Over the last couple of years I have found very little time to write about all of my audio experiences. While publishing has slowed down, listening certainly hasn’t. I visited many shows, including High-End Vienna, CanJam Hong Kong and Shanghai. And of course I tried a bunch of gear to stay up-to-date. Though I cannot feature all products with the extensive care this blog is known for, I want to share my thoughts on at least a few products.
Note: These are quick impressions based on limited time with the products. I cannot consider synergy with other audio components, tip-rolling on IEMs, etc., these are merely preliminary thoughts.
Quick Navigation
CrinEar Reference
The Reference and Daybreak were loaned to me from no other than Caleb from Headphones.com. I bumped into him at Vienna and after a short chat, he decided to bring me some IEMs to try on the following day. I was particularly interested in the Reference, especially since every review or its video thumbnail mentions it being the “flattest” IEM yet – though sometimes with a question mark.
Ever since I started taking online discussions and product reviews seriously, I have tried to understand what “neutral” means, is and entails. I am chasing for a completely transparent IEM for at least 8 years now and I think we have gotten very close. So from that perspective I want to share my thoughts on “the world’s flattest IEM”. And I don’t think it lives up to that claim.
For the larger part of the past decade I have learned a lot about Pro-Audio, mixing, mastering and producing music. I am fortunate to be in a position where I can ask questions and receive answers from award-winning professionals that spend 8 hours a day working with the tools that we count as a hobby. And if you advertise them as a “neutral” headphone, they expect it to “translate” from their reference speakers in a treated room with complex corrections. That means they can continue their work without having to adjust to colorations. I struggle to imagine most professionals switching from a calibrated speaker system to the Reference without having to adapt to its coloration.
The Flattest Tuning?
To my ears, the Reference sounds noticeably thick and warm. That surprised me given the marketing around it. I have no issues with that per se, but it would ruin every record when used as a “reference”. I find the low-end to also be particularly slow-sounding, drowning out texture details in the lows in favor of thump and oomph. A professional especially wants to hear a flat bass with details because that is the biggest challenge in every room. That’s why most mixing desks have a headphone – it’s to double-check the lows.
Moving on to the mids, I actually like the CrinEar Reference. But, but, but… considering we are evaluating “the world’s flattest IEM”, the tonality is honky. There is an audible raise around 1kHz that brings vocals too close and makes them sound nasally.
I personally like the treble tuning most, however I have yet again noticed a coloration that could ruin a mix or master when used by a professional. There’s a dip at 6 kHz that removes sharpness and plays it extra safe to not cause sibilance, but when a mastering engineer would compensate for that, it would sound bad for everyone using actually “flat” speakers or headphones.
Alternatives
I find the original RSV‘s midrange more convincing and ultimately more transparent. On a macro scale, the likes of ThieAudio Monarch MKIV or Softears RS10 are much closer to what most professionals would consider “flat” and transparent.
That said, I really like the CrinEar Reference. And to be very honest, I would have recommended any company to boost the low-end and also to consider dipping at 6 kHz because this makes music so much more “safe” and arguably more enjoyable for consumers. The Reference is an exceptionally well-tuned and fatigue-free IEM. I still recommend it but that loud marketing of “the world’s flattest IEM” really irks me because it risks misleading an entire community. Plus, it has the most ugly carry pouch I have ever seen.
Comparing with Daybreak
I heard from several people that they prefer the CrinEar Daybreak over the Reference. However, Daybreak’s bass quantity really hit my acceptable limit and muddies the midrange. Playing Benjamin Clementine’s Nemesis, the part where he goes “hum hum hum”, the vocals basically become a bass track and ruin the experience for me. It’s not supposed to sound like that on any audio system and that’s that. It took me a whole minute to actually hear bass again on other IEMs after that.
I guess the bass quantity makes it more exciting. And the comparison really makes the Reference sound “flat”, but I personally much rather pick boring over bassy.
YU9 Audio Que
Another loaner from Caleb, the YU9 Que absolutely delivered! It has a huge advantage over the Reference as it doesn’t claim to be neutral but enhance the music – and that it does. It’s colored, it’s beautiful and it’s one of those “unique” IEMs you want to have in your collection.
Unlike claiming that something is neutral or “flat” (boy, I just can’t let it go, can I?), ‘natural’ is a much more forgiving term and it’s also highly dependent on the many different mastering outputs that we enjoy. But with my test tracks, Que’s presentation was just effortless in delivering a believable and enjoyable hifi soundscape with an enveloping warmth that’s balanced with treble clarity. It has the right amount of coloration in exactly the right places, creating depth and width where I can appreciate it.
What I noticed during the limited time I had was that especially piano tracks had a lot of headroom – often a big challenge on IEMs. Although tonally a bit bright, I would make the Que my go-to IEM for piano if I had it.
This is actually an IEM I would consider buying if it weren’t for its nozzle design. The 3D-printed shell has a flat nozzle and I don’t trust it enough to keep ear tips on it. This is an oversight that I don’t want to accept in 2026. I am really looking forward to see if this is a one hit wonder or if YU9 can keep it up in following releases.
DCA Æon Core
The Core is a reference-grade closed over-ear headphone that generally is close to the performance of the Stealth flagship headphones at a considerably lower price. I got to try it on the day it was revealed and collected some early impressions.
Dan Clark explained to me that he tuned the Core in close partnership with Sean Olive, researcher for Harman and the infamous Olive-Welti headphone target response. Although a common IEC 711 coupler was used during measurements to specify a headphone target response, at the time, Harman did not use standardized ear imitations on the coupler. So the target was never applicable to other measurement systems but unique to Olive’s and Welti’s research. The Core is supposed to correct this coloration. In particular, the Core has more body and warmth, with a fuller midrange. The shouty vocal presence area is reduced (1.5-3 kHz). However, the overall treble quantity remains similar as 4+ kHz is boosted.
The sound is fast, punchy and very clear. Personally, I like it a lot! However, it’s not a smooth and relaxed sound, though, and it still exhibits DCA’s characteristic clinical presentation. I think the re-tuning is a trade-off and not necessarily a clear improvement compared to Æon 2 Noire. I still miss something in the timbre that would make it sound more organic or natural. If you were holding back on a DCA headphone, now is probably a good time to give it another shot – that is if you can appreciate the wood veneer on the grey aluminum, which I personally cannot.