Sennheiser CX 400BT True Wireless Review

Last year, Sennheiser made waves in the wireless earbud space with the release of the fantastic sounding Momentum True Wireless, followed quickly thereafter by the Momentum True Wireless 2, which added a longer battery life active noise cancellation.

Now Sennheiser has come up with yet another true wireless earbud, The CX 400 BT, this one aimed at a slightly lower price point, and coming with a rejiggered combo of features.

What’s In the Box?

Upon opening the box you’ll be greeted with a black card inscribed with a “superior sound” guarantee, as well as the quick guide for fast and easy set up. The lay over top of the charging case which contains the earbuds inside. The bottom compartment flips up and houses the USB C charging cable, 3 different sized silicone ear adapters

Design and Fit

As for the design and the materials here, everything is pretty utilitarian in nature. The emphasis definitely seems to be on simplicity and efficiency more so than any aesthetic wow factor. 

The charging case is made from a pretty standard, smooth plastic material with a few nice touches, like the shiny silver Sennheiser logo on the top, and the same thing with the brand name on the inside of the lid. It has an LED indicator light on the back for charge status, that will change from red to yellow to green depending on how much juice you’re at.  Overall the case is definitely not quite as striking as the fabric covered charging case of the Momentum models, but it will certainly get the job done, and doesn’t look bad by any means. 

Now onto the earbuds themselves. Again, we are looking at the same black plastic material here, so it’s all very uniform, very clean, very basic in style, with nothing super distinguishing or notable on the design front. T have a kind rounded rectangular hybrid type shape, presumably to try to cut down on the bulk a little bit but the size is very close to the momentums. The outside, which features another silver Sennheiser logo, is also the touch control pad from which you\’ll be operating most of the features. The only real pop of color are the gold magnets on the inside which are for locking into the case. These work really well by the way, so you don’t have to worry about these falling out at all. Overall, very smooth, very monochromatic and very visually unobtrusive - which kind of seems to be the design philosophy here all around.

As for the fit of these, I like them a lot. This shape didn’t necessarily look the most inviting to my ears when I first took a look at it, but with a simple placement in and twist its sits really snugly in there and lays quite comfortably, not feeling heavy at all. As far as the look, these are still pretty conspicuous. They’re relatively bulky and jut out just a bit farther than you might be used to with an airpod or some equivalent, but it’s by no means a deal breaker - just something to note

Features 

One of the biggest features here that is different from the Momentum 2s is that these CX 400BT do NOT feature active noise cancellation, which is one of the bigger reasons for the lower price point. I do have to say that due to the snug fit and depending on what size ear adapter you use, these do actually provide decent passive noise cancellation just by virtue of the way they lock into the ear. It’s obviously not going to be a suitable replacement if you need all ambient noise replaced, but you can pretty easily block out much of the outward interference of a reasonably noisy place like a crowded room or street for example..    

The battery life here is slated at 7 hours in the earbud, with  20 hours if you keep the case fully charged. This is not a ton, and there are certainly longer lasting options,  but this  definitely enough to get you through the day if you’re going to charge up every night at bedtime.

Controls/Customization

The connection here is super solid, as the CX 400BT is a device that utilizes Bluetooth 5.1 and features both AAC and APTX compatibility, which is  fantastic for a pair of wireless earbuds that’s hovering in this lower price range.

Another thing that you get with the CX 400 BT is that it uses the same Sennheiser smart control app that could be configured with the Momentum 2s. The app is really straightforward and easy to use, and it allows you to customize your experience to a fairly detailed degree.

The app can control multiple Sennheiser devices and it allows you toggle between them. More notably, it also features an equalizer feature that allows you to customize your listening experience depending on what it is you’re out to do. The first interface is a graphic 3d waveform display that you can edit by moving a little circle around depending on which frequencies you want to boost or cut.

Or, if it’s more intuitive or quicker for you, you can use a second interface which has a very simple three lines for bass, mids and treble that can be adjusted along a slider.

Also really nice about the app you can customize the touch pad controls, assigning functions to a certain amount of touches on the pad. Features that can be controlled include skip, previous, volume, and call pick up or rejection. The functions right out of the box are pretty intuitive, so I find I only wanted to change a single tap on either side of the touch pad to pause or play, since these don’t have an auto pause function.

Or if you decide that you just don’t want to deal with it at all, you can go in and disable all the touch controls.

Sound Quality

 As you can see has been the pattern here, both designs and the features on here are very good and functional, but not over the top or super indulgent. They’re standard in a way that won’t get in the way of your enjoyment. After doing some listening, it seems evident that the reason for much of the effort went into producing the best possible sound quality for wireless earbuds at this price range.

For starters, these share the same 7mm dynamic driver as the pricier Momentum 2s, and the sound quality has been replicated here. 

When you first fire these up, the sound signature is relatively flat, providing a pretty equal balance between the different frequencies, which give you plenty of time to play around with the equalizer to customize to what you like.

On the low end, the bass frequencies have a really nice response here in terms of presence and volume, and they provide a great amount of clarity and timbre integrity while not sacrificing the thump that you might want if listening to hip hop, heavier rock, or even some dramatic classical.

I listened to Oh Devil by Electric Guest while I was using these, and the pulse of the electric drums and the synth bass fill the bottom of the sonic picture really powerfully while still maintaining a good amount of separation between them.   

The mid range is very clear and detailed, with great amounts of instrument separation and lots of room for different elements to lay over one another with precision and no muddiness. 

Listening to my same reference song, the higher staccato synth parts hit with a bit more of a sparkly echo than they do in less high resolution headphones, which gave a nice depth to the resonance that I hadn’t heard before in earphones at this same price point.

The high end also sounds clear and crisp for the most part, but the one thing I noticed is that it can get a little piercing in a more trebly song if you’re wanting to crank that volume up pretty high. I took a listen Last of Our Kind by the Darkness which features a lot of high whining vocals and upper range guitar solos, and it seemed to be pushing the sound just a tad. It required a little bit of fiddling with the EQ but still sounded mostly excellent when all was said and done. 

Wrap Up

The CX 400 BT is a truly fantastic sounding wireless earbud, providing the excellence in engineering and sound reproduction that you would come to expect from the good folks over at Sennheiser. It’s a little light on the bells and whistles that took the Momentum 2s to the next level, but if you’re looking for a more affordable option that doesn't sacrifice any sonic integrity, than look no further.

These are great for you if:

You like a minimalist classic design

You want a customizable sound experience

You want real premium quality sound while on the go

These may not be for you if:

You need super long battery life or the lack of active noise cancellation is a deal breaker

You can get a pair of Sennheiser CX 400BT True Wireless In-Ear Headphones at Audio46 today.