KEF X300A Digital Hi-Fi Speaker System
Input: 3.5mm mini-jack, USB
Output: USB (connects right and left speakers)
Dimensions (H x W x D): 11" x 7.1" x 9.6”
Availability: online and through authorized dealers
Here's what I've learned after thirty odd years in the audio business as a high-end audio salesman, and later on as a reviewer: The problem with speakers, including a lot of really good ones, is they sound like speakers. You're always aware the sound is coming out of a box or panel. Most of my favorites minimize that effect and have an "open" quality that lets the sound float free of the speakers. KEF's new X300A speakers are among the most open sounding speakers I have ever used with my computer. They're good, really good.
Like all of KEF's higher-end speakers the X300A features a Uni-Q driver, which bears a strong family resemblance to the driver in KEF's $30,000 Blade flagship speaker. The Uni-Q driver has its tweeter nestled in the acoustic center of the woofer, so it's a true point source, which is an especially great thing to have when you're sitting just a few feet away from a pair of speakers. All frequencies come from the same point in space. You get more coherent imaging with point source speakers than ones with their tweeters and woofers separated by a few inches. KEF patented the Uni-Q driver in 1989, and has been refining it ever since.
KEF's engineers took the high road with the X300A's electronics, so instead of going with the usual, off-the shelf stereo Class D amps, and stuffing them in one speaker, each X300A houses two KEF designed and manufactured Class A/B amps. There's a 50 watter driving the 5.25" magnesium/aluminum woofer, and a 20 watt amp for the 1" aluminum dome tweeter. KEF's cool looking "tangerine" waveguide sits in front of the dome to help produce the desired spherical radiation pattern. Rather than use a "half-round" surround, the Uni-Q driver has a low profile, serrated surround to minimize diffraction effects. The cabinet's vinyl wrap "gun metal" grey finish and pewter hued Uni-Q driver lend a handsome look to the design. The X300A weighs a hefty 16.5 pounds, that's unusually heavy for a desktop speaker.
Connectivity options are limited to a 3.5mm analog input and a mini USB type B port for the built-in 96/24 DAC on the left speaker. The rear panel also has a heat sink, bass port, a small volume control and a two-position EQ switch that optimizes the sound for free space or desktop/wall mounting. The right speaker is similar, but substitutes an L/R balance control for the volume control, and there's a USB input for the cable that connects the two speakers together (the right speaker has its own digital-to-analog converter and amplifiers).
Those amps aren't on all the time, they go into stand-by mode when they stop receiving signal and "wake up" when the signal returns. That's fine, but since I don't always have music playing the X300As clicked on to "ping" when I received an email, and then returned to stand by a few minutes later. The click on/click off sounds weren't at all loud, but I found them distracting. Worse yet, the X300As sometimes miss the first second or two of the music before they came back to life. I wish there was a way to manually turn the speakers on and off, which is what I do with my Audioengine and Emotiva desktop speakers.
A Smooth Operator
The X300A sounds neutral. The purity and speed might at first give you the feeling of an electrostatic speaker. True, it's not as transparent as a Quad ESL, but the X300A can deliver soft to loud dynamics and power that no full-range 'static will ever match. The X300A's built-in DAC sounded sweet, but it didn't come close to my desktop reference Schiit Audio Bifrost DAC ($449). I also preferred the sound of the HRT MicroStreamer ($190) over the KEF DAC, it wins on resolution of fine detail.
Point source monitors like this usually have a nice, wide sweet spot, so even when I was as close as 18 inches to the speakers they nearly disappeared as sound sources. Image depth was excellent, with good focus, and the soundstage extended well beyond the edges of the speakers.
Bass output reached down to the low 50 Hertz range when I had the speakers six inches from the wall behind them, and the bass quickly rolled off below that. This isn't the sort of speaker that adds any extra fullness or warmth to the sound, it tells it like it is. Harsh and gritty MP3s and YouTube videos sound harsh and gritty.
Brian Eno's gorgeous ambient masterpiece Apollo wafted out of the X300As, and occupied a broad swath of the landscape over by desk. Eno's "Here Come the Warm Jets" (the song) raised goose bumps. The tune's dense, buzzy riffing and pummeling drums sounded big and juicy, I couldn't stop smiling.
To finish up I compared the X300As with my KEF LS50 monitor speakers (powered by a Bel Canto REF500S amp), and I can't say the difference was jarring. I had logged a good number of hours with the X300As; returning to the LS50s I felt right at home. It features a similar Uni-Q driver -- but the bass goes lower, dynamics kick harder, the treble is more refined, and the soundstage dimensions were even bigger –- so the LS50s are definitely better speakers. Oh right, they sell for $1,500 a pair, and the REF500S runs $2,500, so at $800 the X300A seems like a steal!