Fit and Comfort

Seen above is the right channel of the I\OAudio SOGNO placed into an artificial ear mold with the included size M IO-TW45 silicone ear tip installed. I have average-sized ears, and the ear mold above represents my own experiences well enough as a proxy. Size M silicone tips are my go-to for testing, since foam tips are not included by some brands, and I found these tips to work plenty fine in terms of achieving a consistent seal as well as measuring how I hear the IEMs too. The IO-TT55 has slightly narrower bores and were actually sounding better—especially with the treble—but they ended up being less comfortable over time to where I went back to the IO-TW45 tips for the rest of my testing. As seen in the photo above, the SOGNO is relatively large and is likely to jut out of your ears. The good news is the ergonomic shape and the nozzle design will help achieve a comfortable and secure fit for most people, at least those who are okay with the 6.6 mm ear canal width at the very end. I had no problems using the SOGNO for 2–3 hours at a time, with the vent on the side being part of a so-called "inner ear air pressure balance system" that ultimately helps prevent any pressure build-up in the ear canals. The cable comes out at an angle already and the pre-formed ear hooks are flexible enough to not be a bother for me once installed. The cable chin slider also works as expected so it can provide more support and help ensure the IEMs remain firmly in place even if you end up moving around. The resin shells weigh ~6 g per side and there should not be any physical fatigue from weight either.

Audio Performance

Audio Hardware

The SOGNO is a hybrid driver set of IEMs in that it uses two different driver types. If you look purely at the driver count and type, it's easy to misinterpret what they do though. Take the dual dynamic drivers for example, with a 10 mm paper diaphragm/silicone surround driver placed coaxially, with a 6 mm PET (polyethylene terephthalate) diaphragm dynamic driver. The larger driver caters to the bass and lower mids, but the smaller driver actually works in conjunction with two custom high-frequency balanced armature drivers for the treble instead. I am not sure how this physically works if both are moving on the same axis, but it could be a case of language translation errors. There are four other custom BA drivers—meaning not Sonion or Knowles, something less expensive and likely domestic—handling the mids. This is a relatively complex 1+1+2+2+2 five-way electronic crossover, with four physical crossovers leading to the four acoustic bores in the nozzle. The SOGNO is easier to drive than the VOLARE thanks to not having less sensitive EST tweeters inside, and has a more manageable rated impedance of 12.8 Ω (@1 kHz) and sensitivity of 126.5 dB/Vrms that converts to ~107.6 dB/mW, thus making it easy enough to drive off even a decent dongle source, let alone a more powerful and capable portable DAC/amp—you don't need to go overboard with more powerful gear.

Frequency Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature with a slightly elevated bass, smooth treble range, detailed mids, and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear that IEMs can feed into enough for decent isolation. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through a capable and transparent DAC/amp—I used the Questyle M15 here. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the appropriate ear mold fitted to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry instead of just the audio coupler. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the I\OAudio SOGNO. The left channel was separately tested from the right one, and colored differently for contrast. I did my best to ensure an identical fit for both inside the IEC711 orifice, so note how the two channels are practically identical across the entire useful 20 Hz to 20 kHz range! Keep in mind that resonance peak matching at 8 kHz can introduce some measurement artifacts, but I certainly didn't notice any channel imbalance in the ears despite what the tiny discrepancies in the upper treble measurements suggests. These couplers aren't that reliable past the resonance peak anyway, so rely on your ears at this point. Measurements taken after 25 hours of testing, which included these playing a mix of various songs as well as white or pink noise and sine sweeps, showed no difference. There was no perceived burn-in effect thus, and none was measurable, either. The response with the anthropomorphic pinna in place matched the ideal scenario in the coupler exceptionally well, and this is more an indicator of how well the IEMs can fit in a human-shaped ear, or at least one that doesn't complain about discomfort. This is a specifically chosen review unit though, so please keep that in mind as it may have undergone more stringent quality checks.




Here is the average frequency response for both channels of the I\OAudio SOGNO plotted against my personal target taken from VSG.squig.link, which also gives you an idea of my personal preferences to better correlate any possible biases. The tuning of a set of headphones or earphones does not have to match my target as long as it is tuned with some direction, makes sense, and is executed well. After all, no one set will appeal to everyone, and having different options is what makes this hobby so interesting and hard to quantify. This is in addition to a second graph comparing it to the Harman 2019 in-ear target as well as a third graph using a newer target that's based on a more scientific methodology involving a -10 dB tilt (-1 dB/octave) applied to the diffuse field target for the newer, more reliable B&K 5128 but then compensated for my exact 711 coupler instead. Do scroll down to the targets in my database linked above and see the new 5128 section to the left where you can click on the yellow question mark for a brief primer. The bottom line is this target is closer to what many people are likely to prefer out of IEMs and headphones alike. I have chosen to plot this graph with the frequency response normalized/compensated to the target to make it easier to see how the SOGNO is tuned—U-shaped, slightly recessed mids, basically conforming to the Harman in-ear target with the smallest of changes here and there.

The SOGNO is a bassy set, with an appreciable 10 dB rise that's predominantly concentrated below 200 Hz. It falls just shy of the Harman target in the sub-bass and perhaps feels less lean in the mid-bass and lower mids than a purely Harman-tuned set, but we are picking straws here. The end result in a blind test will be no different from most others that have released over the past few years which see this as a reference target to aim the IEM tonality for, not necessarily as a preference target only. Even if I was a fan of this tuning style, which I am not, the only thing I can see here as a positive is you get a decently balanced set with the bass output effectively matching the ear gain/lower treble. It's still too much bass for me, especially with the upper treble roll-off, and the ear gain is significantly higher than many who prefer it to the point where vocals can come off shouty and non-pleasant. The SOGNO can certainly make sub-bass lovers dream of an EDM party in their heads though, and wake up to realize it's true when they put these in the ears. I found the bass to be less reliant on the ear tips too, especially compared to the VOLARE, provided you have a good seal. It's fairly dynamic and allows for good contrast between trailing ends of the previous tones and the leading notes coming up, and yet instrumental timbre feels generally plasticky throughout. Some of this could be down to the BA drivers used here, with I\OAudio perhaps relying on domestic drivers that aren't the most sensitive and have been pushed up to where clarity is getting to be an afterthought at times. Vocals are mostly fine, but you will notice the slightly recessed mids and more smeared treble when brass instruments and strings take over. I am not sure what exactly the second DD is doing in the treble, but I was mostly hearing an overly damped sound with pipes and organs in particular. The lack of air and shimmer also contributes to an overall dry-sounding set, which also feels somewhat boxed in.


The I\OAudio SOGNO looks and shares a lot in common with the VOLARE despite the latter costing a good chunk more. In fact there are only subtle differences in the measurements, but they matter so much when put together. This is also especially true when considering the drivers used, and how they are implemented. I noticed some of the brass instrument timbre issue there too, and the VOLARE is another sub-bass dominated set, but it doesn't feel lean or shouty and the ESTs prevent the treble from coming off overly damped and dry. There's enough resolution there combined with the tonality improvements—in my books—to where I went from a set I liked (VOLARE) to one I am mostly apathetic about in the SOGNO despite the positive first impressions out of the box. In fact, making things harder for the SOGNO is the part where there are so many IEMs now with a very similar tuning. Take the Truthear NOVA, for example, with its 1 DD/4 BA configuration and very similar sound despite the fewer drivers. The BA drivers in the NOVA are not the best quality in how they sound either, and yet the biggest factor for this comparison is getting the same Harman-ish tuning, this time with slightly more bass than the SOGNO but otherwise being too close for comfort when the NOVA costs half as much. The Simgot EM6L is another Harman-set to consider perhaps, which costs even less. There will be a new Truthear ZERO:BLUE 2 coming up soon, perhaps even out by the time this review is published, offering an even closer match to the Harman target at $55. Given the SOGNO doesn't impress in the subjective (aka technical) aspects that much either, I am not sure why you would go for the significantly higher priced version. If you are over the Harman tuning style for IEMs, there are a lot of excellent options available for the money. The Moondrop x Crinacle DUSK is a good example, it costs less and has some challenges of its own with fit and the DSP cable, but offers way more versatile tunings (yes, multiple) and costs less than the SOGNO. It's not as premium feeling and certainly lacks in the accessories department, yet bests the SOGNO where it matters more—the actual sound. The ThieAudio Hype 4, Kiwi Ears KE4, XENNS Mangird Tea Pro all seem to be relevant contenders too.