KEF X300A Digital Hi-Fi Speaker System

Device Type: Powered Speaker
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”
Weight: 33lb/pair
Availability: online and through authorized dealers
Price: $800.00/pair

Wide Open
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.

The Point
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!

Aerocraft67's picture

I don't doubt that this will be a useful package for some, but I suspect it's a rather narrow slice of the market that's interested in both an $800 powered desktop speaker system and integrated DAC, even from a venerable name like KEF. Surely the typical hi-fi desktop audio enthusiast with sufficient budget for these speakers already has an outboard DAC, and finds it desirable to maintain it as a separately upgradable module to the system, especially given the far more rapid current pace of DAC price/performance evolution than for speakers.

That said, the subsegment for consumer hi-fi desktop speakers seems a bit underdeveloped. Studio monitors remain the prevailing option for serious desktop listening, in lieu of suitably high-performing near-field speaker options targeting the consumer market. There's a mature and vibrant market for these products, but the problem is, many studio monitors lack consumer niceties like RCA inputs and handsome cabinets. So it seems there's an opportunity here for hi-fi nearfield desktop speakers with consumer-friendly features—but not so boxed-in as to include the DAC. 

Put another way, lose the DAC and $300, and I'd snap these up and volunteer for fanboy of the month.

hotsoup's picture

I completely agree. I'm still hunting for desktop speakers with controls on the front, master/slave configuration, not-too-big footprint, etc. Basically what computer speakers have always been, just sonically upgraded. But I can't seem to find any without strange pricing and feature sets.

I did kick down for Audioengine A5+, but they turned out to be too big. So I hooked them up to my bedroom TV instead. Wow, that was an upgrade... cool

Michael Lavorgna's picture

...the ADAM A3Xs - while each speaker is self-powered, you can master/slave them by using the included cable and the volume control is on the front.

alex629's picture

It will be good to read PC Speakers Reviews for better understanding of their quality as well.

itsratso's picture

why no way to integrate sub why why why why :(

MoonUnit's picture

I found the following comment in your review a little strange: "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."

That comment seems to imply that there is an analog signal path through these speakers. There isn't. You never avoid using the KEF's built-in DAC. The analog input in the KEF X300A is digitized by a WM8782 ADC, then processed by a DSP, then sent to the KEF's internal DAC (a PCM1754 in each speaker).

While I'm not criticizing your listening impressions, I find it hard to believe that by inserting another DAC into the signal path (digital -> HRT MicroStreamer -> analog -> KEF ADC -> digital -> KEF DAC), you get better "resolution of fine detail".

These are great speakers, partly because they do use DSP to EQ the low end (if you're not getting enough bass, flick the switch to "stand mode" on the back... it sounds like the reviewer was using "desk mode"). But people shouldn't be misled into thinking there is an analog signal path here. There isn't, and adding an external DAC probably won't help, because you can never bypass the internal DAC.

Vade Forrester's picture

The X300A Fact Sheet on the KEF web site specifies

Analogue input:

AUX: 3.5mm stereo jack

MoonUnit's picture

Yes, there is an analog input, which is immediately converted to digital, and then converted back to analog by the KEF's DAC (like I said).

Aerocraft67's picture

Sounds like the comparison here is between the DACs in different setups, not listening to the DACs in line with each other, which would not make sense indeed. That is, he's not inserting the Bifrost or HRT into the path to the KEFs. But I suppose this raises another problem—how is he comparing DACs when they're necessarily run to different speakers? The Bifrost to A3X (or whatever) vs. the KEF DAC to KEF tranducers isn't really a robust comparison of DACs. Not that it's a DAC comparison review per se, but to your point. 

Steve Guttenberg's picture

You are correct, so I have to admit I overlooked a crucial aspect of the X300A's design. The analog input runs the signal through an analog-to-digital converter, and doesn't bypass the X300A's DAC. That's a rather unfortunate aspect of the design, and I hope if KEF makes a X300A Mk2 the engineers include a direct analog input. Regarding my comments about adding an external DAC, like my Schiit Bifrost, it changed the sound, and I felt it was a change for the better. X300A owners who already have a DAC might as well try using it and see if their DAC improves or degrades the sound.

simplecl's picture

     I wish it wasn't true, but we can no longer rely on reviews from audiostream, stereophile, etc.  This review clearly exposes their bias toward more expensive products and advertisers.  While it does occur, it's rare that a review will greatly favor a cheaper product over a more expensive one.  It's all done to sell advertising and products.  Never forget to consider the source.

     Listen for yourself.  Trust your own ears.  Almost no one in the audio business is looking out for the consumer.  Their world revolves around money and profits.

Michael Lavorgna's picture

Just because you're paranoid doesn't mean you're also not being just plain silly.

I'll give you a pass this time simplecl just because this comment of yours is so over-the-top no one is going to take you seriously. But if you post another like this, we'll have to say bye bye.

simplecl's picture


     Wow! That sounds a lot like a threat.  Is this an open forum or only a tool edited for maximum profit?  I didn't expect such an unprofessional reaction.  I think people have an open mind and want to be fair, myself included.  Would you please provide a few links to recent reviews where my observations are not valid?  I would sincerly enjoy reading a few.  If not, it's time for you to delete my posts.  Ironically, it would add weight to my observations.  Let's find out if this is an honest forum...Back at ya with the Boo!

Michael Lavorgna's picture

A threat? You really are silly.

guitarist9273's picture

Thanks for the review!

How do the KEF X300As stack up against some of the other comparable active desktop speakers featured in Audiostream's Greatest Bits, such as the ADAM A3Xs?

Comparing them to the KEF LS50 speakers (passive speakers that are twice as expensive, paired with an amp that makes that system 5X as expensive as the KEF X300A speakers!) doesn't do me much good. Even a brief comparison to the Emotiva airmotiv 4s would be appreciated.

attilahun's picture

These speakers are stunning to look at. 

I do wish that the dac was either better or not included. 

A sub option would be nice as stated above. 

I'll definitely consider these when I'm in the market for another active desktop. 

Might be great with a bedroom tv too.

peo's picture

Can you not connect a sub to the standard analog output from the mother board and connect the KEFs to the USB output?

Wavelength's picture

Michael, Steve;

You can specify your alerts in the System Preferences->Sound to have a different output than your main output. You can also turn off the annoying bleep when the volume is changed etc...

Just go into Sound Effects panel of the Sound options and change the output to your internal speaker.


Michael Lavorgna's picture

But thanks for sharing this important tip Gordon.

simplecl's picture

Tonight I heard the x300a for the first time.  They're nice for a "desktop" speaker system.  Bass was substantial and well controlled.  Vocals were clear.  Build quality seemed excellent.  Overall, the speakers presented a good soundstage and filled a small room with enjoyable sound.  I can imagine how they would be usefull in the right application.  Some people need a DAC, others don't.  Either way, I think these speakers should be heard if you're in the market for a small system.

Mattdaddy's picture

The KEF X300A's are in another league...from everything I've heard that sits on a desktop! All this speculation about how they sound, who would buy them, how other dacs are "better." Puh-leeeze. Test them out. Listen to music for once! You'll be shocked and you'll stop all the hand-wringing.

Myanmar's picture

How does these compare to Adam Artist 3? I am planning to buy one but can't decide which one to choose.

luisvm21's picture

How I can get the best sound with the kef adeacuado x300a settings in windows. I have the player foobar2000.
Thank you.

bilan's picture

I am in the market for a high-end desktop speakers and I finally narrowed it down to either Adam Artist 3 or KEF 300A. I mainly listen to jazz, tango and classical music and occasionally to rock n roll. Which one do you recommend and why?

AJvR's picture

For those looking to connect a subwoofer to their X300A (analogue outputs), there is a modification available at