ItsFit Lab Fusion – Serious fun!

If you're looking for a punchy and clear sounding IEM with great soundstage and fantastic imaging, then you'd be hard pressed to find a better candidate than the Fusion especially at its price point. The Fusion delivers great value for money featuring flawless technical foundations, a highly coherent tuning and a superb build.  Competitors take note, a strong challenger hits the market and it hits hard! 


  • Great soundstage with top tier imaging precision
  • Superb upper treble extension and exciting but non fatiguing lower treble
  • Clean, well extended bass with superb control and good textures
  • Balanced and clear articulate mids with slightly forward vocals
  • Exceptionally low distorsion
  • Fantastic value for money
  • Superb build and fit
  • Great customer service


  • None that can’t be EQ’ed (a a bit more mid bass or upper mids if you’re so inclined)

Price : 950$
Product page :

Fit, Build & Isolation

I chose a « plain » cyan transparent design for my Fusion, the picture hardly do justice to the color (hard shade to portray faithfully) but the transparency clearly show top notch craftsmanship, showing the dynamic, balanced armature and magnetostatic drivers as well as the 3D printed acoustic chambers that bypass any need for passive filters. The Fusion are beautifully engineered and the build is flawless, simply the best fit I have had along with my Custom Art IEMs. Hats off to Kiên and team here!

Superb customized metal case to keep my Fusion safe


ItsFit Lab is a very young upcoming manufacturer based in Vietnam which managed to get known very quickly and it’s not surprising. I mentioned this above the packaging as well as build quality is as good if not better as well established  companies. ItsFit Lab certainly is serious about getting things done well from the get go.

The Fusion is their second IEM after the 3 BA reference R3 and it’s already a sales hit. In a world where most tribrids use eStats for treble, Kiên decided to build the « world’s first tri-brid earphone with Magnetostatic™ ». A good way to get noticed but a daring endeavor to pick a new driver tech that has never been implemented yet considering the number of disappointing tri-brids that popped up when the eStats driver came out.

ItsFit Lab also decided to do quite a bit of work and innovation into the acoustics design as well, using « exclusive sound chambers using 3D printing technology. This technique helps delivering original sound through separate signal channels without sacrificing sound with traditional passive filters. This proves to be efficient in reproducing sound at extremely wide frequency response (10-40000 Hz) without losing any sound details. » I have had a few IEMs with advanced acoustics : IE800 and Black have helmholtz resonators, Solaris also features acoustics chambers with T.A.E.C and P.T.C and it plays a big role into soundstage and distorsion. 

With the Fusion, Itsfit aimed at building « a true innovative in-ear that conquer even the most demanding records. Fusion’s soundstage crossed all lines to be a premium in-ear monitor that brings to your ear the extremely wide and deep soundstage of a pro open-back headphones in a tiny, portable earphones. The super luscious highs, detailed & transparent mids and super tight lows now packed with superb space performance, bringing you unforgettable listening experience. » 

Somewhat of a bold claim… does the Fusion hold its promises?

Let’s see!

Image courtesy of Kiên at ItsFit Lab


The first thing that struck me listening to the the Fusion are : bass, treble, clarity, soundstage, imaging. Bass and treble are clearly stars of the show, because they do provide all the excitement in the Fusion’s signature. The Fusion features a toe tapping, tight and perfectly controlled bass with strong sub and spot on mid bass presence. It also features lively lower treble with good energy but done right, as it’s not a harsh or fatiguing treble either. The upper treble is well extended and provides superb clarity and air. Soundstage is quite wide, tall and deep with a fantastic image both pinpoint precise and coherent.

While bass and treble are the star of the show, the mids are the cornerstone of the Fusion signature : they provide coherence and balance to the whole tuning. I read the Fusion as being a technically strong fun IEM, with plenty of excitement but done right (good control, superb imaging, tonally accurate) and in a balanced way. This is somewhat of an unusual signature or at least I fail to find a similar combination in any IEM I have auditioned. 

Now, let’s dig a bit deeper into the Fusion’s bass, mids and treble!


The Fusion is not a bass-head IEM it’s not a massive bass ala Campfire Solaris or IER-Z1R – subs don’t have the same subwoofer like presence – but the dynamic driver is sure able to push air with nice sub rumble and get you toe tapping.

Most impressive is how tight the bass is : the bass presentation is clean and absolutely flawless technically with superb control and layering. You might find yourself discovering a lof of details you didn’t know where there. Note attack is frank and energetic, with very good snap and short decay, the Fusion bass is quite fast for a dynamic driver powered bass.

It’s not as fast as the best balanced armatures but still very good in that respect. The Fusion has no problem keeping up pace with faster tracks or provide a very articulate rendering of bass heavy genres. It’s always a good indication when I spend more time than usual listening to punchier albums and tracks with an IEM and it certainly was the case with the Fusion.

To me the Fusion has an audiophile bass with a good touch of fun and I found myself pushing the volume a bit more than usual, as it’s a great experience with the Fusion where everything remains absolutely clean of any distorsion. Note that the Fusion is vented and it probably helps there along with the custom 3D printed chamber (acoustic work definitely paid off). I didn’t notice any perceptible leaking from the vent and people right next to me didn’t complain.

The three vent holes for the Fusion bass driver

The only thing I could be left wanting is a bit more mid bass presence and textures especially on double bass on Jazz tracks, but I am nitpicking here 😛


Mids are interesting because you could think from what I wrote in the overall sound impressions that the signature is V or U shaped with focus on both bass and treble. Well, it’s not because the mids are definitely not recessed. In the line of the overall signature the mids are clear and clean with very good separation. The Fusion certainly features mids that won’t add any warmth unless the source provides coloration, it’s a reference tuning in my opinion.

Lower mids are clean and balanced, a good call given the bass presence and there is no congestion at all. Vocals and lead instruments are clear and slightly forward in the mix, very articulate with and quite accurate in tone. Upper mids are less present, the mids are as smooth as they can : attack and decay are a little slower than the bass.

I confess, while the Fusion is a fantastic all rounder when listening to Jazz albums the Fusion lacked a bit of upper mids presence which was apparent on saxophones or trumpets. On the flipside the Fusion features a fatigue free midrange.


Treble was a question mark given that the Fusion features a new driver technology that has never been used in an IEM before. It also was a bit of a concern as I have been so disappointed by the first implementation of eStats in earlier eStat tribrids… So what is a magnetostatic  driver and why use them? As stated on ItsFit’s website « Magnetostatic™ drivers use two pairs of permanent magnets located symmetrically and independently from a membrane in between. This ultra-thin 5-layer erromagnetic membrane layer with very high magnetic permeability moves its entire surface without any dead point, minimizing sound loss, transfer delay and distortion ».

The promise of fast transients and low distorsion is certainly interesting and a potential contender to eStats and balanced armatures, and I was really curious about the Fusion’s treble. How did Kiên handle the world’s first implementation of the magnetostatic in an IEM?

Well, let’s spare the suspense, it’s really perfectly integrated in the Fusion’s signature. The Fusion features both superb upper treble extension and exciting but non fatiguing lower treble. This is key to the soundstage air and the overall clarity of the Fusion signature as well as the fantastic imaging ability.

Of note is the very accurate treble tone, and the satisfying weight to treble notes. This is one very differentiating aspect of the Fusion’s treble compared to the eStats I have heard so far. This is not a treble with an ethereal quality, but a physical treble and piano notes have delicious weight when called for. Transients are very fast, but noticeably less than eStats tribrids like Vision Ears Elysium.

ItsFit Lab Fusion with DITA Oslo, my favorite cable pairing


The Fusion is ItsFit Lab’s flagship and only second IEM after the R3, one can only imagine the big stakes around its launch for the young vietnamese company. Choosing to pick a new driver technology and be first to implementing it was certainly bold and this time the saying is true : “Fortune favors the bold”.

Except that fortune has no part there : ItsFit Lab build quality, tuning mastery and customer service is up to par with the best in the business and it’s no small feat. Yes, ItsFit Lab is still a small shop and the Fusion’s success means a bit longer build time but this is a ransom of success rather than a shortcoming and any similarly sized company would have faced the same challenges. I was lucky to be among the first to order during the sales and Kiên helped me get my Fusion in time for my birthday which was therefore quite an happy one 🙂

Does the Fusion deliver on its promises? “Extremely wide and deep soundstageCheck, although probably not up to par with open back headphone – that’s probably not possible – but still top tier very open sounding and fantastic imaging. “Super luscious highs, detailed & transparent mids and super tight lows.” Check, the highs are clearly a highlight of the Fusion and participate in the clear, open souding signature. Check, the mids are clean and clear with a very accurate tone. Check, the lows are indeed tight with superb control.

If you’re looking for a punchy and clear sounding IEM with great soundstage and fantastic imaging, then you’d be hard pressed to find a better candidate than the Fusion especially at its price point. The Fusion delivers great value for money featuring flawless technical foundations, a highly coherent tuning and a superb build. Competitors take note, a strong challenger hits the market and it hits hard!

Listening notes
I spent over a hundred hours with the ItsFit Lab Fusion, listening to Cayin N6ii (A01 and T01 motherboard) and the DX160 mostly with the DITA Oslo using 4.4 balanced. 

I have purchased the Fusion during the end of October Sale with 30% off. As usual, this review is my honest opinion. No incentive was given for a favorable review.

Packaging and accessories

The Fusion are delivered in a quite rare packaging for a custom IEM : the box is sealed with plastic. The unboxing experience is very nice as well with a hand written thank you note, a metal protective case customize to your name and the usual pouch and cleaning tools. The stock cable is above most offerings with a nice braided build. Note that the Fusion also exist as universal IEMs.

  • 1 x ITSFIT Protective premium Case
  • 1 x Cleaning Tool
  • 1 x 48″ Detachable Premium black Cable
  • 1 x Soft cloth
  • 1 x Soft portable bag
  • 1 x Product Manual
  • 1 x Warranty note


  • Driver configuration:
    1 Magnetostatic driver – high
    2 Balanced Armature drivers: high-mid & mid
    1 Electro-dynamic: low
  • Freq. Response: 4Hz – 40kHz
  • Sensitivity: 98 dB/mW @ 1kHz
  • Impedance: 13.1Ω @ 1kHz
  • Isolation: -26dB 

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