IEF Neutral’s Logical Conclusion? A look at the Truthear x Crinacle Zero: RED

Truthear x Crinacle Zero: RED – IEF Neutral’s Logical Conclusion

For all of 2022, Crinacle was a busy boy. He became one of the largest audiophile review channels on YouTube, he single-handedly ushered in the “planar IEM arms race”, and cemented himself as the king of collaborations with products such as the SeeAudio Yume: Midnight, 7Hz Salnotes Dioko, and the Truthear x Crinacle Zero.

After the release of his first Zero, he made it clear he hadn’t even come close to running out of ideas when he started coyly teasing his next IEM, the mysteriously named “Project Red.”

It’s been eight months since I first heard about Project Red, and I’m here to say that the Truthear x Crinacle Zero: RED serves as an indicator of sea change for the market as a whole. Crinacle has yet again raised the bar.

I’m not here to pretend Truthear ZERO: Red is a perfect product. However, I was one of the more skeptical voices of Crin’s tuning choices for Red, and after living with it for a while I kind of have to eat my words a little and admit that Crin was right all along. So begins my penance walk.

What we like

  • Improved sound across the board from its predecessor
  • Smoothest treble in this price category (and perhaps even above)
  • Incredibly affordable and accessible

What we don’t like

  • Comfort issues from the original ZERO remain
  • Sound—while improved—isn’t perfect

Build Quality / Comfort / Accessories

Those familiar with the original Zero won’t get many surprises here. The box contains the same pleather pouch, 2-pin to 3.5mm cable, and generous complement of ear tips. The anime mascot still makes an appearance on the front of the box, this time wearing red.

The main addition that makes Zero: RED’s unboxing unique is the inclusion of a 10 ohm impedance adapter. This adapter downtilts the tonality of the IEM by reducing the output of the midrange/treble driver relative to the bass driver. I chose to leave this out of my review, because it is a non-stock configuration and I preferred the sound without it. If you want more bass than stock, try the adapter. Frequency response measurements with the impedance adapter are available at my colleague Fc Construct’s review, or on my

In terms of build, I have very few qualms here. The shell is made of a lightweight and reasonably solid feeling plastic. The cable is a good mix of flexible and lightweight, but can be somewhat prone to tangling. The faceplate is similar to the original, but with red ribbons instead of indigo swirls.

The biggest drawback in this equation, and possibly the biggest drawback of the Zero: RED overall, is that it shares the same larger-than-average nozzle width its predecessor had. Discomfort while wearing either of the Zeros begins around the 30 minute mark, and after about 3 hours I have to take them out and take a break.

Now admittedly I have smaller ears and don’t have a ton of tips laying around, so just because I haven’t been able to find my ideal fit doesn’t mean other enthusiasts won’t… but I think it’ll be an issue for a good few people, so look out for that.

While there’s not any categorical design improvement here, keeping the accessories mostly the same save for the impedance adapter is a net improvement to a package that was already very good for its price range on release.

Frequency Response/Tonality

The Zero: RED takes a more relaxed approach overall to its tuning, opting for a reasonable (if a bit polite for some) ~7dB bass shelf, a slightly lean and overtone-focused midrange, and a surprisingly gentle treble presentation.

Below is my clone IEC 60318-4 measurement of my Zero: RED placed against both IEF Neutral 2020, as well as my individual preference target. Comparison to my target is to illuminate the reader to how it matches up to my normal preferred taste, but deviation from the target is by no means a deal breaker… especially on a measurement system that only seems less accurate the more I learn about insert earphone measurements.

IEF Neutral Target vs My own preference target


Zero: RED serves an excellent balance of sub-bass size while sounding forceful enough in the mid-bass to still give weight behind movements. Bass guitars have the bouncy roundness they should, but don’t overstep the line into being boomy. Kick drums have just enough oomph to propel the momentum of their arrangements forward but not nearly enough to occlude meaningful transient information in the midrange.

If anything, I could’ve actually done with a bit more upper bass. It’s not actually the stereotypical “bass instruments” where I notice this slight deficit, but in lower male voices where I’m used to feeling a certain chesty warmth that I’m just missing here.

However, the shape and integration here is likely the best compromise between slope and shelf compared to Crinacle’s other Zero(s), and for that reason I find it to be pretty hard to fault, especially regarding how it balances with other regions.

We’ll touch on this more in later sections, but for those worried about if RED is really an upgrade in this regard from Crin’s other collabs, fear not: this is easily the best bass we’ve gotten from him under a kilobuck. Yes, that includes Dusk.


Early on this area seemed relatively unproblematic to me, but once I started comparing RED to other IEMs, I took notice of a few quirks that ultimately make the midrange my least favorite part of the frequency response here. This is perhaps because it’s pretty much “par for the course” compared to other IEMs that Crinacle has released, which may be good news for many of you who prefer his approach to midrange tuning.

For me though, the midrange from 200-2000Hz is just too counter-clockwise tilted for me to sound natural on the things I index for most. Snare drums sound like they favor “bark”, sounding excessively hardened on the front end and a little too shortened in the trailing end.

Male vocals as said prior have diminished note weight and warmth across the board; they sound more translucent than I’d prefer. Female voices tend to share this quality as well, but as their voices get higher, the more forward upper midrange actually starts to resemble what happens when a human reaches the top of their range in real life.

As human voices get higher and higher in pitch, the upper midrange (between 1-2kHz) starts to rise in volume relative to the fundamental, counter-clockwise tilting the response of the voice. Due to this, higher pitched female voices in particular are portrayed quite realistically for me on Zero: RED. This also means that the presentation is most fitting for voices when at the top of their range or yelling, so I could see the term “shouty” being levied at Zero: RED, even though I don’t necessarily hear it being fatiguing because of it.

Unfortunately, tradeoffs in the midrange seem to continue. Electric guitars tend to sound a little too throaty and pinched, but pianos sound crystal clear and very appropriate in decay and color. Horns can sometimes sound super complex in their overtones and nicely textured, but can also sound like they’re shrunk down a size or two. Some wind instruments like flutes actually appreciate the little bit of extra honk, while others like clarinets really don’t, and can sound much too wooden.

Overall, I think this area may not be super problematic to others who are used to the way IEMs as a market segment have been tuned for the last few years. However, I encourage readers (even those who enjoy the stock midrange here) to experiment with using Crin’s 5128 measurements to EQ the midrange to their preferred tilt of the Diffuse Field reference point. I generally prefer a midrange that is closer to that sort of shape, and this preference no doubt colors my perception of the midrange of Zero: RED.


I’m gonna take a second to be frank about the limitations of my frequency response measurement posted above: I’d straight up ignore anything above 4kHz. The result, as measured on my clone IEC 60318-4 coupler, is almost entirely irrelevant to how I perceive the treble here. Crin’s own B&K 5128 measurements will doubtlessly be more informative.

The treble region usually serves as the gallows for whatever product I’m reviewing, but with Zero: RED I think it’s a huge reason why its hype is entirely justified and then some. Whether it’s in comparison to things in its price range or above, I’m genuinely not sure I’ve heard smoother treble in an IEM.

Of course this is where anatomical deviation between listeners is going to vary massively… but good lord is the treble of Zero: RED absolutely addictive to me.

Vocals—my biggest pain point for treble—are neither scratchy due to excess 5-8kHz, sibilant due to excess 8-12kHz, nor overly-silken due to excess upper treble. It’s just right.

Cymbals basically always have the correct balance between stick clack, clang, ring, hash, and air. Even if the treble level overall is perhaps a bit more than I’d normally dial in by choice, I think the shape of the total response above 5kHz is so even that my ear doesn’t have to do any work to get used to it. I can just press play, and don’t have to deal with any wincing.

There are very few transducers that I can confidently say I wouldn’t be annoyed by at all in the treble. This is maybe the 3rd or 4th I’ve encountered.

I could see other listeners thinking it lacks in the “detail” department due to its lack of a lift above 10kHz, or its lack of treble peaks overall. I can neither confirm nor deny this since we all have differing definitions of words like that, but I can say that I never felt that Zero: RED’s texture, portrayal of minutia, or coherence was lacking.

Even if it’s a bit relaxed compared to other things in its price range, I maintain the treble is Zero: RED’s greatest strength, and what sets it apart decisively from other things in its price category and above. It’s certainly my favorite part about it.


Zero: RED is actually quite decent here, but I think it has just one thing that gets in the way of me saying it’s great.

The midrange tuning just causes things to be a little too sharpened and dry. Even in its better moments, decay on Zero: RED never really feels like it’s fully able to stretch its legs and breathe. On certain things (piano) it sounds excellent, but on most things it just sounds a hair too thinned-out in a way that’s noticeable enough to color instrument identity on the whole.

That being said, I think this being an all-DD IEM, as well as the incredibly smooth treble contributes towards helping this presentation sound almost shockingly normal sounding right out of the box. I’d honestly say I even prefer Zero: RED’s timbre to Dusk, which is very similar in tuning, but sounds less coherent and drier in the upper mids and treble by comparison.

Even if you don’t get incredibly rich decay with Zero: RED, you also don’t get excessive treble peaks or incoherence due to poorly managed crossovers or differing driver types. What you do get is solid material-related timbre and mostly neutral frequency response. That’s very good for me, doubly so at this extremely reasonable price.


This is another area I think people are gonna really enjoy about Zero: RED. Bass is punchy and strong without being bulbous or overly long in decay. Midrange, while maybe not timbrally my preference, but sounds like it has ample nuance within the journey music takes between quiet and loud.

I think this may be one area where the 1-2kHz midrange emphasis (and concurrent “dryness”) actually helps a bit. The extra crack for snare and kick drums, the extra crunch on bass guitar, and the extra vocality on piano and horns all contribute to a presentation that sounds lively and engaging despite being overall pretty relaxed tonally.

I’m almost positive that if this tonality was any warmer, dynamics as a whole would’ve suffered. Instead of something overly smoothed or damped like a lot of the single DD IEMs in this bracket, we get low end punch, midrange and treble snappiness, but none of the common downsides like car-subwoofer bass or fatiguing transient harshness.

Zero: RED is clearly the most dynamically nuanced of Crin’s collaborations under Dawn price so far. Is it the most dynamic thing out there? Of course not, but it seems pretty obvious to me that it’s the most dynamic thing under $100, with a less esoteric tuning than many other things recently lauded for dynamics like Ucotech’s RE-2.


Let me be clear: we’re still in IEM land here, folks. Red isn’t bucking any trends or breaking any molds in this category.

I don’t get any amazing sense of image separation out of Zero: RED, but I also don’t hear anything being occluded or mushing together. I certainly don’t get an impression of images sounding particularly large, in fact they’re probably on the smaller side. Their placement within the stage is precise enough to not be a problem, but not laser-focused like some of the more expensive stuff out there.

Soundstage is absolutely average for the form factor. The stage the instruments sit in is firmly in-head and rigidly defined.


Truthear Zero

There are numerous people out there who like the Harman In-Ear target(s), but I think we all know that Crinacle is not one of them. His decision to make a Harman-tuned IEM didn’t make a ton of sense to me at first, except as an effort to fill a hole in the market.

However, now hearing Zero: RED, I understand why he was so excited about this driver platform and why a passive Harman IEM was an interesting beginning to this project. Wherever I may have nitpicked RED, trust that the original Zero is—for me—a downgrade in every possible way.

The tonality on the original is much more hyped, and frankly pretty annoying to me. The bass is much too lumpy and resonant in the mid-bass, with worse sub-bass extension and a bigger scoop in the upper bass. The mids are even more plasticky, while being even less warm and life-like. The treble… ouch. Direct one-way ticket to Shoutsville.

There’s a reason I didn’t buy the original Zero until this review: I’ve never liked any Harman In-Ear target. Even if RED isn’t necessarily super far off from Harman, it deviates enough in the absolutely necessary places that I feel it’s a much more well-rounded and livable IEM.

I could absolutely see a basshead choosing the original Zero due to the increased contrast between bass and midrange, and luckily RED retains the technical underpinnings of this quality without having such a bass-forward tuning. I could see someone thinking the original is more “technical” due to having more treble, but again RED serves as a much more nuanced and appropriate presentation.

For me the choice is clear. Zero: RED is so much easier to listen to, while being the same or better in all of the important technical aspects to the original.

7Hz Salnotes Zero

A common comparison point is going to be one of Crinacle’s most popular collaborations, the 7Hz Salnotes Zero. No doubt you can see why. Zero: RED is more than twice the price of Salnotes Zero, which merits the question: is RED worth the uptick in price?

Zero: RED comes with a much better build and accessories package than the Salnotes Zero, and it’s less close sonically than one might think from looking at the measurements. Especially in the treble, where I think the B&K Type 5128 might show that the responses aren’t as comparable as it may look on my measurement (hint hint).

It’s immediately apparent in a listening comparison that Zero: RED has a superior treble presentation, absent an unfortunate peak around 11.8kHz present on the Salnotes Zero. It also has a slightly more relaxed upper midrange which helps the entire response not be as decisively tilted towards overtones. Even if the Salnotes Zero has slightly more warmth in the low-mids, it’s not especially noticeable in the Salnotes due to the upper mids and treble being more forward overall.

Zero: RED is noticeably more dynamic than the Salnotes Zero, as well as more natural sounding timbrally. I can’t say Zero: RED loses any ground to the Salnotes sonically, which shouldn’t be shocking. However it also cements Zero: RED as being absolutely worth the price for me.

Truthear Hola

(Many thanks to my good friend Tam for sending this unit out for comparison)

Cards on the table: I absolutely prefer Hola’s midrange to Zero: RED’s. The warmer clockwise tilt is noticeable and appreciated when it comes to conveying basically any instrument or voice. This aspect alone would be enough for me to have to ask someone about their preferences before recommending one over the other decisively.

On Hola, male vocals sound bigger and more authoritative, snare drums are more full, and overall everything in the midrange just sounds more correct to me. Additionally, Hola is a more comfortable shell design that I think will play more nicely with a variety of ear shapes. Hola also has a better cable. I fear that is where Hola’s benefits vs. the Zero: RED end, though.

Zero: RED has significantly better bass texture as well as a much more dynamic and punchy bass presentation on the whole. While Hola does have more bass, it’s immediately clear that Zero: RED has better bass.

And when it comes to treble, Hola disappoints in the same way the Salnotes Zero does. They both share a nasty upper treble peak at around 11.8kHz that isn’t shown on measurements taken with IEC 711 couplers but is nevertheless immediately, annoyingly present.

In contrast, Zero: RED’s treble is too smooth and unproblematic for this to even be comparable. It clearly has the edge in listenability, while also being more textured and less damped sounding on the trailing ends of treble details like ride cymbal decay or vocal reverb.

Many, many people are going to ask: “Is Zero: RED worth the price increase vs. Hola,” and my answer is mostly yes. If you prioritize midrange tone and comfort/accessories over everything, I think Hola has a sweeter aural presentation as well as a more livable fit. For everything else, Zero: RED is a better IEM.


People have been hyping this IEM for nearly a year, and there was definitely a part of me that grew more skeptical of it living up to the hype as time went on. Even if a lot of people read way too deeply into the hype and fell victim to their own unrealistic expectations, it’s my view that hype was warranted.

It may not rewrite the entirety of the hobby overnight, but Crinacle has delivered a uniquely well-rounded IEM that clearly seems to have special attention given to the things Crin cares most about in IEMs: tonality, dynamics, and timbre. It provides my favorite frequency response from Crinacle so far (even compared to Blessing 2: Dusk), while also being crazily accessible and affordable. Not to mention that I prefer it to so many other IEMs more than 15x the price. Looking at you, Monarch Mk2.

That’s not nothing, you know. Especially considering Zero: RED also seems to have the best balance between dynamics and timbre in this price range so far. It’s probably the cheapest you can get anything with notable technical chops without also having to deal with poor tuning. Crin said in a recent video that regardless of the price, he saw RED as a flagship IEM… and I honestly kind of get where he’s coming from.

While in the throes of his incipient change of IEF Neutral and embracing targets based on the B&K Type 5128’s Diffuse Field HRTF, Crinacle still felt it necessary to make damn sure—through revision after revision—to offer the best, most well-rounded example of “IEF Neutral 2020 + bass boost” he could. It was clearly worth the trouble. In my opinion, Zero: RED serves as nothing less than both IEF Neutral 2020’s logical conclusion, as well as a clear indication of the shape of IEMs to come.

Zero: RED has the hallmark sonic features of a classic IEF Neutral IEM, but refined to an astonishing polish for its price. Crin has now made a package with good tuning and technicalities more accessible than ever before. If this is the conclusion of IEF Neutral 2020, I’m extremely excited for this new era, and for Crin’s next collab… because it’s clear he’s getting better at this.

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