Sennheiser CX Plus True Wireless vs CX 400BT Comparison Review

Sennheiser CX Plus True Wireless vs CX 400BT

Sennheiser has grown its library of true wireless earphones significantly this year, with their latest release being the CX Plus. This new set of earbuds added a new ANC mode on top of its variety of existing features. The original CX 400BT was the one that introduced interchangeable controls to Sennheiser’s Smart Control app, so you might be wondering what exactly the difference is aside from noise-canceling. Let’s find out exactly where both models differ in terms of functionality and sound quality.

Sennheiser charging case closed

What You Get

CX 400BT CX Plus 
  • CX 400BT True Wireless Earbuds.
  • Silicone ear adapter sets (XS, S, M, L)
  • Charging Case.
  • USB-C Cable.
  • Quick Guide & Safety Guide.
  • CX Plus True Wireless Earbuds
  • Silicone ear adapter sets (XS, S, M, L)
  • Charging Case
  • USB-C Cable
  • Quick Guide & Safety Guide


Sennheiser CX Plus True Wireless vs CX 400BT touch surface

Look and Feel

With the CX Plus, Sennheiser keeps the same basic housing design. The same square architecture is sported on both earphones, but the CX Plus is noticeably thinner than the 400BT both in length and thickness. For most listeners, the CX Plus is going to be the most universally comfortable, but those with bigger ears won’t find many issues with the 400BT either.

Sennheiser CX Plus True Wireless vs CX 400BT charging

Design and Functionality

With both earphone’s interior drivers, the CX Plus can be seen as an improvement over the 400BT. They both feature a 7mm dynamic driver, but the Plus combines its unit with a TrueResponse transducer. This brings a more high-end acoustic system to the CX Plus, which I found provided more ample volume and other sound signature properties that will be further explored in its own section. The only other major difference here is the inclusion of ANC on the CX Plus. The 400BT omits a noise-canceling option, and it wouldn’t be until two upgrades later where it would finally be implemented. Sennheiser designs an effective ANC for the Plus, and having it included makes the 400BT seem more obsolete. While the 400BT gets credit for introducing customizable touch controls, the Plus has better functionality with its responsiveness.


CX 400BT CX Plus
Bluetooth 5.1 5.2
CODECS  AAC, aptX, SBC AAC, SBC, aptX, aptX Adaptive

Battery Life

You’ll get an extra four hours total out of the CX Plus compared to the 20 hours provided by the 400BT. Both earphones will last at least an hour with 10 minutes of charge time.

Sennheiser logo


Both the CX 400BT and CX Plus feature a solid soundstage for true wireless earphones. I’d say Sennheiser has garnered a reputation for it by now with their wireless earbuds, and that’s definitely reflected here. I think both earphones are equally wide, but the Plus had more depth to me, as I felt a lot more clear layers. Spatial imaging is identified and felt throughout my listening to both earbuds back to back which I think is a big accomplishment from Sennheiser, as it creates a certain standard for others to obtain.

Low End   

The bass is a lot less quick on the 400BT compared to the thick and boomy response of the Plus. Of course, both pairs will have a different response depending on if you’re using the smart control EQ, but these low-end tones are tuned very differently. Both their bass response have clarity, but the 400BT lacks some of the fun sub-bass vibrations that the Plus possesses.


There’s a slightly warmer tonality in the 400BT than on the Plus, with the low mids displaying a higher amount of resonance. I preferred tracks with more intimate elements like soft acoustic guitars and baritone vocals. For the Plus, you get a more balanced midrange response, with its own amount of warmth, but with greater emphasis on the fundamental and upper mids as well. It created a much more even texture that I found more enjoyable with a larger variety of tracks. The timbre of the Plus is more crisp and detailed, while the 400BT is smoother.


The treble can be seen as lacking in the 400BT and I felt mostly the same for the Plus. They both have a lack of spark in their timbre, but the Plus is slightly less recessed. Using an EQ on both brought up their liveliness, but naturally, details come across unfocused, with small blooms of tone dispersed throughout. There are more bits of sparkle in the Plus, but it’s inconsistent in most tracks.


Being that the CX Plus is an upgrade from the 400BT, and includes a significant feature for true wireless earphones, it really all comes down to sound signature in the end. With that, the quality on both earbuds is fairly similar in some way, as its warmth and smoothed out the treble. I think when it comes to overall musicality, I found more enjoyment using the Plus over the 400BT, but the smart control app EQ should help you get close to the response you might be looking for in both models. Aside from sound, the functionality is the most immediate improvement on the Plus, and consists of an all-around better build. If you end up seeing the 400BT for a good price, you can’t go wrong with it, but in terms of value, the CX Plus is the clear winner.

Both the Sennheiser CX 400BT and the CX Plus are available at Audio46.

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Alex S. is a sound designer and voice-over artist who has worked in film, commercials, and podcasts. He loves horror movies and emo music.