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Oct 218 min read

NF Audio (Acous) RA15 - For Those Who Like to Tip Roll & Cable Swap - Honest Audiophile Impressions

NF Audio, now known as NF Acous, has produced a range of products across different price points throughout the years. Among these products are in-ear monitors (IEM) that have been specifically designed with a neutral tuning in mind, and the RA15 is no exception. Achieving an audiophile-level neutral tuning is a challenging task, and not all products are able to do so accurately. Can the NF Audio (Acous) RA15 deliver on this front?

Purchase:


The NF Audio will set you back $90 from your bank account. The RA15 is equipped with a dual cavity dynamic driver, boasting an impedance of 32 ohms, a sensitivity of 108dB, and a frequency response spanning from 10Hz to 40kHz, complete with tuning filters.


HifiGo (non-afilliate link):


Simgot LC7 (non-afilliate link):




TRI Clarion (non-afilliate link):


Spinfit W1 (non-afilliate link):


Specifications:

Box/Contents:

The NF Audio (Acous) RA15 is packaged in a black and orange box featuring a picture of the RA15 with branding on the top.

The back of the box displays more images, while the specs are listed on the bottom.

Inside the outer sleeve, there is a black box housing the familiar NF Audio (Acous) CD disc display of the RA15.

Within this box, you will find a square compartment containing the MS42 wide bore silicone tips (XS/S/M/L), a faux leather carrying pouch, the cable, and the alternate tuning filter.


Build/Design:

The NF Audio (Acous) RA15 features a stainless steel shell designed in a sideways teardrop shape. Although compact, they tend to be slightly heavy.

The front showcases an indented faceplate with NF Audio branding, while the back boasts a smooth stepped design.

The nozzle has an aggressive angle and is relatively short in length. This design might pose fitting challenges for individuals with larger ears or those requiring deeper nozzle insertion.


Cable:

The standard cable is rather ordinary in quality. While it has a pleasing appearance, it is notably thin and lightweight. The cable tends to tangle easily and often appears twisted. Many, myself included, are not fans of the 2-pin QDC connectors used. It features a 3.5mm termination.

The ear-hooks are quite aggressive, curling in on themselves. In general, the cable is functional but lacks any remarkable features.


Tips:

NF Audio (Acous) comes with a set of MS42 wide bore silicone tips in sizes XS/S/M/L. While these tips may suit some IEM models, they are not compatible with the RA15 due to their shallow design which barely reaches the filter at the end of the nozzle.

Most users, particularly those with larger ears or needing deeper nozzle insertion, may find these tips unsuitable.


Fit/Comfort/Isolation:


Unfortunately, the fit, comfort, and isolation are sub-optimal with the standard accessories.

The ear-hooks on the stock cable are overly aggressive, causing the RA15 to be pulled out of my ears.

Additionally, the shallow-fitting MS42 tips fail to seal properly, resulting in nonexistent isolation from surrounding noises.

Consequently, I could only tolerate wearing them for approximately 5 minutes before becoming irritated with the entire experience.


Alternatives:


Fortunately, an alternative cable and ear tips can enhance the inadequate fit, comfort, and isolation problems. I discovered that using sturdier cables with a moderate level of tension improved the stability of the RA15. Additionally, longer tips compared to the shallow MS42 tips not only aided in securing the fit but also in achieving a proper seal, resulting in effective noise isolation. An additional point to consider is that broader bore tips contribute to a more spacious sound, while narrower bore tips enhanced the bass and upper mids/lower treble.

I found that using either the DUNU Lyre Mini or Simgot LC-7 cable with the TRI Clarion, Tangzu Sancai Wide Bore or Spinfit W1 tips significantly enhanced isolation. While the RA15 may not excel in this aspect, with different tips and improved stability, they are likely to block out approximately 55% of external noise. This will dampen louder noises like coffee grinders, vacuum cleaners, and loud vehicles, although not completely eliminate them. In terms of comfort, there was a remarkable improvement, as I went from feeling frustrated after 5 minutes to being able to enjoy a listening session for about an hour before any discomfort arose.


Source Pairing:


When using the NF Audio (Acous) RA15, you will quickly notice that they are easy to power but very picky with the sources they are paired with. The RA15 has an impedance of 32 ohms and a sensitivity of 108db. I found that all the USB-C dongles I tried could easily drive the RA15 to high volumes, but many of them produced a sub-optimal listening experience due to their neutral or analytical sound signature. The RA15 delivered a much more enjoyable sound when paired with a warmer source. Whether connected to a desktop setup or a Digital Audio Player (DAP), the RA15 performed adequately, emphasizing the preference for a warmer source pairing.


Tuning Filters: NF Audio (Acous) provides two tuning filters for the RA15.

The stainless steel (Bright) filter is pre-installed, while the brass (Warm) filter is included in the package. These filters significantly alter the sound characteristics of the RA15. The bright filter enhances the mid and treble frequencies, while reducing note weight, resulting in a colder and more direct sound profile. On the other hand, the warm filter enhances note weight, adds some bass impact, and softens the directness of the mid and treble frequencies.


THA Review Process:


THA Terms & Definitions:


Some Gear Used to Review:


Peridioc Audio Rhodium

Hiby FC3

Hidizs XO

AFUL Snowy Night

Tanchjim Space

Fosi Audio DS2

Aune Yuki

Fiio KA17 Fosi Audio DS1

Hiby FC4

Hidizs S8 Pro

NextDrive Spectra X

xDuuo XA-02

Mytek Liberty DAC ii

Fiio K9 AKM

Fiio K19

Hiby R5 Gen2

MuseHifi M5 Ultra


Sonic Impressions:


What is the sound presentation of the NF Audio (Acous) RA15? All sound evaluations were conducted using the default cable, the brass (warm) tuning filter, and the Spinfit W1 ear tips.


Bass:

Upon first listen, I suspected that the lack of bass I perceived was due to an inadequate seal. Having tried different cables and ear tips, I proceeded to listen further but remained underwhelmed by the bass. The bass lacked impact, depth, and enjoyment. Upon switching to the brass filter, the bass slightly improved. My initial disappointment with the bass, particularly with the bright tuning nozzles attached, persisted. If there is warmth in this bass, it is not readily discernible when listening to any track. The warm nozzles emphasize mid-bass, but the response feels shallow and constrained. The lack of sub-bass results in a feeling of insufficient depth and authority. While the bass is defined, it lacks fullness and impact. With the warm nozzles, the bass is somewhat present and kinda satisfying, yet it often feels restrained. It strives for quality over quantity but does not excel in either aspect.

Mids:


The midrange is characterized by its cleanliness and attention to detail. Instruments and vocals are able to shine with fullness and clarity. While the midrange is more prominent than the bass and exudes a high level of energy, the upper-mids stand out with their vibrant energy, bordering on being overly bright and sibilant. Keep in mind that this impression is made with the warm filter; if you prefer a very forward, lively midrange, you might want to experiment with the stainless steel (bright) filter. Despite its idiosyncrasies, the midrange offers some positive aspects, delivering an engaging and energetic listening experience for its price point.


Treble:

Irrespective of the type of tuning filter in use, the RA15 consistently displays vibrant, intense treble. When utilizing the warm filter, the vibrant, intensity is primarily concentrated in the upper-mids and lower treble. Conversely, when employing the bright filter, the brightness and intensity spread throughout the entire treble range. The treble is not suited for those seeking a subdued experience; it is forceful and assertive with the bright filter, while it becomes more enjoyable with the warm filter. In my opinion, the highs are more listenable with the warm filter, as the tone remains vibrant and intense but the peaks are slightly more controlled.

Technical Abilities:


The NF Audio RA15 impresses with its sound stage capabilities, offering ample width to easily showcase the nuances of different venues. The depth of the stage enables you to hear multiple rows in, while the layering provides sufficient air and space for each instrument and vocalist. Imaging accurately tracks from side to side, although it may not be the most precisely focused like a laser pinpoint. Detail retrieval is really good for the price, you won't miss anything even if you aren't exploring new details. Resolution of the details is top notch for the price. However, the tone and timbre lack naturalism; the note weight is thin and light, the heightened midrange and treble make the tonality seem artificial and strained, resulting in a lack of natural reproduction of instruments and vocals.


vs Tanchjim 4U:


The Tanchjim 4U with the natural tuning filter offers more accuracy and naturalism in tone and timbre, along with increased body and note weight. It exhibits reduced aggression and elevation in the midrange and treble, while delivering more impactful bass. On the other hand, the RA15 boasts a broader soundstage, comparable imaging and layering, and slightly superior detail and resolution. The 4U provides three enjoyable tuning filters - pop, atmosphere, and monitor - in contrast to the RA15's bright filter, which is very displeasing to the ear. In general, the Tanchjim 4U offers a more accurate, natural sound compared to the RA15. The Tanchjim 4U serves as an affordable stage monitor, while the NF Audio RA15 lacks a clear identity..


Conclusion:


Achieving an audiophile-level neutral tuning is a challenging task, and not all products are able to do so accurately. Does the NF Audio (Acous) RA15 deliver on this front?

The NF Audio RA15 stands out as an intriguing IEM due to its remarkable technical prowess and lively midrange and treble. However, the engaging and energetic sound presentation leads to an aggressive and tiring listening experience, lacking in the natural rendering of instruments and vocals. While adjustments like cable changes, ear tip variations, and equalization can be made to tailor the sound to be more listenable, one may question the need for such modifications. Although the NF Audio (Acous) RA15 may be well-received by some, it did not resonate with me personally. While I acknowledge the positive aspects of the RA15 such as detail retrieval, resolution, stage width, depth, and layering, I find its tonality and aggressiveness to be overwhelming for my taste. If you seek a more balanced and natural sound, there are alternative choices available.


I am Dave the Honest Audiophile. Thanks for reading, and I will catch you in the next one. Don't forget to enjoy the music and that honesty is the BEST policy!


I am not a professional sound engineer, producer, musician, or vocalist, etc. I have not done any scientific research, measurements, or in-depth testing of any kind; just my own listening, comparing and internet reading/research.  I have limited, real-life experience with recording, mixing and mastering gear.  I have been involved since my teenage years with various churches as an amateur sound booth technician.


Please take these thoughts, opinions and reasonings as just that, my honest audiophile thoughts, opinions and reasonings.


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