Sennheiser CX 400BT True Wireless review: Good sound at a better price

Sennheiser's first two forays into true wireless earbuds came with hefty price tags, putting them out of reach for many who might have otherwise appreciated their great sound. The CX 400BT True Wireless are not so much a consolation as they are a real attempt to compete at the $200 price range.

To get there, Sennheiser cut some corners on features, but not so much on design, and it's that confluence of factors that make these earbuds a more interesting proposition.

Sennheiser CX 400BT True Wireless What I like

It becomes fairly obvious early on that Sennheiser went about creating the CX 400BT True Wireless as an offshoot of its Momentum True Wireless earbuds. Certain specs coincide, whereas others diverge. For instance, there are 7mm drivers in here, but no active noise canceling (ANC) support. There are other trade-offs along the way that I'll get to, but not all of them bode poorly for this pair.

You get four sizes (small, medium, large, x-large) of ear tips out of the box to go with the short USB-C charging cable. Unlike the svelte fabric case the Momentum True Wireless models have, the CX 400BT comes with a pretty standard plastic charging case. There are magnetic connectors to lock the earbuds in place, plus a button in the back to indicate charging level through a tiny LED, but that's about it.

Pairing was pretty easy with a Samsung Galaxy Note20 Ultra, where I was up and running in seconds. I listened for about 10 minutes before heading straight to Sennheiser's Smart Control app where a firmware update was waiting to download and install. With that done, I then experimented with the different ear tips, settling on x-large.

As is often the case, the ear tip size makes a real difference over how well earbuds will sound, especially as it relates to the bass. I found the overall fit here to have more in common with the first Momentum TW, not the more recent Momentum TW2. The CX 400BT earbuds have a chunkier design that contrasts with competitors who have trimmed their size down to enable greater comfort for more ears. That's not to say they were uncomfortable to wear. At least for me they weren't, though I did have to adjust them at times when it felt like they were grating on part of my ear.

What shocked me more than anything from the outset was how neutral and dull the default soundstage was. It was actually awful. I double-checked my phone's volume, and even tried pairing with a second device to be certain. It was at this stage that Smart Control came to the rescue with its embedded equalizer. While not an intricate EQ, by any means, it gave me the chance to ramp up the bass and mid-range to better complement the highs. I saved a few presets, and through them, noticed how much range these earbuds have. The sound now ventured closer to the Momentums, which is exactly what I would've expected, albeit without all the tinkering.

To test this further, I listened to my typical test playlist, but also threw in live music and remixes from YouTube Music Premium to get a better sense of it. What makes Sennheiser's sound so distinct is how clean it is. It never seems like the spectrum skews ridiculously from one end or another. Even with my EQ adjustments, the sound signature was very much Sennheiser's, not an imitation of someone else.

Passive noise isolation is great, and it better be for what you're paying. WIthout ANC to help block out the background, getting that tight seal is all the more important to lock in as much of the audio performance as possible. It helps when codec support is broader, as it is here, with SBC, AAC and aptX all available. The earbuds will use whatever your paired device supports, so Android phones that can do aptX will default to that. And the Bluetooth 5.1 connection was solid throughout. I rarely, if ever, experienced a drop.

The onboard mics are also worth noting because they are solid for phone calls, though not as good as the Momentum models are. Calls were generally fine, with those on the other side not always realizing I was using true wireless earbuds. But if I was outside or in an environment with more background noise, some of that would filter through with my voice as I talked.

The touch-sensitive controls were also pretty good, including the ability to talk to Google Assistant. You can customize the control scheme through the Smart Control app, though the list of features is quite limited. I liked how responsive they were, and the earbuds' thickness proved an asset when it came to avoiding accidental taps.

Battery life is good, but not exceptional. The earbuds themselves can go up to seven hours, though it's more like six or slightly less if you go above the default volume. That's not terrible, but you won't get as much out of the case, which is limited to an additional 13 hours. They charge relatively quickly via USB-C, but there's no wireless charging support.

Sennheiser CX 400BT True Wireless What needs work

Size will matter with the CX 400BT True Wireless because they essentially run into the same challenge the first Momentum TW did. When Sennheiser shaved off just enough from their girth to make the successor TW2, the smaller footprint paid real dividends in comfort. I suspect these earbuds won't feel the same way, especially for those who found the original Momentums too fat for their ears.

It's hard to blame it on the driver, since it's the same 7mm drivers the Momentum TW2 have. And it can't be the extras because there aren't any. Sennheiser left out both ANC and Transparent Hearing, meaning you not only can't actively block outside noise, you also can't pipe it in through the mics, either. The lack of ANC is one thing, but Transparent Hearing should be included here, considering competitors have it for less.

I had to remove an earbud anytime I needed to talk to someone or hear what they were saying. And if I was to do that, I'd have to remember to pause the music first because there is no auto-play/pause when removing and reinserting the earbuds. For a $200 pair, these are some fundamental things that shouldn't have been that hard to throw in.

But it's probably because the value proposition has everything to do with audio fidelity. The CX 400BT True Wireless are very good at that, even if they don't fully match up to their more expensive siblings. They sound miles better than the AirPods 2, and in my estimation, are an audio upgrade from Google's latest Pixel Buds (2020), so they are compelling. You just have to weigh that with what you give up.

A case in point is also the lack of any water or sweat resistance. You can probably get away with using these for a light workout or just doing a leisurely activity, like walking, bike-riding or rollerblading. Just be weary if you're looking to run for miles. There isn't much protection to ward of sweat here. And water? Well, just avoid that entirely.

Competition

At the $200 price range, Sennheiser is up against stiff competitors who bring plenty to the table. Some of the best true wireless earbuds already stand out, as do some cheap true wireless earbuds, so the market provides more than a few to chosoe from. Sennheiser is resting the CX 400BT True Wireless on their audio laurels, but there are others who sound good and add in extras to sweeten the deal.

The Jabra Elite 75t come in cheaper, are more comfortable and include the HearThrough ambient mode. They are easily one of the best available, and come with excellent app support, too. The Sony WF-1000XM3 sometimes drop under $200, and they not only sound great, but are the best ANC true wireless earbuds around. The only caveat is they may not anymore comfortable, given their unique design. And if you really want to try something different on a budget, the Creative Outlier Air sound great and offer amazing battery life.

Sennheiser CX 400BT True Wireless Should you buy it?

Who it's for

• You hate dangling cables
• You care about audio fidelity and codec support
• You don't plan to work out wearing these
• You don't need ANC or an ambient mode

Who it isn't for

• You want something smaller to fit in your ears
• You want active noise canceling
• You want something specifically for working out
• You're looking to spend less

There is no doubt the CX 400BT True Wireless earn their stripes by how they sound, and that's where their utility really begins and ends. There aren't a whole lot of bells and whistles beyond the basics, which is the point behind their existence juxtaposed to Sennheiser's other models. Your choice in going with these has to be based on the demand for good sound, and the trust in Sennheiser to deliver that to your ears.

4 out of 5

They compare really favorably to the best-sounding pairs currently available, and it helps that they're easy to use. If you can get them to fit you well enough to be comfortable, it's hard to see these true wireless earbuds disappointing you.