Sennheiser CX 400BT True Wireless

"The sound is incredible, but the cost for a lower price is a number of missing features."

  • Excellent sound quality

  • Responsive and customizable controls

  • Highly adjustable onboard EQ

  • It lacks features for the money

  • Possible problems with fit and comfort

Sennheiser is known for top-notch sound, and both the Momentum True Wireless and its sequel, the Momentum 2 True Wireless, scored very good results on sound quality when reviewed.

But when you add that excellent sound, it comes at a pretty steep price – you'll pay $ 300 for these earbuds. This of course eliminates a lot of potential buyers.

So the challenge for Sennheiser was to create a range of true wireless earbuds that cost less without sacrificing the main reason they bought them: high quality sound.

The answer to that challenge is the $ 200 CX 400BT True Wireless.

Their price point is definitely more palatable, but do their overall features and performance make them a worthwhile investment considering how many other great earbuds are available for the same or similar buck?

Let's take a look.

What's in the box?

Sennheiser CX 400BT True WirelessSimon Cohen / Digital Trends

The CX 400BT's relatively simple cardboard box contains the earbuds, their charging case, a set of four sizes of silicone earbuds (large, medium, small, and extra small), a short USB-C charging cable, and some printed paper documentation.

All of the packaging is highly recyclable except for the black foam inner padding that is glued to the inside of the box.


Sennheiser CX 400BT True WirelessSimon Cohen / Digital Trends

Big and box-shaped are the words that best describe both the CX 400BT and its charging case.

While Sennheiser has tried to downsize these earbuds by giving them a rounded rectangle shape (the word "squircle" comes to mind), the fact that they are large cannot be hidden.

To be fair, while they stand out more than Apple's AirPods or AirPods Pro, they're not as gigantic as Soundcore's Liberty 2 Pro or Sony's WF-1000XM3 or the WF-SP800N.

The size of the CX 400BT has one advantage: the earphones can be pulled out of the charging sockets relatively easily, despite the strong magnets that prevent them from falling out. They're also a little easier to put in your ears.

The shiny outer surface of the earphones with the stylized Senn logo from Sennheiser serves as a touch control.

There are tiny LED indicator lights on the inside of the earbuds. They will show you the performance and / or pairing status of the earbuds. Solid red means power on, blinking blue / red means pairing mode, and blinking green / red means the earbuds are paired.

The small LED on the charging case near the hinge shows the battery status of both the case and the earphones in different colors (depending on whether the earphones are docked or not). This can be a little confusing.

The lid of the charging case is well built and has a wide hinge that can snap into place between the open and closed positions. A strong magnet keeps the lid firmly closed, but is easy to open.

Unfortunately there is no wireless charging option, just USB-C.

Comfort, fit and control

The CX 400BT are comfortable to wear, but have one caveat: To get the best sound quality from true wireless in-ear earbuds (used with silicone earbuds), you need to bring the tips deep enough into your ear canals to to create a really good seal.

This equation has two parts: you need to find the right size of the ear tip and be able to physically get that silicone tip all the way into your canal.

I found that the sheer size of the CX 400BT prevented me from achieving this comfortably. It was doable, but I had to apply quite a bit of pressure while twisting the earbuds into position.

This had a real impact on my ability to wear them for more than an hour before I felt tired.

This problem is exacerbated by the very defined groove that runs around the body of the earbuds. It has surprisingly sharp edges that I became aware of when moving and pushing the buds around to get a good seal.

The controls on the CX 400BT are possibly the best touch controls I've ever used.

Sennheiser CX 400BT True Wireless AppSennheiser Smart Control App Simon Cohen / Digital Trends

Given that Digital Trends rep Nick Woodard didn't have this problem with the Sennheiser Momentum 2 True Wireless (with a nearly identical ear profile), I can only assume that this isn't a problem for everyone, but it does worth thinking about whether you have small ears or have experienced this problem with other models.

Out of curiosity, I tried the earbuds with a set of Comply Foam tips that came with a different set of buds and they helped tremendously. So there are options if you're willing to go the extra mile and buy third-party earplugs.

The controls on the CX 400BT are possibly the best touch controls I've ever used. I'm not a fan of touch controls because they are so difficult to achieve with a consistent response. Sometimes the taps register, sometimes not. Physical buttons are far more predictable.

However, the touch controls of the CX are exceptional and keep responding. I particularly liked the fact that a subtle confirmation tone is generated when registering a faucet. This is a great way to tell if the faucet worked or not.

The existing typing scheme is easy to remember and gives you control over volume, answering / ending / dropping calls, skipping forward / backward and access to voice assistants (Siri / Google Assistant). If you don't like how it works, you can use the Sennheiser Smart Control app to assign any function to any tapping sequence on one of the earphones – something that all real wireless earphones should offer.

Speaking of the Smart Control app: The CX 400BT does not have to be used (without it, it is paired with your device). However, I strongly recommend using it anyway. Not only can you use it to configure the controls, but you can also access the earphones' built-in equalizer and quickly switch between previously paired devices.

This is not the same as Bluetooth Multipoint, which allows two devices to be paired at the same time, but it is the next best thing.

Battery life

Sennheiser CX 400BT True Wireless "class =" m-Karussell - Bild dt-lazy-no "src =" 640x640 .jpg "srcset =";base64, Cohen / Digital Trends

Sennheiser CX 400BT True Wireless "class =" m-Karussell - Bild dt-lazy-no "src =" 640x640 .jpg "srcset =";base64, CX 400BT True Wireless (above) and Jabra Elite 75t Simon Cohen / Digital Trends

There seems to be a question about whether the CX 400BT should get 6.5 or 7 hours of battery life when fully charged. The box says 6.5, but the Sennheiser website says 7.

I set it to 75% and ran it on a radio stream. Seven hours later they were still on the road, so I'm confident the seven-hour claim is realistic.

In both cases, however, the average for true wireless earbuds is currently in the lower range. The $ 150 AirPods and $ 230 AirPods Pro get you just a little over five hours. Jabra's $ 200 Elite Active 75t gets 7.5 hours. The $ 200 Sony WF-SP800N can deliver up to 13 hours with noise cancellation turned off, and the RHA TrueConnect 2 can last for 9.5 hours. Samsung's Galaxy Buds + are only $ 150 but can run for 11 hours.

The loading case is of greater importance. It can only add your playtime to a total of 20 hours, making the CX one of the shortest earbuds with total duration at any cost. Since the charging case isn't exactly small, I'm not sure why Sennheiser wasn't able to provide a little more portable power.

The quick charge option is a bit better than the competition: with 15 minutes you get an hour. This corresponds to that of the Jabra Elite Active 75t, but is not as fast as the AirPods and AirPods Pro, which can also do this for only five minutes. Meanwhile, the Sonys will get you almost 90 minutes on a 10 minute charge.

Sound quality

Sennheiser CX 400BT True WirelessSimon Cohen / Digital Trends

Do you remember how focused I was on getting a good fit? It's not just about comfort.

It's good that I tried these comply foam tips. From the moment I used it, I was in a sonic ecstasy.

With the factory-supplied earbuds, I began to doubt Sennheiser's claim that the CX 400BT uses the exact same drivers and equalizer technologies as the top-rated Momentum 2. What I heard was not close to the praises of Digital Trends writer Nick Woodard: “I heard some pretty powerful earbuds, but that's just a completely different experience. The sound pulls you into the music and devours you as you record notes and instruments that competitors simply don't have. "

It's good that I tried these comply foam tips. From the moment I used it, I was in a sonic ecstasy.

Sure enough, the CX 400BT can rival the best of true wireless earbuds from head to toe, and when paired with an aptX-enabled sound source, they're very hard to beat.

Stereo imaging, precision, depth and breadth of the soundstage – all are superb. Bass, midrange and treble are treated first-class, with everyone being allowed to shine without stepping on the other's feet.

This type of sound quality arguably helps all genres to perform at their best, but you'll really appreciate it when tracks require fidelity across a range of frequencies. Little Something, a duet by Sting and Melody Gardot – a song I just discovered about Tidal – is a perfect example. It features two singers who are supported by a rich mix of acoustic guitar, bass, drums and synth. But the musicians all apply a subtlety to their playing that a lesser set of earphones would attenuate or mask. With the CX, you can appreciate every detail.

If you're not crazy about the factory EQ, the Smart Control app lets you tweak it using one of two equalizer formats. Regardless of your choice, the changes you make will be saved onboard the earbuds, so you can enjoy the results regardless of the music source or the device you are using for playback.

Call quality

The CX 400BT are supposedly optimized for voice calls, but I've found that they generally do no better than many of the less expensive models I've tested.

The lack of a listening mode proved frustrating.

Voice quality was good when conditions were calm, but as is the case with so many true wireless earbuds, they struggled when other sounds vied for attention.

Cars going by, building noises in the distance, helicopters – each of these noises had a tendency to push the speaker's voice around. At no point did this prevent the speaker from being understood, but it was quite distracting at times.

These Comply Foam earbuds, which created such a wonderful seal on sound quality, also blocked a good chunk of my own voice on calls. The lack of a listening mode proved frustrating.

I would say the CX 400BT is perfectly adequate for the occasional call, but quieter locations should be preferred for something longer than a brief "I'm late for our meeting" message.

What is missing?

Since Sennheiser succeeded in equipping the CX 400BT True Wireless with the same sound quality as earphones, which cost $ 100 more, corners had to be cut elsewhere.

There's no wear sensor that can automatically pause music when you remove an earbud. There is no active noise cancellation (ANC). There is no listening mode for introducing outside noise when you need to have a conversation, and there is no IPX rating for water or dust resistance.

And we've already talked about the CX's overwhelming overall battery life.

Our opinion

The Sennheiser CX 400BT offers great sound for its price of $ 200. If they had just a few more bells and whistles, we'd be in wireless earbud heaven.

Is there a better alternative?

I don't think another set of true wireless earbuds for $ 200 will get you better sound quality, but you can get close to that. The Jabra Elite Active 75t and Sony WF-SP800N both cost $ 200. While they may not quite match the CX 400BT's sonic purity, they outperform all other features like comfort and fit, audibility, battery life, and ANC (in the case of the Sonys) and water resistance.

How long will they last?

With no official protection from water, you may need to be extra careful with the CX 400BT, but it (and its charging case) are very well built and should last for many years. Sennheiser grants a two-year guarantee on them, which is twice as long as with some other brands.

Should you buy it?

It's a tough call. If getting the absolute best sound quality for your money is your number one priority, and you can make peace with the CX 400BT's extensive list of missing features and potential customization issues, then I recommend it. But I would take a close look at the many strong competitors at this price point before buying them.

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