricking at your senses. This is the type of earphone that invites repeat listens of familiar tracks thanks to it’s ability to represent everything available, so you might catch something you’ve missed in the past. It’s a very honest and unbiased presentation with wonderful timbre that doesn’t favour any particular frequencies, unlike something such as the RHA CL2 with it’s stratospheric upper mid boost that nearly throws the entire presentation and timbre completely out of whack. But some people like that. If you do, the S6 Rui probably isn’t for you.

The S6 Rui’s low end is fantastic. Extension is very good for a balanced armature allowing it the ability to move some air and provide a decent bit of rumble. Sure, it rolls off earlier than many dynamics. BUT, at the same time it also extends further and provides a more impactful, engaging experience than many other dynamics. As with other aspects of the signature, the bass find that solid middle ground and makes it home. It sits in a favourable position being a little more emphasized than is considered “ideal” from a measurement perspective, but not so boosted so as to be called bassy or bass prominent. This style of presentation is very versatile since the S6 Rui can skip from genre to genre without the bass being overbearing or underrepresented. Add to that good dynamics and texture along with a realistic, not overly quick decay, and you have yourself some high quality bass.

The S6 Rui has a solid sound stage too, displaying a fair amount of width and additional depth. It can toss sounds away from the head and immerses you in music, just not quite as well as some other earphones I’ve heard. The depth to it’s staging is where the magic happens giving music a very dynamic, multi-layered feel. This is supported by some impressive separation that ensures your music is congestion free. Imaging is also fantastic with crisp and accurate channel to channel transitions. Radiohead’s “House of Cards” is a particularly enjoyable track with the S6 Rui and does a great job of showing off all of the above-mentioned aspects.

Select Comparisons:

Fidue A85 Virgo (399.00 USD): The Virgo’s triple driver hybrid setup has a much more mid-focused sound with roll off at either end. This makes it great for vocals and certain genres, but compared to the S6 Rui feels constricted. The S6’s treble provides more shimmer, sparkle, and air thanks to a more prominent upper region. The Virgo’s emphasis in the lower treble helps it with raw clarity and gives it an edge in mid-range note definition. The S6 Rui’s mid-range is warmer and less forward with less detail but more accurate timbre. Bass on the A85 is slower with more mid- and upper-bass focus. Sub-bass quantity and extension is lacking, even compared to the S6’s use of an armature where the Virgo is using a dynamic. The S6 is more textured too. Sound stage is surprisingly close with the Virgo feeling a touch larger and more open, but lacking the depth of the Fearless. Imaging, layering, and separation are all more prominent and accurate on the S6 Rui.

Build is split imo. While the Virgo’s metal shells are immaculately crafted and drop dead gorgeous to look at, so is the S6 Rui. The two companies simply went about creating amazing looking and feeling products in completely different ways. The S6’s cable is nicer though, looking more suitable for the price range while also handling better. Fit for me is also better with the Rui, though the Virgo’s smaller, lower profile shells will certainly be more universal across a wider variety of users. Isolation easily goes to the sealer S6 Rui. The Virgo is heavily ventilated and has a very shallow insertion.

Overall I prefer the S6 Rui. The Virgo is a good sounding earphone but the limited end to end extension/emphasis leaves it feeling lacking compared to the S6 Rui. On the other hand, some will undoubtedly prefer it’s more laid back, mid-heavy presentation.

Astrotec Delphinus 5 (500.00 USD): The Delphinus5 is one of my favorite iems so the S6 Rui is coming in on the backfoot. That said, I am surprised at how well it holds up to Astrotec’s flagship which as I understand has few fans. Both are armature only with the D5 featuring one less driver per side; 5 vs. 6. The D5 runs with all Knowles while the S6 Rui combines Sonion low-range with Knowles mid and high range drivers. I’m not a huge fan of Knowles low range drivers since I’ve been finding them outpaced by the low range drivers found in the KZ armature-only models. As such, I was not surprised to find myself enjoying the S6’s low end more. It hits harder, digs deeper, and in general feels more engaging. The D5’s low end gets the nod for texture and control, however. The D5’s mid-range is more forward and articulate than on the S6 Rui, but is also colder and a bit less natural sounding thanks to a timbre that comes across more dry. Treble on the S6 Rui extends further and puts more emphasis on the upper regions while the D5 extends just enough to ensure you’re not missing anything, and tosses emphasis at the lower treble. As such, the S6 Rui is brighter and more shimmery, but the D5 feels more forward and detailed. Imaging, layering, and separation is where the D5 always shines and it’s no different here. The S6 does a better job than most of moving sound around in a realistic manner, but the D5 simply does it better. I feel like I’m surrounded by my music with the D5, something the S6 Rui falls just short of achieving. While I still like the D5 more, the S6 Rui provides a different experience and when in the right mood, can’t be replaced by the D5.

In terms of build, this is basically a repeat of the Virgo comparison. A gorgeous acrylic design with flawless construction vs. a stunning aluminum gem, perfectly executed. While both are very comfortable, the D5’s smaller size and rounded interior is superior. I like the D5’s cable but the stiff, memory prone copper cable doesn’t perform as well as the S6’s plush offering. Isolation is quite close too with the S6 Rui pulling slightly ahead. Either would be suitable for a commuter wanting to bring with them a TOTL listening experience.

Overall I prefer the D5, but I wouldn’t hesitate to recommend the S6 Rui over it. While the D5’s flat tune is great from a technical standpoint, I can easily see someone finding it stuck up and boring next to the S6 Rui.

Final Thoughts:

While certainly not inexpensive to most of you out there (myself included), I still consider the S6 Rui a flat out bargain when compared to more expensive gear I have on hand. Not only does it hold it’s own in terms of tuning and technical competence, but it is built just as well or better, has a stellar cable, is comfortable as all heck, isolates well, looks amazing, and comes with a great kit of extras.

The packaging could be flashier I suppose, but people seem not to care about stuff like because it’s packaging and they’re going to toss it out immediately anyway, or maybe it smells wonky so watch out! Hey, at least it’s spacious and completely recyclable. Woo! The right ear piece detaching at random is more of a valid concern, though easily addressed by lightly bending the pins towards each other. You shouldn’t have to do it, but unless you go Hulk on the pins it’s a very easy and low risk fix. Other than that, criticisms of the S6 Rui are as tough to find as Waldo’s most challenging adventures

If you’re looking for a premium product and don’t want to drop 500 USD to 1,000 USD on a unicorn, the S6 Rui is well worth an audition so you can see how good it is, then afterwards go home with one. This is one of the few products I’ve reviewed that is absolutely worth saving up for.

Thanks for reading!

– B9Scrambler

***** ***** ***** ***** *****

Some Test Tunes:

Aesop Rock – Skelethon (Album)

Daft Punk – Random Access Memories (Album)

Elton John – Yellow Golden Brick Road (Album)

King Crimson – Lark’s Tongues in Aspic (Album)

King Crimson – Starless and Bible Black (Track)

Supertramp – Crime of the Century (Album)

Infected Mushroom – Converting Vegetarians (Album)

Infected Mushroom – Legend of the Black Shawarma (Album)

Gorillaz – Plastic Beach (Album)

Massive Attack – Mezzanine (Album)

Fleetwood Mac – Rumors (Album)

Run the Jewels – Run the Jewels (Album)

The Prodigy – The Day is My Enemy (Album)

Tobacco – F****d Up Friends (Album)

Felt – Felt 2 (A Tribute to Lisa Bone) (Album)

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