TRN BAX Pro Review

TRN BAX Pro Review

TRN BAX Pro Review – 1DD+2BA+2EST Flagship IEM

TRN welcomes its latest flagship set of multi-driver hybrid in-ear monitors with the launch of the new TRN BAX Pro. This flagship IEM features a five-driver hybrid setup on each side bringing together a fourth-gen dynamic driver with dual Knowles BA and dual Sonion EST drivers.

TRN BAX Pro now features an upgraded configuration that incorporates advanced electrostatic, dynamic, and balanced armature units, complemented by a customizable design. This enhanced setup has resulted in several notable improvements.

TRN BAX Pro Review
Matte black, finally.

The enhanced high-frequency unit now boasts dual Knowles balanced armature units and an overall enhancement in audio quality.

The use of imported electrostatic units has extended the frequency response range and elevated sound quality to new heights. With two electrostatic units, BAX Pro precisely captures and faithfully reproduces high-frequency signals, resulting in a more transparent and refined auditory experience. Notably, the high-frequency performance stands out.

TRN BAX Pro Review

TRN BAX Pro also incorporates a fourth-generation dual-magnetic low-frequency dynamic driver unit. This 10mm dual-magnetic large dynamic unit excels in terms of frequency response and dynamic range. It delivers clear and robust bass with a rich atmospheric quality, thanks to the beryllium diaphragm that offers exceptional rigidity and response speed.

In the mid to high-frequency spectrum, BAX Pro introduces the new Knowles 33518 dynamic driver dedicated to high frequencies. This addition enhances high-frequency clarity, infusing the overall sound quality. Coupled with the 29689 mid-frequency dynamic drivers, it extends mid-frequency details and layering.


With an electronic three-way technology and a three-stage tuning switch, BAX Pro offers six adjustable tuning styles.


BAX Pro now incorporates lightweight materials, reducing the earphones’ overall weight by 35% without compromising quality. Crafted from an aluminum-magnesium alloy, known for its remarkable strength and corrosion resistance.

The semi-open face cover design alleviates pressure, guaranteeing a relaxing and enjoyable listening experience.

TRN BAX Pro Review

TRN BAX Pro comes bundled with a high-purity stock cable. The pair includes an eight-strand monocrystalline copper cable made with high-purity 6N single-crystal copper material wire cores.

TRN BAX Pro Review

This cable has a swappable termination plug system with 3.5mm, 4.4mm, and 2.5mm plugs included in the package.

What’s in the box


  • Ultimate Flagship-Level Hybrid IEMs.
  • Five-Unit Hybrid Structure(2BA+1DD+2EST).
  • Six Tuning Modes with Three Tuning Switches.
  • Fourth-Generation Dual-Magnetic Beryllium Diaphragm Dynamic Driver.
  •  High Resolving Electrostatic Units by SONION.
  • Dual Knowles High-Performance Balanced Armature Drivers.
  • CNC-Machined Aluminum Magnesium Alloy Cavity.
  • Pursue Impeccable Sound Quality.
  • Eight Strand High-Purity Single-Crystal Copper Cable.
  • 2-Pin Detachable Cable.
  • Swappable Termination Plug.
  • Comes With 3.5mm+2.5mm+4.4mm Plugs


  • Jack type: 3.5+2.5+4.4mm
  • Wear: Ear hook
  • Earphone topography: Quad-driver, Triple-hybrid
  • Frequency response: 7Hz-40000 Hz
  • Connector type: 2Pin
  • Sensitivity: 114dB
  • Impedance: 32Ω
  • Cable length: 1.2m+3cm
  • Weight: 8.7g
  • Price: $382

I would like to thank TRN Audio for providing me with the review sample of the BAX Pro


TRN BAX Pro Review

The first thing that hit me with the TRN BAX Pro sound signature was the speedy, vibrant, and slightly bright top end (depending on the switch) with a full but rather neutral-toned bass response and a somewhat smooth midrange response that is a couple of decibels restrained compared to the top and bottom extremities.

The TRN BAX Pro tuning reminds me so much of one of the latest IEMs I reviewed which also has a rather large millimeters dynamic driver for bass but the BAX Pro treble is more refined and controlled.

TRN BAX Pro Review

I do like the fact that TRN showed some restraint in controlling those Sonion tweeters fairly well. Being familiar with the Sonion tweeters I can attest that the treble can easily get out of hand and be piercingly intense but it’s not so much in this case.

There is a very slight U-shaped signature here but I would consider it a fun amount of tilting and not overly done to mask the midrange becoming too unbalanced sounding or tilting too far from neutral.

TRN BAX Pro Review FR Graph

The original BAX had a peak (around 5khz) and certain recordings can come across as a bit shrill. This is punctuated by the mid treble boost adding any edginess to percussive hits. The bottom line for the treble is that it can get a bit aggressive at times. This is fixed with the BAX Pro with the standard tuning. Also, the treble extension above 10K is present with the Pro.


I tested the TRN BAX Pro with all switches off (so-called Equalization mode).


At first glance, the TRN BAX Pro looks decent. You get a moderately thick rise into the sub-bass, meaning there will be enough versatility and warmth here for a wide variety of genres – at least when it comes to bass tones. I would’ve preferred a more distinct sub-bass shelf for a cleaner transition into the lower mids, but I can see a preference for this type of warmth as well.

TRN BAX Pro Review

There is a slight amount of emphasis in the bass on the TRN BAX Pro, but the bass tonality has a typical characteristic that Beryllium drivers have which is a speedy and fast-responding bass that can keep up with fast-paced music.

Fast and heavy kick drum and the BAX Pro kept up with the fast pace very well while remaining deep and well-behaved with a nice visceral feel behind every kick.


The TRN BAX Pro midrange is fairly smooth and well-presented. There is I would say a rather high amount of detail. These dynamic Beryllium drivers if are producing most of the midrange have a pleasing tone in my opinion with definition, clarity, and realism and mostly remain on the contrary side of harsh, intense, or bothersome.

The lower mids are appropriate for the overall distance of ear gain up into the upper mids. Often what happens when this distance is too extreme is that vocals can sound a bit lean and hollow, and while the BAX Pro does have a significant amount of ear gain, this distance is kept in check.

TRN BAX Pro Review

I love the way you could hear the vocalist’s lips smack together right before she starts singing demonstrating a good level of retrieving micro detail.

Since the midrange is somewhat restrained the gentle signature TRN aimed for is apparent. The tuning combination with the slight elevation in bass response, smooth midrange, and a somewhat bright top-end make this set a fun listen but a somewhat neutral listen.


The treble response depending on the recording sounds fairly realistic and revealing and as long as you have restraint with the volume control these tweeters can perform fairly well by sounding crisp, and airy with some top-end shimmer but most importantly have a realistic tone that makes the drum symbols sound like symbols for example.

There is some treble emphasis here and it gives this set a slight metallic character sometimes in its sound signature but that could work well. Especially when listening to the taping on cymbals which are made of metal anyway so I guess that is where their realistic tone originates.

TRN BAX Pro Review

Highs don’t necessarily highlight extreme quantity or brightness. It makes sense since BAX Pro is tuned for consistency and neatness. Carried with airiness, highs are articulated that expose fine grains and upper-end layerings but always under one circumstance: keeping things smooth.

When you give it a listen, the trebles may come across to be calmer than expected. But then again, you would soon notice that it was the TRN BAX Pro that the drivers were so carefully and seamlessly fused. Highs show clear EST characteristics yet are carefully integrated with the rest.


With the right song, the TRN BAX Pro can do staging very well and they also have good 3D capabilities by being able to project sound beyond the ear. Height, width, and depth, the BAX Pro is capable of them all. I would not call them very wide but I do notice a larger space on each listener’s side versus front staging. It also seems the midrange response remains the narrowest within the staging.

I was surprised many times with the recordings with some exceptional 3D placement and each song seemed to be presented the way the recording engineer intended. The recording itself presented multi-directionality and precise imaging which was a priority with that recording in particular.

TRN BAX Pro Review

The bass and treble being a touch more prominent in the frequency spectrum tend to have more width within the staging. The treble is the best at staging and imaging. The bass has an omnidirectional aspect to it and seems to come from everywhere as it should.

It seems that the highs are creating most of the three-dimensional information by having the ability to place a note mostly anywhere, while the midrange does have good imaging it does not go too far past the ear or too far forward.

TRN BAX Pro Review


The BAX Pro has one of the best treble performance that I have heard in any IEM. This is another level compared to dynamic and balanced armature drivers. With great extension but it is also very smooth without any sharp edges.

The already very good original TRN BAX has evolved into the Pro variant with better default tuning, added tuning switches to play with, and perfected the design with a matte black color and lightweight shell.

TRN BAX Pro is one of the best IEMs in the market for the asking price, with legit Sonion EST drivers, easy recommendation from me.