Kef X300A review

KEF is a legendary name in the world of premium Hi-Fi, so when a company of its stature moves into the world of computer audio, you sit up and take notice. The KEF X300A speakers use KEF’s unusual lemon-squeezer-shaped Uni-Q driver, which positions the tweeter inside the woofer. This means all sound comes from the same place, the intended effect being to make the sound, particularly its positional aspects, more realistic.

The speakers are both individually powered, which means they can produce loads of volume and you don’t have to worry about the kind of whining interference which can affect bus-powered speakers that don’t have a ground connection.

The data connection is also high quality, and uses an asynchronous USB connection. In simple terms, asynchronous USB hardware has a built-in timing chip that controls how much data is being passed through, so the setup isn’t dependent upon computer’s own clock cycle. This eliminates occasional judders and glitches that can occur in USB audio devices using adaptive USB connections.

Although both speakers have their own 3-pin power connections, each has different controls. The left speaker is the primary USB audio device and connects directly to your PC. Internally, it’s equipped with a high-end DAC that supports a sample rate of up to 96kHz. We like its neutral, balanced sound.

Instead of an analogue audio cable, the X300As use a digital mini USB connection to join the left and right speakers. The left speaker also has a 3.5mm auxiliary input for connecting external audio devices such as MP3 players, rather than playing music from your PC through the built-in USB DAC.

The right-hand speaker also has a balance pot, which you’ll probably want to keep at the centre position unless your speakers are unevenly spaced. On the left is a gain pot that lets you set an appropriate baseline volume. It’s difficult to knock the pots out of position once you’re happy with them, but it’s also quite difficult to adjust them if you can’t look at the rear of the speakers. There’s also an EQ switch on the left speaker that switches between modes designed for use on a desk or on speaker stands.

The biggest challenge is finding somewhere to put the speakers. Each measures a hefty 280x180x243mm including its heat sink, which made our standard-issue Ikea desk feel very crowded when we placed them alongside a pair of 22in displays, mouse and keyboard. You can also put them on a slightly elevated set of shelves or on stands, but you’ll ideally want to have them pointed towards your head.

As long as they’re at roughly the right height, and they’re pretty forgiving in this respect, they have a wide sweet spot that produces an absolutely fantastic sense of space. Even with the speakers positioned relatively close together and close to a wall, the sound was incredibly immersive, seeming to surround us from all directions.

If you must have the speakers near a wall, you’ll probably need to limit the amount of bass produced from the ports at the rear to prevent low-frequency sounds from reverberating off the surface behind the speakers. To do this, it comes with foam bungs that you can use to block the bass ports completely or partially. It’s worth taking the time to experiment with bungs to see what produces the optimal sound for your space.

The speakers sound fantastic. As well as providing an immersive listening experience from a wide range of angles, the speakers have the kind of neutral, well-balanced sound we want. This means that bass, treble and mid-range sounds are evenly balanced, allowing the original mix of the track you’re playing to be clearly heard. This is a common goal of high-end speakers and monitors, but it’s great to hear the X300As achieve this natural sound so effectively. We were particularly pleased that the speakers have an emphatic and well-defined bass that nonetheless doesn’t overwhelm the mid-range. The speakers really make the most high quality recordings, although flaws in ultra-low-bitrate audio sources were also clearly audible so make sure you media is recorded in the highest quality format possible. Everything from bass-heavy hardstyle to orchestral music was rendered with great clarity.

The KEF X300As are, without doubt, the best-sounding USB speakers we’ve ever heard. Their built-in audio processing hardware rivals that of our favourite USB DACs, such as the Arcam rPAC. However, we’d also prefer the X300A to have TRS, XLR and RCA inputs for greater connectivity and flexibility. You can only use them with a computer or via a 3.5mm stereo input, which is primarily designed with MP3 players in mind.

It’s hard to fault these beautiful-sounding speakers, but they rely upon a USB connection for optimal audio quality, which could be a hard sell to an enthusiast market that remains obsessed with analogue.