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A First Look: itsfit Lab Fusion

DISCLAIMER: itsfit Lab provided me with the Fusion in return for my honest opinion. I am not personally affiliated with the company in any way, nor do I receive any monetary rewards for a positive evaluation. I’d like to thank itsfit Lab for their kindness and support. The review is as follows.

itsfit Lab is a brand-new manufacturer from Hanoi, Vietnam, specialising in universal and custom IEMs. While a company still in its infancy may have you picturing uninspired marketing, a half-baked website and amateur craftsmanship, itsfit – through sheer preparation – have flipped the script entirely on its head. A mere three months since their debut, they’ve achieved a strong online identity, a feature-rich webpage and a portfolio of impeccable IEMs, all thanks to founder Kien Nguyen’s three full years in R&D. Today, THL is very proud to give you the first look at itsfit’s flagship Fusion: A tri-brid with a clean, refined, dynamic sound, and some of the best imaging I’ve heard yet – all at a refreshingly accessible $950.

itsfit Lab Fusion

  • Driver count: One dynamic driver, two balanced-armature drivers and one magnetostatic driver
  • Impedance: 13.1Ω @ 1kHz
    Sensitivity: 98dB @ 1kHz @ 1mW
  • Key feature(s) (if any): 8mm magnetostatic driver, 3D-printed acoustic chamber
  • Available form factor(s): Custom and universal acrylic IEMs
  • Price: $950
  • Website:

The Magnetostatic Driver

Unlike most tri-brids that’ve recently entered the market, the Fusion does not have an electrostatic driver. Instead, itsfit have utilised the lesser-known magnetostatic driver, which is somewhat of a cross between an electrostatic and a planar magnetic driver. Like the former, the diaphragm is an ultra-thin membrane, sat freely between two plates. But, it moves not via high-voltage static electricity. Rather, like orthodynamics, the membrane is vibrated by two permanent magnets. And, the entire surface of the membrane moves evenly too for lower distortion. So, theoretically speaking, the Fusion’s top-end will receive the benefits of both technologies without the low sensitivity, the weight or the external transformer.

Image courtesy of


itsfit Lab’s integration of 3D-printing have allowed them and their IEMs certain advantages. One is the ability to fabricate custom acoustic chambers in-house, like the one installed between the Fusion’s 10mm dynamic and 8mm magnetostatic drivers to optimise their performance. Another is the ability to create customs from digital STL impressions, in addition to physical ones. That way, you entirely bypass the time, money and risk that typically come with international shipping.

Image courtesy of

Sound Impressions

The Fusion possesses what I’d call a very modern signature: A clean-and-clear timbre that errs on warm, with full-bodied, wet and engaging instruments courtesy of its lower-half. Think Lime Ears Aether, 64 Audio A18Tzar and Vision Ears VE8, and you’re most of the way there. How the Fusion then stands out from the rest (especially among its closely-priced peers), is through raw performance. itsfit’s flagship boasts some of the most stable and precise imaging I’ve heard yet; a stunning accomplishment once you consider its lively, larger-then-life presentation. Stereo separation is absolutely superb, and so is layering. All this means the Fusion’s lively, rich and coherent sig will never compromise its impressive spatial prowess.

Given the 10mm dynamic driver dedicated to the low-end, the Fusion’s bass response is surprisingly balanced, mature and refined. The region peaks at the sub-bass, declining very linearly into the mid- and upper-bass; a subtle downward slope from approximately 20 to 400Hz. This gives the bass a clear, light and airy timbre that prioritises cleanliness and speed over sheer impact. And, it all sits perfectly in line with the mids and treble too. In fact, with most pairings, it sits a hair behind the upper-midrange. So, while those craving a raw, DD bass may find the Fusion a bit modest, it’s a godsend for those who want balance, clarity and accuracy first, then the impact and rumble of a dynamic driver when called for.

The midrange is where the Fusion draws forth its musicality. The lower-mids have been reserved a touch to achieve that clean, well-defined modern sound. But, at the same time, a well-tempered top-end has prevented instruments from ever sounding dry or thin. Notes here toe the line between fullness and clarity expertly well; sounding vibrant, airy and wet all at the same time. Again, note size here is on the larger side, which gives electric guitars and horns great expressiveness. And, the Fusion’s vast headroom gives it the space to breathe and sound effortless as well. Rich in timbre with heaps of resolution, the Fusion’s BA’s achieve stunning harmony with the meat of the DD below and the air of the m-stat above.

The Fusion’s shining star is certainly its magnetostatically-charged top-end. In conjunction with itsfit’s strong tuning, the driver is responsible for the Fusion’s pin-point, holographic imaging, as well as its black background and detail retrieval. Thankfully, itsfit have resisted going overboard with its presence as well, mindfully tempering it to blend seamlessly with the rest of the drivers below. Subtle peaks along 5 and 8kHz bring crisp articulation to hi-hats and cymbals, but the top-end remains calm otherwise for a wet, smooth and lightly feathered response. And, stellar extension and speed bring best-in-class imaging to the Fusion as well, completing its unified, warm-and-clear tone with stereo separation to die for.


While I don’t typically give pair-ups its own, dedicated section, I think it’s an important note to touch on with the Fusion. Its sig and stage are prone to changes depending on the chain, perhaps due to the IEM’s pure silver wiring. For example, Effect Audio’s Eros II can tease a bit of dryness in the Fusion’s 5kHz peak, while Cleopatra keeps it buttery-smooth and adds more guttural, present lows. Han Sound Audio’s 4-wire and 8-wire Aegis sound drastically different in midrange density, stage size and imaging. My K-modded Sony WM1A also brings more lower-treble presence than my Lotoo PAW Gold Touch does. So, while it isn’t compulsory, you may find it worthwhile to be a bit smarter with your Fusion’s pair-ups.

Initial Comparisons

Lime Ears Aether R

The Aether R shares the Fusion’s exuberant-yet-controlled sig, as well as its warm and clear tone. For a full comparison between the two IEMs and and more in-depth impressions of the Aether R, you can check out my full review of it here.

Custom Art FIBAE 4

The Fusion and the FIBAE 4 share quite a few similarities, especially in tonality, midrange positioning and structure. Both in-ears err on neutral with great openness and air. And, they have impressive spatial properties too, though the FIBAE 4 stretches farther in terms of width. Despite the FIBAE 4’s tighter instruments, the Fusion possesses more realistic stereo separation. The FIBAE 4 feels a touch artificially stretched by comparison. Down low, it also has a gutsier mid-bass, while the Fusion’s dynamic driver gives it a more realistic sense of weight and presence. The FIBAE 4’s upper-mids and top-end are more restrained and relaxed as well. By comparison, the Fusion’s are sparklier and more vibrant, but just as smooth.





Church-boy by day and audio-obsessee by night, Daniel Lesmana’s world revolves around the rhythms and melodies we lovingly call: Music. When he’s not behind a console mixing live for a congregation of thousands, engineering records in a studio environment, or making noise behind a drum set, you’ll find him on his laptop analysing audio gear with fervor and glee. Now a specialist in custom IEMs, cables and full-sized headphones, he’s looking to bring his unique sensibilities - as both an enthusiast and a professional - into the reviewer’s space; a place where no man has gone before.


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