Review: Drop X Etymotic ERX Earphone/IEM

Sound Summary

The Etymotic ERX is a cheeky play on the Etymotic formula: a flavour of IEM tailored for broader appeal without sacrificing raw performance. I think this description aptly surmises what to expect from the ERX. Why reinvent the wheel when it ain’t broken?

The ERX has a tiny sub-mid bass rise for thickness and weight in the low-end vis-a-vis the ER4’s original signature. On the top end, the treble region takes a single step back, reigning in the overemphasised ringiness and resonance that some users criticised. But these alterations are very slight, and should not be misconstrued as gargantuan. In short, the ERX takes one step forward in the bass region, and one step back in the upper echelons of the frequency band.

However, it would be completely inaccurate to describe the ERX’s sonic signature as “V-shaped”. The Etymotics ultra-resolving speeds are everpresent, with substantial micro dynamic detailing and clarity across the whole spectrum. Notes, especially in the mid-band, have strong definition and separation, each decaying as fast as it emerges in stanzas of music. The Bass is tonally correct, with a smidgen longer sustain from the tasteful boost in sub-bass regions for a chamber-like experience. The end-to-end extension of the treble on the ER4 is purposefully restricted to curtail the possibility of sibilance and graininess reported by some users.

Nonetheless, the Etymotic house sound proudly remains. The ERX still closely pursues the pathway to ruler-flat neutrality, “telling it as it is” without colouration. Conversely, the ERX is far from just a clinical instrument for coldly picking apart tracks. It’s engaging without being overly exciting. Now, the common complaints raised by audio enthusiasts do not represent the majority of our niche. Instead, it represents the divergent tastes of the diverse fans populating this fabulous hobby. To my ears, the subtle treble tweak does subdue the energetic zinginess that squeezes out detail whilst bordering the possibility of outright brittleness and harshness. It’s not large, but it’s noticeable.

I can’t classify this as an explicit downgrade or upgrade, for that is up to the beholders to decide. Your mileage may vary.


Balanced armatures are not remarkably known for their ability to displace air, a fundamental ingredient for deep bass reproduction. Instead, it leaves listeners with a taut punch that dissipates quickly upon striking. This general rule is 100% applicable to the ER4. It’s present, it’s there, but it isn’t the most exciting. In short, bass heads were forewarned that the ER4 would not tickle their bottom-rumble tastebuds.

The ERX might be an interesting exception to the rule, for it injects a sub-bass-focused cliff for a thicker, meatier bass response. The tasteful complement of sub-bass rumble heightens the perceived realism of timbre. In electronica-themed tracks, this sub-bass flourish is a welcomed addition to what was once a dry -spell in terms of bass weight (from memory at least).

However, no amount of tuning chops can subvert the technical restrictions of balanced armatures. Bass still bears the stereotypical lack of deep-sub-bass rumble and mid-bass slam its dynamic driver brethren can spit out. But what we have is a lean bass response defined by precise hits, followed by a tasteful “echo-like” sustain with planar-like restraint. How this subjective quality affects the grand scheme of things will be discussed in the following section.


The midrange is Etymotic’s bread-and-butter, with the ERX continuing this tried-and-tested tradition. The ERX’s midrange maintains an addictively forward (at least, in comparison to its V-shaped counterparts) midrange presentation. Because of its ultra-resolving dexterity, micro-detail retrieval and tiny microdynamic swings are captured gracefully in an unobstructed image.

Female voicings are front-and-centre in the ERX, alongside mid-forward instruments erring towards the upper-mid and treble registers. Lyrics, in terms of perceptibility, are perfectly legible and identifiable to the ears. These individual elements in the mix are each presented with verve and excitement: weak points commonplace in overly-forgiving IEMs.

The lower mids are not accentuated, nor are they truncated. It’s relatively unblemished for a wholly realistic presentation without the associated warmth and pillowiness that comes from artificial enhancement. This is the Etymotic’s strong suit, and I’m glad to see that the ERX does not stray too far from the ER4 tree.


Etymotic’s house sound also extends to the treble region: a battlefield defined by how much it polarises the most impassioned of audiophiles and enthusiasts. Etymotic’s treble presentation, by mainstream standards, is deeply extended from end to end. By giving it adequate elbow room to breathe, the ER4’s micro detailing in the treble region is within striking distance territory from the “flagship” moniker. This treble presentation has also proven to be a bane for the Etymotic brand, with “harshness”, “shrill” and “sibilant” tossed around as negative adjectives to describe it.

The ERX tones it down a notch, albeit with conservative restraint. There’s a perceptible tapering off in the top end, slightly nullifying the coarser peaks that veer closely to the domain of hissing resonance. While I never experienced considerable levels of sibilant discomfort with the ERX, it still tiptoes along the sidelines of “possible” shriekiness.

Etymotic’s and Drop’s reticence to completely rehaul the treble region was rightly informed. The Etymotic’s hallmark treble response was its original claim to fame. Drastically altering it could lead to a disastrously negative reception from its devoted fanbase.


Because of the ERXs straight-into-your-concha fit, the placement of the drivers vis-a-vis the eardrum is far closer than it has ever been in every floating IEM in the rapidly expanding marketplace. Unfortunately, there is an observable trade-off.

The close distance between the ERXs nozzles and eardrums leads to a closeted-in stage that’s “in your head”. That is not to say that the staging performance is narrowed into a muddled mess. Instead, the standard X-axis width between the L-R channels is difficult to assess or index for in these novel circumstances. Sweeping pans between stay close to the ears, without the horizontal depth that soundstage lovers crave. Listeners who endear themselves to holographic staging capabilities may find themselves disappointed in the ERX’s peculiar presentation.

On the plus side (and a very big one), voicing and instrumental separation is spaciously presented across the horizontal plain. The perceived distance between audible cues exhibits promising depth, where each element is presented independently without converging into one another. Further enhanced by the ERX’s class-leading midrange and treble performance, the distinctive timbres of brass sections and odd-harmonic-focused instruments sound “standalone”.

Because of the ERXs single BA architecture, the faux-separation and artificial segregation characteristic of multi-driver setups is nowhere to be found. Instead, the ERXs imaging presentation maintains strict coherence.

Onto the next page for the rest of the review…



Kevin Goh

Kevin Goh

Raised in Southeast Asia’s largest portable-audio market, Kevin’s interest in high-end audio has grown alongside it as the industry flourishes. His pursuit of “perfect sound” began in the heydays of Jaben in Singapore at the age of just 10 years old. Kevin believes that we live in a golden age of readily accessible, quality audio.


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