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The Sennheiser CX400 BT wireless earbuds have great audio quality, but they are pretty darn uncomfortable
The Sennheiser CX400 BT wireless earbuds have great audio quality, but they are pretty darn uncomfortable IBTimes/Bob Fekete

Who Are The Sennheiser CX400 BT Wireless Earbuds For?

  • The Sennheiser CX400 BT wireless earbuds produce great audio quality
  • The CX400 BT earbuds have decent battery life and don't need to be recharged all the time
  • The CX400 BT earbuds have great microphone quality with loud, clear conversations

Earbuds, earbuds, earbuds. Just about every company out there seems to be making wireless earbuds these days and they certainly are not all equal. Audio powerhouse Sennheiser is back with their latest entry in the earbuds race with the Sennheiser CX400 BT true wireless earbuds. Do these earbuds live up to the storied legacy of Sennheiser?

Bulky Fit

The Sennheiser CX400 BT earbuds are not small. In fact, they're fairly bulky. This means that they actually stick out of my head instead of nestling inside my ear. It also means that the CX400 earbuds are somewhat heavy.


What happens to heavy, unsecured things? They fall down frequently. The same is true for the Sennheiser CX400 BT earbuds. If I am sitting still, the earbuds generally stay put. However, the second I start moving, talking or eating, the earbuds instantly become loose. I've had the CX400 earbuds pop out of my head dozens of times now, making them virtually impossible to use when outside (or even when inside doing things like washing dishes) for fear of losing one.

Even when the Sennheiser CX400 earbuds do get a somewhat snug fit, they are far from comfortable. The earbuds are rectangular, which seems a little counterintuitive for staying in ears. The instructions mention that the CX400 earbuds need to be "screwed" into place, but that just results in the speaker stem getting jammed pretty far into my ear canal. At best the CX400 BT earbuds are uncomfortable, at worst they're uncomfortable and the earbuds still pop out anyway.

Switching to the smaller earbud tips did help dramatically with keeping the CX400 earbuds in my ears, but they still aren't as secure or comfortable as I would like. The smaller earbud tips also mean the speaker stems are driven further into my ears when twisting them in, which I find to be an unpleasant feeling.


The bulky frame does at least go to some use with the CX400's battery life and audio driver size. While many earbuds tend to top out at four to five hours of playback before needing a recharge, the CX400s can go for around seven hours before needing to recharge, and its case holds an additional 13 hours of charge.

Audio Is Quality

The Sennheiser CX400 BT earbuds come packed with seven-millimeter dynamic drivers, helping the earbuds create some very decent sound production. The audio quality with the CX400s is great, which makes their size and proclivity for falling out so much more disappointing.

At neutral levels, the CX400 earbuds offer a very balanced listening experience. Bass is somewhat pronounced, but could use a little more behind it to help it stand out from the mids and treble. This makes the CX400 perfect for listening to podcasts or certain types of music, but some adjustments might need to be made for playing games or enjoying more bass-heavy music. Thankfully, audio levels can be manually modified easily in the Sennheiser app, which we go into more detail on below.


The Sennheiser CX400 earbuds also come with aptX technology included, which provides low latency connections to devices. Bluetooth is an inherently slow connection, so there is a delay between video and audio when listening via a Bluetooth device. Low latency connections help to speed up this delay to make audio better sync up with video.

The CX400 does a decent job with its low latency connection, though I do still notice a bit of a delay. This delay seems to be oh so slightly longer than the delays I've seen with other devices, but I don't have any hard numbers or measurements to confirm this. Regardless, the delay is only noticeable if you're really looking hard for it.

Microphone Quality

The microphone on the Sennheiser CX400 BT earbuds is surprisingly great. Talking to someone on the phone via earbuds rarely offers an experience that provides better audio quality than simply using a phone. With most earbuds I have used, I've been told I often sound washed out, quiet or even like I'm in a hole.

That is not the case at all with the CX400 earbuds. When calling with the CX400s I was told I sounded perfectly fine, like if I were talking into my cell phone normally. While sounding normal may not seem like a big accomplishment, in the world of wireless earbuds it really is.

App Hits And Misses

There is a Sennheiser app that can be downloaded for smartphones to give better control over the Sennheiser CX400 BT earbuds, and it has some great features and some unfortunate misses.


In terms of the good, the Sennheiser app allows for some impressive tuning customization. Users can tweak the settings for bass, mid and treble and the CX400s will react almost instantly to update with the new tuning. It's also possible to save different tunings as presets, so a user could have a music mode with increased bass presence, but then jump to a gaming mode that instead boosts the mids and treble.

It's also nice to see the Sennheiser app provide customization for the CX400's tap controls. Why was the "single tap to the right earbud" mapped to pulling up my phone's smart assistant instead of play/pause? I don't know, but that is easily fixed with the app.


However, the app isn't all peaches and cream. Updating the firmware for my CX400 BT earbuds took well over 45 minutes, which seems very excessive. The updated firmware didn't even add any new features. Thankfully it's possible to still use the CX400 earbuds when they are updating, but this makes the update drag out even longer.

Steep Price

Wireless earbuds come in just about every price range, and price doesn't always indicate quality. For example, the Enacfire G10 earbuds are certainly barebones, but I like how the G10s feel in my ears. For only $20 (after using a coupon), the G10s perform admirably.

However, we're on the other end of the price spectrum with the Sennheiser CX400 BT earbuds. These earbuds are decidedly not inexpensive, as a pair costs $200 without any discounts. That's ten times the price of the G10s. Do the CX400 earbuds perform better than the G10s? Absolutely. Do they offer ten times the performance of the G10s? No.


Thankfully, the CX400 BT earbuds are on sale right now on Amazon for $130. That's still a steep price for what the earbuds offer, but is much more reasonable.

Final Thoughts

The Sennheiser CX400 BT wireless earbuds offer great audio quality and surprisingly strong microphone quality, but with a few big downsides. The most obvious is the size and shape of the earbuds themselves, as even when the earbuds did manage to actually stay securely in my ears, they were still uncomfortable.

The other big downside is the large price tag. At $200 without any discounts, the CX400 earbuds are no minor purchase. They do offer some great audio quality and some clever ways of finely tuning the earbuds to better match each user's preferences, but that's still pretty expensive. I'd wait for a sale if interested in getting a pair of the CX400s.

The Sennheiser CX400 BT earbuds are available right now on Amazon and from other retailers.