Sennheiser CX 400BT Review

Sennheiser CX 400BT Review

With the new true wireless headphones from Sennheiser, buyers have to do without the ANC noise shielding. TechStage shows what the budget model does in practice.

Sennheiser has produced impressive headphones with the Momentum True Wireless 2 (test report). Not only did they get the best rating in the individual test, but they are also the well-deserved test winners in comparison with models from other manufacturers. Moreover, with the Sennheiser CX 400BT, Sennheiser has now brought a significantly cheaper model of wireless in-ear headphones onto the market.


  • Sound is widescreen, detailed, and extremely forward.
  • They are more comfy to wear than they appear.
  • It’s a decent headset for making calls.
  • Momentum True Wireless II is more expensive
  • Connection that is stable
  • Pairing is simple and smooth
  • Onboard EQ with a lot of options


  • With treble sounds, it can become agitated.
  • Battery life is normal.
  • There is no barrier to water or perspiration.
  • Lacks a plasticky feel ANC

Design and hardware

Visually, the Sennheiser CX 400BT differs significantly from the Sennheiser flagships – starting with the charging box, which weighs just 37 g. The shape is reminiscent of a cool box or a toolbox in miniature format. Unfortunately, the plastic used does not look very high quality, and the box is almost too big for your pocket. The earphones weigh 6 g each, and here, too, the plastic does not feel as high-quality as that of the more expensive family members. Instead of a round design, Sennheiser relies on a rectangular back for the CX 400BT – which also serves as a touch-sensitive control panel. The sides are slightly matted and contain microphones for phone calls and voice commands.

Technically, however, the headphones hardly differ from the Momentum because drivers, controls, and app extensions are almost identical. Instead, the CX 400BT with ANC and Transparent Hearing is missing two important main features. First, it is practically negligible that there is no protection against water and sweat, according to the IPX standard onboard. But the lower price has to come from somewhere.

The CX 400BT is available in white and black. In addition to the charging box and a USB-C charging cable and four ear adapter sets in sizes XS, S, M, and L.


Despite the chunky look, the Sennheiser CX 400BT can be easily placed in the ear. After a slight twisting movement, they sit comfortably with enough support – provided the right silicone attachment has been selected. And there is also an advantage of silicone plugs: So ambient noise is physically well shielded. However, there is no way of circumventing this shielding with the CX 400BT. If you don’t want to miss any acoustic cues, you have to remove the in-ears.

The touch control reacts sensitively. A light tap is enough to call up the desired function. Sometimes it would have been a bit more indolent: In the test, a woolen hat that reached over the ears repeatedly activated a command. But, in general, the operation works very well. In the default setting, a tap on the left-back is sufficient to start or stop audio files. With a double-tap on the left side, it goes back one track. On the right side, it goes one track forward. If the finger remains on the touch surface, the volume changes: it is quieter on the left and louder on the right.


As with the Momentum TW 2, the free Smart Control app on the CX 400BT provides significant added value. Of course, this can be used to update the headphones’ firmware. However, more exciting is the possibility of defining touch functions yourself within a narrow framework. For example, if you are not interested in using a voice assistant, you can deactivate this function. And if you think touch is generally stupid, you can turn the controls off completely. However, all that remains is the operation via smartphone. Of course, there is an equalizer on board, with which the sound can be adjusted according to your wishes. We left the settings on neutral for the test.

Sound Quality of Sennheiser CX 400BT

The Sennheiser CX 400BT have the codecs SBC, AAC and aptX on board. Depending on the player, very high sound quality should be available. We’d like to try this out with our test playlist. One More Second by Matt Berninger begins with gentle guitar runs, a subtle bass in the background, and light hits on the drums. The resonant voice of The National singer is warm and soft over the sound. The deep tones offer a good foundation without pushing themselves into the foreground. The highs give the sound a contour. Nothing breaks out at the tips. And despite the clarity, it looks airy and light. The mids give the song a hold, even if they have little character. A tad too dull, as if the contrast of a picture wasn’t perfectly balanced.

Alchemy by Manik MC starts with a nice groove that is slightly reminiscent of old Warren G times. It’s one of those nodding songs that you can hear over and over again with a smug smile. It gets cool when the slow-down singer Maverick Saber puts his soul over the chorus. The sound is warm. The basses are powerful. The highs are provided with fine clarity in the peaks, the differentiation of the many sounds is excellent. The mids are perfectly balanced. The CX 400BT gives the song a good stage.

From smooth to snotty: With Nacht, Caulk has released a song that sounds more like Berlin than their hometown Vienna. The drums begin with a clatter. The guitar plays sound lines over them like a thick brush. Singer Sophie Löw sings her lines of text in her typical, boring-sounding style. Every pore sounds like the 80s, thickened with modern flavor. The true wireless headphones make a slightly dull thud in the ears, but that is a stylistic device and not a defect. As soon as the volume is maxed out, the song takes you straight to the small club, very close to the stage. The vibrations wander from the head to the stomach. The highs and mids are satisfied with the supporting role and thus underline the live feeling.

The CX 400BT pulls out all the stops again to Jeanie from Jim-E Stack and Bon Iver. The sound is packed with all sorts of gimmicks: fat bass runs on the synth, subtle drums, distorted voices. That could have failed massively with less good headphones, but the Sennheiser in-ears bring the sound to the home straight with virtuosity. Every sound is perfect. The basses almost have a club feel, but without dominating the rest. The mids bring tonal richness to the voices. The highs optimally round off the spectrum. If you want to find a flaw, then in a few moments, it would be the lack of dynamics and the slightly muffled sound that repeatedly lays over individual passages.

The sound of the CX 400BT comes very close to that of our test winner, Momentum TW 2 – even if it does not fully match it in all aspects. This may be due to the slightly different design or the not identical inner workings. But the differences are bearable. The overall sound is warm and round – which is what you can expect at a price.

Telephone calls sound good, and conversation partners also spoke positively about their sound experience in several tests. The soundtrack of films is transmitted without noticeable delays, and there were no problems with mobile games either.

Battery Pack

According to Sennheiser, the non-replaceable battery lasts for seven hours – depending on the volume selected – in the test, we came to about six hours. The charging box provides power for a maximum of 13 more hours. A full charge takes about 1.5 hours. Ten minutes at the socket are enough for another hour of music enjoyment. These values ​​are now more likely to be regarded as average and significantly lower than for the Momentum TW 2, which come to a total of 28 hours.


Sennheiser has produced very decent in-ear headphones with the Sennheiser CX 400BT. The sound is great, the operation is simple, and the design is impressive. Understandably, Sennheiser decided not to give the headphones all the features of the top model. After all, they do not want to have any competition in-house. Still, we miss ANC and even more Transparent Hearing functions already available in many good models from other manufacturers. Furthermore, the waiver of protection against water and sweat is incomprehensible.

The app brings useful extensions, but the battery is not strong enough to raise the headphones to a top position. So despite good values ​​for quality, sound, and functions, the CX 400BT has to face very strong competition in this price segment – and probably often lose out. They’re good headphones, no question about it – but they don’t leave a lasting impression.

Sennheiser CX 400BT Review
Sennheiser CX 400BT Review


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