Sennheiser IE 400 PRO

Disclaimer:

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.



Introduction:

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.


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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.

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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.

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Conclusion:

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 .

My review and comparisons of the Sennheiser IE 400 Pro, somewhere else on the site.

Update:
A small but useful tweak.
I used a small strip of medical Micropore paper tape , over the nozzle of the earphones , keeping three holes open.
This significantly reduced the overblown treble output.
Upper midrange is smoother , so is low treble .
it lost almost no resolution as a result.
See Picture:

This review was previously published at audioreviews.org


EXECUTIVE SUMMARY

The Sennheiser IE 400 PRO earphone produced in Germany is a well balanced, gently forward-dipping V-shaped, slightly warm sounding single-dynamic-driver earphone that also impresses by its low distortion and great comfort and fit. It is the second-highest priced but best sounding model of their IE PRO series imo.





INTRODUCTION

The world’s most competent (and now retired) headphone reviewer Tyll Hertsens once called Sennheiser the world’s most competent headphone manufacturer. Their standard staples such as the HD 25 and the HD 600 have delighted us for – yep – decades, and these models still belong to the top of the competition. And Sennheiser have brought us the so often copied earbud.

Sennheiser is a 75-year-old company out of Northern Germany that holds the highest reputation not only in headphones but also in professional microphones (and other products). With the advent of the iPhone in 2008, Sennheiser started developing iems – and they have always stuck to the single dynamic driver because of the cohesive sound and the low harmonic distortion.

Sennheiser’s most recent PRO line comprises three models, the $99/€99 IE 40 PRO (produced in China), and the $ 349/€349 IE 400 PRO and $599/€599 IE 500 PRO (both truly “Made in Germany”).

Biodegraded and I had reviewed the Sennheiser IE 40 PRO [here] and the Sennheiser IE 500 flagship [here] very carefully and in great detail. While I approved the IE 40 as a good sounding budget model, we both were more weary with the IE 500 PRO, which sound congested due to the complete absence of an upper midrange.

The Sennheiser IE 400 PRO and IE 500 PRO, although differently priced, share the same design and even the same 7 mm dynamic driver, but they differ in their tuning. From the sparse useful information on the internet, it appears that the Sennheiser IE 400 PRO is a much better sounding earphone than its more expensive sibling. I therefore approached Sennheiser asking for a loaner to test this. Let’s see what I could find out.


SPECIFICATIONS



Company Website: https://de-de.sennheiser.com


PHYSICAL THINGS AND USABILITY

The unpacking experience of the Sennheiser IE 400 PRO is exactly the same as in the Sennheiser IE 500 PRO and so is the ergonomics. I have tested over 250 earphones and can say that these Sennheiser line sports the best ergonomics out of the lot, perhaps shared with the now discontinued UE900s. The shells are small, they fit snug in my ears, they do not stick out (“bed use”), they are comfortable, and the material feels nice on the skin. And they seal well, which is expected as they have been designed as stage monitors. In fact, you never have the feeling that you have something in your ears – which is also partially contributed to the flexible memory wire. Isolation is very good once again – I have always liked Sennheiser’s silicone tips.



The cable with its round cross section is not too rubbery – and better than the braided version in the IE 500 Pro in that it does not tangle at all. Being black – it is not a grease and dirt magnet. There is some microphonics, though. The connectors are proprietary – you cannot attach a third-party cable – but they are sturdy and reliable. Like all Sennheiser iem cables, this one also comes with a chin slider.

Like their two PRO siblings, the Sennheiser IE 400 PRO, with their very low impedance of 16 Ω work well with just a phone – and the included silicone eartips – a Sennheiser standard – fit my ears well.


EQUIPMENT USED: iPhone SE (1st generation) and MacBook Air, alone or with Audioquest Dragonfly Black 1.5 dac/amp; stock cable and stock eartips.


TONALITY AND TECHNICALITIES

My tonal preference and testing practice

My test tracks explained

The sound of the Sennheiser IE 400 PRO can be described as medium-warm, gently V-shaped, organic, smooth and cohesive, with a bass punch that creates a mild veil. The drive is noticeably speedy.

The Sennheiser IE 400 PRO’s frequency response curve looks unusual compared to most earphones I have measured, independent of price. The good: it pays off, the sound is very good. The graph is forward dipping which indicates a warm signature. The odd part lies in the upper midrange (2-4 kHz) which appears to be below neutral. Such a graph shape should result in a lack of sparkle and a congested and muted – however rich- sound in the vocals department. The good: this does not happen. Yes, the vocals are rich and intimate, but nothing sounds muffled. Sennheiser must have solved this issue with their tuning in the treble – unfortunately, any coupler (ours included) yields unreliable results in this area so that we can only consider this segment or our graph as semi-quantitative.

But what is obvious is a set of peaks in the upper treble that produces overtones which fuel the midrange with the right sheen and sparkle without making them aggressive. The competition, especially from Asia, frequently boosts the upper midrange (2-4 kHz), which results in aggressive, sharp vocals. This signature is popular in the far east. Sennheiser relies on realistic reproduction that comes with fine BritishGerman understatement.





I find the overall sound signature very cohesive, and therefore agreeable, which, together with the organic timbre and the good comfort/fit provides for a pleasant, non-fatiguing listening experience. Stage and headroom are very good for a single dynamic driver, and so is detail resolution. The driver has just the right speed to delight the listener with a realistic attack/decay through the frequency spectrum.

The low end of the Sennheiser IE 400 PRO is well extended and boosted quite a bit above neutral, mainly in the sub-bass area, but this does not affect the vocals of the lower midrange. Although not evident in the graph, mid-bass can be a bit much at times. In terms of quality, the low end is reasonably well focused and medium tight with a natural speed but not as articulate as in the Sennheiser IE 500 PRO sibling. It is punchy, could be a bit sharper and can be perceived as marginally boomy in some tracks.



Moving into the lower midrange, vocals are soft and smooth, intimate, well-sculptured, and N A T U R AL. Very very appealing to my ears. V-shape? Vocals too distant? Just turn the volume up: distortion is minimal and much smaller than what your are used to, even at the highest volumes. There is no hint of harshness as in most of their Chi-Fi colleagues. That’s because the upper midrange is so well behaved. Downside of the tame upper midrange: vocals do not have the biggest sparkle around and it cuts into the transparency…but enough to be appealing.

The highs are very extended into the 15 kHz area recovering some sparkle and sheen but also creating some splashiness in cymbals.

The stage is wider than deep, it deserves a bit more depth. The overall presentation is very accentuated – but detail resolution, layering, and separation are good however somewhat limited by the 7 mm dynamic driver. Sound is as organic as it could be. The Sennheiser IE 400 PRO shine through their coherence and agreeable, inviting sound rather than through its nitty gritty technicalities.


WHY WOULD I WANT IT (OR NOT)?

We at audioreviews.org haven’t had much of a chance reviewing German gear. And that’s exactly where your money is in Sennheiser products: German quality control. Any of the Sennheiser earphones I have measured have impeccable channel balance. The Sennheiser IE 500 PRO and IE 400 PRO are “Made in Germany”, which remains one of the world’s highest quality seals. As a reviewer, I have been disappointed more than once with poorly designed and poorly manufactured, faulty products, that had been thrown on the market prematurely. The other advantage of the IE 400 PRO over their Chi-Fi competition is that they incorporate long (and real) professional experience, that much R&D went into them, and that this product has been so well designed that it is here to stay (on the market). The Chinese competition frequently floods the market with half-baked earphones prematurely, uses their clientele as guinea pigs, and an “improved” version, labelled as “Pro”, will follow so closely that the early adopters are being disgruntled. Sennheiser have the solidity and maturity of a company that they also don’t change their tuning unannounced so that the customer can rely on what they have to expect.


SENNHEISER IE 400 PRO COMPARED

The >$300 4 BA +1DD Anew X-One [here] is superior in most technical aspects (staging, imaging) but does not have offer the same cohesion and degree of natural reproduction, as well as the ergonomics and comfort. It also does not offer the Sennheiser IE 400 PRO’s low harmonic distortion and rigorous quality control (channel balance).





The Sennheiser IE 400 PRO graphs similar to the much cheaper Sennheiser IE 40 PRO[here], but do they sound similar? The main difference lies in the refinement: the IE 40 PRO’s low end is less articulate and slower/less tight and the model also lags in the midrange, particularly the vocals department. The IE 400 PRO reproduces voices more natural, richer, and adds more transparency. The Sennheiser IE 500 PRO [here], in comparison to the other two sounds congested and dull because of its lack of upper midrange/lower treble, but it has a more articulate and layered low end. It also loses against the IE 40 at 1/6 of the price. The $250 JVC HA-FDX1 [here] (with green/least perceived bassy filters) are more upper midrange forward and neutral with a flatter and less extended however realistic bass compared to the warmer Sennheiser IE 400 PRO. The JVCs also have a natural timbre.


CONCLUDING REMARKS

The Sennheiser IE 400 PRO are not only the clear winner against their siblings imo, they are also very good earphones per se. Price aside (sale price is ok), the only criticism could be the boosted bass, which was just fine to my sensible ears. Imaging is immersive, and the overall sound (“Klangbild”) is coherent and pleasant. These are a safe choice not only for expert hobbyists, but also for music lovers who are not so familiar with/overwhelmed by the market’s offerings. It will be difficult to find somebody who would not enjoy these. On top of that Sennheiser give you the piece of mind that their products are well quality controlled and equipped with a 2-year warranty.

Until next time…keep on listening!




DISCLAIMER

The review unit was loaned to me by Sennheiser Canada upon my request for review on the blog audioreviews.org. I thank them for that as well as some German Sennheiser audio engineers for discussion.


Our generic standard disclaimer.

About my measurements.