Sound Analysis.

Heads up! This is primarily for people getting into the world of DAPs. When I as a reviewer write about differences between sources, DAPs in this case, I’m looking at the differences with a high power magnifying glass by going back and forth and A/B-ing the sources extensively to pick out every perceivable nuance. These differences might come across like they’re night and day substantial when you’r reading about them but let me tell you that they’re not as substantial as you may think. Some people perceive and value differences between sources fairly significantly and some don’t as much, and that is completely okay. It’s the IEM’s stock signature that makes up majority of the sound signature and sources, cables and ear tips can only fine tune it to one’s liking. They can’t flip the stock signature of the IEM by 180°. They can only influence it partly with their own colour/flavour and that is why we at Twister6 do a fairly comprehensive Pair-Ups section in the DAP reviews to give you a clear idea.

Sound – RS2 has a natural, warm and organic sounding signature, quite close to what is loosely imagined and expected from an R2R implementation. It goes for a warm and rounded bass presentation with slightly punchier than neutral note weight that makes for quite a fun listen, a slightly fuller lower-midrange that adds in a bit of body and warmth to instruments, a well defined upper-midrange character, a lower-treble response that is fairly neutral and upper-treble presentation that is slightly on the smoother side of the spectrum. Because of a very organic warm tinge to the tonal presentation, I feel it adds nice colour and enriches RS2 with a rich flavour and lots of musicality but the absolute instrument clarity takes a slight hit in return. On the other hand, what RS2 does really well is pair excellently with brighter/clinical sounding IEMs and infuses organic richness and musicality into them, which they otherwise lack.

Technical Performance – RS2 has quite a nice soundstage with good width and depth but since it focuses on a warmer tonality, micro-detailed clarity gets the short end of the stick. It presents the music more as a cohesive unit than go for micro-detailed separation and resolution. It isn’t as resolving of depth layering or separation between instruments as the competing ESS or Cirrus based DAPs like HiBy’s own R5 Gen 2 or iBasso DX170.

NOS Mode – It’s a very minor difference to be honest but I did prefer RS2 with NOS mode on. It sounded very slightly more natural and ‘correct’ to me, for the lack of a better word.

Darwin Digital Filters – The differences between the Digital Filters are so minor, if even audible, that I don’t really care for them to be honest.

Power –  RS2 max outputs figures are 320mW in 4.4mm BAL and 125mW in 3.5mm SE at 32Ω, which are more than enough for IEMs but not sufficient to drive the demanding high impedance headphones. It’s totally fine to drive low impedance headphones like Ollo S5X/S4X, AKG K371 and Audio Technica M50X though. But still, consider RS2 to be more a DAP for IEMs than demanding headphones.

Battery Life – I averaged 8.5-9.5 hours using a variety of file formats and some screen time. Standby time between my random, varied usage and charging cycles was quite impressive!

Quick pair-up impressions with IEMs.

Note – All of these impressions are off the 4.4mm BAL output.

Moondrop Kato – This makes for a very musical pairing but there are things I like and some I don’t. I like the bass note weight as well as the warmth and boom that is added but not the smoothening of the upper-treble. It does make for a VERY musical, organic and natural listen but I do miss a bit of the treble sparkle in this pairing. Very nice soundstage and overall tonal cohesiveness of sound.

Tanchjim Prism – I like this pairing for the added musicality and the fun bass performance. Soundstage is slightly more intimate than what Prism has with something like the DX170 but the added warmth in the lower-midrange with RS2 makes for a slightly richer and more musical pairing.

TRI Starshine – Good pairing. RS2 pairs well to smoothen out the upper-end brightness of Starshine but also adds slightly more fullness to Starshine’s already fuller lower-midrange presentation. The latter makes it too much of body warmth for a reference head like me but I can totally see this being preferred by people who like an extra full bodied presentation of instruments.

Craft Ears Six – This is a good pairing! CE6 has a lean and bright treble tuning, which pairs well with RS2’s warm and organic tonality. I find RS2 filling in the gaps in CE6’s frequency spectrum in most of the right places. It gives some weight to the nice RASEN bass, adds in a bit of body and warmth to CE6’s leaner midrange presentation and smoothens out the much brighter than neutral upper-treble boost. I do cut a tiny bit of AIR from the MSEB too to make it perfectly in line with my preferences. Overall, I do miss a bit of separation but the tonal performance is a fair compromise.

CustomArt FIBAE 7U UIEM – F7U has a slightly fuller bodied presentation with smoother top end when paired with RS2. Its airy upper-treble does not stand out as much with RS2, which can be a good or a bad thing depending on the kind of presentation one prefers. Soundstage is very slightly more intimate than its pairing with DX170, which is the DAP I personally prefer paired with F7U.

CustomArt FIBAE 5 UIEM – This is a really good pairing if you want to tame a bit of F5’s mid-treble sizzle down and add some more weight to its bass performance. Nice soundstage presentation where reverb trails have good depth. Taming of some of the sizzle actually shift focus to the upper-midrange and in return instrument definition, which sounds really good in this pairing.

64 Audio U12t – I find RS2 a little warm for U12t. I like U12t paired with resolving DAPs with clear, crisp and defined upper-midrange and treble. RS2 adds in warmth and makes it sound slightly muddier than I like. U12t’s warmer lower-treble also does not pair best with RS2’s smooth treble tuning.

Softears RS10 CIEM – There are pros and cons to this pairing. It’ll be preferred by people who like a fuller and fatter bodied presentation than neutral with a smoother treble response but not as much who like and value RS10’s very clean and reference-like presentation that highlights good L&R separation and depth layering.

Comparisons with DAPs in its price segment.

HiBy R5 Gen 2 (R5II).

Snapdragon 425 | Dual ES9219C | 2GB RAM | 16GB ROM | Dual Amp Mode | 4500mAh battery

There is no comparison when it comes to features, design and UI. R5-II is the better DAP here as it has an open Android OS, WiFi & BT, a full 720p touchscreen, fast and smooth UI and allows you to install all the apps you’d want to in a DAP. Sound hardware wise too R5-II actually offers something unique – Dual amp modes with Class A as an option, and an unbeatable battery life of 35 hours with the Economy mode.

Coming to sound comparison, RS2 is warmer with a fuller bodied lower-midrange and a smoother treble presentation in comparison. R5-II comes across more neutral and has better technical performance; better left to right separation, better separation and definition of instruments and a better extending and resolving treble balance. I can imagine people calling RS2 more natural because of its warmer tonality but I’d personally take R5-II’s Class A mode over the RS2’s tonal performance because it has a better balance between naturalness of tonality and technical performance.

iBasso DX170.

Rockchip Octa-core SoC | Dual CS43198 DAC | 2GB RAM | 32GB ROM | 3200mAh battery

Like the R5-II, DX170 too has an open Android OS, WiFi & BT, a full 1080p touchscreen and allows you to install all the apps you’d want to in a DAP. But where RS2 does better is UI smoothness and speed. Sound wise, DX170 comes across as a reference DAP with a very clean and clear sound performance that prioritises clarity, micro-detail retrieval, resolution and transient speed. RS2 instead comes across more analogue-ish warm with a slightly fuller than neutral instrument body and a much smoother upper-treble presentation.  DX170 has better treble resolution and clarity but RS2 has stronger bass punch. DX170 has a more open and airy soundstage with better layering and separation whereas RS2 has a more organic, intimate soundstage – which makes for a slightly easier and laid back listen in comparison.

Conclusion.

HiBy RS2 for sure offers something unique and it’s the cheapest entry into the world of Discrete resistor R-2R DAC based DAPs. It has a very attractive small form factor with a rich green and golden colour scheme and comes with a very well crafted green leather case to match. It has a very nice natural, warm and organic tonality that R2R DAPs and DACs promise but it sadly falls short in technical performance against its price competition, where ESS and Cirrus based DAPs perform much better. IMO, if RS2 was priced a little cheaper, it would’ve had better VFM quotient but at its current selling price of $479, it gets a little tough to justify. I personally prefer its own sibling, $449 priced R5 Gen 2, which offers dual Amp modes with Class A as an option and boasts a remarkable 35 hour battery life in the Economy mode. What’ll further question RS2’s pricing is HiBy’s upcoming R6 III that is scheduled to launch soon and is priced attractively at $500. With all of that said, if you’re a fan of R2R architecture, R2R’s smooth and organic sound and would love to own one in your collection, RS2 really is the cheapest entry into the world of R2R DAPs. Definitely give it a shot if that is exactly what you’re looking for! Otherwise, I’d recommend going with the R5 Gen 2 or waiting for the upcoming R6 III if you’d like a HiBy DAP with open Android OS, dual amp modes with Class A as one of the options, a full hi-res touch screen and WiFi and BT for streaming and wireless capability.

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Gear used for testing and review.

• IEMs – Softears RS10 CIEM, 64 Audio U12t, Custom Art FIBAE 7U & 5, Moondrop Kato, TRI Starshine and Craft Ears Six.
• Headphones – Ollo S5X, AKG K371, Audeze LCD-XC & X 2021, Focal Elex, Sennheiser HD 6XX.
• DAPs – HiBy R5 Gen 2 and iBasso DX170.

Reference Songs list.

• Foo Fighters – The Pretender, Best of you, Everlong & Sonic Highway album
• Coldplay – Paradise, Up in flames & Everglow + Everyday Life Album
• Biffy Clyro – A Celebration of Endings & Ellipsis albums
• Ed Sheeran – Thinking out loud, Bloodstream & Galway Girl
• Dave Matthews Band – Come Tomorrow album
• Dua Lipa – Future Nostalgia album
• Chainsmokers – Somebody, Sickboy, This Feeling & Closer
• John Mayer – Slow dancing in a burning room, Stop this Train, Say & A Face to Call Home
• Gavin James – Always & Hearts on fire
• Switchfoot – Meant to live & Dare you to move
• Porcupine Tree – Sound of Muzak, Blackest Eyes & .3
• Our Lady Peace – Do You Like It & Innocent
• Linkin Park – Papercut, Somewhere I belong & Talking to myself
• Maroon 5 – She will be loved, Payphone & Lost stars
• Lifehouse – All in all & Come back down
• Breaking Benjamin – Diary of Jane
• Karnivool – Simple boy & Goliath
• Dead Letter Circus – Real you
• I Am Giant – Purple heart, City limits & Transmission
• Muse – Panic station
• James Bay – Hold back the river
• Zedd – Clarity album