Unlike 95% of balanced-armature in-ear monitors, the S-EM9, like all EarSonics in-ears, uses drivers custom made for them by Knowles instead of Knowles’ off-the-shelf drivers that are found in most other in-ear monitors. EarSonics drivers are the company’s own proprietary designs, which puts EarSonics in a unique position compared to most other in-ear monitor manufacturers.

Along with its proprietary drivers, EarSonics employs a three-way crossover system. Although there’s no mention of whether the crossover employs resistive circuits, a cutaway illustration of the S-EM9 on EarSonics’ website shows there’s scant room inside for much beside the drivers and sound channels. These “channels” are tubes that direct the sound from the front of the balanced-armature driver to the earphone’s tips. The S-EM9 employs a unique three-bore, three-channel cannula profile. According to EarSonics, its design “combines optimal phase management through asymmetrical channels and maximum treble extension.”

Ergonomics & Fit

As you would expect from a top-of-the-line earphone, the S-EM9 comes with a plethora of accessories, including the usual nice, but blessedly compact, cloth-covered presentation case. Inside you will find two pairs of Comply tips, two pairs of silicon tips, one pair of double-flange tips, a cleaning tool, user manual, and hardshell cloth-covered everyday carry case. The exceedingly lightweight (in a good way) cable is replaceable, and uses a fairly standard two-pin connection (on the upper side of the enclosure when in the S-EM9 is in your ears) that is sufficiently robust not to pull loose, even when yanked. The supplied cable does not have any provisions for iOS or Android smartphone controls and is terminated in a standard single-ended mini-stereo plug.