KEF XIO Soundbar Review

Prestigious UK brand KEF has been delivering quality loudspeakers since 1961, with the accent on pushing the boundaries of quality and space-efficiency. With such rich experience, it’s a surprise that we’ve had to wait until 2025 to see it step into the soundbar market. While some brands might opt to test the waters with a budget model or a mid-tier offering, KEF has stepped straight into the big league with the high-spec and premium-priced XIO soundbar.

At first glance, the XIO (pronounced ‘Zee-O’) bears quite the resemblance to Devialet’s Dione soundbar, but without the central orb. While a compliment to be compared to the most elegantly designed soundbar to date, KEF assures me this is a mere coincidence – the similarities are purely the outcome of engineering the largest performance from the most efficient package, which is more evident on audition.

Measuring a not inconsiderable 1,210mm wide, 165mm deep and 70mm high, and weighing a serious 10.5kg, the XIO sits at the larger end of this market. Yet it never looks intrusive thanks to KEF’s intentionally minimalist design. There’s no unnecessary flash here, and instead, careful material selection has resulted in a design with cool aluminium across the top, surrounded by a premium fabric that should seamlessly integrate into any room.

Available in Silver Grey and Slate Black, the only break that indicates function over form is a fabric-covered driver slightly recessed into the top plate. This is actually the centre channel if you decide to wall-mount the speaker. KEF has made this easy, with a wall mount kit included, which appears to be the strongest I have seen in a soundbar package.

There’s a selection of touch controls and status lights on the top, and at the back is a recessed hub with the obligatory eARC HDMI 2.1, plus optical digital and Ethernet connections. Conveniently located power, reset and Bluetooth connection buttons finish off the selection, along with the choice of RCA subwoofer output, or you can purchase the optional KEF KW2-RX accessory to allow wireless connection to compatible subwoofers. KEF, like Devialet, has forgone HDMI passthrough.

Inside are twelve Class-D amplifiers which deliver a collective 820W of peak power to an array of twelve speakers. L/C/R and height channel duties come curtesy of KEF’s proprietary 50mm UniQ MX drivers (six in total, of which five will be functional at any one time to account for the active centre dependent on orientation), flanked by two 50mm full range drivers for surround delivery.

Low frequencies are handled by four KEF P185 LF drivers, which are quite large (50x180mm) oval-shaped units, two front and two back. KEF’s Uni-Q drivers are unique in that they are a coaxial design with a tweeter and a cone driver, but these are integrated cleverly into one package for single-point sound delivery.

The intention is to deliver detailed sound across a wider axis, in a way that a single full-range driver may struggle to do well through the whole frequency range. In the case of the XIO, the 50mm Uni-Q MX uses a single long-throw voice-coil and neodymium motor to drive both the tweeter dome and midrange cone.

However, they have a mechanical crossover, which essentially allows the two drivers to move together at low frequencies. In the manufacturer’s words, “as the frequency rises, the MX decouples the dome from the cone, allowing the tweeter to operate independently for optimal high frequency response”.

Also included is KEF’s Velocity Control Technology, which is able to monitor and control the motion of the driver in real-time. This is claimed to minimise distortion while maximising output, which is the kind of high-brow engineering philosophy that you don’t generally see in a lot of soundbars.

This combination of drivers, KEF says, can deliver a maximum output of 102dB with a frequency response of 34Hz to 20kHz. Outside of the electron shuffling, we have support for Airplay, Google Cast, UPnP, Bluetooth (5.3), Spotify Connect, Tidal Connect, Qobuz, Deezer and more.

Resolution depends on the source, but the XIO can process up to 24-bit, 192kHz audio via HDMI, or up to 24/384 via network streaming, which is available via Wi-Fi up to 6GHz. The only format that is not supported is DSD, which isn’t mission-critical in a soundbar.

Getting going is as simple as plugging in the HDMI to the eARC HDMI port on your TV, but advanced setup and streaming control are handled by the KEF Connect phone app. Its interface is clean, and it is exceptionally fast and reliable – I never experienced any connection delays or issues in my time with the XIO.

The depth of control is impressive for a soundbar, with a room-correction programme using KEF's Intelligent Placement Technology (which thankfully has no loud pings, just a gentle whoosh like a calm day at the beach), subwoofer and high/low pass frequency controls, and welcome EQ controls for bass and treble which I found sorely missing from some competitors.

You also get a choice of sound profiles for listening depending on your source, and unlike many soundbars, my preference didn’t default to Direct for a change, more of which later…

The Listening

KEF has hit the soundbar field with the same gusto that Juan Marichal hit his debut MLB game – a complete shutout! I don’t normally have high expectations of a one-piece soundbar, but the XIO surprised me. It sounds surprisingly dynamic. Rich and clear highs, coupled with deep and powerful lows, are not expected from a package like this.

The decision by KEF to go with four larger bass drivers rather than add additional but smaller drivers has really paid off when it comes to low-frequency reproduction. When you’re watching a movie like Godzilla Vs Kong, the opening scene where Kong is walking around his enclosure gives the type of low-end rumble for each lumbering footstep that you’d normally only expect from a small subwoofer.

The latter attack by Godzilla on the Apex facility is one of the best demonstrations of power and dynamics from a soundbar I have heard. It’s full, impactful and expansive, but the price you pay for this is that dialogue can become a little lost in the mix.

This is normally a problem with larger home cinema setups rather than soundbars, and similarly, while you can bump up the volume to make the dialogue clearer, the surrounding noise can then become a little much. Moving to the Direct sound-setting does help the dialogue aspect, but you lose a good amount of bass in doing so – it might be something best partnered with a subwoofer in those cases.

What this does highlight, though, is that unlike the hit-and-miss sound modes we see from some other brands, the sound options provided by KEF really do work well to maximise performance from the soundbar format.

Options like Movie, Default, Dialogue and Direct, as well as EQ control over bass and treble, make a positive difference and rather than skip straight to Direct as I normally prefer, I actually found myself sticking with the intended profile as it seemed to deliver the most impressive results.

In terms of surround performance, for a one-piece design with reflective surround and height channels, you need to consider the performance in line with similar solutions – and in this regard, the XIO performs on par with its competitors. I found in my listening space that reflected channel performance would vary based on frequency, but this is a room acoustics issue, not an XIO problem.

In the right contexts, the additional channels definitely add to the presentation. Gran Turismo 7 (PS5 Pro) is a game that provides a lot of directional cues that help you position your opponents, as well as plenty of environmental effects that draw you into the racing experience.

I always found a good sense of where my foes were trying to overtake me, and when you were in a race that gets hit with rain, especially while in cockpit view, the sound of the heavy downpour hitting the roof of the car is elevated and immersive.

This continued with The Flash movie, where the opening hospital collapse again, demonstrating the low-end credentials of the XIO, with impressive bass extension as various building components came tumbling down.

But it was the sequences in the time-bubble where you felt the real enveloping presence of the height and surround channels. This brings you into the movie quite well. It’s not just bass performance that is impressive; KEF has used those Uni-Q MX drivers to a great effect.

You get incredible clarity, brightness, and accuracy in the mid and upper frequency ranges, too. Overall, then, the movie performance of the XIO is hard to beat in any soundbar, let alone a single-piece design, and for those who are space-constrained or want a tidy yet exciting home cinema experience, it’s tough to look past.

Musically, the XIO shows confidence and ability. The combination of high-quality upper-range drivers, ample amplification, large low-frequency drivers, and KEF’s special sauce signal processing makes this one of the most musical soundbars I’ve reviewed.

Listening through Tidal Connect, JMSN’s Cruel Intentions was a track that would normally lose some impact via a one-piece soundbar, but the deep basslines were held to a surprising standard, while still maintaining the dynamic headroom to nail the beat clearly over the top.

Not everything needs to be bass-heavy, though, and Stevie Ray Vaughan’s Little Wing has legendary guitar work that needs a quality speaker to bring it to life. Leaning slightly to the warm side, XIO displayed a pleasing richness in the guitar notes, bringing a clear distinction between the moments of energy and silence.

While in the past, I have found some Class D amps in soundbars to introduce an overly processed sound, the KEF manages to hide any trace of this with a clear but smooth delivery.

The incredible balance that the XIO displays across the frequency range is on show here too – not only are the guitar scales rich and detailed, but elements such as drum rolls are delivered with a full and deep texture that lets you close your eyes and imagine the skin of the toms vibrating with each tap.

Indeed, across most musical genres, the XIO delivered smooth vocals, a large soundstage, and real dynamism. The only time I found the XIO lacking was Dua Lipa & Elton John’s Cold Heart PNAU Remix. This song has a bass drum kick which needs plenty of driver movement and power, and in this format, there just wasn’t enough in the KEF to stop it from taking on a slightly hollow character. Despite this, however, the sound remained punchy, energetic and clear.

The Verdict

KEF might have gone for a serene look, but don’t let its size or simplicity fool you – the XIO bursts into the soundbar segment like a velociraptor with a rocket launcher riding a Harley Davidson! It is completely unexpected, highly impactful, and a little absurd – but cements itself as the soundbar to beat at this price-point, delivering exceptional performance with far less compromise than you might expect for the form-factor.

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