Sennheiser IE 100 PRO review: in-ear monitoring just got a whole lot easier

During all my years mixing live sound, it’s inevitable that I should acquire a couple of sets of custom IEMs along the way. I am often asked by bands and artists that are thinking about IEMs but don’t want to shell out the best part of a grand for something they may not like or can’t get used to. The simple answer has always been, ‘you get what you pay for’, but that might be about to change. I was recently fortunate enough to get my hands on Sennheiser’s new IE 100 PRO IEMs.

In the box are a set of ears and a single cable to connect the two together, which features a Bluetooth unit as well as a small controller with on/off, connect, volume controls and a microphone, so you can use this with another Bluetooth device should you wish.

You also get a separate cable so an engineer or musician can use the earpieces in a more traditional manner, say for instance from a mixer or an IEM body pack. There is also a handy little packet with a cleaning tool and a bunch of alternative buds to accommodate different ear sizes.

Now bearing in mind these units are the IE 100s, the entry level in a series which already features the IE 400 and IE 500. I can’t say I was expecting too much, especially when they arrived already attached to the Bluetooth adapter. 

All preconceptions aside, I thought I’d start as they arrived, so I paired them up to my iPhone and stuck a bit of Pink Floyd on. To my surprise they didn’t sound half bad. I had to search around for the adapter you now need to plug up any audio output from a modern iPhone.

I will apologise in advance for this, as it’s something I rarely do on account of the rather poor quality of the conversion and amp stage in modern phones, and unsurprisingly my near £1,000 of custom-built IEMs sounded uncomfortable. One nil to Mr. Sennheiser.

Just to make sure it was the iPhone’s internals that were at fault here, I refitted the earpieces onto the cable and plugged them straight into the iPhone’s little adapter, and low and behold there was a significant drop in quality from that experienced with the Bluetooth adapter. So far from being a sales gimmick or a bonus toy to sway your buying decision, it actually works, and works well.

So to see if this could possibly be the device to accustom potential users to long periods of IEM wearing, I fitted the earpieces back up to the Bluetooth adapter and stuck it on charge. 

After homeschooling was over, I took the opportunity to take a long walk down by the canal and regain my sanity, along with some of that contracted data allowance that never gets used. 

I could also take the opportunity to revise a couple of my playlists and reconnect with some past memories, as well as checking out some of the new artists the Headliner team have been interviewing and writing about.

After a good couple of hours, the IE 100 Pro was still going strong, and even with the phone in and out of my pocket, a random marketing call and a poor network area, there wasn’t a single Bluetooth dropout. 

Sennheiser claims a battery life of up to 10 hours and up to 20 in standby. Personally I try not to spend more than a couple of hours at a time with ears in, but I can’t see this being something that is likely to die on you unexpectedly.

Also useful is the fact that the Bluetooth module, amps, batteries and controls are split between two evenly weighted and evenly spaced little modules, so when you take the ears out they hang evenly around your neck like a necklace without slipping one way or the other. Very neat! 

With the useful range of earbuds available to fit every size and shape of ear, these IEMs create a comfortable full seal, and give you the kind of depth and bass that’s impossible from devices like Apple AirPods, and others of that ilk.

Around 18 months ago, I also had the good fortune of acquiring a set of Sennheiser IE 500s to try out. Equally small enough to comfortably fit in any ear and perfect for introducing IEM newbies to a better onstage sound. Sadly, in my eagerness to do just that, I lent them to somebody who promptly left them in a dressing room, never to be recovered!

It’s evident that there are many similarities to be drawn between the 500s and the new 100s. For a start, they look and feel - if memory serves me correct - identical in size, shape and weight. 

The fitting to attach the cables looks identical and on further investigation, I discover that the Bluetooth device is interchangeable between the IE 100, the IE 500 and the third member of this series, the IE 400. 

The housing on my pair of IE 100s is black, whereas my 500s were clear so I could see the driver inside, but I’m absolutely sure this houses the same type of driver.

The similarities in terms of phase and detail are uncanny. The overall sound however is similar, but not the same. It could be because I’ve had no reason to wear IEMs of late, but I remember the IE500s being loud and having a slight dip in the upper-mids, so you could easily cope with higher voice levels and a more dynamic response in those frequencies. 

Suffice to say for the then price tag of £500 I thought they were possibly the best sounding and most comfortable set of ‘of-the-shelf’ IEMs you could buy.

The IE 100s still have all that rich bass and tight low-mids, but are brighter and a little more sibilant when you try to turn them up loud. If anything, I’d describe them as a little more Hi-Fi; perhaps a conscious decision to make them more universally appealing to a broader market! 

I’m certain I’ll be carrying them around from now on for quick referencing and general Apple Music duties. I might even leave the Astell & Kern in the FOH rack just for system checking. But more importantly I’ll have some spare generics that’ll be perfectly capable of providing anyone who wants to try out in-ear monitoring with a really great sounding mix.

Now comes the rather surprising news on how much the Sennheiser IE 100 Pro Wireless will cost you. £129! Yep, you read that right. 

Should you already own either the IE 400s or 500s, you can pick up the Bluetooth adapter which replaces the cable for £87, and you can also purchase the IE 100s on their own without the Bluetooth adapter for £87.

No more stressing about expensive generics getting crushed or forgotten; this is a stress-free price. Have Sennheiser got it right? Yes, I for one think they definitely have. With the IE 100 Pro, trying out the concept of in-ear monitoring just got a whole lot easier.