Can Sennheiser’s new entry into the IEM marketplace really cover on-stage and general listening duties?

What is it?
Sennheiser IE 100 PRO in-ear monitor and wireless (Bluetooth) headphones

What’s great?
The Price. A balanced sound without distortion. Enough acoustic isolation to be useful on stage. Comfy fit. Everything is replaceable and interchangeable between IE models.

What’s not?
Might not suit some ears shapes.

The bottom line:
A great value IEM that’s also useable as a monitor reference and for casual listening.

Sennheiser IE 100 PRO Wireless: Review
Before the development of In Ear Monitoring (IEM) the lot of a vocalist on stage with a band wasn’t a happy one. Using traditional wedge and side monitors, crosstalk from on-stage amplification and the battering from the drummer (often just behind the singer’s head) made it almost impossible to hear themselves sing. The obvious solution was to wear some kind of headphone but being cut off from the rest of the performers—not to mention having a long wire snaking to the monitor engineer’s desk—is really going to cramp a performer’s style. Early IEMs required bulky wireless/battery packs to be secreted down the back of the singer’s pants, while high-quality miniature headphones were numbingly expensive. However, as in-ear (earbud) headphones have probably become the de-facto way people listen to music these days and almost every digital device now has a Bluetooth capability, the costs have come down and quality has taken a step change upwards. The Sennheiser IE 100 PRO Wireless IEMs look a little like the headphones you’ll see runners wearing but as they come from one of the world’s premier headphone developers, these are very high-quality devices. They are also designed to be used onstage as personal IEMs.

Sennheiser IE 100 PRO Wireless: Build quality
The headphones themselves consist of two detachable transducers that are shaped to sit snugly in the ear ‘s concha. This, along with a range of supplied silicone and foam adapters, means that the headphones should fit most ears. The transducers themselves are sturdily built for such miniature devices—I can’t see them being easily crushed under a roadie’s boot. The IE PRO wireless kit includes Sennheiser’s sturdy patent-pending ‘internal duct’ wired cable terminated with a standard 3.5mm jack and the IE PRO BT Bluetooth-enabled cable. The latter is a ‘round the neck’ type, with the battery pack and Bluetooth device fixed in line. The IE PRO BT cable features volume and track control buttons as well as MEMS microphone and a call answer feature. It’s swappable between Sennheiser’s 400 and 400 IEMs and charging is via USB-C. Sennheiser’s claim of 10 hours use from a 1.5-hour charge was verified by me after a marathon listening session to the Complete Art Ensemble of Chicago Box set of recordings. The headphones are available in red, black or clear finishes, the latter of which would be the most useful for stage use. The IE 100 PRO feature a 10mm dynamic broadband driver with a stated frequency response of 20 Hz to 18 kHz, a maximum SPL of 115dB, 26dB of external noise attenuation and a THD of less than 0,1 % when measured at 1 kHz and 94 dB. The use of a single driver precludes phase issues and other problems inherent in multi-driver designs. The ‘phones come with a small leatherette carry case and there’s also a nifty cleaning tool included.

Sennheiser IE 100 PRO Wireless: Sound
Once fitted with the correct ear adapter, the IE 100 PRO are a really comfortable fit that provided quite a bit of separation from the outside world whilst not feeling too ‘closed in’. Like most over ear designs, they can be fiddly to get on, but once on they stay there! Sonically, I can’t fault them at this price point. They present a reasonably balanced non-fatiguing sound and I enjoyed listening to some of my favorite well-recorded music through them. I preferred them to my Apple Earpods and, perhaps predictably, to the OEM ear buds I use (and abuse) when running. Swapping between the wired and Bluetooth cables is a simple matter of disconnecting and reconnecting them and you can even do it when the phones are in your ears if you’re are particularly dexterous. Many IEMs I’ve used were very effective on stage, but pretty horrible for generalist use, so it was nice to hear that the IE 100 PROs are also excellent as a day-to-day listening device. Connected to a Sennheiser wireless system, the ‘phones were effective as IEMs, shutting out just enough of the outside world whilst providing a clear undistorted feed that should enable a singer to hear themselves above the din. The fit was surprisingly good on my lugs, and the over-the-ear design means you won’t lose them on a wig-out on the encore.

Sennheiser IE 100 PRO Wireless: The Bottom Line
IEMs like the IE 100 PRO will never provide quite the level of performance that bespoke systems specifically modelled for an individual’s ear shape do. But Sennheiser’s latest can be very effective and come at a cost that might tempt other members of the band to join the IEM revolution. What’s nice about them is that you can use them for listening to music, calling, video conferencing, Podcasting, on stage and listening back to the recording of the gig afterwards—all on a pair of phones you can stick in your pocket. You can spend a lot more on IEMs—including some of Sennheiser’s own models—but the IE 100 can be extremely effective if you’re on a tight budget. And the fact they also work as really nice Bluetooth headphones is just the icing on the cake.

Available now – £129.00, $180