Sennheiser CX 400BT – superior earphone sound for the masses

Name: Sennhesier CX 4000BT True Wireless in-earphones Price (RRP): $299.95 Manufacturer: Sennhesier

Sennheiser’s fabulous sound signature is hard to beatGreat battery lifeComfortable fitEasy to use app that stores settings on the buds

Dont confuse noise isolation with noise cancellation


Value for money


Ease of Use


4.6Overall Score

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Sennheiser CX 400BT – superior earphone sound for the masses

4.6Overall Score

Name: Sennhesier CX 4000BT True Wireless in-earphones
Price (RRP): $299.95
Manufacturer: Sennhesier

The Sennheiser CX 400BT in-ear buds focus on sound above all but at an attractive price. That focus is both its strength and weakness.

Sennheiser is 75 years old founded post-WW2 in Germany by Dr.-Ing. Fritz Sennheiser (originally known as Laboratorium Wennebostel (Lab W). Its first products were microphones.

Let me tell you that when I owned an AV/Theatrical staging company in the 80-90s, the sound technicians staff would not use anything but Sennheiser mics. I bought my first pair of Sennheiser cabled ‘cans’ (much to my ex-wife’s disdain of anything that pleased me) at the eye-watering cost of over $700.

And that is the strength and weakness. If you want audiophile quality, Sennheiser is way up there. Its IE 80 S BT earphones are $799 – for buds!

If you want cheap Sennheiser is also way up there (literally). Sorry, the brand is for people that value sound quality.

But times change, and Sennheiser had to introduce a ‘very good’, ‘extremely good’ and ‘off the planet good’ ranges to appeal to the masses.

In the ‘extremely good’ range is its $499.95 Momentum True Wireless 2 buds (review here 4.7/5). For sound, battery, and quality it is a 10/10 but for ANC – well you can get higher levels in other brands.

But that brings me to the question posed by our AV expert Thomas Bartlett to Christian Ern, Portfolio Manager for Consumer Headphones at Sennheiser, Germany.

In essence, Thomas said that while Sennheiser’s ANC (noise cancelling) was good, it was not as good as other brands like Bose. Christian was not exactly apoplectic, but his Germanic response was “Yes, and it ruins sound’.

Christian made several interesting points – not just about the new Sennheiser CX 400BT. (paraphrased)

Sennheiser has one of the oldest sound pedigrees. Its focus is on sound. For example, anyone can make True Wireless earphones or headphones (the term is for the Qualcomm’s True Wireless chip range). They look at the price they must meet, subtract from that the cheapest chip they can get away with, and the rest is for the battery, DSP, speaker, housing and case.

That is why you can get absolute junk under about A$150 and why the Sennheiser CX 400BT is $299.95. We start with the speaker (transducer) – no compromises. We make it, and it is like the original 7mm in the original Momentum. In fact, the whole device is like the Momentum (review here 4.6/5), and we updated the tech. Its how we can produce the CX for almost half the price.

Then we look at how to use BT to connect without altering the sound signature – to be neutral to the sound. That means a lot of work on the digital signal processor and using three codecs – SBC, AAC (Apple) and aptX (Android).

ANC, especially heavy ANC, destroys the sound quality. The stronger ANC, the weaker the sound. That us why Momentum 2 costs so much more and why we try to be light-handed with ANC.

The CX 400BT uses noise isolation via the right size silicone tip into the in-ear canal section. It does not go very far in – it’s all about a good fit.

Finally, we have quite an amazing Sennheiser Smart Control app that has a ‘finger’ drag to make the music you want.

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