Verdict
Pros
- Excellent, coherent sound
- Great value
Cons
- Large
Key Specifications
- Review Price: £68.77
- 13.5mm driver
- Remote
- Flat cable
What are the Audio Technica CKX9is Sonic Fuel?
The Audio Technica CKX9is Sonic Fuel are earphones with rubber ear grips to make them suitable for running and other activities that might make normal earphones pop out. However, they don’t have any of the gaudiness of most sport headphones.
A slightly sporty style may put off some people, but the CKX9is deserve to be heard. They offer some of the best sound you can get for £70.
Audio Technica CKX9is Sonic Fuel – Design and Comfort
The Audio Technica CKX9is Sonic Fuel earphones are very large. Their earpiece stems and the rubbery grip that snakes around your ear make them far bigger than the normal IEM buds we tend to review.
They are bulky, and hardly the prettiest earphones in town. However, there are practical benefits to the Audio Technica CKX9is Sonic Fuel design.
These are earphones that sit in your ears very securely. Yank them and they don’t fall out. This makes them perfect for running. However, they are not waterproof.
The earhook does introduce some potential comfort issues. We found the Audio Technica CKX9is comfy enough, but those with very sensitive ears may not like them. 
Audio Technica supplies three different sizes of rubbery in-ear hooks, four pairs of rubber tips and one pair of Comply foam tips with the Audio Technica CKX9is. That’s not a bad haul – you rarely get foam tips with anything but the most expensive earphones. You also get a semi-hard carry case.
The earphones themselves have a handsfree remote with a single button that’ll act as a call and play/pause button with most phones, including Androids, Windows phones and iPhones. We’re less keen on the plastic volume slider on the remote, though. It cheapens the feel of the headphones, and basic resistor-based sliders like these aren’t well regarded in the audio community.
It’s not a big problem, but it does feel slightly misguided. Audio Technica also makes a version of these earphones without the remote unit, and they’re called the ATH-CKX9.
Audio Technica CKX9is Sonic Fuel – Sound Quality
The Audio Technica CKX9is Sonic Fuel earphones use large 13.5mm dynamic drivers, and they offer excellent sound. All complaints about their odd looks and naff volume control fade away when you hear the things.
They have a slight bass skew, but the low-end is superbly integrated, meaning that the bass is not a limelight-stealing influence. The treble is exceptionally coherent, and there’s more airiness to the sound than you usually get with a pair of mid-range earphones.
Clarity is great, and the tone is fairly bright (not to everyone’s tastes) but the treble is smooth enough to avoid serious sibilance and harshness. It’s a very impressive performance, especially given they use ‘standard’ dynamic drivers rather than balanced armature ones.
The Audio Technica CKX9is Sonic Fuel can stand up to some multi-driver earphones well – and given that those sell for around twice the price or more, that’s an impressive feat.
The slight bassiness stops the Audio Technica CKX9is Sonic Fuel from being incredibly accurate, but then we imagine very few people use earphones like this for serious monitoring purposes. And in terms of producing a sound that makes music sound enjoyable, fun and exciting, these Audio Technicas ace it. 
Should I buy the Audio Technica CKX9is?
The Audio Technica CKX9is Sonic Fuel earphones are unlike to stir desire in the same way as something like the Bower & Wilkins C5, earn as much recognition as the Shure SE535s or sell as much as a pair of Sennheisers. However, they deserve success.
With a good price, truly excellent sound for the cost and a practical design, the Audio Technica CKX9is are some of our favourite earphones released this year. If you don’t like the sound of their slight bass focus, check out the Phonak PFE012, but otherwise these earphones get a solid recommendation.
Verdict
The Audio Technica CKX9is are some of the best sub-£100 earphones, offering great sound at a sensible price.
Next, read our best headphones round-up
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Professional conduct
We also expect our journalists to follow clear ethical standards in their work. Our staff members must strive for honesty and accuracy in everything they do. We follow the IPSO Editors’ code of practice to underpin these standards.
Editorial independence
Editorial independence means being able to give an unbiased verdict about a product or company, with the avoidance of conflicts of interest. To ensure this is possible, every member of the editorial staff follows a clear code of conduct.
Professional conduct
We also expect our journalists to follow clear ethical standards in their work. Our staff members must strive for honesty and accuracy in everything they do. We follow the IPSO Editors’ code of practice to underpin these standards.
