NF ACOUS NM25 OSSUARY Silver Edition Review: Same Voice, New Jewelry

 

General / Packaging / Build / Comfort

NF ACOUS NM25 OSSUARY Silver Edition ($299) is the special edition sibling of the standard NM25 ($199), and this time NF ACOUS teamed up with OSSUARY, an independent handmade silver accessory studio, to give the NM25 a completely different visual identity. The shell itself is still milled from a single piece of aviation-grade aluminum, but the faceplate is now hand-carved 925 sterling silver with a skull motif, done through traditional lost-wax casting. To my ears the theme leans gothic, almost like something you'd dig out of an old tomb rather than a modern audio product, and honestly it works. It doesn't look like just another shiny metal IEM.

Build quality is excellent, full stop. The shell has a nice heft to it without feeling heavy in the ear, and the silver faceplate is properly hand-finished, not just a sticker or a plated shell pretending to be silver. I did notice a bit of driver flex when inserting, nothing alarming, and no pressure buildup even after longer sessions.

Comfort is good for me, the shell shape follows the standard NM25 mould so if you already got along with that one you'll have no surprises here. Isolation is decent once you get a proper seal, though obviously not in ANC territory.

Accessories-wise, it's a mixed bag. You get the same MS42 silicone tips in four sizes, a compact hard case, and the same twisted 5N silver-plated OFC cable terminated in 3.5mm as the standard NM25. For a $299 special edition, I was hoping for at least a 4.4mm balanced option or a nicer braided cable, but NF ACOUS kept this identical to the cheaper model. Purely nitpicking, but at this price point it would've been a nice touch. I'd also recommend picking up a small pouch separately, since the case doesn't leave much room to protect that silver faceplate from rubbing against the shell or the cable.

Gears Used for This Review

• Aune S9C Pro

• Burson Conductor Stellar

• FiiO M21

• xDuoo Link3

Sound Impression

I ran the NM25 OSSUARY Silver Edition through approximately 30-40 hours of burn-in on my rig before sitting down for serious listening. Treble settled slightly over that period and sounds a touch more composed, though the character remains fundamentally the same.

To my ears, this is a neutral-bright IEM with a forward vocal presentation and a surgical, monitor-first approach to tuning. And here's the thing that matters most for anyone eyeing this special edition: the sound is essentially identical to the standard NM25. Same driver, same tuning philosophy, same dual magnetic circuit dynamic driver doing the work. NF ACOUS didn't touch the internals at all here, so if you've heard the regular NM25, you already know what to expect sonically. The $100 premium is entirely for the silver faceplate and the collaboration with OSSUARY, not for a different listening experience.

Bass

• Sub-bass has decent rumble with good texture, though it's more mid-bass focused than sub-bass focused

• Mid-bass punch is tight, fast, and controlled, no bloat or overhang

• Doesn't bleed into the mids at all, keeps the lower registers clean

• Best results come from a slightly deeper insertion, which helps unlock more of the low-end presence

• Not a basshead tuning by any means, but there's enough texture and speed here to keep tracks like Slipknot's Duality sounding punchy rather than thin

Mids

• Vocals are pushed forward, picture the artist as 3-4 steps in front of you

• Male vocals lean slightly lighter on chesty weight, listening to Zhao Peng confirms the lower mids don't have quite the density I'd want for full baritone body

• Female vocals fare better, Faye Wong's vocal texture comes through with good clarity, though there's a tinge of nasal energy from the elevated upper mids

• Note weight leans analytical rather than lush, this is a tuning built for revealing flaws, not smoothing them over

• Clarity is excellent, it's unforgiving with poorly mastered tracks

Treble

• Extended and detailed, treble peaks can get quite energetic in the upper registers

• Borderline fatiguing on longer sessions if you're treble sensitive, take it with a pinch of salt if your library leans bright already

• Cymbal decay and hi-hat presentation on Metallica's Lux Aeterna comes through crisp and fast

• Manageable with foam tips or a touch of EQ if the brightness gets to be too much

Soundstage / Imaging

• Soundstage is intimate rather than expansive, more of a tight studio room than a hall like effect

• Imaging is precise, instruments and vocals land where you'd expect in the head stage

• Separation and layering are a strength, handling denser tracks like Hans Zimmer's Why So Serious without congestion

• Background is pitch black, no noise floor to speak of

• Not 2D-ish by any means, there's a reasonable sense of depth even if width is a bit reserved

Driveability

• FiiO M21: Plenty of drive on tap, the NM25 OSSUARY doesn't need much power at all. NOS mode adds a slight warmth injection that tames some of the upper mid energy nicely.

• xDuoo Link3: Easily driven straight off this little dongle, no volume struggles even on a phone.

• Aune S9C Pro: More about refinement than raw power here, the amp stage adds a bit more body to the lower mids and takes some edge off the treble.

Comparison

NF ACOUS NM25 (standard, $199): Since the sound is unchanged between the two, this comparison really comes down to build and value. The standard NM25 uses the same aluminum shell without the silver faceplate, and for pure audio performance per dollar, it runs circle around the OSSUARY edition since you're getting the identical driver and tuning for $100 less. If you just want the sound, get the standard model. If you want a piece that doubles as jewelry and a talking point, the OSSUARY edition is the one to get. Personally i prefer the OSSUARY edition due to the design, go for the standard NM25 if you don’t really care about the collectible aspect..

Final Thoughts

At the end of the day, the NM25 OSSUARY Silver Edition doesn't try to reinvent what the standard NM25 already does well, it just wraps it in a much more special looking shell. Sonically, I couldn't find any real difference between the two, and I don't think NF ACOUS intended there to be one. What you're paying the extra $100 for is the 925 silver faceplate, the OSSUARY collaboration, and the fact that this is a genuinely well-crafted collector's piece rather than just another metal IEM on the shelf. If you already own the standard NM25 purely for the sound, there's no reason to upgrade. But if you appreciate the craftsmanship, want something that looks like it belongs in a display case, and don't mind that reference-leaning, treble-forward signature, this is a lovely thing to own.

The NM25 OSSUARY Silver Edition was sent over by NF ACOUS for the purpose of this review. Big thanks to the team for the support and opportunity as always.

Head over to their store if you are interested in getting a pair:

• NF ACOUS Official Store — NM25 OSSUARY Silver Edition — Non Affiliated