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High-resolution, transparent mid-ranges, precise soundstage, and a robust design fit for any stage - meet the all-new IE400 Pro. 

Note: 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.

Sennheiser HE-1, 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!


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.

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.

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

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 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.

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 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.

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: 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.

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.

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.


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.


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.

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.


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.

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

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!

Rating: 4.5 / 5.0


  • 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


  • Rare Pentaconn Ear connector

About Teo Yong Shun

Yong Shun is a chemical engineer by training and an audiophile with years of experience in the audio industry as an audio consultant in one of the major Hi-Fi shops in Singapore. Appreciating good music is my daily task and I love to share the greatness with the community. Love what you listen to, with what you have, where you are. Founder of The Audiolocheese.

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