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KEF X300A Powered Speakers Review

KEF X300A HiFi Powered Monitor Speakers

KEF X300A HiFi Powered Monitor Speakers


  • Product Name: X300A HiFi Powered Monitor Speakers
  • Manufacturer: KEF
  • Review Date: November 19, 2013 21:00
  • MSRP: $799/pair
  • First Impression: Gotta Have It!
  • Buy Now
  • Two-way bass reflex bookshelf loudspeaker
  • Drive Units: 5.25in. Uni-Q, 1in. aluminium dome HF
  • Frequency Response(+/- 3db): 58Hz - 28KHz
  • Frequency Range(+/- 6db): 49Hz - 45KHz
  • Max SPL: 104db
  • Amplifier type/class: Bi-Amped Class AB amp
  • AC Power Outputs: 100-120VAC, 50/60Hz
  • Power Output: LF: 50W HF: 20W
  • Input Impedance: AUX 47K ohms
  • Analog Input: 3.5mm stereo jack
  • Digital Input: USB: Mini USB type B connector
  • Controls: Balance Control, AUX Control
  • Accessories: power cord x 2, USB x 2,
  • Resolution: Up to 24bit
  • Sampling Rate: Up to 96 kHz (depending on source resolution)
  • Internal Volume: 47L
  • Dimensions: 11.1 x 7.1 x 9.6 in., Weight: 16.5 lbs. each
  • Finishes Available: Gun Metal

I've been listening to and reviewing speakers like these KEF X300A's for quite some time. In fact, a lot of bookshelf speakers as well as many powered monitors come across my desk—literally. Well, not literally. They're more or less next to my desk. On stands. The point is—I've listened to a lot of these speakers and I know what I like. I love solid bass, but it doesn't have to sound like a subwoofer is in the room. It just has to be punchy, you know? Where it hits you right in the chest. If your speakers do that, you've got bass pretty much covered. As for highs, what you're listening for is clarity without that brittleness that can come from a tweeter that not integrated well or receiving signal through a poorly thought-out crossover. The KEF X300A's have none of that either. The high frequencies have tons of detail. That just leaves the mids—you know, all the stuff in the middle that most speakers just presume will come from somewhere. No, mids are important and I loved the way the Uni-Q driver array pulled this off. I'll get specific in my listening tests, but let me jump into why I'm impressed with how these speakers are made.

For one, the X300A powered monitors use two class AB amplifiers in each speaker. A 50 watt amp drives the woofer and handles the low and mid frequencies, and a 20 watt amp powers the 1" vented aluminum dome tweeter. It's brilliant and really effective. Each speaker actually has a high-end toroidal transformer and the other really unusual thing is that each speaker houses its own 2-way or twin amplifiers. You can tell they mean business, too, as each has a large heat sink right on the back. The speakers are 11-inches tall and nearly as deep. They also weigh over 16 pounds each. There's no speaker cable connecting the two, either, it's actually a USB cable. So...these speakers each get fed digitally and the onboard DACs, which are capable of 96kHz, 24-bit decoding, take care of the conversion right at the point of output. And there's no noise. They're completely quiet when they're not on. Dead silent. They also are designed to go into standby mode after a few minutes, but connected via USB, the small front LED, which is normally green, never did turn amber until my Macbook Pro went into sleep mode.

KEF beauty

Build Quality and Finish

The KEF X300A speakers are very attractive. They have a black baffle with the attractive Uni-Q driver array mounted flush to the face. There is no grill for these speakers—and there shouldn't be. They look awesome as-is. The veneer of the cabinet has this brushed aluminum look to it and the edges are nicely rounded in a continuous wrap. The rear-facing port is flared and the hefty speaker seems very well-made.

 KEF X300A brushed aluminum KEF X300A UniQ driver

Features and Functions

So, when I said these speakers dip down low, they extend down to around 58Hz +/- 3dB and 49Hz at -6dB. That's why they're punchy. At 60Hz you can really get some power in your chest at high output—and I measured these speakers putting out 97dB SPL playing some modern music tracks—without even a hint of distortion. KEF's specs says they can hit 104dB, but I have no interest in listening to a test tone or pink noise that loud, know what I mean?

Now you can connect these speakers to an analogue audio input—there's an 1/8" stereo jack on the back of the primary left speaker. But what you really want to do, unless you're using a high end DAC already, is feed these from the USB output of your computer. Then you're really getting the benefit of the onboard DAC, which by my standards does an incredible job for something built into a speaker. Also on the left speaker is a balance switch that goes between Stand or Desk mode. It essentially rolls off the low end just a bit for when you place the speaker on your desk as opposed to on stands. You can also use the included foam bung plugs (I swear that's what they call them—just insert your own joke there) to tighten up the bass a bit in the event your speakers are close to a wall.

KEF X300A rear

Listening Tests

In setting up these speakers for my listening tests, I made sure the gain staging was set properly. That means that since you have a volume level for the system, and a volume level for the speakers, as well as a volume level for the app you're listening to—you need to know what to set each one to and how to best control volume overall. There are several schools of thought here. One maximizes the bit-depth of the playback system and gives you the most dynamic range. That involves maxing out the application volume, setting your PC or Mac volume to around 3/4, and then setting the KEF X300A speakers at a volume that is comfortable. I actually prefer to max out the amps on a system that doesn't audibly distort. Once I realized that the KEF X300A powered speakers could handle a complete maxing out of all volume stages, I cranked up the onboard output all the way and also raised the volumes on all my source apps. Then, I found I could control volume from the keyboard which adjusted my global volume output. If you find that your system alert sounds, etc. are too loud, be sure to go to your Sound control panel and adjust the volume settings for those items independent of the master volume output.

KEF X300A angled

The first thing I listened to on these speakers was Steely Dan. Sound was only coming out of the right speaker, though. I had turned both of them up which perplexed me...until I realized that I hadn't turned them both up. The small dials on each speaker actually have two separate functions. On the master speaker, the one on the left, the dial controls the master volume for both speakers. The dial on the right speaker actually controls panning between the two. It didn't take long to figure that out and I was cranking up the music in no time. "Hey Nineteen" is one of my favorite tracks and that's where I heard that really tight bass and clear highs. I kept turning it up...and up...and up...and there was no distortion. These speakers are awesome—they just keep sounding better and better the louder you play them. Of course, I don't recommend 95+dB for long in close quarters.

I also brought up some Toby Mac. Who am I kidding, I listened to hours of music on these speakers; but with respect to Toby Mac, I really liked how "Eye On It" sounded but I also realized at this point that the KEF X300A's don't have far-reaching bass. They just don't; but I think that's what makes them work. Speakers like this that tend to be all things and reach down lower than they should often have a problem of bottoming out, or the mids and highs just get trashed. The KEFs don't do this. They're well-balanced and they sound great—even when they're maxed out. So if you want more bass, get a sub. The only difficulty you'll have is that there's no parallel analogue output on the X300A's so you're going to need to use an external DAC that gives you either a way to split the analogue output or pull a parallel feed for the sub. Not a deal-breaker, but something to consider.


In case you can't tell by now, I love these speakers. They're $800/pair and worth every penny if your focus is on midrange, high frequency detail, natural-sounding vocals and the ability to drive a speaker as hard as you want without fear of distortion. If you're a bass-head, you're going to want to look at something else or figure out a way to add a subwoofer into the mix.

Our question for this video is this: Do you want a subwoofer in your office or at your desk? Do you need a subwoofer there? Would you sacrifice clarity or output for bass response? Actually, that's three questions...Pick one and let us know in the comments below. Or answer all three—we don't care. And subscribe to our YouTube channel so we can bring you even more videos. Plus you can Like us on Facebook to hear about what else we're doing.

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.

About the author:
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Clint Deboer was terminated from Audioholics for misconduct on April 4th, 2014. He no longer represents Audioholics in any fashion.

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