Design & Construction

Sennheiser is back again and this time, they are going after the budget-friendly crowd who enjoys the signature Sennheiser sound. Dive straight into the design, Sennheiser stuck to the basic monotone finish on the face of the earbuds themselves. The earbuds themselves are of a square shape and a tat bit large when compared to the Momentum True Wireless 2. The earbuds also come with different size silicone ear tips to ensure a tight seal and secure fit. Throughout long listening sessions, I never experienced any wearing fatigue or pain in my ear canal. All controls for music playback and calls are controlled via both touchpads on the earbuds themselves. Besides that, they feel much more responsive to taps and do not register accidental taps. And the best thing yet, you can finally customise the touch controls. Now for the controls, a single press on the left earbud will play/pause your music, a double press skips backwards while holding it down will decrease the volume. Moving to the right earbud, a single press will bring up Google Assistant, Amazon Alexa or Siri, a double press to skip forward and holding it down will increase the volume. For calls, there is yet another set of controls and tapping on either bud will do the same command. A single press will pick up the call and a double press will reject the call. You can hold down both earbuds for 3 seconds to enable Bluetooth pairing. It takes about 1.5 hours to charge both the case with the earbuds and it does offer quick charge. With a 10 minutes charge, you will get 1 hour of playback. However, the earbuds are not water-resistant and do pick up fingerprints smudges. Moving on to the case, it is rectangular and fits right into my palm of my hands, it isn’t the smallest true wireless case when compared to the competition but it will still fit in tight jeans pockets with a bulge. A USB Type-C port can be found on the rear of the case. The hinges holding the cover and body of the case is strong and is likely to survive a couple of accidental drops. The earbuds do magnetically click into place when they are docked into the case. Throughout my use, I dropped the earbuds couple of times and no signs of damages and scratches can be found on the exterior of the finish and also no compromises on the sound quality itself. Like all true wireless earbuds, they do dock in fairly easily and will not fall out when the case is flipped since there are magnets inside to keep them secure.

Sound Quality

The 7mm drivers produced an energetic sound signature out-of-the-box just as enjoyable as the Momentum True Wireless 2. So let's start off with the bass response. In short, it is deep, full and tight. It never managed to distort at loud volume nor did it bleed into the mids. It doesn't hit as deep bass-heavy kings such as the Jaybird Vistas but it definitely clean and strong bass that resonates with a wide soundstage to give every single bass drop that depth and detail. The highs sound very bright and filled with plenty of details. The mids do sound very crisp with vocals being in the forefront. The soundstage definitely the widest I have heard. The instrument separation is excellent and distinct left and right channels could be heard. If you are not so much of an EDM or Hip-Hop fan, I am glad to report that they do work perfectly with all other genres ranging from Pop to Jazz after you fiddle with the customisable sound settings in the Sennheiser Smart Control App available for download from the App & Play Store. In the app, you will first see the Sound Equaliser which you can choose to customise your very own. This time, you can save presets and switch between them seamlessly. If you are looking for the cleanest sound signature, leaving the equaliser on Neutral will do the job. Moving on, you can also Auto Accept Calls, update the earbuds firmware or change to use either voice or tones prompts. If you ever lose your earbuds, you cannot trace them back since they do not have Tile integration like the Momentum 3 Wireless Headphones. There is no Transparent Hearing feature or active noise-cancelling on the CX 400BT, only passive noise isolation. Lastly, not to forget about the call quality. The CX 400BT call quality is usable but definitely, it is still not on par to the Apple Airpods Pro or Jabra Elite Active 75t which are the widely acclaimed champion of call quality experience. My voice comes through pretty clear and the ambient surrounding noise is suppressed greatly.


Connectivity & Portability

The earbuds support the AptX, AAC and SBC codecs together with Bluetooth Version 5.1. The earbuds also automatically power on/off when docked or taken out from the case. The battery life peaks at 7 hours per use and up to a total of 20 hours. The package also comes with a USB Type-C cable for charging. If you are planning to watch videos or movies with these, I am glad to report that they do not suffer from any latency. Should you also wish to only use one earbud at one time, the right one is available only since it does still use the master and slave connection, unfortunately.



  • Durable Construction

  • Bluetooth 5.1

  • AptX Support

  • Responsive Touch Controls

  • In-App Equalizer

  • Long Battery Life



  • No Wireless Charging

  • No L/R Dual Connection


The Bottom Line

In all, the Sennheiser CX 400BT is still the budget audiophile's go-to for the best sound quality in any true wireless earbuds ever made till date. With the excellent sound settings, decent build and easy to use controls, it makes it worthy of its slightly high budget price. This time, Sennheiser does only offer these in black and white with matching case colours.



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