Underrated Gemstone - Sennheiser IE40 Pro


Sennheiser Electronic GmbH & Co. KG produces a lot of high fidelity products which impressed audiophile community since 1945. Being a family business, the legacy is built and passed down generation to generation without compromising the details. Sennheiser HE-1, the most expensive headphone system is a status that show where Sennheiser stands in this audio market - king of the kings.

Sennheiser HE-1

During 2018 4th quarter, I had the opportunity to attend grand opening of 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.

Mr Daniel Sennheiser, CEO of Sennheiser Sennheiser electronic GmbH & Co. KG

When Sennheiser is mentioned, people will immediately think of their TOTL such as HD820, HD800s and IE800s. Indeed, being TOTL, these gears created high benchmark for competitors to follow their footsteps in the market. Sennheiser does not forget those who do not have deep wallet to invest on the TOTL. Last year, Sennheiser launched a consumer range IEM, IE40 Pro. It is retailing at SGD159.00 in Singapore - attractive right? In this review, I wil slowly introduce the greatness of this underrated gemstone to you in this review!

Sennheiser IE40 Pro


  • 1 IE 40 Pro

  • 3 Silicone Adapter (S, M, L)

  • 1 Foam Adapter (M)

  • 1 Soft pouch

  • 1 Cleaning tool


  • Impedance: 20 Ohms

  • THD: < 0.1 % (1kHz, 94dB)

  • Frequency response: 20 - 18,000 Hz

  • Cable length: 1.3m (4.3 feet)

  • Attenuation: < 26 dB

  • Sound pressure level (SPL): 115 dB (1kHz / 1 Vrms)

  • Transducer principle: Dynamic

Build, Fit and Isolation

The shell of IE40 Pro is built using plastic. I got the black colour variant which the finishing is a little matte - giving an expensive looks although it is built using plastics. This results the IEM to be lightweight and does not ‘carry any weight,’ even during lengthy sessions. This small housing IEM does sit well in my ears and create a good isolation. I believe the fit will be good for most of the people because of its small form factor.

IE40 Pro in a closer look

The cable of this IEM is detachable but as usual, Sennheiser chose a proprietary connector for this IEM like what is done on IE80s. As mentioned by Sennheiser, the cable is deigned with innovative internal cable duct (patent pending) which is fit for stage use. Cable upgrade will be difficult for this IEM now but I hope cable manufacturer can take this connector into consideration.

Proprietary connector is used for IE40 Pro


I used one of my favorite music players, Opus #3 for this review. Cable and eartips are original from the box.

IE40 Pro with Opus #3

Test Track

  • Hotel California (DSD) - 90/160 on high gain

  • Somewhere, Somebody (DSD) - 90/160 on high gain

  • Billie Jean (24 bit/96 kHz FLAC) - 80/160 on mid gain

  • Misery (16 bit/44.1 kHz FLAC) - 80/160 on mid gain

  • Perfect (24 bit/ 44.1 kHz FLAC) - 80/160 on mid gain

  • Don't Know Why (16 bit/44.1 kHz FLAC) - 80/160 on mid gain

  • Red (16 bit/44.1 kHz FLAC) - 80/160 on mid gain

  • Hello (16 bit/44.1 kHz FLAC) - 80/160 on mid gain


This IEM can be easily driven by DAP or phone. Opus #3 is not a powerful DAP so I need high gain to be triggered for DSD files. Soundstage is always the secret weapon of Sennheiser. Without any disappointment, Sennheiser ace it in IE40 Pro. I think this is the widest soundstage I can get in this price range. It is wide at the X-axis and sufficiently deep at the Y-axis. Impressive! This IEM is sitting in between neutral and bright. I would say it might be described as bright. As a bright signature lover, this fulfill my desire.


I am really impressed by the performance of this mighty IEM at the low frequency region. Solid bass with sufficient depth and it is well controlled. The lows attack fast with synergy and decay fast without bleeding to other frequency region in the spectrum. This is what I describe as quality bass - presence when it is needed, leave when it is not the right time. The DAP I used to review this IEM is not the most bassy one but I believe the lows of this IEM can feed the desire for those bass heads.


For those who read my previous reviews will understand how much I appreciate mids as a pop songs lover especially mandopop. As a matured listener, I believe the mids can be recessed because of the positioning of the staging but the quality should be preserved always. IE40 Pro hits the sweet spot for mids - neither forward or recessed. Nicely sit in the center of the stage, being the star for the stage. Now the show is for the vocalist. Male vocalist like Ed Sheeran sounds full of energy and emotions. When reviewing this IEM, I hesitate to pause the music because I am too into the quality which is presented. The upper mids are breathy and spacious. When I am listening to Jennifer Warnes’s Somewhere, Somebody, the layering is done flawlessly. Her vocal is silky smooth with soul. Very neutral.


Being a bright IEM, the highs are definitely more prominent. A great space is designed for the highs - Spacious and airy without any congestion. The cymbal sounds crisp without distortion. Within this price range, a lot of IEMs have difficulties to present the highs with low noise content but Sennheiser manage to overcome this general issue. It extended well and rolled of well too which results a gentle presentation. It will not torture your eardrums - no piercing highs.


Shure SE215 Speical Edition

SE215 Special Edition is a warm IEM which is one of the favorite for beginners. I like the presentation of SE215 - silky smooth but in term of details presentation, IE40 Pro does a better job. The soundstage is wider and deeper with more space and air. One winning point for SE215 is the use of MMCX connector - easier to find a replacement cable for this IEM.

SE215 Special Edition vs IE40 Pro

FiiO F9 Pro

This comparison is a slight disadvantage for IE40 Pro because of the retail price. F9 Pro is in the SGD200 price bucket. F9 Pro utilised three drivers which attracts a lot of beginners - the more the merrier. In term of details presentation, F9 Pro does not perform a lot better as compared to IE40 Pro - both IEMs are on the same par. F9 Pro is a more neutral IEM as compared to IE40 Pro. If you not a fan of bright IEM, F9 Pro might be more suitable for you.

F9 Pro vs IE40 Pro


This IEM might be rare for a lot of beginners. I like how RHA build their IEMs - rigid and sturdy. The finishing is supremos. In term of sounds, I find MA75o is colder as compared to IE40 Pro. The emotions presentation is better on IE40 Pros. This is no longer a fight on quality but feel. Colder IEM does ace better in details presentation but MA750 is not far ahead in this region as compared to MA750.

MA750 vs IE40 Pro

1More Triple Drivers

One of the favorite IEM by beginners - 1More Triple Drivers wins a lot of beginners' hearts. Again, the more the merrier. This is always a misunderstand. I always find the presentation of 1More Triple Drivers is a little bit noisy. The overall presentation is sweet but the distortion is killing me sometime. IE40 Pro presented the music in a leaner and cleaner way which should be appreciated by the community. IE40 Pro is easier to drive as compared to 1More Triple Driver too.

1More Triple Drivers vs IE40 Pro

Symphonium Audio Mirage

Symphonium Audio, a Singapore company created 2 IEMs last year. One of them is Mirage. Mirage utilises one B.A driver. Is it another underrated gemstone? Not really. The presentation of Mirage is darker and I always find it blanketed. When my ears are used to the presentation of IE40 Pro, I find Mirage presentation is muffled. This is a clear win for IE40 Pro.

Symphonium Audio Mirage vs IE40 Pro


As mentioned in the title, IE40 Pro is really an underrated gemstone within the SGD200 bucket. Clear presentation with proper bass management, IE40 Pro will not disappoint you no matter which genre you are listening to. At the same time, your pocket will love this IEM because you do not need to burn your pocket a hole when you decide to purchase it.

Well done Sennheiser!