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Review: Drop X Etymotic ERX Earphone/IEM

Disclaimer: I would like to formally thank Kyri from Drop for graciously providing us with the Etymotic ERX for review. I am not affiliated with Drop, and the views shared below reflect my honest thoughts surrounding the product.


  • Full-metal jacket design boasts fantastic longevity and build-quality
  • Etymotic signature resolution broadly across the frequency spectrum
  • Class-leading deep treble extension
  • Fast PRAT and resolving transients
  • Excellent layering and positioning of voicings and instrumentation within the stage


  • Proprietary Estron T2 connectors limit cable swapping
  • Included cables lack flexibility and are prone to memory
  • BA-timbre and lack of displaced air in the bass region


Etymotic (meaning: true to the ear) Research has delighted astute listeners for the last three decades with a focused catalogue of IEMs. Originally formed in 1983 by the founders, Mead Killion and Edwin Vildebliss, the titular company was initially focused on the research and development of precise instruments to detect and assess permanent hearing loss.

In 1984, Etymotic Research broke significant waters with the momentous release of their deep-insertion IEMs. Striking when the iron was hot in 1991, Etymotic Research captured lightning in a bottle in the form of the groundbreaking ER4 IEM, fashioned from a pair of high-performance balanced armatures. This watershed debut served as the metaphorical launchpad for following releases, where its following successors can be classified as derivates of their ancient formula. And for better or worse, the Etymotic’s infamous deep-insertion fit has been the mainstay quirk across the board.

Even in modern interpretations of the ER4 in the form of the ER4XR/SR and EVO, its ancestral DNA courses deep. In fact, the “Etymotic” house sound, described to convey “music” as it was intended to sound by studio engineers, stays the course, albeit with new flair to cater to a diverse array of sonic palettes. Based on first-hand research, prevalent fanfare suggests that all their releases following the ER4 have been more-than-favourable.

In the last two years, Etymotic Research (purchased by Lucid Research in 2013) and Drop, an e-Commerce company noteworthy for its affordable-but-competent product collaborations in niche sectors, shook hands to release a new breed of “Etymotic” IEM for a humble price. Both partners strategically sought to harness the gentler fit of the EVO’s contours with the single-balanced armature topology of the ER4 series.

And these deliberate modifications were not just limited to cosmetics or ergonomics but to the flavour of the sound. Both companies add a minuscule boost in the bass sub-registers, appealing to a broader base of consumers with a penchant for bass-forward mainstream music. These sweeping changes culminated in the Drop X Etymotic ERX, a product borne out of a healthy partnership between community-celebrated companies.

The Etymotic ERX is sold exclusively on Drop for $229 (originally $299). Today, we dive deep into its inner workings to see if it is worth its salt amidst the intensifying portable audio competition.


If you’re familiar with the Etymotic brand, then you shouldn’t be surprised that the ERX utilises a single full balanced armature on each channel. Balanced armatures, originally intended for usage in pacemakers, are measurably resolving and mid-range forward in their presentation, decaying rapidly for a clean finish.

Their architecture comprises a diaphragm in a see-saw configuration, vibrating upwards and downwards in a small rectangular chamber. Typically, balanced armatures are harnessed in multi-driver arrays, utilising either active or passive crossovers to relegate segments of the frequency band to different drivers. Typically, balanced armatures, while highly resolving, struggle to represent the full spectrum of frequencies if used individually.

However, the immutable caveats of the multi-driver schema are possible phase issues and transient smearing from timing delays between each one. Overall sonic coherence tends to suffer in poorly-implemented configurations as well. Etymotic Research mitigates this pressing issue by opting for one balanced armature instead of multiple on either side.


The ERX package could be described as minimalist rather than maximalist. The black cardboard box it comes shipped in is rather sparse, save for a blueprint-style print of the ERX on the top lid, and its accompanying specifications and inclusions at the base of the box.

Upon lifting the box’s top lid, you’ll find the package has been conveniently segmented into subdivisions containing the following: the Cordura hardshell carry-case (containing the ERX and the attached Estron T2 to 3.5mm unbalanced cables) in the “ERX” labelled section, and miscellaneous earwax guards alongside a removal tool, and a mix of Etymotic’s ear tips in silicone and foam in the “accessories” section.

It’s a straightforward package that covers all possible use bases for years of service.

Design, Comfort and Durability:

On first impressions, the ERX shells are surprisingly hefty: a characteristic accurately attributed to their machined stainless-steel jackets. The ERXs are only available in an all-black colourway, achieved using a polyvinyl deposition (PVD) technique for an even coat. The injection-moulded shells are some of the best built at the price point, reminiscent of the no-nonsense, overbuilt shells designed by Campfire Audio. Sharp-eyed observers would’ve noticed the ERXs uncanny resemblance to their flagship multi-driver IEM, the Evo. And they’d be right! The difference I could identify is the shrunk-down silhouette of the ERX, but it still retains the svelte profile of the EVO.

And of course, we can’t overlook the infamous deep-insertion nozzles. For the uninitiated, Etymotics, to the chagrin of a select few, require you to bore the nozzles ground-deep into the untouched recesses of your inner ear. Jokes aside, Etymotic’s novel insertion depth enables it to achieve unparalleled levels of isolation of 35-42dB: an introvert’s dream turned reality. I can substantiate this lofty claim with my firsthand experience.

And because balanced armatures do not displace or propel a voluminous amount of air, the ERX has zero need for venting, the ERX is the best isolating IEM I currently have circulating within my personal collection. The ERXs deep insertion depth did not prove to be a point of contention with my ears, sitting snugly and comfortably. The ergonomics of the ERX are excellent, sitting in my outer ear with zero discomforts.

Cable Quality

As mentioned earlier, the ERXs utilise an uncommon connector type, the Estron T2. Proprietary connectors restrict the user from tailoring the ERX sound profile to their preferences via cable-switching. The biggest downside of this decision is the monopoly Estron has over the availability of aftermarket cables with the discussed connectors. If the provided stock cables either shear or break, the widespread inaccessibility of the T2 connectors forces users to purchase replacement cables from a select few manufacturers. And they don’t come cheap.

The included T2 cables, sadly, detract from what is a competent design. The T2 cables, to my dismay, bend and crease with the slightest pressure, rendering it difficult to uncoil or coil neatly for storage. Microphonics are fairly present, with cable noise proving to be an unwelcome distraction. This phenomenon is especially annoying on my daily commute amidst external surroundings. The explicit thinness of the wire gauge used strikes me as a possible point of mechanical failure in the near future.

The ubiquity of the ER4’s MMCX connectors should have stayed on in the releases following it, including this one.

Onto the next page for details on sound…



Picture of 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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