Comfortable and isolating, Warm, full but clear midrange, Well-integrated and detailed treble
Stiff cable, Mediocre soundstage expansion, Fairly recessed male vocals
The v1.1 is a nice choice for commuters searching for a well isolating earphone with a warm, focussed sound that doesn’t disperse in the presence of ambient noise.
Kalkul is a new Japanese audio manufacturer striving to bring cutting-edge innovations to the audio world. Their first in-ear, the V1.1 sports 3D printed housings with an intriguing laser sintered finish. Internally, the V1.1 utilises a dual BA setup featuring a high-volume, vented woofer in order to produce a full sound well suited towards portable use. Kalkul implements an acoustic horn in the nozzle similar to Jomo’s Haka in addition to 3D printed sound chambers to provide an extended treble response.
The earphones also feature a handmade cable with palladium jack, all high-quality and costly materials. From perusal of the V1.1’s specifications, it’s clear that Kalkul are a serious contender and their IEM carries a confident $300 USD price tag to match. I recently took a few months off my website due to work. I feel that living with the products I receive for review for an extended period of time has given me an appreciation of their intended uses in addition to a stronger understanding of their shortcomings during daily life. You can read all about the V1.1 and purchase one for yourself here.
I would like to thank Kalkul very much for reaching out to me and for providing the v1.1 for the purpose of review. All words are my own and there is no monetary incentive for a positive review. Despite receiving the earphones free of cost, I will attempt to be as objective as possible in my evaluation.
The V1.1 has a very minimalist unboxing congruent with the company’s philosophy. The earphones ship within a static-proof foil bag inscribed with the buyer’s name and basic model number and specifications. A separate bag contains 6 pairs of ear tips, 2 pairs of each size. In addition, medium sized tips come pre-installed on the earphones.
The tips are of the memory foam variety, well suited towards the V1.1’s particular style of tuning and their increased isolation aids an uninterrupted listening experience when on the go. Of note, the earphones and accessories are all made in Tokyo, definitely not something you see every day. It’s strange to see the absence of any kind of case seeing as the earphone is built for commuters.
The V1.1 is intriguing and unlike any earphone I’ve ever tested. Its nylon housings are on the larger side but still find an ergonomic fit. They have a two piece construction with very visible and palpable seam, however, in the context of the V1.1’s design, it compliments their aesthetic rather than detracting from it. What surprises most is the finish of the earphones with a very aggressive, tactile texture. Finish is a common issue with 3D printed products, and I find it impressive how Kalkul have used this to their advantage, using laser sintering to exacerbate its rougher edges. Though far from the immaculate Campfire Audio products I recently reviewed, the result is a product that finds an unconventional appeal in its chaotic complexion.
Despite being on the larger side, the earphone’s design places the bulk of the housings outside the ear, minimising contact and therefore the formation of hotspots, enabling higher long-term comfort. As the plastic housings are very lightweight, the v1.1 has no issue maintaining a stable fit during commute, aided by an over-ear fit. This impression is reinforced by their strong passive noise isolation. Like the CA Comet, the V1.1’s drivers may be vented, but its outer housings are fully-sealed. Combined with long nozzles that promote a deep fit and the exclusive inclusion of foam ear tips, the V1.1 provides excellent isolation, retaining low-end in the presence of ambient sound.
The V1.1 has a fixed cable, not ideal within this price range and strange considering that they were designed for commuters. That said, the cable itself is thick and very sturdy with long strain relief on both the earpieces and jack. Kalkul state that the cable is coaxial copper shielded silver. I can’t comment on its particular sound due to its fixed nature, but it is a mixed bag ergonomically. The two channels are separated below the y-split, a good idea sonically, however, it does introduce the risk of splitting. The cable is also fairly stiff, it doesn’t conform especially well over the ear and introduces more microphonic noise than most over-ears – though still significantly less than a cable-down earphone.
I most preferred the included foam ear tips. Though the low-end becomes cleaner with silicone tips, highs can become slightly sharper, though some may prefer the additional energy. The v1.1 received 200hrs of burn-in prior to review to ensure optimal performance.
The v1.1 has a modestly V-shaped sound with emphasized mid-bass, a laid-back lower-midrange and crisp lower-treble. It is full-bodied with a warmer tone throughout set to a clean background. It’s hardly a thick sounding earphone or a congested one despite this due to elevation of the upper-midrange and lower-treble that aid clarity. Kalkul developed the v1.1 for portable use and its bassier, fuller sound is well suited towards listening in louder environments.
The v1.1 has an emphasized low-end that aids a warm, full-bodied sound. It doesn’t sound overly enhanced in any particular region, with emphasis focussed slightly around mid-bass and gentle slope into a full upper-bass. Kalkul made sure to emphasize their use of an enlarged, vented bass driver. In listening, sub-bass does extend very nicely, delivering more solidity than vast majority of BA earphones I’ve heard. Sub-bass has a touch of emphasis, it’s well-present and provides pleasing slam when called for but mostly takes a backseat to mid-bass.
Mid-bass itself is very punchy; its enhanced presence set to high levels of control that enable concise impact and higher definition as one would expect from a better BA earphone. Decay is slightly quicker, though on the natural side for a BA, delivering higher definition and a smooth texture. Upper-bass is modestly emphasised, providing a warmer, fuller voicing. In general, separation remains commendable due to the v1.1’s quicker decay and higher control. The result is a full, bold and dynamic low-end that sounds just a little bloated but never tubby or ill-defined.
Mids are laid-back on a whole relative to bass, especially the lower-midrange and bottom half of the centre midrange. This heightens bass/midrange separation, preventing congestion and over-warming of the midrange. As a result, male vocals are noticeably more laid-back than female vocals and instruments. They can sound a touch distant on certain tracks, especially older ones, but as they’re presented in a clear manner, they never become overshadowed. Due to the v1.1’s emphasized upper-bass, male vocals also never sound thin rather, they are neutrally bodied. As the earphone begins a gradual climb in emphasis through the upper half of their centre midrange through to the upper-midrange, female vocals are full and well present.
Accordingly, the v1.1’s midrange is pleasantly clear on a whole as well. In this regard, the v1.1 is quite restrained as most Japanese earphones that tend to sound thinner and more upper-midrange biased. The V1.1 is slightly on the brighter side, however, it is warm and retains a full-bodied voicing due to its upper-bass tuning combined with its more modest upper-midrange emphasis. Lower-treble is also quite even with the upper-midrange, avoiding over-articulation and exacerbation of sibilance while providing plenty of detail presence. Mids are therefore easy to listen to, warm and full-bodied but also pleasantly clear. They don’t fatigue with their brightness and flatter during longer listening.
Crisp and clear, the v1.1 has a touch of lower-treble emphasis, however, it’s well integrated and impressively even with its upper-midrange, producing well-bodied instrumentation. As a result, the earphones don’t sound too thin or spiked in any regard; instruments such as cymbals shimmer and decay appropriately and strings, high-hats and triangles don’t pierce the ear while remaining well-resolved. The v1.1 has accurate attack and great foreground detail retrieval. Combined with its slightly detail forward presentation, it has plenty of crispness for genres such as rock and acoustic yet it isn’t fatiguing or overly articulated.
This character can also be attributed to its considerably attenuated middle treble that produces a very dark background, drawing focus to the foreground. However, though very clean sounding, the highest instruments can sound a little thin and truncated as a result. The v1.1 also doesn’t extend significantly at the very top. Take note that I am accustomed to significantly more expensive products, and extension is on par with similarly priced models, but not outstanding. Still, though it has good resolution and a very pleasant signature, air, sparkle and micro-detail retrieval are not its strengths. Rather, the v1.1 focusses its energy on well-resolved, well-bodied foreground instrumentation.
As a result of its mediocre treble extension, the v1.1 has just modest soundstage expansion. It isn’t claustrophobic, stretching just to the periphery of the head, perhaps a smidge beyond on certain recordings. However, it is a nicely rounded presentation and quite coherent, depth is quite impressive. Imaging is sharp though layers aren’t especially well defined as the v1.1 doesn’t have much air and its background sounds compressed due to its attenuation, rather than open and extended. Separation is quite good considering its fuller tuning. Tracks mastered with more upper-bass can sound slightly congested, however, mids are well separated from bass and treble instruments are easily discerned from each other. In general, bass demonstrates a higher level of separation due to its faster decay.
The v1.1 has a higher 43ohm impedance and unspecified sensitivity. Subjectively, it has fairly mediocre sensitivity requiring more voltage than most competing earphones to reach the same volume. This is not to be taken as a negative as it still reaches high, likely dangerous volumes from smartphones and will be easily driven by a dedicated DAP. In addition it should be less sensitive to output impedance than most multi-driver earphones. The v1.1 is perfectly happy from a phone though it does scale with a dedicated source, especially with regards to dynamics and background detail retrieval. Some comments on synergy below:
HTC U11: Slightly less defined bass, well extended but lacking a touch of sub-bass slam relative to dedicated sources. Clear midrange, accurate placement. Treble is crisper but well-detailed, mediocre extension produces a more one-dimensional presentation. Less background detail but still nicely separated, limited air and expansion. Unknown output impedance, but didn’t sound significantly different in signature from the DX200.
Hiby R6 ($470): The R6 is a fairly neutral source in its own right though it has a 10ohm output impedance that can skew low-impedance multi-driver earphones. From the R6, the v1.1 sounds a smidge warmer, its bass is a touch less defined and sub-bass impact is softer. The upper-midrange and treble is most notably affected, they are both slightly attenuated, female vocals and treble instruments sound notably laid-back, producing a smoother, darker sound.
DX200 ($900): Firm sub-bass with great extension, focussed midrange and prominent detail presence. Bass is well-controlled with high definition. Mids are clear and well-placed. Highs are crisp and resolution is high. Nice soundstage expansion with greater separation between foreground and background.
Campfire Audio Comet ($200): The Comet is slightly more balanced chiefly due to its greater midrange and lesser bass presence. The v1.1 has better sub-bass extension and delivers greater slam. It has more mid-bass producing a fuller, punchier low-end. The v1.1’s low-end is slightly more defined and more dynamic, both have similar upper-bass presence, creating a slightly warmer sound. The Comet has a more present midrange. Its male vocals are more present and its female vocals more neutrally toned. It sounds slightly more focussed where the v1.1 is a touch laid-back and diffuse by comparison.
On the contrary, the v1.1 has a more open upper-midrange as it lacks the same attenuation for density. The V1.1 has more lower-treble emphasis and it’s more even, delivering more detail and instrument body. Neither extend terrifically at the very top. The Comet has more middle-treble, producing a brighter background with more air where the v1.1 has slightly more resolution and greater detail retrieval. The v1.1 has a slightly larger soundstage, neither have outstanding layering. The v1.1 images better.
LZ A5 ($270): The LZ A5 provides a hybrid 5-driver setup for less than the v1.1 though this is an example of how driver count really means little when it comes to real-world performance. The A5 is immediately brighter and more V-shaped. It delivers slightly better bass extension in addition to greater slam with considerably greater emphasis. The v1.1 has similar levels of mid-bass emphasis and a touch more upper-bass, it’s more defined and aggressively textured. The v1.1 has a more even midrange where the LZ A5 has a sharper upper-bass/lower-midrange attenuation combined with a sharper upper-midrange spike.
As such, it is generally more vocally recessed and though it’s quite clear, it doesn’t sound as even or natural as the v1.1. Chiefly, vocals sound distant, thin and raspy. The A5 has a considerably brighter treble response, mostly lower-treble. It sounds disjoint with its recessed midrange, sounding spiked, thin and sharp even with the most attenuating filter. The v1.1 is more detailed and appropriately bodied, it is significantly more natural. The v1.1 has a smaller soundstage and less separation than the thinner, brighter A5. However, its imaging is more accurate and it is more coherent.
Rose BR5 MKII ($300): The BR5 MKII is more balanced but also brighter through its upper-midrange and treble. The v1.1 has significantly more sub-bass extension in addition to greater slam where the BR5 MKII has little sub-bass but is also a lot faster. The BR5 MKII has fairly neutral mid-bass creating a neutral tone. The v1.1 has a fuller upper-bass where the BR5 MKII is similarly neutral here and similarly recessed within the lower-midrange. The BR5 MKII has more centre midrange presence combined with a greater upper-midrange presence.
It is brighter and thinner, but not to the extent of the A5 and the BR5 MKII is considerably smoother than that earphone. The BR5 MKII has a touch more lower-treble than the v1.1, it also has a more middle-treble presence, delivering more extension and air than the Kalkul. The BR5 MKII has slightly more resolution and is similarly well-detailed if thinner. It has better micro-detail retrieval and a wider soundstage. The BR5 MKII separates slightly better and is more layered. The v1.1 is more coherent due to its greater body.
Oriveti New Primacy ($300): The New Primacy is considerably more balanced than the v1.1. It has similar sub-bass extension but a more neutral mid-bass delivering a more neutral tone. The New Primacy is more defined and separated. It has a similar upper-bass emphasis but a more even midrange, its lower-midrange, in particular, is more present as is its centre midrange. It isn’t as bright, rather slightly darker with a dip in its upper-midrange. As such, it sounds dense and full-bodied, but also well-resolved. Vocals are significantly more present, perhaps even slightly forward, it’s also more evenly weighed between male and female vocals.
Both also have a hair more body than neutral without sounding outright warm like the Kalkul. The v1.1 has more clarity in addition to a slightly warmer upper-midrange. Both have similar lower-treble emphasis, the v1.1 is more detailed as its upper-midrange feed more linearly into treble. Both also have a very laid-back background and modest extension at the very top. The New Primacy has slightly better extension, however. It has a larger soundstage and its more neutrally toned sound is more separated and layered.
Cardas A8 30th Ann. ($300): The A8 is a similarly V-shaped earphone with more bass and a slightly cleaner, more present midrange. It has significantly more sub-bass extension and more sub-bass emphasis producing greater slam. The A8 has a similarly full mid-bass but has a cleaner transition into its midrange with less upper-bass emphasis. Similar to the v1.1, also it employs lower-midrange attenuation to separate vocals from bass. Its midrange is slightly more recessed overall, however, it has a touch more centre midrange presence, bringing vocals slightly more forward.
That said, as it lacks the same upper-midrange emphasis, it also lacks the same sense of clarity. The A8 climbs to a slightly emphasized 5KHz peak before significant attenuation that produces a cleaner background similar to the v1.1. The Kalkul is more linear here, it isn’t as spiked creating a more detailed presentation with greater instrument body. The A8 has slightly better extension and resolution of micro-details. The A8 has a larger soundstage, it has less bass and treble separation than the v1.1, but its midrange is slightly cleaner and more layered.
It’s hard to know what to expect from new companies such as Kalkul, however, from testing, their first earphone offers competitive performance in its price class. Its tuning is nicely considered, especially for its intended uses, providing a full voicing counterbalanced by a modest upper-midrange emphasis that redeems clarity. It has a crisp, well-integrated high-end that isn’t pushed to the point of fatigue or thinness. It’s great to see Kalkul adopt the same technologies implemented by established names such as Jomo in addition to introducing new innovations when it comes to construction; their laser sintered finish genuinely aiding the impression of quality. Some aspects of the v1.1 don’t excel, its cable is stiff and uncompliant and its treble extension and soundstage expansion are just modest. The v1.1 still remains a competitive offering and a nice choice for frequent commuters searching for a well isolating earphone with a warm, focussed sound that doesn’t disperse in the presence of ambient noise.
The v1.1 can be purchased from Kalkul for ¥27,900 Yen or ~$300 USD at the time of writing. I am not affiliated with Kalkul and receive no earnings from purchases through this link.