Producing professional in ear monitors since 2014, NF Acous has been enthusiastic in producing high quality audio products ever since catering to musicians, audiophiles and even gamers around the globe. Their simple yet effective mindset has produced superb creations such as the NA20, RA15, NM 20 to the flagship NE4 has been really well received and recently they have decided it is time for an evolution of their Professional lineup by introducing the all new NF Acous NM25 that is poised to be a successor of the more recent NM20 with their signature MC2L-100A single dynamic driver IEM that has been tuned even further and now comes in a solid all metal shell. Eileen from NF Acous has kindly sent us a pair of the NM25 for us to have a look to give an honest review and we are truly grateful for the opportunity. How will the NM25 perform? Will they bring back the glory of a single dynamic driver? We shall find out here.

We are not affiliated nor taken any monetary exchange for these products and the review is an honest take which is an opinionated view.

Functions & Specifications

Before we start the review, here are the specifications of the NF Acous NM25 taken from their website;

Product Specification

• Driver: MC2L-100A Dynamic Driver
• Sensitivity: 108 dB / mW
• Impedance: 32Ω
• Sound Insulation: 25dB
• Frequency Response: 9-40kHz
• Distortion: < 1%
• Max SPL: 125dB
• Cable: 0.78mm dual pin 5N Silver Coated OFC
• Connector: 3.5mm

The NF Acous NM25 can be purchased at their official store and various platforms worldwide

NM25

Packaging & Accessories

The packaging here is similar to the other professional line of NF Acous but they have a more premium look and feel to them. Opening up like a CD case with their CD theme holding the earphone heads, it is unique and original. Here are the accessories included;

• Earphones
• 0.78mm 2 pin 5N Cable
• User Guide
• Storage Box
• NF Acous MS42 Eartips (MS,S,M,L)
• 3.5-6.35mm Adapter

High quality accessories are included but I do wish it comes with a 4.4mm balanced cable but I do understand that aiming for studio and professional use, single ended termination is mostly used.

Design

Now on to the design and they are fresh looking for NF Acous that abandons the polycarbonate body for a 5-axis, CNC carved aviation grade aluminum alloy body that has a matte texture with glossy edges and their brand on the faceplates. It is light in weight that has a premium feel and they do look sleek. There is also a small brand stamped on the lower, inner side of the shell in blue on both sides. The fit here is very ergonomical as they took the experience and data from their custom IEMs products to mold a shell shape for a better fit for most people out there. Really well executed design and the finishing here is top notch.

Now into the heart of the NM25, their signature MC2L-100A dynamic driver that NF Acous created and has gone through some tweaks to further optimize their performance. It has a dual magnetic circuit with dual acoustics chamber, an electronic tuning crossover and a new damping system by separating the chamber zones that they claimed to effectively and accurately control the dynamics of different frequency bands, with a bandwidth of up to 9-40kHz.

Also, their patented Selective Reflection Adjustment 2.0 technology has been renamed Clutter Trap 2.0 which is a unique engineering structure which works like a passive EQ that precisely attenuates the peak to give a smoother listening experience while still having a detailed, powerful sound. The NM25 also possesses professional damping to reduce sound reflections and making the sound purer by 5 air pressure controlling damping nets and 2 tuning sponges, adjusting the air pressure balance between the front and rear to create a reference class sound.

The front nozzle is fitted with metal mesh to prevent moisture and dust entering. Nozzle size is normal with a maximum of 5.5mm diameter with a medium length.

There is 1 vent hole on the inner side of the IEM for pressure relief and with 1 pin hole situated below the 2 pin connector in charge of the back dynamic driver vents. No driver flex and pressure build up is present which is great for the driver’s longevity as well as comfort.

The connectors being used is a 0.78mm convex style which is similar to QDC but isn’t their reversed polarity terminals style. So if you were to use the normal 0.78mm type of 3rd party cables, you don’t need to reverse the cable but if you were to use the normal QDC reversed polarity, there might be some out-of-phase issues especially with balanced output. Nothing significant as it is mostly beyond human’s auditory range for reversing the polarity but it is cool that NF Acous pointed this out in their packaging to prevent misunderstandings.

The included case is a square zippered fabric hardcase that is rather small but it does the job of protecting the IEM for travel but I do wish that a bigger case will be better especially when matched with thicker cables.

Cable here is a 4 core silver plated oxygen free copper cable that has a 4 core twisted braid and they actually look pretty basic apart from the 3.5mm plug which is metal based with their branding on it.

Gears Used for Comparisons

Songs list

Tone and Presentation

The tone of the NF Acous NM25 is a neutral tuning as expected from a monitoring IEM and they do have a bright tone that has a focus towards the high range giving them a clear sound that is packed with details. The overall sound here is quite balanced and although having a boosted high range, they are still able to give a rather full sound with a good midrange and bass presence without any hollowness. Tuning of the NM25 is a true refinement over their sibling, the NM20 in all aspects in my opinion while still instilling their top shelf technicalities that can go toe to toe with IEMs above their asking price. The NM25 does have a rather clinically sterile sound that stays true to a clean, unaltered sound but it does have a unique, crisp overall sound that manages to prevent it from sounding too dull or dry.

Soundstage

The soundstage here is expansive with great width and height to their sound. They have a diffused sound field that actually gives an almost out of head soundstage that possesses a great amount of air while still having a decent intimacy for vocals. Headroom here is spacious with no boxiness whatsoever but I do realize that the isolation here isn’t as good as some IEMs albeit still isolates pretty well. Their sound placements are accurate and give a 3D, holographic sound with directions of sound easily distinguished making them a good pair for gaming and movies but it may lack immersion.

Separation and Timbre

Separation is impressive and probably the main strength of the NM25 as they are able to provide spot on imaging with a wide stereo width that separates the channels in great accuracy and finesse usually found in IEMs above their price range. The sound here is full and possesses a wide dynamic range with a coherent sound as expected of a single dynamic driver. Safe to say that there are no crosstalk or coherency issues and they scale up even better in this region with balanced outputs. Timbre is neutral with a piercy, bright and breathy signature that aims to reproduce sound as intended without any coloration but for those who seek a warm, coloured sound might want to look elsewhere.

Drivability

Rated at 32 ohms with a 108 db sensitivity, they are an easily driven IEM with sufficient volume even with a simple dongle and will scale better with cleaner source. Their revealing, transparent sound actually gives them the capabilities to show even minor flaws in recording which makes them a great pair for editing and monitoring as well as for those critical listeners but isn’t really suitable for casual listeners with low bitrates files like certain streaming sites or YouTube videos albeit still possible. In terms of scalability, the NM25 doesn’t really scale up much with powerful sources but they tend to match a balanced neutral to warm source such as AKM, Cirrus Logic and Burr Brown but with certain Sabre based chipset with the infamous “hump”, the treble and timbre will suffer from being too unnaturally piercy.

The Bass (Low)

The bass on the NM25 is a neutral bass that is almost flat as they do seem to possess a mild mid-bass lift that gives the bass some authority when called upon and they have a decent amount of energy. The amount here is actually natural or correct that shows the bass is intended but the bass is still able to have its dynamic presence. Details here are superb with great texture that audibly shows layers of the bass in a clean, clear manner that is free of any bloats and they have no bleed issues with their controlled bass. The pace here is quick and nimble with a tight slam that has a slightly fast roll off giving a clean bass decay. The amount here is certainly not for bassheads as they don’t have a lingering bass rumble and they may come off as light in weight notes in this region but perfectly suited for its purpose of being a true monitoring IEM. Sub-bass here has a good depth that is natural with a clean but slightly soft rumble that has its presence. Overall, a true purists bass without being anemically light in amount.

The Mids

The midrange here is again a neutral flat type of midrange that has a slight climb towards the upper region that gives the overall bright tone of the NM25. The amount of detail here is spectacular that punches well above their asking price into the flagship territory. Their ability to display macro details in a clean and clear manner alongside superb micro details retrieval is respectable with every single note presented in a transparent manner. Their accuracy here is also great with a natural timbre that has near to no coloration present while still having a mild vividness that resolves well. The midrange here isn’t a warm, thick type of midrange which may deter some users who seek a more immersive midrange but a perfect pair for purists or professional usage as they reproduce the mids as faithful to the original state as possible. The vocals here are breathy and possess a good amount of brilliance that suits female vocal tremendously and a clean, natural vocal for male’s vocals but they aren’t the type that has thick or deep. Instruments sound natural and they perform well especially with strings, percussions and high staccato instruments but not so much for drums or some low emphasis stuff.

The Highs

The high range here is a mildly boosted type of highs with a small amount of peak that extends from 8khz all the way to 15khz region and they are energetic and mostly inoffensive while having a good extension that mimics a piezoelectric tweeters without the pierciness. Details and clarity here is superb with a strong, clean sparkle and a superb crisp decay producing a fun overall high range for those who love a strong amount of high range. Though being boosted, the high range actually manages to sound natural with a clean timbre that portrays high nuances well without any sibilance of inoffensiveness albeit it is bordering both of those aspects and that being said, those who are treble sensitive might want to take note on the high range strength. The extended high range gives the overall sound a decent amount of air that creates a livelier overall sound that makes music more enjoyable. Treble here has a decent dose of intensity that contributes to the overall clarity of the NM25 while still staying within the realm of accuracy.

Comparisons

VS Twistura Wood Note (169 USD)

The current flagship of Twistura, which is an upcoming brand from China and they are fitted with a rather unique dynamic driver diaphragm which is wood based that is similar to the JVCs and they cost slightly less than the NM25 at 169USD. Their build is similar to an all metal based shell but the Wood Note has the inclusion of tuning nozzles for a more flexible sound albeit marginally.

The high range on both is very similar with a strong, piercing high range but the NM25 does sound airier with a smoother, crisper decay. Details and clarity here is similar with a stronger treble on the NM25 making the clarity perceived as better. The high range on the NM25 does sound a tad more refined.

Midranges on the Wood Note Nite do sound slightly thicker and they do have more warmth present with a more forward mids that has very mild coloration. The NM25 does have the edge in details but their clarity here seem on par with each other. Transparency on NM25 is better while the Wood Note is slightly more resolving. Female vocals on NM25 are livelier while the Wood Note has better balance.

Bass quantity on the Wood Note is greater with a bigger mid bass lift that gives more meat into the bass but only marginally as the Wood Note bass amount is still relatively low from a bassheads perspective. While the NM25 bass is more accurate with a more natural amount, it does lack extension like on the Wood Note. Sub-bass amounts on both are similar but the NM25 seems to possess more air. Pace on the bass of the NM25 seems a tad faster but has a faster roll off that makes the bass sounds a tad polite

The soundstage on the NM25 is wider and taller with better air and their headroom is also slightly but both sets have no boxiness issues.

Verdict:  NM25 for their pure performance but the Wood Note does sound slightly more fun

VS Tigerism Dark Magician Revised (499usd)

A revised classic flagship single dynamic driver from Tigerism or previously known as MIM audio, the Dark Magician. Equipped with a single carbon nanotube driver and they are indeed pricier than the NM25. The tuning is a well balanced neutral sound that is velvety, airy and luscious. The packaging is rather barebone but the included accessories are high quality.

High regions amount and strength is dominant on the NM25 with a noticeable boost that has a stronger, livelier and crisper sparkle and on the other hand, the Dark Magician has a smoother approach, almost laid-back style of presentation with more air and naturalness. Details are slightly better on the NM25 but clarity is similar. Treble on NM25 is more intense while the Dark Magician is more balanced.

Midrange on the Dark Magician is thicker, more forward and has a fuller body with a mild lean towards the lower region giving a deeper sounding midrange. The NM25 mids do sound brighter in the upper mids and have more brilliance and clarity while details are similar. Vocals are more balanced on the Dark Magician but aren’t as lively as the NM25.

Bass quantity on the Dark Magician has a bigger mid-bass lift with a more evident slam that possesses better energy alongside a stronger sub-bass rumble but depth on both are similar. The NM25 bass seems more natural but isn’t as organic. Details and clarity here is slightly better on NM25 while extension and air on the Dark Magician does sound better.

The soundstage on both has great width and height but airiness is on the Dark Magician side.

Verdict: NM25 for their amazing value proposition and higher technicalities while the Dark Magician for their pure dynamic sound allure.

Synergy

For synergy, I would recommend pairing them with a warm to balanced source to mitigate the high treble intensity while also providing some extra warmth for it to be more enjoyable than it is. Source chipsets such as AKM, Cirrus Logic and Burr Brown are highly recommended but not much can be said for untamed glare of the Sabre based chipset. Amplification is not a must for the NM25 as they do not need massive power to perform but a clean source can actually make their technicalities almost, if not at the flagship realm. Their super resolving sound actually binds them to file selections and a well mastered, high bitrate tracks will indeed perform better but still doable with normal files.

Suitable genres/usage: Acoustics, rock, pop, instrumentals.

Not suitable genres/usage: EDM, metal, ACG, hip-hop.

Good pairing

FiiO BTR7, Qudelix T71, Questyle M15, 7HZ Artemis39, Hiby FC6, EPZ TP35, IFI Diablo, Hidizs S8 Pro

Not so good pairing

FiiO Q7, FiiO KA5, EPZ TP30

Who Is It For?

The NF Acous NM25 is for those who love a strong yet inoffensive high range that has a great overall neutrality alongside top class technicalities performing above their asking price in this region. It is a true in-ear monitor that possesses a transparent and revealing sound suited for audio monitoring, live stage and also purists audiophiles out there. Trebleheads will find these tuning alluring but the same can’t be said for bassheads. Details lovers will find the NM25 more than adequate but for some casual users may find them fatiguing. Vocals on these IEM is truly one of the liveliest and most accurate. Gamers will love the soundstage accuracy but it may lack immersion especially for movies.

Final words

NF Acous are getting better and better especially this year and proving with just a well implemented dynamic driver, they have the capabilities to fine tune them into some truly special and it shows with the NM25. It really caught my attention by having top tier technicalities, monitoring sound without being too sterile and the refinements they made in a matter of months is respectable. Some caveats like a piercy treble and fast roll bass are rather preferential and some minor things like the case or cable are rather nitpicking at this point. A salute for the evolution of NF Acous and I am looking forward to what’s in store for them in 2026.

I would rate the NF Acous NM25 a solid 4 and a half stars for their monitoring sound quality in their price range.

Pros

• Solid build, full metal designed with an ergonomic shell
• Superb technicalities with a masterclass in dynamic driver tuning
• Neutral tuning, almost reference
• Top tier details and clarity
• Expansive soundstage and headroom
• Accurate, breathy, piercy timbre
• Quick, tight, accurate bass response
• Flat, clean neutral midrange
• Natural amount of midrange body
• Amazing sparkle with great crisp decay
• Revealing transparency and highly resolving
• Easily driven
• Intense treble that has great extension
• Fair pricing for a high quality professional IEM

Cons

• Carry case a little small (nit-pick)
• Treble might incur fatigue with bright source and high volume
• Bordering sibilance
• Midrange slightly dry and cold
• Not for bassheads
• Not a highly musical, immersive pair of IEM (expected for monitoring purposes)
• Convex connectors with normal 2 pin polarity (subjective)
• No 4.4mm terminations (nit-pick)