A High-End Earphone and In-Ear Monitor Primer

As I mentioned in my recent TAS survey of six top-tier headphones, there is an emerging high-end audio universe that runs parallel to our own- one driven by a new generation of audiophiles whose attention centers squarely on earphone or headphone-based music systems. Within that alternate universe, there are numerous sub-categories of enthusiasts, each with their own preferred listening contexts, source components, electronics, transducers, and so on.

One key question listeners face is whether they plan to listen on the go (meaning a truly portable solution will be required), or in a static location anchored perhaps by a desk or a favorite listening chair (meaning portability is not required), or perhaps a bit of both. Loosely speaking, two fundamental classes of solutions emerge: those based on earphones or in-ear monitors, which are inherently portable, and those based on full-size headphones, which-depending on configuration-mayor may not be suitable for portable use.

For this article, let’s focus specifically on earphones and in-ear monitors.

Terminology

Among high-end audio traditionalists and personal audio cognoscenti you will sometimes hear the terms “earphone,” “in-ear monitor,” and “headphone” used interchangeably, which is confusing to say the least. For our purposes, however, we will make an effort to give each of these terms consistent and specific meanings.

Earphones

In this article (and in product reviews) I will use the term “earphones” as verbal shorthand for the longer, more descriptive, phrase, “universal-fit in-ear headphones.”

The “universal-fit” part of this moniker is important, because it implies tacit recognition of the fact that there is no such thing as a true one-size-fits-all earphone, given that human ears each have different sizes and shapes. For this reason, universal-fit earphones are expected to provide adapters-usually taking the form of various sizes and types of flexible ear tips (often made of soft silicone, rubber, or compressible foam materials)-that enable the earphones to fit a reasonably broad range of ears.

The “in-ear” part of the name implies that earphones will be worn within the user’s ear canals-not fitted loosely in the outer ear as with inexpensive Apple-type “earbuds.” A further unspoken implication is that, for optimal sonic performance, universal-fit earphones require an airtight seal between their ear tips and the wearer’s ear canals (if the airtight seal becomes impaired, then all sonic bets are off).

While it is true that there are many loose-fitting earbud-type solutions on the market, the overwhelming majority of today’s better high-performance earphones are designed for within-the-ear-canal use.

Sadly, some traditional high-end audio enthusiasts rashly assume universal-fit earphones are little more than gussied-up versions of the cheap earbuds included as accessories with many digital music players and smartphones. Frankly, they couldn’t be more wrong. Today’s better-quality earphones enjoy substantial performance advantages vis-a-vis freebie earbuds, as open-minded auditions will quickly reveal. In short, today’s better upper-tier earphones are very serious high-end audio components and deserve to be treated as such.

In-Ear Monitors

Although not all earphone and in-ear monitor aficionados would agree on this point, many would say that the most highly-evolved of all in-ear listening devices are true “custom-fit in-ear monitors”- or “in-ear monitors,” for short.

Devices in this category were first created for use as very-high-performance, personal music-monitoring systems intended for professional musicians performing on stage. Several factors drove musicians (and their sound engineers) in this direction. First, loudspeaker-type stage monitors were large, bulky, feedback-prone, and tended to “beam,” meaning performers had to stand in certain “sweet spots” on stage in order to hear themselves sing and play. But perhaps the biggest drawback was that speaker-type stage monitors had to play extremely loudly to be heard above the din of onstage amplifiers, instruments, PA systems, etc. Obviously, the last thing musicians needed was to have their hearing damaged by their own monitors.

In contrast, personalized, custom-fit in-ear monitors offered a host of benefits. Each singer and player on stage could have his or her own small, unobtrusive custom-fitted monitor that offered very accurate monitoring-grade sound, was compact and thus allowed freedom of movement on stage, and offered a tremendous amount of noise isolation so that sensible, non-damaging playback levels could be used. Finally, since the earpieces of custom-fit in-ear monitors were typically larger in cubic volume than those of universal-fit earphones, there was enough room inside for designers to install sophisticated arrays of miniature drivers for even higher sonic performance.

The key to the whole custom-fit in-ear monitor concept revolves around the ability to take custom ear-mold impressions (a service typically provided by qualified professional audiologists) and then build earpiece housings for monitors that are an exact fit for the wearer’s ears. The upside is that the resulting monitors give a truly optimized fit for their owners, but the downside is that the monitors fit one person only (for obvious reasons, there’s no “universal-fit” aspect to custom-fit in-ear monitors).

Over time, what started out as an answer to the needs of working musicians turned out to be a great high-performance personal music-monitoring option for professional sound and recording engineers, record producers, and, naturally, for serious audiophiles. Three things-all of them desirable-set custom- fit in-ear monitors apart from their universal-fit earphone counterparts: superior noise isolation, superior comfort and fit (especially for those with hard-to-fit ear shapes), and-at least in principle-superior sound quality.

Note: Certain makers of universal-fit earphones have begun to call their products “in-ear monitors,” and a few may be capable of delivering the sound quality to back up their claims. Even so, I would suggest that custom-fitted earpieces are one of the defining characteristics of true in-ear monitors. Without the superior noise isolation that custom-fit earpieces provide, universal-fit earphones typically allow too much noise leakage

for on-stage use (or for use in other environments where noise may be present). Audiophiles can verify this for themselves by comparing the performance of universal-fit earphones vis-a-vis custom-fit in-ear monitors when traveling, say, on jet aircraft. Having performed such comparisons many times, I can vouch for the fact that the superior noise isolation of custom-fit in-ear monitors makes them the creme de la creme for on-the-go listening.

Earphone and In-Ear Monitor Driver Technologies

Most universal-fit earphones and some custom-fit in-ear monitors use traditional voice-coil-powered, piston-type, “dynamic” drivers that may be housed either in sealed or vented earpiece enclosures (although a few designers have also experimented with enclosures that use various other resonance-control systems). You could think of these drivers as being conceptually similar to the pistonic drivers used in any number of loudspeakers, but executed in miniaturized form. One key difference, however, is that these drivers typically are run full-range, so that crossover networks generally are not required.

Example: The German firm Sennheiser’s flagship IE 800 earphone ($999) uses a single very high-quality driver that is fitted in a rigid earpiece housing equipped with a set of resonance- control vents.

Some universal-fit earphones and the majority of custom-fit in-ear monitors use alternate types of drivers known as balanced- armature drivers. From the outside, balanced-armature drivers look like very tiny rectangular metal canisters, with sound outlet tubes on one side. Internally, each balanced armature-type driver features a tiny rod-like metal armature balanced in the center, almost like a teeter-totter (hence, the name “balanced armature”).

The armature is surrounded by an electrical coil and positioned within the center of the gap of a magnet. As musical signals are applied to the coil, the metal armature becomes magnetized (as you may recall from physics class), so that it now reacts to the magnetic gap in which it is positioned. As the music signal fluctuates back and forth, the armature responds by swinging back and forth, tilting up and down (again, somewhat like a teeter-totter in motion). Sound is produced because one end of the armature is coupled to an extremely small diaphragm that in turn produces sound waves in the sound outlet tube.

What critical listeners appreciate about balanced-armature drivers is that they are light, small, self-contained, inherently well balanced in a mechanical sense, and extremely responsive (because they have exceedingly low moving mass). What is more, balanced-armature drivers are so small that several of them can be fitted within an earpiece housing, where this is desirable.

Examples: The U.S.-based firm Westone’s flagship Westone 4R earphone ($709), which is a marvel of miniaturization, contains four balanced-armature drivers (configured as two woofers, a midrange driver, and a tweeter) per earpiece. JH Audio’s flagship JH16 PRO in-ear monitor ($1149) uses a whopping total of eight balanced-armature-type drivers grouped as “double dual” woofers, dual midrange drivers, and dual tweeters. What is more, the latest JH16 PRO units feature JH Audio’s proprietary “freqphase” technology, which provides a high degree of time/phase alignment between the drivers across the entire audio spectrum.

Although these are relatively rare, some high-end universal- fit earphones and custom-fit in-ear monitors use a hybrid combination of dynamic drivers and balanced armature type drivers. For example, AKG’s very exotic flagship K3003 earphone ($1299) uses a dynamic driver-type woofer and two balanced armature-type drivers to cover midrange and treble frequencies.

Custom-Fit In-Ear Monitor Earpiece Technologies

As mentioned above, the performance of in-ear monitors hinges in a very significant way on the quality of their custom-fitted earpieces. You might think that since all such earpieces are based on mold impressions taken from your own ears they would be virtually identical, but in practice that is not necessarily the case. Different manufacturers have different processes and techniques for transferring ear-mold impressions to finished custom earpieces and there are significant differences-both in fit and in resulting sound quality-between brands.

There can also be significant differences between the earpiece materials used in custom-fit in-ear monitors. Many manufacturers (e.g.,JH Audio and Logitech/Ultimate Ears) mold earpieces from relatively rigid acrylic materials. Other manufacturers (e.g., ACS Custom and Sensaphonics) fabricate earpieces from much softer cold-cure silicone-gel-type materials. Still others (e.g., We- stone) split the difference by molding earpiece bodies from acrylic, but with the ear-canal section of the earpiece molded from a temperature-sensitive material that softens just a bit after the in-ear monitors have been worn for a minute or two.

One key point to bear in mind both with universal-fit earphones and custom-fit in-ear monitors is that superior fit always, always translates into superior sound quality. Think of getting the fit right, then, as the earphone or in-ear monitor equivalent of getting loudspeakers correctly positioned within your listening room.

Summing Up

While some may think of devices in these product categories as mere “toys,” my view is that an open-minded audition of today’s better quality earphones and in-ear monitors will show they have genuine sonic merit. What is more, high-performance earphones and in-ear monitors open a world of serious musical enjoyment for listening at home (ideal, for example, for late night listening) or on the go. Indeed, many serious audiophiles wouldn’t dream of traveling without their preferred earphones or in-ear monitors.

In the next article in this series, I will focus on full-size headphones and their several variants.