When it comes to premium audio gear, Sennheiser have it down pat with their microphones and speakers that continue to be revered by professionals for their acoustic qualities. For audio aficionados, their HE-1  remains the quintessence of audio perfection wrought in marble. For more pedestrian users, their recent line-up of Momentum True Wireless earbuds are among the best in their class. This time around, they’re gunning for the mainstream market with their new workhorse CX 400BT True Wireless earbuds.

Where the likes of their recently launched Momentum True Wireless II are intended for the premium segment, the new Sennheiser CX 400BT true wireless earbuds are intended for a more mainstream segment while featuring the same 7mm full range dynamic drivers as the Momentum True Wireless II.

Sennheiser CX 400BT True Wireless  top

Sennheiser CX 400BT Build and Design

In terms of build quality, the Sennheiser CX 400BT prioritises functionality over form with a chassis built primarily of plastic which does look a bit cheaper than what you’d typically expect from Sennheiser. It’s a contrast from the premium fabric-textured charging case and lashings of cool metal in the True Momentum Wireless II that we reviewed a while back. 

While the CX 400BT’s charging case and earbuds look somewhat plasticky, they, fortunately, feel a lot sturdier when you hold them in your hands; though a slightly more premium material would have been appreciated. 

Closer inspection reveals magnets embedded in the lid of the charging case to keep it closed until needed while the hinge mechanism itself proved to be relatively sturdy. Unfortunately, the CX 400BT is not rated for water resistance which does not make them ideal for outdoor excursions in the rain or near bodies of water or, for the matter, intensive workouts.

Sennheiser CX 400BT True Wireless  one handed

The magnet on the lid and sturdy hinges allow for easy one-handed opening

The charging case and the accompanying earbuds are done up in a matte black finish with Sennheiser’s distinctive logo emblazoned on the top of the charging case in silver and on the touch controls on each earbud. The back of the charging case sports a USB Type-C port for charging duties along with a tiny button that lights up an accompanying LED to show the remaining battery level at a glance. Green indicates a mostly full charge, amber midway and red indicating that it’s below a 30% charge.

Each of the CX 400BT’s earbuds sports a rather bulbous and squarish external housing for the battery and 7mm drivers that terminate in a pair of soft-tipped silicone ear tips. It ships with one pair of ear tips preinstalled but you have a choice of three other pairs in different sizes for you to swap out at will in order to ensure a better fit for your ears. The rest of the hardware in the box consists of the obligatory user manual, warranty card and a USB Type-C cable to charge it.

Sennheiser CX 400BT True Wireless  earbuds

Sennheiser CX 400BT True Wireless Specifications and Performance

While the presentation isn’t much to write home about, it’s what it has under the hood that impresses as the CX 400BT is loaded for bear with the sort of hardware that let it go toe to toe with pricier offerings.

Each earbud packs the very same 7mm dynamic drivers used in the higher-priced Momentum True Wireless 2 though as a concession to its price point, the CX 400BT lacks the active noise cancellation tech of its pricier sibling. Here’s what it packs in detail:

Price RM999
Drivers 7mm dynamic drivers
Supported Codecs SBC, AAC, aptX
Frequency response 5 – 21,000Hz
Bluetooth 5.1
THD, total harmonic distortion <0,08% (1kHz / 94dB)
Microphone frequency response 100Hz to 10 kHz
Supported profiles A2DP, AVRCP, HSP, HFP
Battery Lithium-ion, 7 hours (earbuds) 13 hours (charging case) / 20 hours total | 1.5 hours full charge, 10 minutes for 1 hour usage
Size/Weight 59 x 33.8 x 42.3mm (charging case) / 6g (per earbud), 37g (charging case) | 59g (total)
Sennheiser CX 400BT True Wireless Specifications

This means that it is reliant on users getting a good passive seal with their silicone ear tips to ensure a better listening experience though Sennheiser has also added in a transparent hearing mode that lets important sounds filter in especially when you’re outdoors.

Paired with it is Bluetooth 5.1 connectivity along with SBC, AAC and aptX codec support to ensure high-quality low latency audio performance.

Of note is that you can customise the sound signature of the CX 400BT via a paired Sennheiser Smart Control app that’s available for free download on iOS and Android.

With the app, you’re able to tweak the bass, mids and treble via an equaliser curve. By default, it’s set to a flat, neutral profile but you can adapt it to personal taste. The Smart Control app also lets you update the firmware for the CX 400BT as and when they’re pushed out by Sennheiser.

The touch controls for the CX 400BT are relatively straightforward with a series of single and double-tap as well as long taps to get about. On the left earbud, tapping once controls playback and pausing tracks while double-tapping rewinds a track. Holding it down reduces the volume. On the right earbud, tapping it once lets you take calls or fire up your voice assistant of choice.

CX 400BT side profile

Tapping it twice lets you turn transparent hearing on or off and reject calls. Holding it down increases the volume. There’s also an unused triple-tap command on both the left and right earbuds that you can assign to any of the existing commands as a redundancy measure.

Getting it paired up with our phone was a relatively easy task though getting the Sennheiser Smart Control app to recognise it took a couple of tries. In terms of fit, it proved to be exceptionally comfortable though we had to swap out the ear tips to a large-sized one for a better fit. As per Sennheiser’s recommendation, you’ll need to pop the earbuds in your ear and then twist them slightly to offer a better seal.


When put to the test across a variety of tracks, the CX 400BT certainly punches above its intended price tag and weight class with a sound close to what the Momentum True Wireless II is capable of delivering.

The 7mm drivers are capable of acoustically creating a beautifully realised sound stage, great bass and lots of detail. Vocals were also handled in a delightful fashion without being drowned out by the rest of a track. 

The quirky ‘Anthems For a Seventeen Year Old Girl’ by Broken Social Scene that gradually layers on a series of additional instruments as the track goes on was tackled in a beautiful fashion with a banjo and violin segueing in midway through the track.

Ed Sheeran’s quintessential track ‘ Shape of You’ is acoustically challenging especially if you want to clearly hear instruments like the marimba used as an accompaniment but the 7mm dynamic drivers did not disappoint. 

We also tested it on a few movies and it did a decent job with Saving Private Ryan’s opening scene with MG42’s and explosions going off in the Normandy beach landings and managed to handle Wonder Woman’s one-woman assault across no-mans-land well with good soundstaging while keeping the vocals audible.

Sennheiser CX 400BT True Wireless  rear

We also used it for several hands-free voice calls and voice quality was good on both sides of the divide. Most important of all, the CX 400BT’s proved to be sufficiently comfortable for extended use – we used it for stretches of three to four hours at a time on the train and walking around town on errands without major discomfort.

It also proved to be fairly secure though the lack of water resistance or ear wings means it may not be the most ideal option for workouts.

In use, it’s contingent that you get a good audio seal to avoid external audio sounds from getting in and if you do it right, the CX 400BT sounds fantastic. If you’re wearing it outdoors though, the Transparency mode, fortunately, lets in just enough sound to cue you in on the more dangerous things in the urban landscape like oncoming traffic.

CX 400BT long pull shot

CX400 BT Battery Life

In terms of battery life, the CX400 BT delivers fair endurance with a rated seven hours per earbud and an additional 13 hours in the charging case for a grand total of 20 hours of usage in the field. We got close to the advertised battery life with about 19 hours of usage before it needed a recharge with an hour and 30 minutes getting it to full.

Sennheiser CX 400BT True Wireless  distant shot

Sennheiser CX 400BT True Wireless Verdict – Is this worth buying?

As a midrange pair of earbuds, the CX 400BT True Wireless represents a rather unique proposition in Sennheiser’s stable with a mid-ranged price for an offering that has one of their best drivers in a somewhat pedestrian looking casing.

Battery life is decent by the by though there are earbuds with better endurance out there. If you’re looking for a pair of wireless earbuds with excellent sound quality on a modest budget and can live without the active noise cancellation, this is an easy and more affordable recommendation.

What we liked Comfortable for extended wear, detailed and balanced sound, responsive controls, customisable equaliser settings
What we didn’t Build is a bit plasticky, earbuds are rather chunky, no water resistance
We say The Sennheiser CX 400BT True Wireless earbuds have an understated design but pack 7mm full range dynamic drivers for the detailed and wide sound that belies its modest looks. Add in a light build and comfy ear tips for comfortable extended wear when working from home or on the go and you have an ideal, high performing pair of earbuds suited for the new normal.

Review unit courtesy of Sennheiser. Available for purchase at all Sennheiser concept stores at KLCC & Lot 10 and all good retailers nationwide as well as the Sennheiser official online store at https://shopee.com.my/sennheiser.os. For more details check out www.sennheiser.com

Sennheiser CX 400BT True Wireless earbuds
  • Design
  • Performance
  • Battery Life
  • Value
  • Comfort
4.2

Sennheiser CX 400BT Review

The Sennheiser CX 400BT True Wireless earbuds have an understated design but pack 7mm full range dynamic drivers for the detailed and wide sound that belies its modest looks. Add in a light build and comfy ear tips for comfortable extended wear when working from home or on the go and you have an ideal, high performing pair of earbuds suited for the new normal.

Leave a Comment