With the rise in popularity of truly wireless earphones, hundreds of brands and companies have come up with their take on the audio device concept. Today's review will take a look at Sennheiser's latest creation: the CX 400BT TW earbuds. Sitting a tier below the premium MOMENTUM True Wireless 2, the CX 400 BT buds were designed to deliver superior sound quality with everyday usage in mind.

The real question is whether the CX 400BT can stand their ground against alternatives with similar price points from competitors like Jabra or Sony. At an asking price of $199.95, no ANC and a lack of an IP rating, will the world-renown German engineering fail to deliver? Let's find out.


Weight 49 grams (6g each earbud + 37g charging case)
Design In-ear, closed acoustics
Connectivity Bluetooth 5.1 | USB Type-C
Battery 5V, 600 mA | Up to 7 hrs, 20 hrs with charging case
Speaker Sennheiser 7mm dynamic driver
Frequency response 5Hz to 21,000Hz
Frequency response (microphone) 100Hz to 10kHz
Total harmonic distortion
Codecs SBC, AAC, aptX
Supported Profiles



Right off the bat, the CX 400BT TW earbuds have a nice premium feel to them. The truly wireless earphones come in a matte silicone case with glossy highlights here and there which accent the finishing of the product. As it has a matte coat, the charging case does not track any fingerprints. It also has a nice weight to it, neither too light nor too heavy.

Turn the case around and you will find a USB-C charging slot (a compatible cable comes in the box), a small LED light and a button - the only physical button on the entire device. You can press the button to learn the battery status of the earbuds. If the battery is high, the light flashes green, if it's been used about midway, it blinks yellow, and if the charge is low, it turns red.

Moving on to the stars of the show, the earbuds that are housed inside the silicone case are small, sleek and ergonomic. Each individual earbud has a touch panel on its exterior to navigate controls. The right earbud has three tiny little holes in a corner which are barely visible. These serve as the microphone. You can tap each bud once, twice or hold down to trigger different controls such as pause, play, volume controls, voice assistant, and answering or declining calls.

Owing to the small size and squarish design of the earbuds, they fit in nice and snug when worn. I found no issues while wearing and using them for long periods of time. Rather, I would often forget that they were on in the first place. Contrary to my fears, the buds are not prone to falling out either. Overall, it was a very comfortable wear experience.

One of the biggest disappointments for me was the lack of an IP rating on this thing. Although it also lacks active noise cancellation, the water and dust resistance certification is a bigger priority for me personally. Through an unfortunate incident, I was able to discover that despite the missing IP rating, the CX 400BT earphones are considerably durable.

While walking to work one unlucky morning, I happened to drop the case in a nearby pool of drain water. My immediate reaction was to pick it up and douse clean water all over it. After several hours of sanitization and intense cleaning up with tissues at my workplace, I was amazed to find out that the earbuds were working just as good as before! Following this incident, I think from a durability standpoint, the CX 400BT are pretty good despite not having any sort of resistance certification.


Speaking of the actual performance of the Sennheiser TW earbuds, the sound quality is simply excellent. Music and calls sound very crisp and clear, and the bass and treble also sound great. Though it doesn't have ANC, the in-ear closed acoustic technology manages to shut out outside noise very well. The only time when I could hear external sounds with the CX 400BT on was in the midst of heavy traffic and even that was reduced to a low, barely audible hum.

The microphone works pleasingly well, despite the petite nature of the buds and their distance from the mouth. As for the touch panels, they are also great and respond perfectly without any accidental touches. All controls are completely customisable and can be changed via Sennheiser's mobile phone app. It is called Smart Control and is available for Android and iOS. It also has an equalizer, allowing users to adjust the sound preferences to their liking.

Battery life

On paper, the battery specifications state that the earbuds can stay alive for up to seven hours with continuous playback. When factoring in the silicone case, the battery life is further extended to a cap of 20 hours of back-to-back playback. I decided to put this to the test and my results were well above satisfactory.

After fully charging up the CX 400BT, I was able to use the TW earphones (including the case) for 14 days straight. I tend to listen to music while working, so the actual playback time according to my estimates would be about 21 hours of real-world usage. Once drained, it took me 1hr 6m to charge the case back up fully, as opposed to the 1hr 30m official charge time. The results speak for themselves, the battery life deserves applause.


In the end, I would say that if you're an average Joe living the nine to five corporate life but have a penchant for music on the go (coupled with a tendency to be clumsy like me), these earbuds will work as a fabulous fit. The sound quality is wonderful, they look really stylish and are very comfortable to wear.

Some other plus points that make up for the lack of ANC and IP rating are the unexpectedly good durability and the easy-to-use controls. Add to that the brilliant battery life and you have an absolute winner on your hands.

If you're looking to buy a pair of Sennheiser's CX 400BT TW earbuds, you can purchase them for a temporarily discounted price of $129.98 from Amazon.

As an Amazon Associate, Neowin may earn commission from qualifying purchases.

Sennheiser CX 400BT
- Superb sound quality - Easy and responsive touch controls - Ergonomic design - Long-lasting battery
- No ANC - No IP rating
15 September 2020


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