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Sennheiser CX 400BT TWS Review • Good TWS headphones with excellent sound

Sennheiser CX 400BT TWS headphones are an excellent offer for those who, for some reason, do not fit the Momentum 2 model , which we recently met. The CX 400BT lacks active noise cancellation, but it does have a slightly lower price tag, great sound, and interesting tuning features. Well, traditionally, there were some nuances.

The headphones come with a short Type-C cable and three additional pairs of silicone ear cushions in different sizes. Unfortunately, there are no additional ear clips included.

Design and usability

Getting to know the headphones starts with the charging case, and it looks a bit like the one in the Momentum model. But there is no decorative fabric, just plain and slippery plastic. The headphones themselves are also made of it, which makes them not very convenient to use. Especially at the moment of taking them out of the case: they must be held firmly, otherwise there is a risk of dropping them.

There are also questions about the size of the case. It is small, but it feels good in a jeans pocket because of its thickness. It is also worth considering the thickness of the modules themselves, because of which they bulge out of the ears. In the summer there will be no problems, but in the winter, if you wear a hat, it will noticeably press the headphones into the auricle. Of course, this is an individual parameter, but it is highly recommended to do a fitting before buying.

Another important point – Sennheiser CX 400BT are not suitable for sports. Even with a properly selected ear cushion, they still risk falling out with sudden movements.

But I definitely like the design of the headphones. The same can be said about the case itself, and how the headphones look in it. There are no questions about the practicality of the light version that was tested. The plastic, though slippery, is not easily soiled.

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Sennheiser CX 400BT sound

For starters, some dry facts: 7mm dynamic drivers, a frequency range of 5 Hz to 21 kHz, Bluetooth 5.1 for connectivity and support for SBC, AAC and Apt-X codecs.

The sound quality of headphones is one of the main and sure advantages. The sound is clear, with moderate but noticeable bass. High frequencies are detailed, in almost all compositions, except for orchestral ones, the headphones did not have problems.

There are no problems with the quality of noise isolation, here it is worth saying thanks to the thick headphone cases. Of course, Momentum 2 wins in this parameter due to the active noise cancellation system, but it is worth remembering the different price tags of these models.

As for the range and quality of the connection, there are no questions either. At a distance of up to 20 meters with direct line of sight, the headphones kept a confident connection with the smartphone (iPhone 11).


The headphones themselves are outwardly quite simple – on each side they have a touch button, one per module. It can be used to adjust the volume, switch songs, answer calls and call the voice assistant.

If necessary, you can use only one earpiece, but it can only be the right module.

For Sennheiser CX 400BT, the manufacturer has provided a special Smart Control application, in which you can reassign button functions or disable them altogether. You can also update the headphone firmware via the app.

Sennheiser  claims up to 20 hours of battery life, and each module can work up to 7 hours on a single charge, which is quite good. The case and modules are fully charged in 1.5 hours. There is support for fast charging, thanks to which the modules are able to get enough charge in 10 minutes to play music for 1 hour.


Sennheiser CX 400BT are good TWS headphones with excellent sound, but controversial ergonomics. Most of all I liked the sound and autonomy in them. But with regard to ease of use, this is an individual question and headphones require fitting. Otherwise, if you like the TWS form factor and need clear, pleasant sound, then the Sennheiser CX 400BT is worth checking out.


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