TRN Shell review: Mirror liquid metal and hybrid quad-driver design

TRN recently launched an in-ear earbuds with a similar appearance style to TRN Conch – TRN Shell. It features an acoustic architecture design with three dynamic drivers and one planar driver. The earbud cavity is crafted using an electroplating process, giving it a very refined appearance.

TRN Shell Specs and Features:

Streamlined shell design & Liquid metal cavity
Triple dynamic driver + planar diaphragm driver
Four-strand silver-plated hybrid replaceable cable
2Pin detachable cable design
Interchangeable nozzle design
$60 – Check latest price on AliExpress, Amazon US, Amazon Germany or other Amazon countries

Design and Comfort

The appearance style of TRN Shell reminds me of another low-end model – “TRN Conch“. Both share a silver, metallic, mirror-finished look, but the TRN Shell’s liquid metal craftsmanship offers higher gloss, more uniform electroplating, and stronger visual contrast.

The cavity is made of liquid metal with an electroplated, polished surface that reflects light exceptionally well. During my time using it, no noticeable scratches appeared, though minor bumps may occur with prolonged use (it is indeed easy to leave fingerprints). The gap between the front and rear cavities is relatively uniform, and there is no problem with the workmanship details.

The inner side of the cavity features a relatively regular curved surface, and the fit is average. For those with smaller ears, there’s no strong sense of pressure, though the cavity may feel slightly suspended. Stability is decent, with all coupling concentrated near the eartips and nozzle base. The comfort is quite good, but side-lying wear is not recommended. The earbuds don’t exhibit noticeable air pressure balance issues, and the passive sound insulation ability is average.

The interchangeable nozzle design is a relatively thorough solution. Removing the nozzle reveals no additional damping, just the front drive unit’s cover plate. The default green-ring nozzle has a smooth inner wall with no special structure, paired with a front metal cover plate and a layer of fiber damping.

Headphone Cable and Accessories

The Shell comes standard with a four-strand silver-plated hybrid replaceable cable. Each strand consists of 89-core high-purity oxygen-free copper and silver-plated Litz wire. The cable is slightly thick but offers good flexibility and easy storage. It includes two interchangeable plugs: 3.5mm single-ended and 4.4mm balanced.

The replaceable cable system is based on a 0.78mm 2PIN structure. The included waterproof storage case is excellent, it doesn’t take up too much space, and the storage space is just right.

The TRN Shell comes with various eartips made from different materials, with varying inner diameters and hole sizes. Combined with the three acoustic nozzles, this theoretically allows for extensive sound adjustments. Experienced audiophiles can make significant tweaks to the energy of different frequency ranges, imaging, and soundstage size/distance while maintaining the fundamental tonality. The sound review below is based on the transpareny silicone eartips and the reference nozzle.

The two alternate nozzles differ from the default one only in damping density – their shape, inner diameter, length, and material are identical. The red-ring nozzle has higher damping density than the black one.

Acoustic Architecture and Driving

TRN Shell is equipped with a hybrid four-unit structure with three dynamic drivers and one planar driver. The low-frequency is handled by a 10.5mm beryllium-plated diaphragm dynamic driver. The midrange features an 8mm PET diaphragm dynamic driver. The treble is driven by a 6mm titanium-plated diaphragm dynamic driver, while the ultra-treble is managed by a 6mm micro planar driver.

In actual listening, this hybrid quad-driver system delivers relatively consistent tonality – firm and fast across the board. The transitions between frequency ranges are decent.

The earbuds have an impedance of 16Ω and a sensitivity of 110dB/mW. The Shell is relatively easy to drive, with most entry-level mini headphone amplifiers capable of delivering good volume and fullness.

Sound Quality of TRN Shell

Tested with the green-ring nozzle, liquid silicone eartips, and the stock cable in 4.4mm balanced plug, meeting the necessary driving conditions. The general sound characteristics are: solid and full vocals, grand bass, delicate and natural treble, rich weak sound details, reasonable brightness, and a smooth overall tonality.

Bass: Moderate in quantity, slightly thick, with controlled fullness. The bass has good elasticity and extension, with abundant sub-bass detail. The speed of retraction and release is moderate, and the reverberation is not much. Overall, the bass is clean and not overly emphasized energy.
Midrange: Vocals are moderately thick, slightly forward, with a smaller-than-standard mouth size. Since the mid-bass is handled by two different dynamic drivers, the imaging solidity isn’t particularly high, with no clear bias toward texture or lines.
– Female vocals perform better than male vocals, suiting brighter, less thick voice types. Graininess is minimal, and vocal smoothness is high. The tonal coloration is subtle, with no obvious artificiality. Sibilance is polished, noticeable only in certain tracks. The vocal transparency is excellent.
Treble: The brightness is moderate. Thanks to the treble dynamic driver, overall smoothness is good, with only slight peaks. Ultra-treble extension is strong, rolling off a bit quickly but not prematurely.
Instruments: Most instruments strike a balance between texture and lines – neither overly thick nor overly sharp, presenting a smooth performance.
– Violins, violas, and guitars exhibit high delicacy. While thickness isn’t emphasized, the plucking and bowing details are impressive for the price.
– Cellos are slightly softened, avoiding a harsh presentation.
– Brass instruments deliver decent grandeur, with trumpets having appropriate brightness.
– Woodwinds sound natural, with slightly enhanced airiness and accurate tonality.
– Instrument harmonics are abundant but not overly prominent. For percussion, kicks aren’t overly dominant, snares are quick, and cymbals have brightness with a slight metallic edge.
Soundstage: Neither width nor depth feels cramped, though the layout isn’t highly structured, and edge clarity isn’t emphasized. Vocal-instrument separation is good, with only slight stickiness. The resolution is outstanding, with a mild “resolution” touch. Dynamics are strong, while transients are average.

After several days of testing with different eartips, nozzles, and playback devices, I found that aside from a slight excess in the vocal low-frequency range (around 100Hz), which might make vocals sound less “refined” at high volumes, everything else is well-tuned. Though the bass is notably rich, the overall tonality remains pleasant and natural.

Conclusion:

Compared to the TRN Conch, the TRN Shell places greater emphasis on bass quality – transitioning from one dynamic driver to three dynamic drivers + one planar driver brings significant changes and clear improvements in sound framework. For now, the Shell can be recommended to audiophiles who enjoy electronic music and female vocals.