Kumitate Lab KL-Sirius

Pros: Silky mids, delicate treble, scale with upgrades, excellent technical performance, good stage width and depth
Cons: Reference bass (meaning light), minimal sub-bass, lack of accessories, stock cable is too thin
List Price: $800.00 (¥90,000 JPY)

Product Website: http://www.kumitatelab.com/kl-sirius/?sl=en


Rating Disclaimer: ratings are subjective. Audio quality and value do not mean the same thing across all prices. A headphone with a 5 rating on audio at $5 does not have equivalent sound quality as a 5 rating at $500. Likewise, value at $5 is not the same as value at $5000 dollars.

The Kumitate Lab KL-Sirius was provided to me free of charge by Kumitate Lab. I do not have to return the unit, but I cannot sell it or give it away. I have received no compensation for this review and the thoughts contained within are my honest opinion. Thank you Kumitate Lab for supplying the review unit.

This review originally appeared on audioprimate.blog, and is now being shared with our followers on Head-Fi. This community is still at the heart of the headphone world.

I first ran into Ito Ryosuke, the leader of Kumitate Lab at the 2017 Indulgence Show. They really caught my eye at the show with their gorgeous Raden pieces, and they really captured my ear with their KL-Ref. After hearing the KL-Ref I made sure to get in contact with Mr. Ito to try to arrange a review and/or review tour, and after some persistence, he agreed to send a review unit, but not the KL-Ref, the KL-Sirius.

Kumitate Labs isn’t well known outside of Japan, but when I saw them, I thought they should be. They started as a DIY lab experimenting with drivers and custom acrylic shells inspired by videos of how to make a CIEM on Youtube from 1964 Ears (the old name of 64Audio). Over the years they’ve developed a huge following in Japan, where some folks own a dozen custom IEMs—they wear custom IEMs like earrings, apparently. Kumitate Labs has such demand that Mr. Ito has to open and close orders taking periods as he fills up his production queue a few times per year. I feel very privileged to review the KL-Sirius.

The KL-Sirius is one of two entry-level ¥90,000 JPY custom IEMs from Kumitate Lab (the other is the KL-Meteo). The sound signature is described as infinitely flat, with delicate high frequency expression. I take that to mean that this is the entry level take on a reference signature from Kumitate Lab.

Usability: Form & Function
Japan has a reputation for elaborate packaging with clever use of paper folds, specially textured containers and prize-worthy gift boxes. When I received my package from Kumitate Lab I was excited to see what kind of lavish presentation would be in the box. There wasn’t any. Inside the box was a small black press-close case (same as HiFiMAN RE2000 without the painted letters) surrounded by butcher paper arranged to protect the IEM. It felt a bit like I was being sent a wrench rather than a high end headphone. Monkey see, monkey use.


There was no retail box with artfully designed compartments, no fascinating textures, no pomp and circumstance. There weren’t even any accessories. It was a bit disarming and unexpected.

The package is no more than it needs to be and nothing else. Inside the non-descript tin, however, magic is concealed.


When the simple press-close metal case was opened I was greeted by solid acrylic custom IEMs with flame tempered titanium faceplates. Titanium burnishes to rainbow colours if this is the chosen effect, but Kumitate Lab’s choice on these gives them a purple hue with some brown undertones. They look lovely. The gold writing provides more description than most custom manufacturers I’ve seen, where frequently you can’t list what headphone model you are decorating your ears with. The Kumitate Lab options allow me to choose from several fonts and to choose whether the model name is listed.

The number of options for what you can do with your customs at Kumitate Labs is nearly unrivalled. I suggest checking out their lookbook. Also, their Raden gallery. Raden are special units that use seashells to create works of art in an in ear that are unique to Kumitate Lab. Too much gorgeous. Check them out on twitter and instagram, too. They are always tinkering with new designs.

The acrylic construction is perfectly smooth with a bit of sheen. There are no bubbles or imperfections. The craftsmanship from a hand-made acrylic shell is better than what I see on the 3D printed UERR in my headphone stable.

Inside the Sirius there is silvery wire—this is not silver. I asked Mr. Ito what it was and to my surprise it was tin-plated copper. The gauge of the wire is quite high for internal wiring on an IEM and the silvery sheen is a nice effect. Inside my unit the four drivers and crossover are clearly seen.


The Sirius is custom and has a more robust feel to the ear-tip than the UERR. The UERR has a long extended taper at the end of the ear-piece, while the Sirius terminates earlier in a thicker more full tip. I found that both took some getting used to, but now the Sirius tends to be more comfortable than the UERR and has better isolation.

The Sirius has three sound bores, each with a filter inside the bore preventing ear-wax from getting into the inner workings of the IEM. It’s a pragmatic design that I imagine is part of the sonic tuning also. The Sirius does not come with an brush and earwax tool, which is standard with most custom IEMs. Mr. Ito told me that he recommended people use a toothbrush. Personally, I would have included the tool and a basic retail box.


The cable that the Sirius came with consists of 4 wires of relatively thin gauge arranged in a double twist configuration. The cable has pre-formed heat-shrink ear-guides with good springiness, this is my favourite type of ear-guide. The cable is light and comfortable on top of the ear and grips the top of the ear without being imposing. The connectors on the top appear don’t appear anything out of the ordinary. They are silver, with smooth exteriors that were initially hard to remove from the IEM, a little grip on the outside would help. There are no explicit marks for right and left. I used the direction of the groove on the IEMs to determine right and left. I would use the standard colour-coding scheme that is out there, red = right and blue = left. There is also a metal Kumitate Lab logo bead on the left earpiece. The y-split is made of two layers of heat shrink, with a Made in Japan label. Apparently a large amount of the IEM is made in Japan. The wire is from a Japanese company that is well known in pro-audio in Japan, the 2-pin connectors are made by a company called Bispa (well known in Japan), and the assembly of the cable is done by Kumitate Lab hands with 10 years of experience. A heat shrink chin slider is above the y-split. The cable I received was terminated in a good quality verified Oyaide 2.5mm termination (there are lots of ‘Oyaide style’ terminations).

I tried multiple aftermarket cables with the Sirius, but the one that I’ve settled on as the best cable is the Double Helix Cables Symbiote Elite SP (8-Braid). The DHC Symbiote Elite extracts more detail than the basic cable that the Sirius comes with, and sounds fuller, with a bigger stage. It takes the IEM to a whole new level. The Sirius is probably the most sensitive IEM to cable change that I’ve tried.

Audio quality
Overall sound impressions
Overall the KL-Sirius is tuned more to the reference side of the spectrum. It has light but accurate bass with good extension and no particular bands emphasized. The mids are silky smooth and more organic sounding than your average reference tuning. These mids are liquid, smooth like butter, baby.

Cable Rolling

I’ll start with some brief cable rolling impressions. Truth be told, I wasn’t going to do that here. I was going to save it for another review, but then after I’d already determined that I liked the DHC Symbiote Elite SP (8 Braid), I decided to do a quick switch back to the stock cable that I hadn’t listened to since the first couple days I had the KL-Sirius. The difference didn’t feel as big. The DHC Symbiote Elite is much prettier, maybe that has been driving my impressions. Attractive food tastes better then the same ingredients with no presentation. Our brains are wired for expectation bias. Maybe I’ve had a bit of that. So I decided to go back with doubt, and listen again.

For this little exercise I checked to see if there were any major impedance deviations through some volume matching. There weren’t. If there are differences in impedance, it’s resulting in less than 0.2dB difference in sound, so all the differences in sound will be due to cable construction.

I start out with the DHC Elite and Smashing Pumpkins – Mayonaise, and then switch down to the stock balanced cable that came with the KL-Sirius. The stage shrinks in on the switch, cymbals sound thinner, and the mids sound thicker and more forward. Billy Corgan’s voice loses some breathiness. Bass gets a touch more midbass. There is a reinforcement of the centre image. The biggest losses were in overall resolution and stage. In the past I’ve observed that the amount of wire matters, it could be that if the cable guage were higher this would sound more even. I think even a switch up to 28 AWG would make a difference. I think the current wire is around 32 AWG. Switching back to the DHC Elite, there is also more bass texture and note depth. The stock cable sounds comparatively laid back and fuzzier.

I wish my comparisons could be blinded, but that is probably impossible given the different feels of the cables. In this brief face-off, the DHC Elite won, but it is an $800 cable with better conductors and more of them, so there is that.

All the impressions in this review are done with the KL-Sirius paired with the DHC Symbiote Elite SP (8-braid) cable. Short story on the cable, the Sirius is capable of more than the cable it comes with. Review comparisons were made with volume matching. Volume matching was done using an SPL metre and white noise. I position my IEMs in my home-brew coupler with the IEMs perpendicular to the ground. I’ve found this allows the most consistent measurements and ensures that the dB in custom in-ears match up to universals. I’ve listed the comparators in the table below.



When I went to use the Kumitate Lab KL-Sirius with the Soundaware M2PRO, the mids sounded hollow, so I hooked up the iFi iEMatch 2.5mm and that fixed the problem. The fun thing about balanced armature based IEMs is that each armature has a different impedance, and the differences can be extreme. I’m not convinced that sources listing their output impedance have the same impedance across the frequency range either. So maybe a mismatch explains the hollow sound I got out of the M2PRO. I have not had any problems with matching the Kumitate Labs KL-Sirius on any other rig. In fact, I found it worked equally well on the QP2R with and without the iFi iEMatch2.5.

Unless otherwise noted, I used the QP2R for comparisons. In all comparisons using iFi iEMatch2.5, the setting was high. I find most IEMs clip if I turn the setting to Ultra sensitivity on the iEMatch2.5. I don’t like clipping.

UERR ($1049 with balanced cable) vs. Kumitate Lab KL-Sirius w/ DHC Symbiote Elite (~$800 + $800)
Metal! Slayer – Necrophobic is a showcase of speed, and it’s short, which means I can switch back and forth or listen to the whole track repeatedly. Luckily, it’s a great visceral track that I like listening to repeatedly. The mids on the UERR have a harder character while also being airier. The UERR feels faster through the lower mids and midbass. The vocals are a touch further back on the Sirius. The guitar solo about half-way through the track is faster and better defined on the UERR. The smooth silky sound of the KL-Sirius is not as good during speedy guitar solos as it is during female vocals slow jazz riffs.

When I want some sultry female vocals, Natalie Merchant – Carnival is always a solid standby. She’s got a heavy, rich voice. The rest of the track is laid out very well too. On this track, I prefer the voicing of the Sirius. It has a tighter snap to the percussion, and the silkiness of the mids works well with the slow guitar and female vocals. As with Necrophobic, the vocals are positioned a little further back on the KL-Sirius than vocals on the UERR. On both IEMs, bass grooves with good definition, but neither emphasises it. The UERR has a touch more bass.

The edges of the stage are nicely populated on the KL-Sirius when listening to Macy Gray – Annabelle. The stand-up bass has accurate timbre, but isn’t as pronounced as the track should call for with the KL-Sirius. The sound is very well integrated, just a pleasing tuning. Bass is a little more forward on the UERR, but the overall stage has less depth. Guitar is really gorgeously presented on the UERR.


These are both such capable and good IEMs, I really can’t pick one. They have slightly different tonal and technical profiles. The UERR has a more immediate feel, and is more resolving during fast complex passages. The overall timbre of the KL-Sirius is neutral organic, and quite lovely. From a technical perspective, the KL-Sirius and UERR are a push on stage width, but the Sirius has greater depth. The UERR has a taller stage. The UERR has a resolution advantage, but it isn’t a night and day comparison. The UERR costs a bit more, but not more as tested. I think that with a $200 upgrade cable, the KL-Sirius likely still competes. I think folks wanting a more silky musical version of neutral who like easy going music will go for the KL-Sirius. If you are looking to portray classical music, or speed metal, the UERR is the better choice.

Noble Encore w/ PlusSound X-Series GPC ($1699 + $399) vs. Kumitate Lab KL-Sirius w/ DHC Symbiote Elite (~$800 + $800)
I start out getting my dance rhythms on with some STRFKR – Tape Machine. The KL-Sirius has liquid mids, delicate treble, and a slightly warm chugging bass on this track. The track doesn’t have a ton of depth, but I’m getting just slightly outside the ears width with on the Sirius. Treble is a touch harder with the Noble Encore, a little more forward, with a touch more detail resolution. The bass is bigger with more rich and full timbre on the Encore. The Encore gets more texture out of this track. Soundstage is a push between the two. The Encore has more of a v-shaped inflection to the tuning. It’s more fun, while the Sirius tilts more towards a reference tuning.

After getting FKed up in space, I decide to stroll to a decidedly more earthen location and throw on some Stevie Ray Vaughan – Tin Pan Alley (aka Roughest Place in Town). This track has an underlying electrical noise, while still exhibiting some intricate blues guitar work. The Sirius has very fluid mids with good detail layered into vocals from Stevie. The bass guitar is tuneful without extending remarkably deep. The bass is neither forward, nor recessed on the Sirius, but many would interpret it as such. It’s got kind of an HD600 kind of feel to it. Mids are more airy on the Noble Encore. The whole sound is more lively and realistic feeling. Bass is elevated on the Noble Encore, but satisfyingly so. The bass on the Encore has more texture, but it has decidedly more mid-bass than sub-bass. The sub-bass on the Sirius sounds more balanced due to lack of emphasis on the mid-bass. Clarity around the 5 minute mark in the track is similar between the two. I really like the mids presentation on the Sirius.

Can I get some sibilance? Rush – The Trees, is generally good for that. The Sirius doesn’t accentuate sibilance, what’s there is an accurate amount. Geddy Lee loves to elongate his ‘s’ sounds, so if there isn’t sibilance it’s from heavy-handed downtuning of the sibilance range between 6kHz and 8kHz. Cymbal strikes sound harder on the Noble Encore, with less fluidity. The decay is slightly shortened on the Encore. The Encore slightly reduces sibilance compared to the Sirius.

The Noble Encore exhibits good hard rock power when thrashing on Rage Against the Machine – Know Your Enemy. The Sirius has more natural sounding cymbals. The Encore rocks the crap out of the Sirius, with the Sirius sounding comparatively dull on this track. Easy win for the Encore on this track.

If soaring female backing vocals is what you are looking for when listening to Pixies – Where is My Mind? you’ll get it with the Encore. It has great clarity and separation in the upper mids. I get the same soar with the Sirius, but it has greater depth in the representation and is silkier. It’s hard to pick a winner on this track. The Noble Encore has those enhanced bass notes that give a more lively feel, but my oh my are those female backing vocals alluring on the Sirius. Both give similar stage width, but the female vocals project and expand from deeper in the stage on the Sirius. I’m enthralled with both.

What about Bob—I mean jazz. On Miles Davis – Spanish Key the Noble Encore has more immediacy, but sounds a bit busier due to pushing some bass and treble elements forward in the mix. The more neutral tuning of the Sirius is a better match for this complex and busy track, stylistically. The Encore has more resolution on this track, but misses on the ambiance.

I think the Noble Encore has a more resolution, but the Sirius has a touch more stage, so the advantage on technical aspects is slightly in the Encore’s favour. The Sirius has silky alluring mids and a non-fatiguing reference-like signature. It has a more fluid treble, while not losing detail in the treble. The bass is more balanced than the Encore, but also what would be considered a touch light for many. The Encore rocks much harder, so if hard is what you are looking for, the Encore might as well be a little blue-grey pill. I like both, a lot, but given my usual listening habits, I’d probably reach for the Encore more often, even though I think the Sirius is probably more timbrally accurate. In a 10 driver competition versus 4 driver competition, it was a lot closer than I expected.

Unique Melody Mason v3 ($2699) vs. Kumitate Lab KL-Sirius w/ DHC Symbiote Elite (~$800 + $800)
I decided to do this comparison using the Soundaware M2PRO as the volume setting difference is only one point, but on different gains, which means that switches should be fast. The switch isn’t as close on the QP2R. For this comparison I had the Mason v3 set with the dB-Go switch turned to the back, and the silver cable on, which is my preferred setting.

2Pac – Troublesome ’96 shows some nice bass texture with the Unique Melody Mason v3. The Masons are not bass light. They have nice fully developed low bass notes. 2Pac’s vocals are a little back of where I’m used to. Bass texture is still good on the Sirius, but the Mason reaches deeper. The Mason has more resolution through the mids, with more texture to 2Pac’s voice. The slight dip in the mids gives a bit more feeling of depth. I’m a little surprised to detect the dip in the mids on the Mason. Stage depth is more pronounced on the Mason v3.

The Mason v3 delicately arranges the stage on Bob Dylan – Like a Woman. The slight recession in the mids creates some illusion of additional depth, but when considering the rest of instruments, depth is still extremely impressive, so one wonders why not just tune the vocal bands completely neutral? Bass is more prominent on the Mason v3 than the KL-Sirius. Bob Dylan’s voice is silkier and more prominent in the stage on the Kumitate Lab KL-Sirius. This song sounds better on the KL-Sirius. It just sounds more whole and real.

A band that far too few people think of as audiophile listening fodder is Wilco, especially their a ghost is born album. On Handshake Drugs, the Sirius gives nice clear presentation to vocals; the bass chugs along nicely without overpowering anything; and the drums are exactly where I want them to be. The bass guitar is better represented on the Mason v3, with much more full sub-bass development and more texture to bass. The stage has an effortless breadth to it with incredible instrument separation. Every instrument really gets to shine on the Mason v3, with all sounding at appropriate depth. The only exception is the slightly recessed male vocal from Jeff Tweedy. The Mason v3 is better at taking on the complex interplay of instruments on this track.


Katherine Bryan – Flute Concerto: II. Alla Marcia presents a complex sonic landscape that will expose over-bright treble and inadequate driver speed. Katherine Bryan has some masterful flute trilling. The Mason v3 doesn’t miss a beat with any of the broad sonic range of expression in her flute vocalisations or in the various individual instruments. The scene never sounds busy on the Mason v3, and every instrument is well-resolved. Mmm, those silky mids on the KL-Sirius. The Sirius sounds a bit sharper on flute, but also a bit fuller. The overall speed of the KL-Sirius doesn’t match the Mason v3. Complex notes are more fluid and less delineated. They have a little bit more heft to them, whereas the Mason v3 is more light on its touch. Stage width isn’t close to the Mason v3 on the KL-Sirius, and the Sirius’s instrument separation is similarly bested by the Mason v3.

Overall the Mason v3 is technically superior, though the slightly recessed mids turn it off of being a full-on reference tuning. The Sirius has a more reference tuning but can’t match the stage, instrument separation, resolution, speed or bass depth of the Mason v3. The Mason v3 and Sirius are from the same signature family, but the Mason v3 is the higher technical performer.

The Kumitate Lab KL-Sirius has liquid mids that are to die for, given the right circumstances. Speed metal with over-complicate for the KL-Sirius, but smooth bluesy presentations absolutely shine. They extoll the virtues of female singers, and do an excellent job resolving a good size stage with impressive depth and width. The build quality is excellent, but they could use more in the way of accessories to make the overall buying experience stand out as a more boutique experience. They scale with better cables and better sources, and can run with more expensive IEMs. These are artisanal IEMs, and I really appreciated the design and performance.
Very exhaustive and comprehensive review, as always. I have a Qp2R on demo and I just ordered the M2Pro and I see from the review that you have both. Any impressions you care to share here, or is there a more appropriate thread where I could look? Thanks