Review: Zero Audio Carbo i – Something of a marvel


Let’s get back to Carbo i’s micro driver. The great thing about it is that it keeps the earphone small, comfy, and eminently pocketable. Carbo i sounds good, with great high-frequency resolution, a pretty damn flat frequency response, and as far as I can tell, great dynamic range.

At 101dB, it’s also not overly sensitive. This means that you’ll not get much hiss from it even when plugged into hissy and semi-hissy sources like Astell & Kern’s original AK70 or Sony’s ZX300. Hell, it just barely hisses when plugged into my iMac and doesn’t hiss when plugged into Lynx’s excellent HILO ADC/DAC. It’s 16Ω, and only barely affects the voltage output of mediocre devices.

Carbo i’s forte is vocals, both male and female. They are clear, perfectly delineated from the surrounding instruments, and emotive. High mids and highs are sibilance-free, and cymbals crash and recover immediately. Highs and high mids are free of resonant splash and harsh reverb. That said, highs are hard-edged. Carbo i isn’t that bright-sounding, but it pushes out a lot of outgoing high-mid sound pressure. Stereo detail is deepest in the vocal range, creating a central-focused vignette which I’d like to call its sweet spot. It’s not as sweet a vocal range as Grado’s exceptional GR8e or GR10, nor is as liquidy as Ultrasone’s IQ, but it is sharp, well defined, and forward.

Despite Carbo i’s small driver, lateral stereo spread is wide with plenty of left/right detail and height far in excess of the average. This is certainly true at its price point let alone its driver size. Armin Van Buuren’s Pulsar crunches in and around from all angles before pounding with heavy, measured bass. The effect is more nuanced than a typical wall of sound, sending upper mids to just behind the shoulders and highs spreading out from the eyes. Bass clusters around the chest. Talk about vertical spread.

What Carbo i misses is depth and stereo feel in both the bass and lower mids. At its price point by no means is this a bugger, but as nearly everything else is perfect it its noticeable. And, it’s the reason that tend to stay away from heavy electronic and trance, which prefers a differently-located vignette.

If I were less of a trance head, this point wouldn’t bother me. Carbo i has enough impact, and enough stereo emphasis within the lows to pack a punch, but it’s got next to no z-axis depth in the bass and lower mids.

The deep pathos of Akhenaton & Faf Larage’s throaty rap really needs more z-axis in the lower mids and upper bass. Without it the duo’s rap is no more than surface deep. The other problem is that bass guitar can bloom under the mids with less vibration detail than is optimal.

Bass sound pressure is surprisingly high, even down low. As expected from such a small driver, forward edges are pretty sharp, if not terribly detailed through the decay. Markus Schulz’s Mainstage rumbles in like it was riding a much larger, thin-film diaphragm. Nevertheless, heavy bass lines never overpower the mids. If bass sound pressure is raised above the mids, it’s only just. More likely, it is absolutely flat in ear-acoustic terms against the mids, but damn responsive even down to the lowest registers.

And of course, Carbo i’s brilliant stereo vignette and vocal clarity fend off nearly any attack from down below. High-frequency clarity and decay speed cut through some of the vignette, but only enough to keep the overall signature bright and happy.

Carbo i has driven me into country music, alternative piano, and away from trance. It’s just slightly more aggressive in the upper mids to be truly emotive for sexy female vocals. But it damn well nails everything else. For 45$.

End words

Zero Audio know dynamic drivers. I’m truly surprised by how good Carbo i sounds. I’m truly surprised by how much sound pressure it can coax out of the lowest registers. I love the vignette surrounding its midrange. I love how well it fits, how well finished it is, and I love its noiseless cable. Carbo i keeps away the worst hiss and sounds damn good. The only thing I wish it had was more z-axis detail in the lows.

Well done.


Back before he became the main photographer for bunches of audio magazines and stuff, Nathan was fiddling with pretty cool audio gear all day long at TouchMyApps. He loves Depeche Mode, trance, colonial hip-hop, and raisins. Sometimes, he gets to listening. Sometimes, he gets to shooting. Usually he's got a smile on his face. Always, he's got a whisky in his prehensile grip.


  • Reply February 7, 2018

    dale thorn

    Wow! I bought Sennheiser’s Ambeo recently and was thinking how much better it sounds than most of what I’ve listened to for the past several months, and now this – something probably close to that sound, and only $45.

    Now, where to get the Carbo i?

    • Reply February 8, 2018

      ohm image

      Well, good luck getting it, you know?

  • Reply February 7, 2018


    Hey, great review.

    I was wondering how carbo I compared to etymotic, what are their differences? Are they more similar rather than different in terms of sound signature and resolution ?

    • Reply February 7, 2018


      I’m afraid I have the Ety’s and Nathan has the Carbo. Not sure Nathan knows the Ety’s to reply

    • Reply February 8, 2018

      ohm image

      Next to Ety ER4 (long-time fan here), this one hasn’t the same peaks up top, and its bottom end has far more sound pressure. Not as good instrument separation, though.

      • Reply February 28, 2018


        How about in comparison to hifiman re0 or re-ZERO? especially about bass tightness, mids neutrality, and treble extension?

  • Reply February 12, 2018

    Rizqy Halim

    How was it compared to carbo mezzo? Soundwise

    • Reply February 12, 2018

      ohm image

      Alas I don’t have that earphone.

    • Reply October 18, 2018

      Vladimir WOZNY

      It’s definitely more on the neutral side compared to the mezzo thanks to the less boomy bass.

      It’s closer to the clasical tenore.

  • Reply June 20, 2018


    How does it sound in comparison to Zero audio carbo doppio? Would it be safe to assume carbo doppio is similar but upgraded version (detailed/bassy/etc) of carbo i?

    • Reply June 21, 2018

      ohm image

      I’m sorry but I don’t own the Doppio.

  • Reply April 24, 2019


    Without equalization, this new, shiny, more expensive ZH-DX240-CI is simply unbearable. It has a very recessed middle of the spectrum; every voice, music, and anything is painfully thin, peeping. The balance, that the Carbo Tenore was good in, has completely gone.

    But. If you take the take to carefully and over-aggressively set the equalizer in your each and every sound sources for this earphone – at last the sliders’ positions will resemble a boa constrictor with significant up and down waves -, you will be rewarded by a suprisingly big-headphone-like sound with more details, surely beyond the Carbo Tenore’s capabilites. I don’t know yet, how good it is, I simply have not enough time to compare them.

  • Reply April 24, 2019


    By the way, the flat cable is a double-edged sword as well. It is really easier to handle (the color coding is nice), but also has a higher mechanical force to loose the cans in your ears.

    You can’t caper too much with this earphone, even a simple walking may twist and loose it in your ears, and outer world breaks in – or at least this happens to my ears.

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