Previously known as sub30
Pros: Bass, midrange, and treble quality
Soundstage, imaging, and instrument separation
Very easy-to-drive
Made in Germany (higher QC standards compared to other countries)
Cons: Has a lot of bass
Not detailed-sounding
Midrange would sound veiled to some (takes some listening to get used to)
Cable shouldn’t be like this in a 350 USD IEM (release price, 2019)
As stock tips are part of the tuning, third-party tips might cause issues
Proprietary connectors – gotta go custom-made


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.


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.


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****

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Well written and objective review in my opinion.
I've own these for a year, having picked them up in a Sennheiser sale for less than 200euros.
They truly sound fantastic. I've recently coupled them with IE Pro Bluetooth cable which has an amazing battery life with not much effect on SQ relative to wired (though midrange depth and details improve if coupled with a decent DAP).
Truly great an IEM for the price (especially if you can get them at a discount).


1000+ Head-Fier
IE 400 Pro review and comparisons
Pros: Low Distortion
Sub-Bass extension
Ear thumping fast Bass
Treble Clarity
Midrange clarity
Good practical cable
Cons: Upper Bass bloom
V-Shaped sound
Muted midrange
Stiff cable plugs to the earpieces can make the "Fit" difficult
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Thanks for leaving your comments!
The actual review in depth is HERE
Thanx for responding.
Como o honeydew se compara ao IE400pro? obrigado!

Otto Motor

Headphoneus Supremus
Sennheiser IE 400 PRO Review – The 2nd Mouse Gets The Cheese
Pros: Smooth, cohesive, organic sound through fast driver; ultra-low distortion; unparalleled ergonomics; perfect channel matching; 2-year warranty; Made in Germany.
Cons: Sennheiser pricing (watch for sales); a bit too punchy and bassy for some; proprietary cable connectors (but they work reliably).

This review was previously published at


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.


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.


Sennheiser IE 400 PRO

Company Website:


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.

Sennheiser IE 400 PRO  Review

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.


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.

Sennheiser IE 400 PRO  Review

Sennheiser IE 400 PRO  Review

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.


We at 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.


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).

Sennheiser IE 400 PRO  Review

Sennheiser IE 400 PRO  Review

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.


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!

Jürgen Kraus signature


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

Our generic standard disclaimer.

About my measurements.
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Thanks for the comprehensive review.
I have been using the ie400 pro for 6 months systematically. I came to prefer paring it with Fiio M11 which boosts a little bit the mids to empower that area which I find a little on the thin side (but just a little). This is apparent when AB these with a multi-BA as the Mackie MP-460. In that case the midrange area steps discernibly forward and becomes 'weighty'. Of course the senn is, for the same reasons, a less fatiguing listen.
Como o honeydew se compara ao IE400pro? obrigado!
Otto Motor
Otto Motor
Don't know.


1000+ Head-Fier
Pros: Neutral and balanced sound signature
Excellent build quality
Deep extending sub-bass
Well-controlled mid-bass
Good isolation
Transparent and airy mids
Smooth and well extended highs
High quality storage case
Cons: Rare Pentaconn Ear connector
High-resolution, transparent mid-ranges, precise soundstage, and a robust design fit for any stage - meet the all-new IE400 Pro.

Thank you, Melvin and team from Sennheiser Singapore, for sending me the IE400 Pro in-ear monitors (IEMs) despite facing the Circuit Breaker implementation in Singapore. It was provided to me free of charge in exchange for my honest review and opinion.

Sennheiser Electronic GmbH & Co. KG has produced numerous high fidelity products - impressing the audiophile community since 1945. Being a family business, founded by Prof. Dr. Fritz Sennheiser, the legacy is built and passed down from generation to generation without compromising details.

, one of the most expensive headphones, is a status that shows where Sennheiser stands in this audio market - king of the kings.

During 2018’s 4th quarter, I had the opportunity to attend the grand opening of the Sennheiser HE-1 Experience Center in Singapore. The CEO of Sennheiser, Mr. Daniel Sennheiser flew all the way from Germany to Singapore to attend this memorable event. Andreas and Daniel Sennheiser, the third generation CEOs of Sennheiser, continue to extend the spirit of their grandfather in designing high quality audio gadgets for all purposes.

In 2018, Sennheiser released the IE PRO series IEMs. This series is designed for all purposes - no matter if you’re in a studio, on stage or simply an audiophile like me. I reviewed the entry level IE40 Pro last year and now I’m continuing to experience this series.

The IE400 Pro is the middle-range model in this series. In this article, I’ll walk you through the greatness of Sennheiser’s legacy!

Sennheiser IE400 Pro

My pleasure to witness the grand opening of Sennheiser HE-1 experience centre in Singapore with presence of Mr. Daniel Sennheiser, CEO of Sennheiser.

One of the world most expensive headphone systems by Sennheiser, the HE-1

The unboxing experience for the IE400 Pro is pleasant. It comes in a relatively large box compared to other brands. The Sennheiser branding, the model’s name and photo are printed on the outer paper sleeve.

The brand, model's name and photo are printed on the outer sleeve of packaging.

Removing the outer sleeve, the inner hard box provides protection to the IEMs. The IE400 Pro makes its first appearance when we open the box, with the cable and medium-sized silicone ear tips attached.

The inner hard box of the packaging
Opening the box, IE400 Pro makes its first appearance

There is a hard case provided for storage purposes. Removing it, we can find the accessories provided:
  • 3 pairs of foam ear tips (small, medium and large)
  • 2 pairs of silicone ear tips (small and large, medium is pre-installed on the IEMs)
  • 3.5mm to 6.3mm adaptor
  • Cleaning tool
Ear tips card, adaptor and cleaning tool

Technical Specification
  • Impedance: 16 Ohms
  • Frequency response: 6 - 19,000 Hz
  • Sound pressure level (SPL): 123 dB (1kHz / 1 Vrms)
  • THD, total harmonic distortion < 0.08 %
  • Cable length: 1.3m
  • Transducer principle: Dynamic
  • Weight: 18 g
  • Attenuation: up to 26 dB
The shell of IE400 Pro is built using plastic. I got the smoky black color variant. I can look through the almost transparent shell - the neat driver and cable arrangement gives it an expensive look. The choice of material results in the IEMs to be lightweight.

IE400 Pro with cable attached

IE400 Pro has a detachable cable design. This is a requirement for those who are working in the studio or on stage because some of them will use a mono cable, which connects to the single side of the IEMs. For audiophiles, the detachable cable is an advantage too - for cable replacement or even an upgrade.

Detachable cable

The 3.5mm jack on cable

Sennheiser is using the Pentaconn Ear connector, designed and innovated by Nippon Dics on IE400 Pro. This makes it easier for audiophiles to get upgraded cable from various cable manufacturers. As mentioned by Sennheiser, the cable is designed with an innovative internal cable duct (patent pending), which is fit for stage use.

The Pentaconn Ear connector
The Pentaconn Ear connector

The nozzle is in one piece with the IEM shell. There are a number of small holes on the nozzle. The nozzle is relatively short. There is a lip on the nozzle to provide a better catch on the ear tips. This makes ear tips rolling better.

Nozzle with lip to provide a better catch to ear tips
Multiple bores on ear tips

Fit and Isolation
The shell is well-designed and does not have any pressure spot that causes irritation in the ear after lengthy listening sessions. This small housing IEM sits well in my ears and creates good isolation. I believe the fit will be satisfying for most people because of its small form factor.

There is a small vent on the external side of the shell to mitigate driver flex. I didn’t experience any driver flexes during this period of audition. Due to the circuit breaker, I didn’t have a chance to test the isolation in a noisier environment, such as during commuting. However, IE400 Pro does offer me decent isolation and passive noise cancellation.

[note yellow]Driver flex is when the driver bends due to the pressure of air against it. Usually, it occurs when you're inserting the IEM into your ear and air in the shell creates pressure to bend the driver.[/note]

Sound Analysis
To analyze the sound quality of the IE400 Pro accurately, I paired it with my new all-time favorite reference digital audio player (DAP), the Lotoo Paw 6000. Paw 6000 has the same output power on both 3.5mm unbalanced and 4.4mm balanced. I’m using the stock 3.5mm unbalanced cable for this review.

Rated at 16 Ohms for impedance, IE400 Pro can be easily driven with DAPs or even smartphones. This makes IE400 Pro a multipurpose IEM for different usages - no matter if you are in a studio, on stage or for casual usage.

Pairing IE400 Pro to my Lotoo Paw 6000.

Sound Signature
The IE400 Pro has a neutral and balanced sound signature. I would class it as a reference gear. I use it for critical listening most of the time. However, this IEM does not have the signature of a typical studio monitor - a cold and dark sound signature. It is a slight touch on the warm side, making it a suitable candidate for casual listening too.

The soundstage of the IE400 Pro is above average both horizontally and vertically. The overall presentation is spacious and it’s neither overly forward nor distanced. The distance between the listener and performers is accurately positioned - resulting in a precise and comfortable experience. The positioning of individual instruments and vocals are accurate. Closing your eyes, you can tell exactly where those instruments are - just like listening in a theatre or concert.

Powered by a single dynamic 7mm wideband transducer, IE400 Pro delivers a lively bass - punchy and full of dynamic.

The lows are extending deep and punching sufficiently strong, triggering the excitement in listeners. Despite having a punchy and rich texture bass, Sennheiser didn’t compromise any fidelity quality in designing the IE400 Pro. The bass is speedy in both attack and decay. The presence is significant and accurate. This makes it a pair of reliable reference IEMs for sure.

The IE400 Pro has a good sub-bass extension. The well-extended sub-bass creates a good depth in the soundstage. Moving to the mid-bass, the presence starts to be more conservative. This makes space for the upcoming mids. However, the mid-bass is not overly shy. The connection and transition between lows and mids are great - no gap in between.

IE400 Pro with Paw 6000

This is where I love IE400 Pro the most. The mids presentation is transparent and spacious. Minimum color is injected to the mids, giving the purest presentation. Pairing with my Lotoo Paw 6000, the presentation is lively, just like listening to a live concert. Listening to male vocals, they exhibit the slightly rich texture from the lows, making them firm and well-penetrated.

The slightly warm and rich textured male vocals result in a presentation with emotions and souls, bringing the end result a step nearer to live concert.

The IE400 Pro is handling the female vocals well too. The way it delivers the female vocals is sweet and swift. There is no sluggishness in the presentation. The upper mids are spacious and airy. In terms of overall mids, the positioning is slightly forward, as compared to the bass. The layering between mids and bass has further enhanced the accuracy of the whole presentation from IE400 Pro.

IE400 Pro with Momentum Wireless

I have auditioned numerous Sennheiser’s models, from entry level like Momentum In-Ear to the top of the line like HD820. Highs are always a weapon for Sennheiser - clear, well-handled, free from distortion, smooth. There are endless positive terms that I can use in describing it. Without any disappointment, the IE400 Pro exhibits the same characteristic as its predecessors. The highs are very well-extended, making the overall fidelity to be high quality.

During my time as a headphone specialist in one Singapore’s audio shops for four years, I received occasional feedback from Sennheiser users saying that the highs in some of the models cause fatigue after long listening. For IE400 Pro, the highs are smooth and easy to listen to. I don’t face any fatigue after long listening. It actually became a companion for me during this Circuit Breaker.

Queen of Audio Mojito (QoA) (USD$399)
Standing beside QoA’s flagship model, the IE400 Pro has a dull appearance. QoA uses stable wood to build the Mojito’s shell, making it unique. IE400 Pro will be a more professional looking IEM with a smoky black or clear shell for stage and monitor use.

In terms of fitting, QoA offers a deeper insertion. However, I am getting better isolation and passive noise cancellation from IE400 Pro. I believe this could be due to the ergonomic shape of the shell. Sennheiser has much experience in designing a good pair of IEMs that is great in both sonic quality and fitting. This could be a good lesson for other manufacturers to learn from.

In terms of sound, Mojito is having a warmer sound signature compared to the well-balanced and neutral IE400 Pro. The IE400 Pro is offering a better soundstage. The positioning is more accurate on IE400 Pro, too. Personally, I choose IE400 Pro over Mojito because of the soundstage and fidelity.

IE400 Pro vs Mojito
Mojito (Left) vs IE400 Pro (Right)

Avara Custom AV3 (USD$340)
Avara AV3 is one of my favorite reference IEMs. Putting it together with IE400 Pro, I really faced difficulties in choosing the winner. In terms of fitting, the custom AV3 without a doubt provides me with a better isolation. However, IE400 Pro is not too far behind. It’s a close fight here.

In terms of sonic quality, I think both of them have a unique characteristic. AV3 is closer to a neutral stage monitor, like Westone UMPro 30. Flat response across different frequencies and no bias for or against any spectrums. The IE400 Pro is more lively compared to AV3, offering more ups and downs in the presentation. Both of them are suitable for critical listening but I would choose IE400 Pro during casual listening because it’s more lively.

AV3 vs IE400 Pro
AV3 (left) vs IE400 Pro (right)

The Sennheiser IE400 Pro is, indeed, a satisfactory pair of IEMs that serve different purposes. No matter what your need, IE400 Pro will have a solution for you. Excellent fitting along with its neutral and lively sound signature won my heart over from other models.

[bq]The accuracy and maturity in tuning a single dynamic driver has once again portrayed the success and expertise of Sennheiser in this industry.[/bq]

Sennheiser IE400 Pro is retailing at SGD$539 (~USD$349). You can purchase it from Sennheiser Official Website for individual countries. For those who are in Singapore, it’s definitely a great time for you to acquire a pair. Celebrating their 75th anniversary, Sennheiser Singapore is running a 44% off for IE400 Pro, retailing at SGD$299 now. This deal will expire at the end of May.

With the launch of IE PRO series, the legacy of Sennheiser continues and they have proven to the world that they are still relevant even after more than half a decade. Congratulations, Sennheiser!
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Thanks for your review, congratulations on finishing writing it!
Thank you @Sennheiser ! It's indeed a great pair of IEMs!


100+ Head-Fier
Pros: Balanced signature, dynamic sound with great bass, clear mids, shimmery treble. Great overall clarity
Cons: Bass is a bit bigger in quantity. Instrument separation and micro-details could be just a little better.
Simple Man’s review – Sennheiser IE 400 Pro (350 USD)
This is called simple man’s review because they are based on the sound of these earphones directly from my mobile phone (HTC 10), using 320 Kbps mp3 tracks. No expensive gears nor lossless tracks,no EQ, and all that hi-fi stuff.

Product Specs :
Driver: 7 mm “broadband transducer” Single Dynamic Driver
Impedance: 16 Ohms; Sensitivity: 123dB/mW
Weight: 18g
Cable: 1.3m; proprietary detachable cable (Compatible only with IE 400 and IE 500 Pro - Not compatible with IE 40 Pro)
Shell: Hard Plastic Shell
Nozzle: ~5mm
Total Harmonic Distortion: < 0.08 %
Release year: April, 2019

box accessories.jpg

Accessories – 5/5
The unboxing experience was really nice, and the presentation is elegant.
Apart from the earphones themselves, we get the following accessories.
  • 3 Silicone adapters (S, M, L)
  • 3 Foam adapters (S, M, L)
  • 1 Transport case – really spacious and can hold 2 of these earphones easily.
  • 1 Cleaning Tool
  • 1 6.3 mm jack-adapter
400 accessories.jpg
What more can one ask for ?

Build – 3.5/5
The build quality is very similar as its little brother IE 40 Pro, which had no flaws to speak of. The hard plastic shell and the black wires are retained in the IE 400 Pro (Note that the IE 40 Pro connectors are not compatible with the IE 400 Pros). The plastic shell might sound cheap, but this really keeps the weight of the housing and wearing comfort at an optimal level. They’re also using their expensive 7mm micro driver in this model, the IE 40 Pro had a larger 10mm driver. I’m happy with the build in general as I had no complaints against the design or build of the IE 40 Pro.

There are, however, a couple of small enhancements incorporated in the IE400 Pro if you take a closer look. The earphone nozzles now have a protective mesh. This is very thoughtful, and for the asking price I would have been slightly bummed if they forgot to add this trusty mesh. . IE 40 Pro instead has some foam inserted into the nozzle to keep dust out. There is a change in the nozzle length and thickness in the 400 and 500 Pro models, the IE 40 Pro has a slightly longer and thinner nozzle. Detachable cables are great and easy to use and replace.

EDIT 23.01.2020: AFTER 10 months of continuous use and tip rolling with the IE500 Pro which has the exactly same build as IE400 PRO the driver housing in the left earpiece just popped out yesterday. To be fair i tried so many tips with these IEMs (including ones with smaller diameter than the nozzle, twisting them back and forth, etc.) I had to re-glue it back in. Sound quality is the same. If you're not playing too much with tip rolling, you should be good! Bringing down the rating in this section from to 3.5 due to this.

pro bros.jpg 40 v 400.jpg

Fit – 5/5
Fit is excellent. Over ear universal fit can’t get better than this. The slim housing sits very comfortably and seamlessly in the ear concha. Sleeping with this won’t be a problem at all.

Isolation and leakage – 3.5/5
Sound Attenuation is rated at <26dB, and they are OK with music ON. Perfect for indoor use, however, if you are talking a walk outside, outside noise tends to creep in letting you know of your surroundings. The earphones even allow you to have a conversation without taking them off when no music is playing, as would be preferable for on-stage musicians to get together for a small chat between tracks. Sound leakage is very minimal at normal listening levels and shouldn’t bother a loved one trying to sleep.

Microphonics – 5/5
None. There is no touch noise from the cable, and walking with these are a pleasure indeed. Just make sure the earbuds are placed securely in the ear and you wouldn’t notice any cable noise.

Drivability – Easy to drive with a smartphone. With my HTC10s i’m mostly between 40-60% of the volume. It gets a slightly louder than the IE40 Pro, as the sensitivity is nudged a bit higher here.

Before we get to the sound-
Eartips: I’m using the stock tips, which have some foam filter in it. These tips are right in between Final E tips and JVC spirals in terms of bore width. I think the stock tips works as good as any.

Sound –
The general signature can be called balanced, again very similar to IE 40 Pro. They sound very similar. With the Pro series Sennheisers are going for what they call a “precise” sound as opposed to neutral. This is basically a balanced tone with a little nudge in the bass to sound more natural, and a little push in the treble to get that treble extension and splash.

Sennheiser IE400 Pro LR.JPG

We have good bass emphasis, the mids aren’t forwarded like ATH or Donguri, for instance, they play on the right level without sounding restrained. The highs really extend well and display great amount of clarity. It’s up there with the masters in terms of detail retrieval. Every treble touch with the snares and crash will be delivered precisely to the listener’s ear. We can see more about sound in the following passages.

The soundstage is nice and wide. They really stretch from left to right and if you like wide soundstages the IE Pro line-up will not disappoint. The stage is not very tall seeing they tend towards a monitoresque presentation. The presentation is rather lateral, with good pin-point localisation of individual instruments. They never get clinical so as to distract from the music, thanks to the bass emphasis which keeps things together. Overall, the stage is very similar to ER4XR


The bass delivered by IE 400 Pro is punchy and impactful. If your track is bassy, you will feel all the bass fun intended by the artist. The same holds true for the entire series. You get that impactful bass with very decent definition and separation. The sub-bass quantity is slightly below the mid-bass from what I hear. The bass is tight and defined, and mostly stays in its spot without disturbing the clarity of the mids. The mid bass impact is also good, it is the kind of bass that hits and lets the impact sink in for a moment before vanishing. Not the fastest driver. The timbre and natural quality of the bass instruments come through very authentically. The reverbs from cello and double-bass can be enjoyed to the fullest.

The mids are neither forwarded nor pulled back to sound like a V-shaped tuning. The slight bass emphasis and treble tilt gives it a kind of reserved positioning. The intention is to present the mids in a more level-headed manner, rather than boost the mids to get that intimate W sound. Staying where they are, the mids never get out of the spot-light and plays with authority and great clarity, even. The vocalists don’t pop out (unless recorded that way) and sing at a decent distance in the stage. There is a certain airiness to the mids and they sound breezy and happy. This probably plays out more due to a certain drop in the sub-bass emphasis. And of course, with a balanced signature the timbre is mostly right on with a dynamic driver and the IE 400 Pro scores in this respect. Mids sound very natural and defined. The instrument separation is also very evident and commendable.

The treble really extends well beyond 10Khz unlike many IEMs that I’ve had the pleasure of using. Again, true for the entire line-up. Every tick on the snare is clearly presented in its accurate position. The signature tilts bright due to a certain emphasis in the treble region. It’s not overly done, but one will not go and call this smooth (think Final E series, or even Etymotic for that matter). As a result, there is great clarity in the region which sounds crisp, sharp and refreshing. This also gives that little splash which some of us audiophiles crave in an IEM. Due to the great extension here, the transient harmonics are very impressive. If you have songs with a lot of echoes and such, think Pink Floyd or Chemical Brothers, both the IE 400 and 500 Pro sound really mesmerising. The dying echoes of the strings and the high-notes have a beautiful spread in the soundstage and makes for an immersive experience.

Round 1 – Vs Sennheiser IE 40 Pro (~100 USD)
Obligatory comparison with the lesser brother. Let’s see if the IE 400 Pro sounds a whole 250 bucks better than its younger brother.

Sennheiser IE40 Vs IE400 Pro.JPG

The general signature of the two is very similar. IE 400 Pro gets slightly louder in the same volume than the IE40 Pro. The bass is tighter in the IE 400 Pro, and also has a slightly lesser sub-bass slam. IE 400 has slightly better bass definition as well, being relatively faster. The mids, also pop out slightly better with the IE 400s, and is clearer by some margin. Vocals comes through with better intelligibility compared to the cheaper IE 40 Pro. The IE 40 Pro’s highs are little more on the splashier side and have some rough edges. This is tamed in the IE 400 Pros, and they also sound much clearer and have more precise positioning. As a result, they also display better micro-definition in the treble.

Clartiy and definition is better throughout the spectrum with the IE 400s compared to the younger brother.

You can say, these are a direct upgrade to the IE 40 sound, not very different from how the IE 500 Pro is a direct upgrade to the IE 400 sound.

Round 2 – Vs Acoustic Research AR-E10 (discontinued)
Fairly new IEM released by Acoustic Research. I wanted to do this comparison to check how the IE 400 Pro stands against this hybrid IEM, which has very good resolution despite having a big meaty bass.

AR E10 has a big emphasis in mid-bass, and sub-bass. The mid-bass bloom, although not very bloaty, is very evident and colours the signature dark. The driver being a little on the slower side does not help as well. This also masks certain mid frequencies and affects clarity. The E10 are also tuned towards a W-shape response, with the mids/upper mids pushed up to add extra clarity, and has a little emphasis on lower treble as well to give that shimmer up top . When switching to IE 400 Pros, the increase in clarity is quite surprising, and we can readily see how the linear response greatly helps to increase resolution and clarity throughout the spectrum. The driver is tighter, mids clearer, and vocals also have better clarity.

Easy win for IE 400 Pro.

Round 2 – Vs Olasonic FLAT4 NAMI (discontinued)
Only challenging comparisons here on out. FLAT4 NAMI is renowned for its treble clarity and vast soundstage. They are armed with 2 dynamic drivers.

NAMI’s separation is very distinct in their super-wide soundstage. The treble is clearly up in the mix, and the extension is really great. Treble transients fly through the shimmery soundscape. The Nami also hits a little close to the sibilance region, never really touching it, ever teasing. The upper-mids emphasis is also apparent with NAMI. The bass has great definition and decent impact.

Switching the IE 400 Pro, we immediately notice more weight in the bass, with great impact and fullness. Compared to the wide and spread out presentation of the NAMIs, the Sennheisers sound rather intimate. The mids are also clearly in front of the mix in comparison. The NAMIs sport a U shaped tuning where the vocals are slightly pulled back in relation. NAMIs are an easily brighter earphone and the treble splash comes across as slightly thinner. The relatively lesser sub-bass quantity of the NAMIs also help to extract more definition from its bass.

This round must be called a tie. The Senns score some points with vocal clarity and a slightly closer, true to source presentation. The NAMIs are a touch more resolving, and extract slightly more details, but at the expense of sounding slightly harsh and taking the bright signature. IE 400 Pros sound more balanced and the warmth and splash nicely even out for a natural presentation.

Round 4 – Vs Etymotic ER4XR (~350 USD)
I use these with SpinFits. Another relevant and challenging comparison since they are similarly priced.

The Etymotic clarity impresses straight-away, and being XR, the bass is also delivered precisely with nice impact. Detail extraction is, well, Ety level. Mids are crystal clear, and the vocals precise. They do reach a little close to sibilance with the zzzs and sssszs.

Switching to the Senns, we notice better attack and impact of the dynamic driver. The IE 400 Pros add a dash of warmth coming from the ER4XR. Sub-bass impact seems similar, with some added mid-bass attack in the IE 400 Pro. Clarity of the mids are slightly better in the Etys, with the vocals coming through as dry, neutral. The 400 adds that little warmth and soul to the sound. The highs of the Etys are rather thin and the quick hits don’t help much in delivering any sense of depth to the treble. Here, the Sennheisers portray a more convincing treble presentation. The Cymbals and crashes are more life-like, with that added weight. The dynamic driver also has impressive extension into the treble, and yet avoid sounding bright or thin, like the Ety.

The Etys sound a touch cleaner, and leaner, sacrificing warmth and bass impact to the Sennheisers. You might get bored with the Etys, not so with the Senns

Round 3 – Vs Sony EX800ST (~250 USD)
Another single dynamic with a massive soundstage. Also tooted as a monitoring earphone. Let’s see how this fight goes.

Amazing soundstage depth and width, with great clarity in the mids- this is EX800ST. The bass is precise and linear. Mids get the necessary warmth and timbre is top notch. The upper mids are slightly bumped to sound really nice.

Switching to Sennheiser IE 400 Pros, the sub-bass impact is better, with equal warmth spreading to the mids. The treble is slightly nudged up front with the Sennheisers, which make it the brighter of IEM. The notes are all slightly weighty with the Senns, with vocals carrying a little more body. There is better instrument separation with the Sonys as they put their wide stage to perfect use. The Sennheisers squeeze all the sounds a little closer to each other, thereby giving us some extra intimacy as well.

Sonys score with Soundstage, separation, mid-bass, upper-mids.
Sennheisers score with sub-bass, treble, cohesiveness, also outdoor proof.

I had to go back and forth between the two so many times, and i would say they stand in the same tier, while leaning slightly toward Sony, because they have that upper-mid nudge.

Round 5 – Vs Ultrasone IQ Pro (~450 USD)
A very highly competent hybrid from IQ Pro packing 1 BA and 1DD, also aimed at monitoring professionals. I can already say we are near the top of the food-chain here.

The IQ Pro soundstage is vast with great depth, width and height. They display amazing clarity and timbre that it’s quite astonishing. Instrument positioning and spacing is also impressive. Sub-bass is reserved with decent dynamic impact and the driver is quick and resolves extremely well. IE 400 Pro impresses again with equal clarity and I would go so far to say slightly better resolution as well. Despite delivering a much better impact with sub-bass, we can see that the vocals are a touch clearer in the IE 400 Pro, and slightly forward in comparison. The upper treble as well extends further, and you hear slightly more details in the mix.

In terms of sheer detail retrieval and resolution, the IE 400 Pro might just edge the IQ Pros out. Where there IQ Pro impresses is with its greater soundstage, layers and instrument positioning. The Senns hold their lateral positioning, with a relatively constricted space, not so different from Etys, which is preferable for monitoring purposes. Before comparing I thought IE 400 Pro might be on the losing end of the stick. I’m completely surprised by how the Sennheisers rose up to the occasion with their clear and dynamic sound!

Round 6 – Vs InEar Stage Diver SD2 (~450 USD)
OK. This is summit. SD2s loaded with 2 BAs, are a bit pricier than the IE 400 Pros. We already saw how the SD2s put up with its elder brother IE 500 Pros’ punches. Let’s see how the 400s fare against the SD2s.

SD2s are immensely clear with a strictly linear bass, that adds a nice warmth to the mids enabling excellent timbre reproduction. The soundstage is deep and wide quite similar to the IQ Pros. And the sheer clarity in the mids is staggering. The notes have good depth and weight to them and comes across as very real. Treble extension and clarity as well is top notch.

Switching to IE 400 Pros, we can immediately notice a bigger sub-bass reach and impact, but at the same time the driver this time is a bit slower and we can notice layer of muddiness in the bass-mid region. The constricted soundstage does not play to the IE 400 Pros advantage as well. The Sennheiser highs show impressive extension and reach, but not enough to out-do the SD2s in this regard. The note weight is also slightly lacking in the IE400 Pros and they come across as slightly thin. The sheer clarity and greater soundstage earn a convincing win for the SD2s this time. For 350 bucks, the IE 400 Pros are still unbeatable from my little experience.

Bonus round: Vs IE 500 Pro here in the detailed review.
Sennheiser IE500 Vs IE400 Pro.JPG

A word on the single dynamic driver – Sennheiser, with their Pro series, have more than convincingly busted this whole “BA driver for Clarity” myth. The treble resolution and the vocal clarity are TOTL – especially with the IE 500 Pro. Using the dynamic driver also means that bass is on point, and the timbre is closer to the natural sound. Sticking to the single dynamic is also a class-act and I really commend Sennheiser for not condescending to take the multi-driver route.

Both final and Sennheiser will have my respect for sticking to their core values.

Overall Sound rating of Sennheiser IE 400 Pro: 9.1 / 10
Vocals 4.2/5
Soundstage 4.4/5
Instrument Separation 4.2/5
Positioning/localisation 4.3/5
Details 4.3/5
Timbre 4.3/5


Conclusion –
The entire Sennheiser IE Pro line-up are decently priced and deliver great quality sound for the money. The IE 400 Pros are a significant upgrade from the IE 40 Pros. They are highly resolving and stand to contend against the best in the price range. The IE 400 Pros also take you one step closer towards the fully realised 7mm driver, which is the IE 500 Pro. If you're looking for a fun, detailed sound you cannot go wrong with the IE400 Pros.
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Thanks fablestrick, this helped a lot. I see no problem when the record is bad. I also don't want this to be supressed by large dips. It just should not be more sibilant than on other neutral reference devices. :.)
In that case, I think you'll be happy with the 400s.
Happy to help.
Fill me in with your impressions if you get them in the end.
Thanks for the detailed coverage!