Etymotic MK5: Isolator, Reborn.

If you’ve been in this portable audio hobby for any length of time, then you’re aware of Etymotic Research. The Ilinois company, founded by Dr. Mead Killion, is legendary. Its flagship ER4 models (of which there are three variants) are a true mainstay in any portable listener’s collection. It has been tested and verified both by professionals and hobbyists alike to be amongst the most accurate sounding in-ears, decades running.

Even as the in-ear segment of the portable market has exploded, however, Etymotic has largely marched to the beat of its own drum. They don’t release products without due purpose, and it has been years since Etymotic last made any additions to its lineup of in-ear audio products — the last ones being smartphone compatible versions of their existing products, along with the EtyKids (EK5) earphone that catered to children with MP3 players. It makes total sense — the firm concentrates on research and hearing preservation, not necessarily on absolute  shareholder return.

So it was a surprise when Etymotic announced the MK5 last fall. As the MK5 is dubbed the ‘Isolator‘, it is, from a marketing perspective, the spiritual successor to the ER6/ER6i (the very first Etymotic IEM to dip under the century mark). However, while the ER6 was a single balanced armature product, the MK5 utilizes a dynamic coil transducer like those of the EtyKids EK5 and the MC5. Interestingly, the MK5 shares overlapping product roles with the MC5, namely in retail price, but differs from it with regard to size.

The Etymotic MK5 Isolator is the company's first new release in years.
The Etymotic MK5 Isolator is the company’s first new release in years.

Why then, did Etymotic bring out the MK5 if it doesn’t seem to fill a new product space? It certainly is a curious question. The answer is probably many-fold.

Firstly, the MC5 is (in many peoples’ eyes) a flawed product, and perhaps the least well-received audio product Etymotic has ever produced. With a large, long barrel, the MC5 produced fit problems for some people, and the sound signature, while true to Etymotic fashion, was not nearly what most people expected. People had come to expect the kind of quick, clean balanced armature sound that the ER4, HF series, and even ER6 series had epitomized. The MC5 had a very similar sound from a frequency response perspective, and Etymotic managed to achieve that response despite using a cheaper dynamic driver, but many others thought the sound to be a bit stilted. When Etymotic released the EtyKids, some audiophiles actually preferred its sound, as well as fit (smaller barrel), to that of the MC5, despite its lower price tag and high impedance voice coil.

However, Etymotic couldn’t really sell the EK5 to audio enthusiasts — there was a marketing paradox. The earphone, as can be surmised from its name, was specifically marketed as a sound pressure limiting earphone (hence the high 300 Ω impedance) to protect kids from excessive SPLs and consequential premature noise-induced hearing loss (NIHL). What Etymotic needed was a low impedance version of the EtyKids.

And yes, the MK5 seems to be just that — thanks to its smaller 6 mm driver, it sports the thinner barrel body of the EK5, and thereby shares similar acoustic resonances with the kid-oriented earphone, but has an all-new 32 Ω driver voice coil. And with that, the MK5 kills various different birds with its one stone; it fulfills the market niche of the MC5 with the added ergonomic improvements of the EK5, at the same time evoking fond memories of their ER6 Isolator series.

Clearly, then, the MK5 Isolator is an important strategic product for Etymotic; as its first product release in years, it needs to score high on a good number of categories.


The MK5 doesn’t come with much, but as a $59 product, it doesn’t need to, either. So for the price, the MK5 is relatively well-appointed, complete with a nylon soft carry case, two tie clips (why two?) a set of small/medium ER38-15SM frost grey triple flange tips, a pair of large ER38-18CLL clear triple flange tips, and a pair ER38-14F cylindrical foam tips.

Fit and Comfort

Let’s start with the bad news. When it comes to Etymotic, fit and comfort have become a polarizing, love or hate deal; people who have a difficult time getting along with the fit pan Etymotic earphones for their deep-fit seal. That’s not changing with the MK5. In fact, Etymotic has long been adamant about sticking with its notorious deep fit in order to provide the industry-leading 36-42 dB of noise isolation that each of its products provide.

Right now, you might be thinking — can’t Etymotic just make a more comfortable earphone by reducing insertion depth? Westone and Shure earphones always seem to both good comfort and isolation ratings! The solution isn’t so simple, however. In order to guarantee the sound quality promised by Etymotic‘s accuracy scores, Etymotic earphones must be inserted to the 2nd bend position of the ear canal, due to the belief that ear canal quarter-wave resonances past the 2nd bend are both predictable and controllable. Even though they’re merely anatomic landmarks within the ear canal, however, they’re called “bends” for a reason, and long, straight barrels just don’t play well with bends. The deep fit is by far the most complained about issue with any listener new to Etymotic earphones.

However, it’s not just the IEM neophytes that take issue with the fit of the Etymotic fit; many veteran IEM users also complain. For me, the issue isn’t the “intrusive” feeling of a deep fit (I wear custom-fit IEMs all the time, as well as other deep-fit universal IEMs), but the long-term comfort.

With the standard size triple flange tips, my small ear canals would end up feeling sore after about 20 minutes; using the softer-textured larger size tips weren’t of any help. The included foam tips were too stiff to insert into the correct 2nd bend position of the ear canal as recommended by Etymotic. Thus, the only way to achieve a perfect fit with the MK5 (or any other Etymotic earphone) would be to get custom-molded silicone tips (but who spends that kind of money on a pair of $59 earphones?) or to use third party tips, such as Comply Foams like the Ts-100 (which necessitate repeat purchases, driving up the life cycle cost). Thankfully, I found that bi-flange silicone tips from Klipsch were a good compromise, delivering adequate comfort (but still the proper deep fit) at the slight expense of some noise isolation.

To its acquittal, at least the MK5 clearly fits a larger range of ear canals than does the MC5. Putting in the MC5 into my ears was a big hassle, as my narrow-bodied ear canals just couldn’t fit the pudgy housings inside all that well. The thinner bodies of the MK5 fit much better — they’re just a tiny bit larger than the housings on the ER4. In my book, its improved fit and comfort over the existing MC5 at least constitutes an iterative improvement, but don’t expect a revolution in comfort with the MK5 — it’s ironic that a company dedicated to hearing preservation and with inextricable links to the hearing aid industry has products that engender such a varied response when it comes to comfort.

The Etymotic MK5 Isolator, pictured with the ER38-15SM frosted grey triple flange silicone tips.
The MK5, pictured with the ER38-15SM frosted grey triple flange silicone tips.

Sound and Electroacoustic Characteristics

Let’s continue with what remains a holding pattern, and a very good one at that: the MK5 is an Etymotic earphone, so that inherently means it is clean, composed, and very accurate.

It’s not Etymotic‘s most accurate earphone according to their own standards, but to my ears, it possesses the most compelling sounding bass response of any Etymotic that has come before it, and while the treble response isn’t perfect, it performs beyond adequately, with performance standards that extend way beyond any expectations at the $59 price point.

While bass decay is very quick, its levels are quite ideal for a neutral sound signature. It won’t offer too much by way of impact, but the detailing available in the low end is about as good as it gets for an earphone of this caliber — it audibly reaches low, which is better than what can be said for even the flagship ER4S. The bass should be considered the highlight of the new MK5. Etymotic products delivering good bass? Who would’ve thunk it?

As expected, the $299 ER4S is a more accurate earphone than the $59 MK5 Isolator, but the MK5 isn’t far off — the main issue is the lesser treble extension, which — while not poor — is lacking compared to anything higher-end in the Etymotic ecosystem. The MK5 can also sound a little thin in the lower midrange, together with a hot upper midrange. Thus, some voices can come off as a little “shouty” as a result. The extra energy around 3.5 and 6 kHz are perhaps a consequence of the way Etymotic has chosen to equalize the breakup resonance nodes with their patented “acoustic side branch” that effectively acts as a Helmholtz resonator for treble frequencies.

All in all, though — as can be seen — the MK5‘s frequency response characteristics should be regarded as excellent for what Etymotic is trying to achieve.

Frequency Response (Raw, Uncompensated)

Here, we see the MK5 juxtaposed against the ER4S:


The ER4P (now known as the ER4PT) is actually a warmer earphone than is the MK5 — corroborated by both these measured results and by subjective experience:


Frequency Response (Compensated for Equalized Target Response)

Shown below are the compensated responses, measured with the various tips included:

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If equalized for the Harman International target response, the MK5 falls short of linearity across the board, as Etymotic targets a response lightly modified from that of pure diffuse field (sound sources are emitted from all around a listener).

However, Olive/Welti’s target response accounts for listeners’ subjective preferences collected from statistically significant data, and while the preference is subtle, listeners do prefer a little more bass in the lowest registers, relative to the midrange.

We won’t comment too much on the upper treble response, as even industry standard ear simulators are not believed to be reliably accurate in the upper treble. Here, the measured treble response is tantamount to a ballpark estimate. It does seem that the bandwidth of the MK5 is not quite as wide as is that of the ER4 series; rolling off between 10-14 kHz, depending on the choice of ear tips (ER38-15SM small frost triple flange, ER38-18CLL clear triple flange, or ER38-14F black foam).

Etymotic has a few other tips available on their website, such as the glider foam tips and various size cylindrical foam tips, but they’re not included in the basic retail packaging.


In subjective testing, no audible distortion was detectable, remarkable for an earphone in this price category.

The actual measurements themselves exhibit an average to below average performance in terms of distortion, but is perfectly acceptable, especially at this price point.

Can Etymotic improve on the distortion response? Absolutely. Perhaps with a metal housing and/or special nano-treatment of the diaphragm with materials such as titanium. Though these improvements would be welcome changes to the audio enthusiast, they would surely drive up the cost and perhaps cannibalize sales of Etymotic HF series of earphones. Etymotic also has never been particularly aggressive about marketing to the audiophile crowd; they’ve always maintained a market-neutral stance, insisting their products are made for anyone and everyone.

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Sensitivity, Impedance & Source Matching


At 32 ohms (mostly flat across the board from 20 Hz to 20 kHz because the transducer is of the dynamic moving coil type rather than balanced armature), the MK5‘s impedance is fairly reactive in nature, rather than resistive.

Thus, the MK5 definitely seems to enjoy robust current delivery from audio sources. It seems far more at ease when paired with sources that possess capable current buffers, such as Resonessence Lab Concero HP’s and Celsus Sound Companion One’s AD8397.

Those with just a smartphone as a source needn’t fret, however. The MK5 is easily driven to loud volumes, just not as loudly or easily as other earphones around.


For many EtyHeads, modifying their Etymotic earphones has been a rite of passage. We managed to test the response of the MK5 with various different acoustic dampers affixed to the front of the output to test the level of smoothing that the dampers have on the frequency response.

Here, speakerphone suggests modifying the with a white (680 Ω) acoustic damper for the most pleasing sound, but it will be up to personal taste should any EtyHeads choose to modify these earphones.

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Conclusion and a Message for Etymotic

In many ways, the MK5 Isolator is Etymotic‘s best all-around product yet released.

It fits better in the ears, sounds better, and is equally priced to the older MC5; it even has the most palpable bass of any Etymotic product I’ve ever tried. Its sound quality is without reproach, especially considering that it sells at $59 USD, and it does so by sticking to its long-held guns about target accuracy in frequency response.

Yet, simultaneously, while testing the MK5, I felt waves of discontent waft across my brain. In my eyes, Etymotic has far too long “stuck to its guns”, and it is overdue for a paradigm shift. Decades ago, Dr. Mead Killion founded the company by coining a Greek-derived neologism for being “true to the ear” — etymotic. But did that mission statement only connote that sound be true to the human hearing system? One of Etymotic‘s biggest stated goals as a company is to provide hearing preservation for all people. That’s why they’ve continually attempted to bring the price down on their earphone products, and that’s great — awesome, really. But who’s going to use your products if they find them uncomfortable? Only the “ordained”? The people “who know better”?

The whole point of developing hearing protection/preservation products is so that people will actually wear them. According to most occupational safety surveys, the number one reason why people neglect to wear PPEs (personal protective equipment) is inconvenience, as the device might hamper the way they work, or that the device is uncomfortable. Etymotic has taken steps to improve functionality of their earphone products on both of these counts, such as developing the Etymotic Aware! smartphone app to allow for convenient outside communication, but has only taken a half-step toward improving comfort. They can make the barrel smaller on the MK5 and EK5, but many people will still take issue with the deep fit.

That’s why Etymotic should really begin thinking out of the box when developing new products, exploring new ways to guarantee treble linearity and bandwidth, without requiring the deep second-bend fits or workarounds to the “missing 6 dB” in the bass.

Already, other companies are stepping up to the plate, like South Korea’s Wavelet Design. Their upcoming OPUS1 earphone utilizes forward-thinking balanced armature technology, and also bases its acoustic principles around a modified diffuse field target (unquestionably inspired by Etymotic’s scientific approach), but does away with a super deep fit and still manages admirable treble extension — these attributes make this new, relatively-unknown product very appealing to people who enjoy an accurate sound but cannot get along with the finicky fit of Etymotic earphones. With experience spanning over three decades, Etymotic can surely do better. This company is a technical leader in the field of acoustic research. It’s time to start acting like it once again — it’s not enough to rehash a three year-old product with tweaks here and there.

The MK5 is truly an incredible value for its sheer acoustic performance. However, I challenge Etymotic to outdo itself. The company clearly has the capability to do better, and the people certainly deserve it.

Special thanks to Gail G., Au.D., audiologist and marketing director for Etymotic, for sending out an evaluation unit. For more information on the Etymotic MK5 Isolator, please visit:

About Mr. T

Mr. T is an in-ear fanatic by day, and writes SOAP notes by night. He pities the fool who actually has the patience to read through his stuff.
(Full Author Bio)

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Mr. T

Mr. T is an in-ear fanatic by day, and writes SOAP notes by night. He pities the fool who actually has the patience to read through his stuff.

4 thoughts on “Etymotic MK5: Isolator, Reborn.”

  1. Ok, problem solved. I can see the pictures now. I would really appreciate if you could also test them with Shure Olive Tips. Thank you.


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