Disclaimer

*As always, with each review I try to improve and better demonstrate my experience as a regular but avid and passionate user!

*I try to make my reviews understandable and enjoyable for anyone, whether they're a newbie or an experienced audiophile.

*If you are looking for a super technical and in-depth analysis, please feel free to look for another review. There are many guys here who have much more knowledge than me and have been doing this for much longer.

*This time, the unit to be reviewed was kindly delivered by NF ACOUS through Ms. Eileen in exchange for my honest opinion/review.

*I will try to be as brief as possible, "straight to the point!" And as unbiased as possible.

Gear Used

- FiiO K11R2R (NOS), TEMPOTEC MARCH III 2025, HDS S8 PRO Robin, EPZ TP35, DUNU DTC800, TEMPOTEC V3 Blaze, (Local WAV, FLAC files and Tidal Streaming)

- Motorola Edge 60 Pro (UAPP), (Tidal)

- Notebook (Windows), (MusicBee), (Tidal)

- 4.4 bal. Cable, and High Gain as Always!™

Price: $190.99~205.00 USD

Specs

- Drivers Config: 1 Single DD (MC2L-100A Proprietary Double Cavity Dynamic Driver)

- Sensitivity: 108

- Impedance: 32Ω

- Frequency Response Range: 9Hz-40KHz

Overall Build and Unboxing Experience

The unboxing experience is typical of NF Acous.

I find it one of the coolest and most enjoyable unboxing to do.

A medium-sized box with a sleeve showing the NM25. Removing the sleeve reveals the box, which opens in the middle, showing the very cool foam and card, similar to a CD, where the shells are securely held. Removing the "CD" reveals the cable and the really good MS42 eartips.

For this review I used the MS42 eartips, and it might be the first time I've used a stock eartip for a review. Sonically, the MS42s paired perfectly with the NM25, and the passive isolation was incredible. Totally flush with my little girl's ears.

On the other side, there's a manual and information, a small, fully portable semi hard case that fits easily in your pocket, and a 6.35mm adapter.

The cable, with the NF ACOUS, is always a difficult point to digest. 5N Silver Plated Copper, on the thin side and prone to tangle, but with good construction and great hardware. I tested it wearing it behind my neck like a "Pro", down my back, with the grip very close to my neck, and it fits perfectly, i mean, PERFECTLY. However, not everyone, and probably most people, will use it that way, and as the only option in 3.5mm, it's definitely a low point.

*Regarding the QDC type connection, it's a matter of personal preference, so I wouldn't say it's a negative point.

*In any case, I used the Hisenior 2-pin Manta cable in 4.4mm balanced to do this analysis.

The Shell's construction is super solid, made of a single piece of aviation aluminum, which is precisely carved by 5-axis CNC. It has a high-quality texture while maintaining a very light weight and is very compact shell.

Sound Signature

Analytical, super fast, I've heard Magnetic Planar that can't keep up with this thing, and it's a monster in detail, especially in the quality of the high and super highs frequencies. (NF ACOUS definitely did something magical with this new patented technology and in the overall DD).

SURGICAL is the right word to describe all the NM25!

Bass

The bass frequencies on the NM25 are indeed very low in quantity, but that doesn't mean they're absent or lack quality.

On the contrary, here the priority was quality over quantity. It's SUPER fast, very well textured, very fast decay and recovery; the midbass is more prominent than the subs. The subs appear when needed, but they don't have a great extension and are quickly overshadowed by the very, very good punch that the mid-bass provides.

*No bleed at all on the mids

Mids/ Vocals

Clean and super detailed, these mids won't forgive bad recordings!

The male and female vocals have enough weight and body to maintain naturalness while still being so clean, distinct, and detailed.

The female vocals are very close to becoming shouty. This can happen depending on the track. For my analysis playlist, I managed to pick up something like that. In my personal playlist (most tracks are Metal of all genres), I didn't have any problems or discomfort. Unfortunately, many of my metal tracks recordings are bad, and as I said before, the NM25 will make you hear all the bad things that you may never have noticed in this type of recording.

Treble

A true oasis for treble lovers. Honestly, this was the best high frequencies I've ever heard in a dynamic drive, perhaps one of the best of any set up to, say maybe, $500 USD.

The details are everywhere, detail retrieval is so good, the extension is great too with an excellent airyness sense, resolution is top noch, and yes, it's energetic, spicy, but never harsh or sibilant.

It might be too much for the more sensitive, but to tell the truth, even for them I would recommend it. Just lower the volume a little, maybe use a warmer source, and you're good to go.

Technical Performance and Soundstage

It's incredible that I'm talking about a single DD again, but now I was surprised by this linearity and excellent posture right up to the upper mids, and throwing all the perfect highs that the NM25 can produce right in your face. Damn, this is a single Dynamic driver, how can it produce such good highs, no, such magical highs?

Soundstage is adequate and average. It's on par with other IEMs in the same price range.

Now, in terms of resolution, image, and layers, it's a step or two ahead of its price and its competition.

Overall Verdict

Work tool, serious toy for fun, okay, it can be both because NF ACOUS knows how to do it!

It's not an iem for everyone, but everyone should have an iem with this capability.

Thanks NF ACOUS for the fun time you provided me with this wonderful set.