About the Sennheiser CX 400 BT
Wire-free earbuds with top-shelf sound
The Sennheiser CX 400 BT true wireless earbuds fit securely, sport a low-profile look, and deliver clear sound with depth and detail.
Wire-free earbuds with top-shelf sound
With the CX 400 BT true wireless earbuds, Sennheiser adds value by taking some features away. What do I mean by that? Their super-premium Momentum TW 2 in-ears are the best-sounding true wireless earbuds I've ever heard. And these headphones feature the EXACT same drivers and sound signature. So if you can live without noise cancellation, water resistance, and some of the extra Momentum design touches, these headphones are a great way to get excellent sound quality and true wireless convenience for less.
Music plays wirelessly via Bluetooth version 5.1, the strongest, most reliable Bluetooth yet. I was able to get some serious distance away from my phone without an audio dropout. And there is no connecting cord between the left and right earbud.
Listening impressions: Incredible detail and true sense of space
The CX 400 BT earbuds deliver Sennheiser's signature smooth highs, articulate mids, and satisfying bass. They also have a large, "outside-the- head" soundstage with accurate imaging. It's much more spacious and well-defined than you might expect from a set of in-ears.
On Stevie Wonder's "Big Brother" — from 1972's Talking Book — percussion leapt out at me with urgency and energy. Other instruments laid back, everything occupying its own place in the mix. Stevie's vocals sat dead center as expected, and so did his harmonica, but somehow I had the impression it was behind him.
Even with the brilliant separation, clarity, and detail, there was a toe-tapping cohesiveness that you don't always get when listening to lesser 'buds. A powerful presentation, worthy of the song itself.
Lightweight, ergonomic design with secure fit
The CX 400 BT earbuds also sport a a more understated look than the Momentums — for the earpiece and logo, they've inversed the color scheme, so that the logo pops with sparkling silver. But while their appearance is a little more subtle, the dimensions, shape, and weight are practically identical.
These earbuds slipped right into place with a slight twist and remained stable when I moved my head. Sennheiser includes four sizes of silicone ear tips for finding the right fit. That helps for comfort and also ensures you have a tight seal for proper imaging and strong bass punch.
The pocket-sized charging case banks enough power to wirelessly recharge the earbuds twice on the go.
Responsive touch controls
The earbuds turned on automatically when I put them in, and paired up immediately to my phone when it was in Bluetooth mode. From there, you can control music and calls by touching or tapping either earbud. It took me a few tries to learn everything, but it became second nature rather quickly.
Plus the controls are snappy, and the touch pad is not as sensitive or finicky as it is in some other small earbuds. I could adjust the fit without accidentally pausing music or skipping tracks. Yet, when I wanted to change the volume or activate Google Assistant, the controls were intuitive and responsive.
Charging case banks hours of power
The ultra-light earbuds arrive packed in a compact charging case. It's a little taller than the case that comes with the Momentum TW 2s, and there's no designer fabric lining. Instead, this case is lightweight, functional hard plastic — small enough to pocket, but durable enough to drop in a bag.
You get about six and a half hours of listening on a single charge. And the case banks enough power to recharge the earbuds twice while you're on the move. Plus you can pack it neatly, with no worries about pulling out a mess of tangled wires when you're ready to use the earbuds.
- 100% wire-free headphones
- no connecting cord between left and right earbuds
- 7mm dynamic drivers for detailed sound across a wide frequency range
- spacious soundstage with precise imaging
- Bluetooth version 5.1 for wireless music listening and phone calls
- aptX® and AAC decoding provides high-quality music streaming from compatible devices
- aptX Low Latency decoding helps sync audio and video on compatible devices
- free Sennheiser Smart Control app for Apple® and Android™ allows you to adjust settings and customize the sound
Battery and charging info:
- built-in rechargeable batteries offers 6-1/2 hours of listening
- carrying case banks up to 13-1/2 hours of power to wirelessly recharge headphones
- USB-C cable included for charging case
General info and specs:
- includes 4 sizes of silicone ear tips for a customized, comfortable fit
- touch controls on each earbud let you answer calls and control music
- access Siri or Google Assistant voice controls assistants from your phone
- frequency response: 5-21,000 Hz
- sensitivity: 107 dB
- weight: 0.42 ounces (both earbuds)
- warranty: 2 years
- Our 60-day money-back guarantee
- MFR # 508901
What's in the box:
- Left (CX400TW1 L) and right (CX400TW1 R) wireless ear buds (white)
- 4 Pairs of silicone ear tips (1 pair installed)
- CX400TW1 C Charging case (white)
- 10.5" USB charging cable (Type A USB on one end and USB-C on other end)
- Quick Guide
- Safety Guide
- Compliance Information
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More details on the Sennheiser CX 400 BT
Features & specs
|Fit Style||True Wireless|
|Earcup Width x Height||0.734" x 0.884"|
|Mic For Taking Calls||Yes|
|Voice Assistant Access|
|Frequency Response||5-21k Hz|
|Parts Warranty||2 Years|
|Labor Warranty||2 Years|
Overview: The Sennheiser CX 400BT True Wireless in-ear headphones are two individual ear buds with no connecting wires. They connect to your smartphone or tablet (and to each other) via Bluetooth. Four pairs of silicone ear tips (XS, S, M, L) are included for a comfortable fit. The CX 400BT headphones come with a charging case for storage, and for recharging the batteries.
Drivers: The CX 400BT features 7mm dynamic drivers that delivers high-fidelity sound with clear treble, natural midrange, and deep bass. You can tailor the sound using the equalizer found in the Sennheiser Smart Control app, available for iOS and Android devices.
Bluetooth 5.1: The CX 400BT headphones feature Bluetooth version 5.1 which pairs to your phone or audio device in seconds. You can make and receive phone calls and stream audio wirelessly in a range of up to 33' (10 meters), depending upon environmental conditions. The headphones have a maximum of 10mW of output power, and have the following profiles: Headset Profile (HSP), Hands-Free Profile (HFP), Audio/Video Remote Control Profile (AVRCP), and Advanced Audio Distribution Profile (A2DP). If your audio source supports aptX or AAC, music is automatically played in high audio quality. Otherwise, the headphones will play in standard audio quality (SBC).
Voice Assistants: The ear buds are compatible with the voice assistant that is activated to your smartphone, such as Siri or Google Assistant. Tapping the right ear bud once activates the voice assistant for you to make a request or ask a question. You can also activate voice dialing through the voice assistant.
Rechargeable Batteries: The CX 400BT headphones are powered by built-in 3.7VDC Lithium-Ion rechargeable batteries. Each earbud has a 55 mAh battery, while the charging case has a 650mAh battery. The complete charging cycle of the charging case and earphones is approximately 1.5 hours. A 10-minute Quick Charge provides about 1 hour of playback time, and a 60-minute charge brings approximately 5 hours of music playback. The battery in the charging case charges via USB-C power (5V, 650 mA) using the supplied cable from a laptop, an AC-powered USB charging port, or a mobile 12-volt USB charging port. Fully-charged batteries in the earbuds provide approximately 6.5 hours playback. The charging case provides enough stored power to charge the earbuds approximately 2 additional times, to extend the playback time to 20 hours.
Phone/Music Controls: Controls for music playback and phone call functions are located on separate earbuds. Both earbuds are equipped with 1/2" x 5/8" touch control panels. The left earbud controls Volume Down (hold), and music playback functions Play/Pause (1x) and Previous Track (2x). The right earbud controls Volume Up (hold), Voice Assistant (1x), and Next Track (2x). For phone call functions, you can use either ear bud to accept (1x) or reject (2x) calls. Touching both control panels simultaneously lets you pair and connect the earbuds to your Bluetooth mobile device.
Microphones: The CX 400BT true wireless earbuds are equipped with a dual microphone system. This pickup pattern helps to reduce ambient noise.
Smart Control App: In addition to the on-board controls, the CX 400BT in-ear headphones can be controlled by Sennheiser's Smart Control app for Android and iOS devices. The app lets you customize the ear buds' on-board controls as you desire. Firmware updates for the earphones are also available through the app. The Smart Control app is compatible with iOS devices running version 12.0 and later, and Android devices with version 7.0 and up.
- Frequency Response: 5Hz - 21kHz
- Transducer Size: 7mm
- Total Harmonic Distortion (THD): <0.08%
- Sound Pressure Level (SPL): 107dB (1 kHz/1mW)
- Frequency Response: 100Hz - 10kHz
- Pickup Pattern: 2-mic array for ambient noise reduction
- Earbuds: 0.734" (w) x 0.884" (h) x 1.025" (d)
- Charging Case: 2.314" (w) x 1.659" (h) x 1.334" (d)
- Earbuds: 0.22 ounces (each); 0.45 ounces (pair)
- Charging Case: 1.3 ounces (1.75 oz with earbuds)
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