Sennheiser IE 40 Pro Review Page 2


When dealing with in-ear monitors, a proper fit is critical. Over the last couple years, I've had some of the most highly regarded models in the world pass through here without earning a review. Why? Because they didn't play well with the physical shape of my ears. It's gotten to the point where I very rarely bother trying out universal IEMs, as they just don't typically fit me very well, and nearly all of my listening is now done with custom-molded models. 

Thankfully the IE 40 PRO is one of those rare universal designs which happens to work very well. From the size and shape of the shells, to the nozzle angle, to the cable routing, everything just works like it was purpose-designed just for me. Obviously this is a subjective, case-by-case situation. But having seen many larger/more clunky designs out there with which most folks have no issue whatsoever, I suspect the IE 40 PRO will work for the vast majority of users. 

I did the bulk of my listening with the included foam tips, which made for a great seal. Regardless of tip choice, these IEMs only isolate moderately well – don't expect to feel completely cut off from the world as is the case with some other models. The upside to that equation is comfort, which is quite good here thanks to the relatively shallow insertion. 


Sennheiser's product page  uses the term "precise sound" and I actually think that sums up the IE 40 PRO rather well. I was worried that the focus on stage use might make for an overly warm, bass-oriented signature, which is typically what you want in that sort of loud environment. In reality the IE 40 PRO is very well balanced. As I cue up my usual test tracks, which include some amazing "audiophile-grade" recordings like Eric Bibb's Good Stuff (DSD128) but also plenty of "lesser" material such as I Against I from Bad Brains, Amon Amarth's Fate of Norns, various ancient Big Joe Turner recordings, and DJ Boring's 2017 EP Different Dates, all streamed from Tidal or Qobuz or even Spotify (gasp!), I'm greeted by an impressive sound which very much brings to mind the last set of stand-mounted speakers I owned, the $3k Studio Electric M4. That means tactile treble, full-bodied midrange and tight, clean bass that perhaps focuses more on accuracy than depth... though the Sennheisers do extend lower than any sanely-sized stand-mount I've heard.

To be overly simplistic, the IE 40 PRO has a generally neutral, monitor-style presentation. That means low-end kick is present and very clean but lacks the boost which has somewhat become the norm in many headphones/IEMs these days. The trick here is that it doesn't veer into analytical territory (think classic Etymotic Research house sound) which means the Sennheiser still has broad appeal regardless of genre being played. There's enough presence to do justice to kick drum impact from Aesop Rock or Cannibal Ox, while not overdoing Gary Karr's amazing double bass tonality. As a percussionist (in a former life), I would perhaps desire a bit more prominence in the lower regions while performing in a loud stage environment. But as a general listener I find the balance just about ideal for everything I throw at it. Would I enjoy some additional sub-bass slam? Sure, and I assume that's one benefit the more expensive upcoming siblings will bring. But I can certainly live with things as-is, just like I can enjoy a stand-mount speaker in terms of low-end performance. 

Midrange is clear, open, and just meaty enough to satisfy without going too far. Again, I can think of situations where more forward mids would be welcome, but for all-purpose listening the IE 40 PRO is pretty much ideal. That means the nasal tone of Al Green, the richness of Barry White, and the clarity of Chet Baker (yes, he sang from time to time) are all reproduced with equal fluency. There's a sense of delicacy and refinement here that I have rarely encountered from an IEM in this price bracket, and I would extend that to full-size headphones as well. I would have expected this sort of performance from a $300+ IEM, but for $99 I'm quite impressed.

My favorite aspect of the presentation has to be the huge, immersive soundscape it generates. Much like the previously-mentioned Studio Electric M4, the IE 40 PRO excels at reproducing the scope and space of a performance. Obviously this needs to be in the recording in the first place, so many modern releases don't apply. But when I throw on my SACD rip of Tsuyoshi Yamamoto's Midnight Sugar, I can hear the dimensionality of the various instruments as if they are laid out in my own room and then confirm what I'm hearing by using the "microphone setting" chart in the liner notes. I've owned plenty of more expensive IEMs with superior resolution, extension, and other technicalities, but only a select few improve upon the sense of space available in this little $99 wonder.

Treble on the IE 40 PRO is the one area which might not be ideal for all users. It's slightly brighter than neutral, and although it is well controlled, at times it may feel like a bit much relative to the smooth presentation of the older IE 80S. It's fairly clean and well controlled, so listeners are spared from annoying treble peaks, but it still comes on a tad strong in general. Interestingly, it also runs out of steam in the extreme upper frequencies, which takes away from a sense of airiness to the presentation. The end result: cymbal strikes sound clear, capturing the initial "splash" of the attack without being overly harsh. But they also lack a bit of that natural shimmer and decay, which for me separates the good from the great in terms of realism. Still, I'll take a somewhat bright yet well-controlled presentation any day over a peaky, grating sound, even if it does come at the expense of some top-end air. 


In the end, I'm thoroughly satisfied with Sennheiser's accomplishment here. The IE 40 PRO is a superb IEM which I would rate highly even at twice the price. Bassheads may not quite be satisfied, but I'd argue they are already well-served by any number of existing IEMs in this price range. For everyone else, the IE 40 PRO offers a coherent, timbrally-accurate presentation, with even-handed frequency response and excellent imaging. They sound great from a smartphone and even better from a dedicated DAP or headphone amp, and the fit – for my ears, at least – is among the best out there. If Sennheiser maintains this trajectory with the IE 40 PRO's upscale siblings, they have the potential to really shake up the market. But even if those fall short, this affordable model remains a very welcome entry into a crowded playing field. They really do raise the bar in terms of what users can and should expect from a sub-$100 expenditure. 

Sennheiser Electronic GmbH & Co
Am Labor 1, 30900 Wedemark, Germany

Rmusic's picture

Thanks John,
Your reviews are always jam packed with useful information.

crazywipe2's picture

It's always good to find a $100 product that is very well performing.
Can you compare with the ety er4xr?

charlesx31337's picture

Great review, very impressed with these for the price!
Would love to get your thoughts on / see a review on the Sennheiser ie400 pro in comparison.
Keep up the great work :)

Benjdbs10's picture

A friend very interested in this new babies (he's a treblehead, hence the interest). Got Eric Bibb's album, too. so i could relate, but in the real world Not all albums are made like that Superlative. I reckon an upgrade cable perhaps a hybrid one, could just do the trick. thanks...