I would like to thank Mr. Wenbin and Sennheiser for providing a review unit of the IE 400 Pro. Rest assured that my impressions written in this review are my own personal thoughts and opinions and in no way influenced by outside parties.
I am not an expert in this hobby nor claim to be an audiophile. I just love listening to music and am fond of writing articles.
I guess there’s no need for an introduction with a brand as established as Sennheiser. Released in 2019, the IE 400 Pro was initially sold for 349.95 USD. It’s the embodiment of keeping things simple, with a single dynamic driver responsible for sound reproduction (123 dB, 16 ohms). Marketed for musicians to be used while performing on stage, does it fit this hobbyist’s taste?
These were plugged to my Oppo Reno 4/Asus X409 with the Earstudio HUD100 MK2 (bypass, high power). No need for external amplification or more power, as a phone will do.
Build and Comfort: While it is in no way made of premium feeling materials, it sure is built well (German-made). Shell is arguably the most ergonomic design for all ears I’ve tried, tied with the Moondrop SSP. Practical, small, light and functional – it disappears in your ears once you put them on. Only time will tell how long the plastic shell will hold up but considering that this was intended as a stage monitor, Sennheiser’s confident that it will be able to handle abuse without breaking.
Nozzle is of below average length and average width. Would fit most third-party tips but I won’t recommend it as the stock tips play a part in the overall tuning of this specific IEM.
Cable’s usable but isn’t the best. Jack, splitter, slider and connectors are all made of plastic. Earhooks is memory style, meaning that it will hold its shape. Slight microphonics are heard when turning your head. In using them, I found that widening the cable “opening”, then putting on the IEM, and pinching the part where the cable starts going over your ear provides the easiest, fastest and best fit for my ears. I can’t say I love the choice of memory earhooks. However, I do see the reason for this, as again, this is intended as a monitor, and it’s a given that plastic parts would last longer than metal on the stage. Memory earhooks would also be able to hold onto the musician’s ear better while performing than other designs. It also does used proprietary connectors designed for said purpose.
While the stock cable’s fine, there was something that I really wanted to do – make my own cable for the IE 400 Pro. With that, I started browsing for parts on Shopee and settled on a set of connectors and cable to start making my very first self-made custom cable. In the time of this review, I still have not made the cable, but it will surely be done in the future.
Average isolation. Slightly microphonic stock cable.
Package: 6.3mm adapter. 3 pairs of silicone tips (S/M/L). 3 pairs of foam tips (S/M/L). Cleaning tool. Stock cable. Carrying case. Paperwork.
Now, onto sound:
For this review, the IEM was left in stock mode, without mods, using the stock small silicone tip with a listening volume of low-medium to medium. As there is nothing offensive in the tuning, turning up the volume would cause no issues (i.e., harshness). FWIW, I mainly listened at medium loudness with the IE 400 Pro.
Bass: Easily the best bass response I’ve heard in an IEM. It’s detailed, sufficiently fast, well-textured, and drops to the deepest sub-bass frequency. This is premium bass quality right here. It’s engaging and embraces wholeheartedly sought-after characteristics of a DD bass – weight and impact. While the driver size is of the smaller side for a dynamic at just 7mm, what surprises you is with how deep it can go effortlessly. It’s more of a sub-bass focused tuning but mid-bass doesn’t sound lacking/light, which I personally see allows for better transition to the midrange. I do have to warn that this has A LOT of bass. But while it is more-than-elevated, due to the quality, it doesn’t eat away the soundstage of the IEM nor smear across the spectrum (unlike a certain IEM I reviewed recently), staying focused and defined all throughout the listening session. Overall an engaging bass response that would play along with any genre. No bass bleed at all. Visceral.
Midrange: Neutral with a hint of warmth. The listener would need some time to get used to the rather low pinna gain of the IE 400 Pro, way different than the “Chi-Fi” tuning with the more than elevated upper midrange/lower treble. It would sound “muffled/veiled” at first due to said pinna gain. Once you get set and your ears have gotten used to it, it’s pure bliss. The naturalness of the midrange of the IE 400 Pro is something you’ll always be looking for, for the rest of your life. Vocals are rich, and while not the most transparent-sounding (tuning plays a role on this), does resolve well to not sound overly smooth. Male vocals exhibit a slight warmth which adds in the weight and richness of each line. Female vocals stay close to neutral without any coloration and is balanced in presentation with male vocals. No harshness or graininess heard in the IE 400 Pro. While it may sound vague, the tuning of the midrange is something that touches your heart and triggers several emotions in the music. There’s just this magic in IE 400 Pro.
Treble: On the brighter side, but very much welcome. With the conservative tuning of the midrange and the elevated bass, the treble compensates with a sparkly, crisp, airy, and brilliant presentation. That airiness also affects the midrange, giving this sense of “air,” especially with vocals (and in extension, soundstage). Echoing sounds run across the stage exceedingly well. No instances of excessive splash that leads to strident highs and pierce that causes fatigue. I did write that the treble is tuned brighter-than-neutral, but even in higher volumes, there is nothing offensive/harsh about it. Might be a different case for treble-sensitive folks.
Timbre: Organic-sounding. Nothing sounds wrong at all. Also very cohesive, with it being a single-DD.
Soundstage, Imaging, and Separation: Considering that it’s a single DD and how tiny it is, soundstage is exceptional. With the way-more-than-neutral bass response and conservative midrange, one would have expected a more in-your-head presentation. But that is not the case at all due to the overall quality. This is the most realistic sounding soundstage in an IEM I’ve listened to where no dimension is favored than the other and height, width, and depth show remarkable performance. Imaging is sharp and you’ll be able to create a mental image of where instruments are located in a stage and where exactly sound is coming from. Separation is also impressive for a single-DD and no region goes over each other with every layer having a space of their own to operate, staying distinct throughout the listening session.
Detail-retrieval: Not the IEM for this. The upper midrange/lower treble, while resolving enough, is too “relaxed” of a tuning to highlight macrodetail. It does show, but doesn’t jump at you. Microdetail-retrieval, meanwhile, is a different story. As treble is shimmery and extends well, lots of them are perceived while listening, even with the elevated bass though not on the same level as say that of a piezoelectric.
Sonic-wise, I’d give it a 5/5. A 6 even, if possible. However, with the package you’re getting for 349.95 USD (base price), there are more premium options out there at a cheaper cost (though I haven't tried them, just read about them). But then again, is it German ? Good thing you won’t be looking at your IEM when you’re comfortably listening with the IE 400 Pro in your ears and it’s also now easier than ever to purchase aftermarket cables even with the proprietary connectors. With that, I give the Sennheiser IE 400 Pro a score of 4.5/5.
As this is a rather old IEM, wait for sales and grab it fast .
****If you have other questions/concerns with the IEM mentioned, feel free to message me****