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ikko OH1s Review – Master of None

Sound –

Testing Methodology: Measured using Arta via IEC 711 coupler to Startech external sound card. 7-9KHz peaks may be artefacts/emphasised due to my measurement setup. Measurements besides channel balance are volume matched at 1KHz. Fit depth normalised to my best abilities to reduce coupler resonance. Still, due to these factors, my measurements may not accurately reflect the earphone or measurements taken by others. I gave the OH1s 100hrs of burn-in to ensure maximum performance prior to subjective breakdown.

Tonality –

The OH1s is an intriguing earphone indeed, being surprisingly faithful to reference curves in some regards whilst wildly deviating in others. The net result is an articulate, airy and altogether clearly coloured presentation but also one that remains naturally voiced and tonally clean. It is brighter leaning with an inverse L signature; moderately biased towards treble and, to a lesser extent, vocals. While bass is laid-back by comparison, it is warm and well-structured with a small mid-bass focus, retaining body and power. The new driver and housing design brings a well-controlled sound with some interesting note characteristics throughout. The OH1s feels like an authentic and thought-out design albeit isn’t the most versatile as a result of its colouration. While this means it won’t appeal to everyone, I feel the company has been able to achieve an articulate, vocal-forward sound without fewer drawbacks affecting many competitors.

Bass –

Ikko has combined a warm, full tuning and overall laid-back positioning to provide a solid foundation whilst upholding tonal cleanliness in the midrange. This means that though bass doesn’t announce its presence, plenty of warmth remains to be enjoyed. Its tuning is somewhat atypical with emphasis sustaining quite linearly through the mid and upper-bass but with roll off towards the sub-bass. This is not to be mistaken for a lack of extension as the CNT dynamic driver provides plenty of pressure and slam, albeit I did find this could be overshadowed by the mid-bass on some tracks due to the moderately laid-back positioning. It goes without saying that the OH1s retains plenty of punch and impact in addition to a good amount of gusto and power. As the emphasis is wideband in nature, the timbre is sound, notes are simply slightly thicker and fuller, imbued with a medium but not excessive warmth. Its notes are structured with an emphasis on higher weight rather than plumpness or rounding in the mid-bass as the tuning may initially suggest to some.

This works in tandem with the driver characteristics. The OH1s has relatively slow decay, reinforcing its thick note presentation, and the sub-bass roll off does make some sense here as it aids separation in the mid-bass. I didn’t hear any smear or muddiness however, due to the sub-bass roll off, it doesn’t have the most assertive slam or rumble that has become popularised as of late. Nonetheless, its structured nature and slower decay give it large amounts of texture and the impression of greater dynamics despite attack not being especially aggressive. This reminds me in part of the Moondrop Starfield which shared its CNT diaphragm construction. However, as the driver control is clearly better here, a great performer in-class, the OH1s comes across as more coloured rather than sloppy, upholding strong note definition. It’s a unique bass presentation with a primary focus on note weight and texture whilst still managing to be impressively articulate due to its higher control. This means the OH1s is surprisingly adept at reproducing bass heavy genres such as hip-hop but equally flatters more responsive genres such as pop, funk and jazz.

Mids –

The midrange sits in front of the bass and has a very intriguing mix of qualities. Whilst I was initially inclined to call this a revealing monitor, that isn’t exactly the case. It is, however, well resolved for such an economical earphone, an impression aided by its forward nature. As the OH1s peaks earlier than most at 2kHz and sustains emphasis through to 3 kHz, vocals are brought forward and are increased in size relative to instruments and bass. With a neutral lower-midrange positioning and just ample bass quantity, note weight lies on the leaner side. However, the lift in vocal size works in tandem with a hint of euphonic warmth stemming from the upper-bass to grant a sense of robustness that prevents it from skewing overly lean, metallic or strained. The tuning is pretty solid here and the voicing is natural despite the abundant colouration surrounding. Vocals possess ample coherence and structure on most tracks. A noticeable fall off a 4kHz also helps to counteract the lift in treble brightness and forwardness, meaning it is a low-intensity sound despite being clear and vocal-forward.

I would characterise it more as a vocal-forward monitor here rather than a bright, revealing or clarity-focusing one. This is a great approach as you get intimate, large and well-textured vocals with minimal tonal colouration yet also a good sense of weight when needed. At the same time, extension is maintained via its articulate lower-treble, with a small peak at 5kHz. Accordingly, note definition is lifted and small details are brought to the fore, delivering above average in-class resolving power. However, so too does a little sharpness creep in albeit not to the extent of sibilance. It does give vocals a somewhat breathy and esoteric presentation rather than a full, organic or dense one as the upper-mid nadir might suggest. I did find this to define its voicing more than leanness or dyness in the lower midrange. However, on some pop tracks with heavy vocal processing, I did find this could give the monitor a rather unforgiving character. Altogether, the OH1s is great for those wanting clear, forward vocals executed in a tasteful way and without excessive intensity.

Foreword –

Do note that though my measurement showcases a large 8k peak, this region is emphasized by coupler resonance and may not necessarily be audible. In addition, this region is fit-depth specific, I found I was hearing more brightness around the 10kHz region that was lower in intensity than the lower-treble, which is to my preference. Adjust the tips and fit depth accordingly. Depending on your preferences and ear anatomy, the top-end will either sit at the front of the presentation or just in front of the midrange – greater treble variability is an unfortunate repercussion of such a shallow fit depth. I say this because I’ve seen a range of impressions on the OH1s, some find it neutral, some find it fatiguing. Either way, I would posit that the majority won’t find the enhancements here to be overdone, though do note this isn’t remotely a smooth monitor especially when combined with the slightly laid-back bass and forward midrange.

Highs –

The voicing of the top-end showcases a vibrant, airy performance that avoids fatigue and intensity due to its relative lack of sharpness in the audible range combined with a lift in overtones. Emphasis lies chiefly at 5kHz, instigating a crisp foreground and drawing slightly more focus to the leading edge of notes. However, transient response is on the softer side, leading to an airy and free flowing over hyper-defined or focused foreground detail presentation. The 6kHz nadir could contribute to this impression as well. Instruments sound slightly thin, and notes have a delicate presentation. However, notes decay nicely, imbuing impressive shimmer and vibrance. Still, I didn’t find the OH1s to have the best fine detail retrieval nor the best texture or realistic instrument timbre, it is defined more by the atmosphere it creates in the overall image, rather than the minutiae it discerns within the treble itself.

Above, my ears were hearing level emphasis through the 8-10kHz range sitting just behind the lower-treble. This contributes to an airy, open and atmospheric sound; one that retains good but not outstanding focus on the foreground. Still, I found the balance ample to provide a stable image and, at the same time, weave a convincing sense of headroom. Background detail retrieval is above average but nothing exceptional. The driver does start to break up in this region, so you don’t get an immaculate background or sparkly top-octave. It contributes more to a pleasing sense of air, dimension and layers rather than notable audible detail. The airy and open voicing contributes to the impression of an extended treble despite relatively low resolving power in these regions. It works to the benefit of detail presentation over retrieval and accordingly, small details are brought to the listener’s attention without introducing glare or excessive brightness.  

Soundstage –

The OH1s provides a moderately intimate stage but with strong separation/smaller note size that means it still feels relatively open. I has an atypical bias towards height, being more intimate in terms of depth and width but well-proportioned between them. Imaging is quite sharp, you get a strong centre image and a nice lateral spread. Directional cues aren’t super sharp nor is localisation. In tune with the treble note presentation, the overall image too is floatier with less stable positioning. While it lacks the speed to attain holography, the image is fairly multi-dimensional, just not especially sharp. The same goes for layers, there isn’t huge separation between background and foreground due to the airy nature, but the OH1s does have a better resolved background than many around this asking price. Separation is the main strength on display. You get a nice foundation in the bass that remains very well separated from the mids at all times. Note size lies on the leaner size throughout so each note is surrounded by a pleasing sense of air and space.

Driveability –

With a moderate 32-ohm impedance and a higher 109dB sensitivity, the OH1s is relatively efficient and also shouldn’t be exceedingly source sensitive. However, in subjective testing I was surprised at how well this IEM scaled with better amplifier sections especially.

Output impedance sensitivity

Going by the rule of eighths, you would ideally want to pair the OH1s with a source with a sub 4-ohm output impedance. Empirically, I tested this by switching between the Shanling M2X (1-ohm) and Hiby R6 (10-ohms) which revealed a surprisingly similar listening experience. The changes were in tune with individual source colouration though I would posit some of this is also impedance coming into play. The R6 sounded a little tubbier in the bass with a softer note presentation. Treble was thinner but similarly positioned as on the M2X. As a result, I wouldn’t concern too much about output impedance here as the changes are quite small even in sub-ideal circumstances. Of course, a lower number is more ideal.

Driving Power

The OH1s definitely benefits from a dedicated source in this regard, for though the tonality was balanced and volume levels were fine from my Xperia 5 II, I did find the bass performance lacking. In this regard, you don’t need to go overkill, even a dongle like the PEE51 or Hiby FC3 will do just fine. But surely having some sort of dedicated source helps to round out the bass. Swithcing to the FC3 for instance, yielded a noticeably more defined and controlled bass alongside better extension and slam. Stepping up to my desktop stack revealed a larger, airier soundstage. Unfortunately, due to the sensitive BA tweeter, the OH1s does pick up more hiss than most IEMs despite not being especially efficient overall. I was hearing faint hiss on the M2X, but this wasn’t an issue when music was playing. Low volume listeners will want to use a source with a quiet/black noise floor.

Suggested Pair Ups

The OH1s doesn’t require an especially low output impedance but benefits from a dedicated source with regards to driving power and noise levels. Tonally, it pairs well with most source, though those with any form of treble brightness should best be avoided. A warmer or more dynamics source such as the M2X/THX789 are great pairings for bass performance, it definitely benefits from a more aggressive note attack. This applies equally so to the treble due to its softer attack however, again, brightness should be avoided.

Next Page: Comparisons & Verdict

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