Ultimate Ears has been making high-quality, custom-fit, in-ear monitors since 1995, but I would argue their new In-Ear Reference Monitors are the firm’s most significant product to date. Here’s why. Where many in-ear monitors are designed primarily for performing musicians and thus have response curves designed to cut through the din of (sometimes exceedingly loud) onstage performances, the In-Ear Reference Monitors were designed from the ground up with just one goal in mind: sonic accuracy. While other in-ear monitors offer admittedly colorful response curves that may have a certain charm all their own (but that ultimately are not terribly accurate), the IERM’s were designed to provide ruler flat frequency response whose objective is to show you precisely how your favorite recordings really sound, without introducing questionable sonic embellishments, enhancements, or “sweeteners” of any kind. In short, Ultimate Ears’ IERM’s are designed to serve as a transparent conduit for the music at hand—a design goal we think most Playback readers will instinctively appreciate and applaud.
In approaching the IERM design, Ultimate Ears chose to collaborate with the engineering staff at Capitol Studios (of Capitol Records fame), in order to develop the optimally flat, neutral, and uncolored response curves that were required. According to Ultimate Ears the goal was to create an in-ear headphone so faithful to the input signals it is fed that its sonic character will be, “consistent, natural and revealing creating an accurate base line of pro audio reproduction that can be trusted by the professional recording engineer and producer no matter the environment.” Excellent noise isolation was also a prime concern. In short, UE’s intent was to create a versatile and credible in-ear monitor that could reliably be used to monitor and mix recordings both in the studio and at live events—a goal that UE and Capitol collaborators say the IERM successfully meets. And the same qualities that make the IERM a good monitor are also sure to make it a favorite among audiophiles.
From a technical standpoint, the IERM seems comparatively straightforward. It is a three-way, in-ear monitor that uses three high-performance balanced armature type drivers (serving as woofer, midrange driver, and tweeter), which are connected via a passive electronic crossover network. Output from the three drivers is directed through “dual acoustically tuned sound chambers” (which some competitors refer to as “bores,” as in the phrase, “our headphone uses a dual-bore design”) for what UE terms “the ultimate in separation, detail and clarity.” Custom-fit earpieces are made of solid acrylic material, and the IERM’s are fitted with “rugged, low-profile, low-distortion” signal cables.
Unlike most other UE in-ear monitors, whose earpieces typically would be offered in a rainbow-like array of custom colors, the IERM has been given a distinctive look all its own—and one that reflects the product’s design heritage. The IERM earpiece housings are therefore molded in clear acrylic with jet-black outer panels, with the Capitol Studios logo displayed on the right earpiece and the signature “UE” logo on the left earpiece.
How do the In-Ear Reference Monitors sound? You’ll want to read the rest of this review for a detailed answer, but suffice it to say the IERM’s are among the most neutral and evenly-balanced in-ear monitors we’ve yet heard, and they are very revealing. In our view, it is to UE’s credit that the firm had the vision and open-mindedness necessary to think outside the box and to create this studio/audiophile-grade product in the first place.
Consider this custom-fit in-ear monitor if: you have always wanted in-ear monitors that for the most part honestly reveal how recordings actually sound, without injecting interesting but inaccurate colorations of their own. The IERM’s are—as is so often the case with really fine audio components—sonic chameleons, meaning they don’t really have a signature sound of their own, but rather take on the tonal colors of the individual recordings you choose to play. The IERM’s are also very quiet and comfortable to wear for long periods of time
Look further if: you require the most detailed sounding in-ear monitors available (both Westone’s ES5 and the JH Audio JH16 PROs offer stiff competition, here), or the highest degree of noise-isolation possible (where the Sensaphonics 2MAX is our reigning class leader). Note, too, that the IERM’s response can sound very subtly rolled off up near the top of the top octave (which spans the range from 10 kHz to 20 kHz), meaning the IERM doesn’t necessarily capture the elusive sense of “air” surrounding instruments as effectively as some competitors do. But for overall balance and the sheer smoothness of its response curve, UE’s In Ear Reference Monitor is tough to beat.