Current deal: The Apple Airpods Pro have dropped by $50 on Amazon.com. See all Black Friday deals on headphones.

Sennheiser CX 400BT True Wireless Headphones Review

Tested using Methodology v1.4
Reviewed Nov 25, 2020 at 09:06 am
Sennheiser CX 400BT True Wireless Picture
6.9
Mixed Usage
6.7
Neutral Sound
7.3
Commute/Travel
7.9
Sports/Fitness
6.4
Office
5.4
Wireless Gaming
5.3
Wired Gaming
6.7
Phone Calls
Type In-ear
Enclosure Closed-Back
Wireless Truly Wireless
Noise Cancelling No
Mic Yes
Transducer Dynamic

The Sennheiser CX 400BT True Wireless are sleek in-ears that resemble the Sennheiser MOMENTUM True Wireless 2 in look and performance. They have a similarly warm sound profile and can passively isolate as much noise as their ANC-equipped relative. If you prefer a different sound, their companion app offers both a graphic and parametric EQ to adjust them. However, they have a disappointing battery performance. Still, if you're looking for a pair of well-built and customizable truly wireless headphones, they're a solid choice.

Our Verdict

6.9 Mixed Usage

The Sennheiser CX 400BT are alright for mixed use. They're fairly comfortable and are stable enough for moderate exercise. They can also reduce quite a bit of mid-range sounds like ambient chatter at work. However, they struggle to block out bass-range noise like bus engines, which can be annoying during your commute. Their battery life most likely won't be enough to get you through your 9-5. While their warm sound may not be perfect for neutral sound, they have a graphic and parametric EQ via their companion app.

Pros
  • Graphic and parametric EQ available.
  • Great build quality.
Cons
  • Disappointing battery performance.
  • Bulky design.
6.7 Neutral Sound

The Sennheiser CX 400BT are alright for neutral sound. They have a warm sound profile that lacks a bit of low-bass. There's also a dip in the low-bass, which veils vocals and lead instruments. Due to their in-ear fit, their soundstage is very closed-off. On the upside, they deliver audio consistently and their companion app offers a graphic and parametric EQ to customize their sound.

Pros
  • Graphic and parametric EQ available.
Cons
  • Disappointing battery performance.
7.3 Commute/Travel

The Sennheiser CX 400BT are decent for commute and travel. They're fairly comfortable and very portable, but they struggle to cut down bass-heavy noise like bus or plane engines. Their roughly five hours of continuous battery life also may not be long enough to get you through a long flight. That said, they're well-built and their carrying case offers around two additional charges.

Pros
  • Great build quality.
Cons
  • Disappointing battery performance.
7.9 Sports/Fitness

The Sennheiser CX 400BT are very good for sports and fitness. Even though they don't have stability fins, they're lightweight and feel stable enough for moderate exercise. There's no cable to get caught on something while moving, either. However, although they're fairly comfortable, they have a bulky design that sticks out of your ear. They also don't have an IP rating, though we don't currently test for this.

Pros
  • Great build quality.
  • Stable in-ear fit.
Cons
  • Disappointing battery performance.
6.4 Office

The Sennheiser CX 400BT are passable for office use. They're fairly comfortable and they can reduce an impressive amount of ambient chatter. Their leakage is quite low so you shouldn't bother people around you if you're listening to audio at a high volume. However, their battery life may not be enough to last a full 9-5. Luckily, the carrying case offers around two additional charges.

Pros
  • Great build quality.
Cons
  • Disappointing battery performance.
5.4 Wireless Gaming

The Sennheiser CX 400BT aren't suitable for wireless gaming due to their high audio latency when connected to Bluetooth-enabled PCs. They're also incompatible with PS4 and Xbox One consoles.

5.3 Wired Gaming

The Sennheiser CX 400BT are Bluetooth-only headphones and aren't compatible with any wired connections.

6.7 Phone Calls

The Sennheiser CX 400BT are alright for phone calls. The integrated mic ensures your voice is clear, although it sounds a bit thin and lacking in detail. It also struggles to separate your voice from moderately noisy environments. These headphones also do an alright job of passively isolating noise around you, but you may have trouble hearing your call if you're surrounded by bass-range noise like bus engines.

Pros
  • Decent recording quality.
Cons
  • Disappointing battery performance.
  • 6.9 Mixed Usage
  • 6.7 Neutral Sound
  • 7.3 Commute/Travel
  • 7.9 Sports/Fitness
  • 6.4 Office
  • 5.4 Wireless Gaming
  • 5.3 Wired Gaming
  • 6.7 Phone Calls

Test Results

perceptual testing image
Design
Design
Style

The Sennheiser CX 400BT are square-shaped in-ears with a very plain design. Unlike the Sennheiser MOMENTUM True Wireless 2, they lack a shiny silver accent on both their controls and instead, use a simple flat gray color for their logo. These headphones are available in black or white color variants.

6.5
Design
Comfort
Weight 0.03 lbs
Clamping Force
0 lbs

These headphones are fairly comfortable. Although they're lightweight and don't go too deep into your ear, they're quite bulky and stick out when you're wearing them. On the upside, they come with four sets of ear tips so that you can find a fit that suits you best.

6.9
Design
Controls
OS Compatibility
Not OS specific
Ease Of Use Good
Feedback Great
Call/Music Control Yes
Volume Control Yes
Microphone Control No
Channel Mixing
No
Noise Cancelling Control No
Talk-Through
No
Additional Controls Voice Assistant

The Sennheiser CX 400BT have alright touch-sensitive controls. Touching the left earbud once plays/pauses audio while touching it twice skips to the previous track. You can also hold down the left button to lower the volume. One touch of the right earbud activates voice assistant and two taps skips to the next track. If you hold down the right button, you can raise the volume. Taking calls is easy as you can touch either the left or right earbud once to accept or end calls and touch either bud twice to reject a call. You can also remap the controls via the app.

9.3
Design
Portability
L 1.2 "
W 1.4 "
H 1.2 "
Volume 2.1 Cu. Inches
Transmitter Required No

The Sennheiser CX 400BT are very portable headphones. They're smaller than the Sennheiser MOMENTUM True Wireless 2 and can easily fit into small pockets or bags. Their charging case is also somewhat small and can fit into most pockets.

7.5
Design
Case
Type Hard case
L 2.3 "
W 1.3 "
H 1.7 "
Volume 4.9 Cu. Inches

These headphones have a good charging case. It has a button to turn on the status light indicator, which shows its battery status, and there are magnets to hold the buds in place. The case is made from hard plastic, which makes it feel sturdy.

8.0
Design
Build Quality

The Sennheiser CX 400BT have a great build quality. Both the earbuds and their carrying case are made of dense plastic, which feels sturdy. The earbuds also have touch-sensitive controls and the carrying case has indicator lights to display battery life, which are nice touches. However, they don't have an IP rating.

7.5
Design
Stability

The Sennheiser CX 400BT are stable enough to wear for moderate physical activity. They don't move around too much but they could fall out with more intense movements. Luckily, they don't have any cables that could get snagged and pull them out of your ears.

Design
Headshots 1
Design
Headshots 2
Design
Top
Design
In The Box

  • Sennheiser CX 400BT True Wireless headphones
  • 4x Ear tip options
  • Charging case
  • USB-C Charging cable
  • Manuals

Sound
Sound
Sound Profile
Bass Amount
-0.41 db
Treble Amount
-2.19 db

The Sennheiser CX 400BT have a warm sound profile. They have a slightly boomy bass but vocals and lead instruments lack detail and presence, which can hurt vocal-centric genres like audiobooks or pop music. They also lack low-bass, so genres like EDM and hip-hop may miss a bit of thump and rumble. That said, their companion app offers a graphic and parametric EQ to customize their sound to your liking.

8.8
Sound
Frequency Response Consistency
Avg. Std. Deviation
0.24 dB

The frequency response consistency is excellent. Like most in-ears, if you can achieve a proper fit using the included tips, the treble and bass response should be the same every time you use these headphones.

Sound
Raw Frequency Response
8.4
Sound
Bass Accuracy
Std. Err.
2.12 dB
Low-Frequency Extension
35.64 Hz
Low-Bass
-3.68 dB
Mid-Bass
-0.08 dB
High-Bass
2.13 dB

These headphones have great bass accuracy. Their low-bass is underemphasized, resulting in a lack of thump and rumble. In comparison, the mid-bass is fairly neutral and delivers punch. The high-bass is a bit overemphasized, which makes some mixes sound boomy and a bit muddy.

8.8
Sound
Mid Accuracy
Std. Err.
1.64 dB
Low-Mid
0.85 dB
Mid-Mid
-2.21 dB
High-Mid
-0.1 dB

The mid accuracy is excellent. The low and high-mids are relatively flat and neutral. However, there's a dip in the mid-mids, which nudges vocals and lead instruments to the back of the mix.

5.2
Sound
Treble Accuracy
Std. Err.
6.42 dB
Low-Treble
-7.48 dB
Mid-Treble
-0.17 dB
High-Treble
-3.8 dB

The Sennheiser CX 400BT's treble accuracy is disappointing. There's a large dip in the low-treble, which veils vocals and lead instruments. The mid-treble is better-balanced, though, and sibilants like S and T sounds are bright and present.

6.9
Sound
Peaks/Dips
Peaks
1.8 db
Dips
2.13 db

The Sennheiser CX 400BT's peaks and dips performance is alright. There's a wide peak concentrated mostly in the high-bass that adds a boomy and muddy quality while a dip in the mid-mids nudges vocals and lead instruments to the back of the mix. A peak in the high-mids makes some parts of the vocals and lead instruments honky and harsh, only to become veiled and lacking in detail by the dip in the low-treble. The peak in the mid-treble also makes sibilants like S and T sounds piercing.

9.2
Sound
Imaging
Weighted Group Delay
0.12
Weighted Amplitude Mismatch
0.47
Weighted Frequency Mismatch
1.19
Weighted Phase Mismatch
1.48

The stereo imaging is outstanding. The entire group delay response is below the audibility threshold, resulting in a tight bass and a transparent treble reproduction. The L/R drivers are also well-matched in amplitude, frequency, and phase response, which is important for the accurate placement and localization of objects and instruments (like voices and footsteps) in the stereo image. However, these results are only valid for our unit and yours may perform differently.

0.8
Sound
Passive Soundstage
PRTF Accuracy (Std. Dev.)
N/A
PRTF Size (Avg.)
N/A
PRTF Distance
N/A
Openness
3.4
Acoustic Space Excitation
0.3

Like most in-ears, the Sennheiser CX 400BT's soundstage is poor. The outer ear needs to be activated by resonances to create a speaker-like and out-of-head soundstage. However, in-ears bypass the outer ear altogether and don't interact with it. Their closed-back design also makes them sound less open and spacious than that of open-back headphones.

0
Sound
Virtual Soundstage
Head Modeling
No
Speaker Modeling
No
Room Ambience
No
Head Tracking
No
Virtual Surround
No

These headphones don't have any virtual soundstage features.

8.3
Sound
Weighted Harmonic Distortion
WHD @ 90
0.151
WHD @ 100
0.083

The Sennheiser CX400BT's weighted harmonic distortion performance is great. All frequencies fall within good limits, resulting in clear and pure audio reproduction.

Sound
Test Settings
Firmware
2.13.0
Power
On
Connection
Bluetooth 5.0
Codec
aptX, 16-bit, 48kHz
EQ
Neutral
ANC
No ANC
Tip/Pad
Silicone (small)
Microphone
Integrated

These are the settings used to test these headphones. Our results are only valid when listening using these settings.

Isolation
6.6
Isolation
Noise Isolation
Isolation Audio
Overall Attenuation
-17.41 dB
Bass
-4.07 dB
Mid
-16.41 dB
Treble
-32.91 dB

The Sennheiser CX400BT have an okay noise isolation performance. They really struggle to block out low bass-range noise like bus and plane engines. They're much better at reducing mid-range noise like ambient chatter or high-pitched sounds like the hum of an AC unit.

9.8
Isolation
Leakage
Leakage Audio
Overall Leakage @ 1ft
22.41 dB

The Sennheiser CX 400BT have a fantastic leakage performance. Leaking audio falls below the noise floor of an average office, so you should be able to listen to your music at a high volume without disturbing those around you.

Microphone
Microphone
Microphone Style
Integrated
Yes
In-Line
No
Boom
No
Detachable Boom
No

These headphones have an integrated mic.

7.0
Microphone
Recording Quality
Recorded Speech
LFE
261.43 Hz
FR Std. Dev.
3.1 dB
HFE
5424.45 Hz
Weighted THD
1.24
Gain
6.76 dB

The Sennheiser CX 400BT's integrated mic's recording quality is satisfactory. While you shouldn't have too much of a problem being understood, your voice may sound a bit thin and lacking in detail.

6.7
Microphone
Noise Handling
Speech + Pink Noise
Speech + Subway Noise
SpNR
18.69 dB

The microphone's noise handling performance is alright. It struggles to separate your voice from noisier environments and is best suited for more quiet spaces.

Active Features
5.3
Active Features
Battery
Battery Type
Rechargable
Continuous Battery Life
5 hrs
Additional Charges
1.9
Total Battery Life
14.5 hrs
Charge Time
1.5 hrs
Power-Saving Feature
No
Audio While Charging
No
Passive Playback
No
Charging Port USB-C

The Sennheiser CX400BT have a disappointing battery performance. Although the manufacturer advertises them to last seven hours, they offer around five hours of continuous playback time. Luckily, there are roughly two charges in the case so you can top their battery off when you're on-the-go. The manufacturer also advertises a 10-minute quick charge, which is supposed to give you an hour of playtime, but we don't currently test this feature. These headphones don't have any power-saving features, either.

7.0
Active Features
App Support
App Name Sennheiser Smart Control
iOS Yes
Android Yes
macOS No
Windows No
Equalizer
Parametric + Graphic
ANC Control
No
Mic Control No
Room Effects
No
Playback Control
No
Button Mapping Yes
Surround Support
No

These headphones have a decent companion app called Sennheiser Smart Control, which is available on Android and iOS. With this app, you can check the battery level, turn voice prompts on/off, and remap buttons. There's also a parametric as well as a graphic EQ and you can even create your own equalizer presets.

Connectivity
6.9
Connectivity
Bluetooth
Bluetooth Version
5.1
Multi-Device Pairing
No
NFC Pairing
No
Line Of Sight Range
140 ft
PC Latency (SBC)
339 ms
PC Latency (aptX)
328 ms
PC Latency (aptX HD)
N/A
PC Latency (aptX-LL)
N/A
iOS Latency
0 ms
Android Latency
0 ms

The Sennheiser CX 400BT True Wireless have alright Bluetooth connectivity. Unfortunately, they don't support NFC or multi-device pairing, which is a little disappointing. They also have very high audio latency on PC. However, they have no latency at all on iOS and Android, although it could be that they're over-compensating for latency. That said, apps and devices compensate for latency differently and your mileage may vary with real-life usage.

0
Connectivity
Non-Bluetooth Wireless
Non-BT Line Of Sight Range
N/A
Non-BT Latency
N/A

The Sennheiser CX 400BT are Bluetooth-only headphones.

0
Connectivity
Wired
Analog Audio
No
USB Audio
No
Detachable No
Length N/A
Connection No Wired Option
Analog/USB Audio Latency
N/A

The Sennheiser CX 400BT are Bluetooth-only headphones and can't be used wired. They come with a short USB-C cable to charge their case.

Connectivity
PC / PS4 Compatibility
PC/PS4 Analog
No
PC/PS4 Wired USB
No
PC/PS4 Non-BT Wireless
No

These headphones can only be used via Bluetooth on Bluetooth-enabled PCs and they aren't compatible with the PS4. Due to their high latency, they aren't recommended for gaming.

Connectivity
Xbox One Compatibility
Xbox One Analog
No
Xbox One Wired USB
No
Xbox One Non-BT Wireless
No

These headphones are Bluetooth-only and aren't compatible at all with the Xbox One.

2.2
Connectivity
Base/Dock
Type
Charging Case
USB Input
No
Line In
No
Line Out
No
Optical Input
No
RCA Input
No
Dock Charging
Yes
Power Supply
USB-C

These headphones come with a charging case that holds around two charges. It uses a USB-C connection to charge. Unfortunately, it doesn't support wireless charging.

Differences Between Sizes And Variants

The Sennheiser CX 400BT come in two color variants: 'Black' and 'White'. We tested the 'Black' variant and you can see its label here. If you come across a CX 400BT that's different from our own, let us know in the discussions and we'll update our review.

Compared To Other Headphones

The Sennheiser CX 400BT are truly wireless headphones. Although they're very similar to the Sennheiser MOMENTUM True Wireless 2 and have a comparably warm sound profile, they can isolate just as much noise passively without an ANC feature. Their companion app also offers both a graphic and parametric EQ. However, their battery performance falls a bit short when compared to other truly wireless headphones like the Sony WF-1000XM3 Truly Wireless. Check out our recommendations for the best wireless Bluetooth earbuds, the best true wireless earbuds, and the best earbuds and in-ear headphones.

Sony WF-1000XM3 Truly Wireless

The Sony WF-1000XM3 Truly Wireless are better headphones for most uses than the Sennheiser CX 400BT True Wireless. The Sony are more comfortable, have a more neutral sound profile right out-of-the-box, and offer a virtual soundstage feature. They also have an ANC feature that isolates more noise and their battery performance is better. They even support NFC pairing and their app offers lots of customization features. However, the Sennheiser are more stable, and their integrated mic has a better overall performance.

Jabra Elite 75t Truly Wireless

The Jabra Elite 75t Truly Wireless are better headphones for most uses than the Sennheiser CX 400BT True Wireless. The Jabra are more comfortable and have a better-balanced sound profile. Their battery performance is significantly better too, and you can pair it with up to two different devices at a time. However, the Sennheiser can passively isolate more noise, and their integrated microphone performs better overall.

Sennheiser MOMENTUM True Wireless 2

The Sennheiser MOMENTUM True Wireless 2 and the Sennheiser CX 400BT True Wireless are very similar headphones but the CX 400BT are slightly better. While both earbuds are similarly comfortable and well-built, the CX 400BT have a very similar noise isolation performance to the MOMENTUM, even though they don't have an ANC feature. The CX 400BT also have a better-performing integrated mic and their companion app offers both a parametric and graphic EQ.

Apple AirPods Pro Truly Wireless

The Apple AirPods Pro Truly Wireless are significantly better headphones than the Sennheiser CX 400BT True Wireless. The Apple are more comfortable and stable, have a better-balanced sound profile, and have an outstanding noise isolation performance thanks to their ANC feature. Their battery performance is better too and they have an H1 chip so it's easy to pair with different Apple devices. However, the Sennheiser have a better performing integrated mic and their companion app offers a lot more customization features.

Price trend (United States Last Year)
Retailers' prices Amazon.com BestBuy.com B&H
Black
SEE PRICE
SEE PRICE
SEE PRICE
White
SEE PRICE
SEE PRICE
SEE PRICE
Deals

Recommended Articles

LOG IN

JOIN RTINGS.com

Be part of the most informed community and take advantage of our advanced tools to find the best product for your needs.
Join our mailing list:
Become an insider
EARLY ACCESS

Gain early access to all tests results for new products

Early Access UI
PRICES LISTED

Prices will now be listed directly in reviews and tables

product prices UI
MORE VOTES

Have 5 votes per product category to choose which product we’ll review next

Additional votes UI
UNLIMITED ACCESS

Gain unlimited access to detailed test results in tools and results (no blurred results)

test table UI

Create Post

Create Deal