Details: customizable universal in-ear from a branch of customs manufacturer Sensaphonics
MSRP: approx. $399
Current Price: approx. $399 from j-phonic.com (available in Japan only)
Specs: Driver: Dual BA | Imp: 27Ω | Sens: 109 dB | Freq: 20-16k Hz | Cable: varies
Nozzle Size: 2.5mm | Preferred tips: Comply foams (stock), Shure Olives
Wear Style: Over-the-ear
Accessories (4.5/5) – Comply T100 foam tips (6 sets in 3 sizes), shirt clip, cleaning tool, and Pelican 1010 water resistant carrying case with carabiner
Build Quality (4.5/5) – The housings are made out of plastic but seem to have been built for strength and lightness above all else. Nozzles and cable entry points are reinforced and the cable is smooth and strong, twisted below the beefy y-split and terminated in one of three lengths with either an I-plug or an L-plug. The lightweight ‘memory wire’ section doesn’t have much memory but also doesn’t get in the way
Isolation (4/5) – Very high due to the fully-sealed, ergonomic shells and foam tips
Microphonics (5/5) – Nonexistent
Comfort (4.5/5) – The ergonomic shells are slim and very lightweight, reminding me of the lower-end Westone earphones except that the notched nozzle places the eartips further inside the ear canal. The shell may be a little too long for smaller ears but with proper insertion depth it should fit most very comfortably. The soft memory wire works well, unlike what Sony’s EX-series monitors use
Sound (9.2/10) – Billed as a custom monitor in a universal shell, the j-phonic K2 SP is tuned to deliver reference-level sound quality at a more reasonable price and in a more versatile form factor. Its sound differs from conventional stage monitors offered by Westone and Earsonics and slightly less so from flat-response reference sets such as the Etymotic ER4S. The K2 SP is borderline analytical in signature and presentation, and yet its bass offers up power and depth more akin to the dynamic-driver VSonic GR07. The low end effortlessly combines the cleanliness of a TWFK-based earphone with the power of a beefy dedicated bass driver. It is not quite as bassy as the Earsonics SM3 and Westone UM3X, but the low end performs brilliantly overall.
On a technical level there is not much to fault with the lows of the K2 SP – mild sub-bass roll-off aside, it’s got fantastic resolution and articulation, surprisingly realistic note weight, and very good speed. Not only is the low end extremely detailed as a result, it makes some dynamic-driver sets sound underpowered. The bass of the HiFiMan RE272, for example, despite being quick and detailed, simply sounds weak, veiled, and lacking in rumble next to the K2 SP. Compared to the Etymotic ER4S, too, the low end of the K2 SP is significantly deeper, fuller, and more prominent. Of all my current monitors, the dynamic-driver VSonic GR07 is closest to the K2 SP in punch and bass balance, though the softer note presentation makes the GR07 sound a touch fuller, and bassier on some tracks as a result. The K2 is disadvantaged only by the inability to move a whole lot of air – for example it will never sound as fleshed-out and dynamic as the consumer-oriented Sony EX1000 with its 16mm dynamic driver.
The midrange of the K2 SP offers up top-notch clarity and detail, coming across resolving and controlled but at the same time very crisp and edgy. The notes are not smoothed out in the least, causing the j-phonics to sound a bit raw and dry next to the HiFiMan RE272 and ATH-CK10. The clarity keeps up with the ATH-CK10 and ER4S but the note weight of the K2 makes the other analytical earphones sound lean, and yet there is still enough crispness to make sets like the ACS T15 and VSonic GR07 sound slightly fuzzy in comparison. Balance-wise, the midrange of the K2 SP is a touch forward – more present than that of the CK10, for example – and picks up a little towards the top, in contrast to the CK10’s flatter mids. As a result, the K2 sounds a touch brighter up until the treble peakiness of the CK10 comes into play.
The treble of the j-phonics is sparkly and extended, not lacking in emphasis by any means but flatter than that of the CK10. It is clean and clear, never getting smeared, but also integrates into the soundscape better than the slightly splashy, hot highs of the CK10. The K2 is not a forgiving earphone, however, and will point out any flaws in the equipment chain or original recording. Its aggressive nature also will not stop it sounding too clinical for some listeners, and it’s worth noting that it only performs at its best with foam tips, such as the included Complys.
The presentation is perhaps the most underwhelming part of the K2’s sound. The soundstage is very slightly above average in size – hardly congested, but far from spacious. It is well-rounded and engaging but simply doesn’t sound as open and airy as the Sony EX1000, HiFiMan RE272, or even VSonic GR07. Instrument separation, however, is easily on the studio monitor level and the K2 can almost match the imaging of the CK10. It sounds more layered than the Ety ER4S but just isn’t for those expecting an IE8 or EX1000-like headstage. Then again, I don’t see why reference earphones should be expected to have the presentation of a consumer-class earphone. Another reason why the K2 SP isn’t a great pick-up-and-go consumer earphone – it’s got a tendency to pick up hiss and electronic noise so don’t expect it to mesh well with the average smartphone or laptop. A solid audio chain or at the very least a decent dedicated audio player or external DAC will make the j-phonics shine.
Value (8/10) – The j-phonic K2 SP is a purpose-built reference monitor and works wonderfully in that respect. It is solidly constructed, ergonomic, and very user-friendly – exactly what an audio professional would want from a universal in-ear monitor. The sound it produces is clear, detailed, and well-separated, with excellent presence across the spectrum. It is very well-rounded technically but the signature will be far from ideal for many listeners. Those looking for warm and organic, or airy and open can pretty much forget about the K2. It sounds a bit cold and bright compared to stage monitors from Westone and Earsonics, as well as ‘concentrated’ – though not congested – due to a slightly aggressive presentation and average headstage size. Non-analytical listeners might find it a bit lifeless for music, which presumably is what the alternative MX tuning was designed to cover. The K2’s requiring a clean audio source also bears repeating in this age of staticky smartphones and noisy computer audio. That said, those who have their audio chain figured out and are after a reference earphone will be hard pressed to do better than the K2 in any respect.
Pros: Comfortable, well-built, highly isolating; easily one of the best reference earphones on the market; several customization options
Cons: Not well-suited for casual listeners