Introduction:
 
Two years ago, I first met Jack Vang at the labs of Earwerkz, a then-new IEM design and manufacturing company that was born from his father's hearing aid firm. I had read @shotgunshane's great review of Earwerkz's flagship IEM, the Legend-R, and was intrigued. Not only was Earwerkz local to me being just outside Atlanta, but the positive reviews of the company's entire IEM lineup had my interest piqued. Prior to meeting Jack, I had a personal policy of only purchasing universal IEMs for the purposes of resale value. I figured if I would ever consider purchasing a custom IEM, I would need an audition ahead of time before locking myself a product I couldn't resell as easily. Jack greeted me at the door with a smile and a firm handshake befitting the size of his biceps, then sat me in a conference room with demos of the entire Earwerkz lineup. An hour later I left with my wallet lighter and a receipt for the Legend-R in my pocket, having been mightily impressed by the demo as well as Jack's friendly professionalism.
 
In the past two years since that day, there have been a lot of changes for the company. What once was Earwerkz became Empire Ears as the business grew by leaps and bounds and matured in both their product design and sound quality. They launched a new lineup crowned by the Zeus XIV, a 14-driver-per-side IEM. Later, Jack and company announced a re-tuned evolution of the Zeus design that was named the Zeus-R, with the R standing for "Remastered." The latest version of the Zeus is the Zeus XR ADEL, a product that incorporates Asius' well-known ADEL technology as well as a tiny physical switch on the faceplate to alternate between the XIV and R tunings at will. 
 
My own personal Zeus began life as the Zeus XIV and then became the first production Zeus-R when that version was announced. Let me preface this review by saying that I personally prefer the Zeus-R tuning as it's more of a neutral and "reference" sound versus the more romantic nature of the original XIV. Many head-fiers prefer the original tuning, and I can't really blame them either way as it comes down to pure personal preference. The following impressions are taken from a large variety of sources, but mainly with the Cowon Plenue S DAP, Google Pixel XL phone, Schiit Gumby DAC, and a Mitsubishi DP-EC1 turntable feeding a Parasound Halo Integrated amplifier.
 

 
 
Sound:
 
I've seen the general sound signature of the Zeus-R described as neutral with a slight uplift in bass and mids pushed forward. It's a slightly warmer-than-neutral signature, but one that has fantastic treble definition and extension. Tonality leans towards the thicker side, which adds a pleasing impact and dynamism to music. We all know that driver count is not indicative of performance, but the 14 drivers that each side of the Z-R along with the 8-way crossover network seem to work some magic in creating a sound that is simultaneously smooth-yet-revealing, clear and cohesive.
 
Bass:
 
The bass of the Zeus-R reminds me a lot of the old Earwerkz Legend-R, and clearly shares some DNA with that earlier flagship model. While the bass quantity is slightly greater than an absolutely neutral sound signature, it's incredibly chameleon-like in nature, a trait that I also loved about the Legend-R. During one my favorite Beethoven sonatas performed by Yehudi Menuhin and Wilhelm Kempff, Kempff's piano has an appropriately solid presence and substance in the lower octaves that feels very linear and proportional in nature with the expected resonance and timbre of a grand piano. In other words, it sounds accurate and realistic. Flipping the track to something more modern, Big K.R.I.T.'s club banger "Money on the Floor" gets my toes tapping and head bobbing with it's grinding, greasy bass line. Big K.R.I.T. is well known for creating tracks to flex subwoofer drivers into oblivion, and it's impressive how much subbass the Zeus-R produces while maintaining quality. Bass texture and definition is also impressive. While decay isn't the fastest, the Zeus-R never feels slow or loses tautness. Indulging my inner metalhead, the bands Baroness and Mastodon are well known for having spectacularly talented drummers. Putting on a few tracks by both bands is a gory assault of stampeding double kick drums and furious tom fills, demonstrating that the bass drivers of the Z-R can keep up with some of the best heavy metal drummers on the planet. I can't think of many headphones or IEMs I've heard that can handle the bass from such wildly disparate genres of music and do justice to both of them. Tonality of the bass is a bit on the thicker side, but I personally wouldn't want it any thinner as it would compromise the heft and texture.
 
Mids:
 
The mids are the real star of the show on the Zeus-R and are what I would consider the Empire Ears "signature" sound. They are forward and intimate, a tad lush, and intensely detailed. Vocalists and instruments that live in the midband sound movingly emotional and driving in their beauty. The touch of lushness does not interfere with the clarity of the mids whatsoever. This is where the Zeus excels and sinks its hooks into you. These seductive mids consistently give me chills of euphoria, and is also where the most soundstage depth occurs. Listening to complex orchestral tracks or a rock song with lots of instrumentation and intertwining melodies really demonstrates the Zeus-R at its best. There are layers upon layers of instrumentation that wash over and envelop the listener. Again, tonality errs towards warm and lush with thicker lower mids, although in general it is significantly more neutral than the original XIV version of the Zeus.
 
As a sidenote, this is probably the biggest differentiation from the the original Zeus XIV. Compared to the XIV, the R is a bit drier in sound as it pushes the mids back a bit in the presentation, but gains significantly more clarity as a result. There's a level of detail in the spatial cues that wasn't present before. There are subtle reverb effects from the recording space that are quite evident now compared to the XIV. It's a delight to listen to tracks that were recorded in one take as you get a really incredible feeling for the "room." Listening to Led Zeppelin's "The Ocean" and "The Rain Song" with the Z-R are enveloping experiences, like you're standing in the middle of the band in the recording studio.
 
Treble:
 
Let me preface this section to say that I have yet to hear a better treble tuning out of a balanced armature-based IEM design than what Empire Ears has accomplished across their model line. In my experience, balanced armature implementations often have a hashy, splashy treble section most noticeable with rock music. Hi-hats and crash cymbals become indistinct and distorted without realistic definition. IEM designers seem to sometimes compensate for this by making the treble so laid back that the end result seems stuffy or veiled. Empire Ears's head of R&D (and Jack's father), Dean, has consistently wrangled very impressive performance out of BAs, and the Zeus truly reflects that work. It's the most detailed treble I've heard from an IEM, with striking resolution particularly in the lower treble. The end result is an airy and highly extended presentation that has class-leading definition while never managing to be fatiguing or harsh. You truly feel that you're getting the entirety of the frequency range.
 
Prior to owning the Zeus-R, I owned the Noble K10 universal in aluminum. While it was a fantastic IEM in clarity, smoothness and especially soundstage, it really fell short when it came to treble. To my ears the K10UA was fatiguing after short periods of time, and I found myself wincing on recordings mastered to be a bit "hot." The K10UA really seemed to accentuate the rougher qualities of those tracks to the point of discomfort, and treble definition suffered as cymbals were particularly splashy and grating. Incidentally, I've heard rumors that the custom version of the K10 has a more subdued treble, but I have yet to try it.
 
My one minor issue with the Zeus-R in terms of sound is that the IEM seems to accentuate some sibilance. There is a bit of a peak in the treble that takes the essesssssss and presents them in a way that I would prefer to be toned down just a tad. I think this is noticeable perhaps by a dip in the frequency response before the sibilance frequency, making the peak after more prominent. I want to caveat this by saying that the Zeus-R is quite source-sensitive, as this sibilance is more obvious on some sources than others. Again, keep in mind that I can listen to the Z-R for hours at a time with no issue so I'd think of this issue as more of a personal preference as I tend to be very sensitive to treble unevenness. 
 
Source matching:
 
The other quibble I have with the Zeus models is also minor, but worth noting. Empire Ears' IEMs tend to be very sensitive. They can be driven easily by nearly any headphone output, from smartphones to the highest-end DAPs, but keep in mind that any sources that have poor noise floor performance will be obvious in their faults right out of the gate when paired with the Z-R. Also noticeable is any distortion from digital files towards the beginning and end of songs. I'm struggling to describe it accurately as I'm not sure what the technical term for is, but perhaps it's a form of IMD. For example, my Google Pixel XL has a surprisingly quiet noise floor, but I can hear a bit of "digital" sound as tracks fade out when using the Z-R. Needless to say the Zeus-R is very revealing of all source imperfections, and so a source that measures well is helpful to truly do justice to how high the Z-R can scale in performance.
 
The best DAPs for my personal preferences are the Cowon Plenue series. The Plenue 1, Plenue S and Plenue D all have very low-to-zero levels of hiss, with the Plenue D impressively having no perceptible noise floor to my ears. They also have a less antiseptic and analytical presentation than most DAPs on the market, and have a musicality that's sadly rare in the audiophile portable world.
 
Conclusion:
 
You can probably tell that I love the Empire Ears Zeus-R. It's by far the best in-ear I've heard, and it's so good that I really saw no need to keep any other headphone I owned with the exception of the venerable Sennheiser HD650, which is really only used for PC gaming these days. It's incredible to experience an IEM that sounded good enough to have my heavy Audeze LCD-3 collecting dust and eventually consigned to the For-Sale threads here. It is reference-level in technical proficiency while also possessing a musicality that keeps it from ever being boring or neutral to the point of sterility. I really do think Jack and Dean have created a fantastic IEM, and with the new ADEL integration as well the XR switchable model out, there's so much flexibility and customization possible along with the renowned level of customer service that Empire Ears is known for. If you have the cash, it's well worth a listen.