- Written by Jim Clements
- Published on 04 August 2011
Over the years, KEF has released 11 different versions of their Uni-Q drivers. That just shows you the importance KEF places on keeping their products at the forefront of the latest technology. KEF's newest version of their Uni-Q driver is the design centerpiece in the All New Q Series. The Q300's are the larger of two bookshelf models in the line.
The engineering team that developed the drivers for the All New Q Series is the same team that did the Concept Blade project. Naturally, many of the concepts implemented in the Blade design have trickled down to the Q300's. Ultimately, the two projects resulted in four patented technologies: the Tangerine Waveguide, Optimal Dome Shape, Stiffened Dome and the Z-Flex Surround.
The Uni-Q drivers combine the tweeter and midrange into a single assembly. The drivers emulate a "single acoustic source coherent in position, directivity and time." I have been impressed with the Uni-Q speakers I've heard in the past. So I was really looking forward to testing the new models.
- Design: Two-way Bass-reflex
- Drivers: One 1" Aluminum Dome Tweeter, One 6.5" Aluminum Mid/Woofer
- MFR: 42 Hz – 40 kHz ±3 dB
- Crossover Frequency: 2.5 kHz
- Sensitivity: 87 dB at 2.83 Volts/1 Meter
- Nominal Impedance: 8 Ohms
- Recommended Amplifier Power: 15 ‒ 120 watts
- Maximum Output (SPL): 110 dB
- Dimensions: 14" H x 8.3" W x 11.9" D
- Weight: 17 Pounds/each
- Finishes - Black Oak, English Cherry, or European Walnut
- MSRP: $599.99/pair USA
The KEF Q300's feature KEF's latest version of their popular Uni-Q drivers. KEF originally introduced the Uni-Q speakers back in 1988. They have continuously improved upon the original design through a diligent R&D effort. The culmination of this effort has led to the "All New Q Series" of speakers. The Q300 is the larger of two bookshelf speakers in the line.
"Uni-Q" is what KEF's calls their coincident midrange/tweeter array. In this arrangement, the tweeter is mounted at the acoustic center of the midrange cone. KEF's claim about the Uni-Q drivers is that they mimic a point source and so the sound waves retain greater coherency as they propagate through your room. Coincident drivers also have improved off-axis response characteristics because lobing effects between the two drivers are negligible. Take a look at the exploded illustration immediately below and the close-up of the finished product just below that image and you'll get the idea of how it all goes together.
The aluminum drivers in the new Uni-Q speakers embody numerous technical advances that have trickled down from KEF's Concept Blade project. Let's start with the tweeter. Using FFT analysis, KEF has determined that there are two different optimum geometric shapes for each of two important properties of an ideal metal dome tweeter. An elliptical profile is best to optimize the driver's mechanical properties while a spherical shape is best for the dome's acoustic properties. So they found a way to meld these ideas when they layered a spherical cap onto an elliptical substrate to form the tweeter dome.
The KEF Q300 tweeters have tangerine wave guides. The guides protect the tweeter and are said to improve "the coupling between the tweeter dome and the air". The waveguide on the Q300's is more aggressively designed than in past KEF Uni-Q models. They look really neat too!
Another design innovation of the tweeter is a larger sealed duct behind the tweeter. This chamber is filled with a damping material to reduce resonances in the column. The air behind the driver acts as a spring mechanism that dampens the driver and reduces distortion.
The mid/bass driver has a few innovative features of its own. For example, KEF implemented "Cone Breakup Control" in the Q300's. In this system, a "decoupling moulding" is situated between the driver's aluminum cone and the rest of the motor structure. This reduces mid range resonances. Speaking of the motor, the KEF Q300's have a larger, longer-throw motor than in past designs. Consequently, the overhung voice coil is rather large. So KEF wound this coil with aluminum to reduce the weight. It seems like there is a lot of aluminum in the Q300's . . . I finally realize what happens to all those empty soda and beer cans when we recycle!
The last word on the driver design is the choice of surround for the mid driver. KEF calls this ribbed design the "Z-Flex" surround. It ostensibly has two inherent advantages over a common design: it flexes more readily in the bass than in the mid range while the ribs create a waveguide to reduce diffraction in the tweeter's response characteristics.
The All New Q Series speakers come in a variety of finishes that are made from recycled wood fiber. The finish choices are Black Oak, English Cherry and European Walnut. My review samples were European Walnut. I must say that the KEF Q300's are built to a remarkably high standard. And with the brushed aluminum drivers, the tangerine waveguides and KEF logos on the front baffle, these are some very nice looking speakers particularly with the grilles removed.
I set up the KEF Q300's on a pair of super heavy duty 26" speaker stands; 9' apart and 12' from the main listening position. They were toed in about 30 degrees from straight ahead. I found this arrangement provided the best balance between center fill and the width of the sound stage.
For most of my listening, I drove the Q300's with the front two channels of an Anthem MRX 500 receiver. I listened to the Q300's full range most of the time, but I also used one of two subs from time to time; either a Klipsch SW 311 or a HSU Research VTF-3 Mk3. The crossover was set to 60 Hz in these instances. This is the lowest crossover frequency from the Anthem receiver. I think it would be worthwhile to try a crossover setting of 40 Hz between the KEF Q300's and your sub if your receiver has a 40 Hz setting.
The back panel features a bi-wirable input cup. KEF even came up with an innovative feature for the inputs - knobs that you turn one way or the other to open or close the shorting straps. This is a nice touch (and a good idea). But I worried that if you were to bi-amp the speakers, then the knobs might drift shut, shorting the amps. Yikes! In actual practice, this is implausible because it takes several turns to seat the knobs in either direction.
The KEF Q300's have a mounting bracket attached to the back panel. It looks awkward the way it sticks out. This is to allow use of he-man speaker cables with banana plugs when the speakers are mounted to the wall.
My initial impression of the KEF Q300' was that they were smooth, laid-back but detailed. This impression was formed straight away as I broke in the speakers on a small bedroom system with a proportionately small 25 wpc integrated amp. This smooth, laid-back and detailed sound eventually became my enduring impression of the KEF Q300's. This signature defined the Q300's even after I broke them in and installed them in my big system. They nevertheless benefitted substantially from an increase in amp power (and quality) at this point.
I even used the Q300's with a pair of Mark Levinson amplifiers just to test the limits of the speakers. Surely the KEF Q300's did not reveal all the air and transparency of the Levinson amps. But they aren't supposed to be able to do that! Not at $600 a pair. But I consider these speakers to be professional-grade studio monitors with a nice finish. They far surpassed my performance expectation for the price.
I started my serious listening with the LPCM 2.0 track of the Chris Botti Live in Boston Blu-ray. This is an excellent concert Blu-ray disc with high quality production values. It stars trumpeter Chris Botti leading his own band backed by the Boston Pops Orchestra. The speakers were being driven by the Anthem MRX 500 receiver with the ARC room correction off and no sub.
Botti's band is stacked with big time talent - think of Mark Whitfield on guitar, Robert Hurst on bass or Billy Childs on piano. But in my humble opinion, Billy Kilson, Botti's drummer since 2004, steals the show. He has his own unique style that he uses to really work over the cymbals producing world class polyphonic rhythms and amazing dynamic shadings. Give "Indian Summer" a whirl . . . Wow was all I could say! Over the Q300's, Kilson's cymbals really shone, although they didn't quite have all the air and extension of much more expensive speakers.
The KEF Q300's have great imaging and preserved the reverberant nature of the hall amazingly well for 2-channel set up. Botti has a very pure tone with his instrument and it came through the Q300's almost largely unscathed. With music, these speakers don't *need* a sub even in a larger room.
Although this concert is a veritable "Cavalcade" of stars, my favorite parts are when Botti is fronting his own band as in "Flamenco Sketches". That opinion quickly changed when Yo Yo Ma came on stage and later when the vulnerable Lucia Micarelli performed on "Emmanuel". With both of these stringed instruments, Yo Yo Ma's cello and Micarelli's violin, the Q300's really got the midrange right. And the coincident array as always provided excellent imagery on these tracks.
Keeping with a Boston-y theme, my next listening selection was the SACD remaster of the Living Stereo production Beethoven: Violin Concerto in D, Mendelssohn: Violin Concerto in E minor. This disc features Jasha Heifitz on violin with the Boston Symphony Orchestra as conducted by Charles Munch. I listened to the two-channel layer over the Anthem receiver and KEF Q300's. No sub was in play again this time.
These KEF Q300's are proving to be very musical speakers with all types of music but I feel they really come in to their own on orchestral works. The solo violin is nearly as clean and distortion-free as I've heard from this disc. The Q300's do not reproduce the lowest octave but you can still sense the "liveness" of a quality recording. With most material, I was perfectly happy with their bass reproduction.
True to their British pedigree, the KEF's displayed hair-raising rhythm and pace. Take Track 6, "Allegretto Non Troppo/Allegro Molto Vivace". There are a jillion notes a minute! Whew!!!! It gave me goosebumps. The soundstage was a little flatter than I'm used to on this disc, but you really don't give up a whole lot to much more costly options in this area.
Next I played the CD of The Decemberists – The King is Dead through my Oppo BDP 83SE. This is one of the discs that sounded better with a sub. So I activated my trusty old HSU Research VTF3 Mk3 sub. With this setup, the sound was about as good as you can get from a redbook CD – there was an uncanny naturalness to the sound. This CD played over the KEF Q300's had its own brand of synergy.
I love the instrumentation on The King is Dead; steel strings, harmonicas, fiddles, banjos, guitars, drums, etc. Plucked strings had a clean, round sound over the Q300's. The forlorn voices were far-off at times keeping their proper perspective. Track 6, "Down by the Water", just simply rocked the house. The drivers in the Q300's are surprisingly accomplished at this price point.
I also watched a couple of Blu-ray movies with the KEF Q300's. The first movie was the quirky film starring Robert Duvall and Bill Murray, Get Low. The bluegrass music on this movie is a big part of the story telling. It is well recorded as well. The artists include Alison Krauss, The Ink Spots, Jerry Douglas and the Steeldrivers. The fiddles sounded just right with the smooth KEF signature sound – warm and tactile. Allison Krauss's performance at the end of the movie was so pure sounding.
In the numerous quiet parts in Get Low, I could hear most every nuance in the environmental sounds. Voices too were nicely presented over the KEF Q300's. They could tend toward being a touch nasaly, but there was nary a hint of chestiness. This became most apparent with the controlled richness in the PA system at the Funeral Party. "Buy a ticket, tell a story!"
I also checked out the Blu-ray of the recent Denzel Washington release, Unstoppable. This movie was generally very good even as it became a little laborious in the third act. Although you may know the outcome of certain scenes, the filmmaker has a way of crafting the production so you stay on the edge of your seat. This is an art.
This Movie has a very high octane soundtrack that I thought would be a real test for the KEF Q300's. So, even in a large room with a 2.1-channel set-up, the Q300's produced remarkable dynamics and SPL capabilities. They are more sensitive than you may think. Although the speakers don't have great subjective HF extension, their sound is smooth and rich.
On the Bench
All the below measurements shown are in-room response. The frequency response tests were performed at 1-meter while the distortion measurements were taken on-axis in the near field.
The on-axis response of the KEF Q300 shows a remarkably flat response over the broad spectrum of 35 Hz to 20 kHz. The response is a little choppy in the isolated band between 350 Hz and 1.5 kHz. This was not generally audible with regular program material.
At 30 degrees off-axis, the Q300 speakers had a response curve that was actually smoother between 10 kHz and 20 kHz than the on-axis plot, demonstrating that the KEF Uni-Q design promotes fine dispersion. Elsewhere, the response is much flatter than expected for an off-axis measurement. This is a very good test result.
The THD+N at 1 kHz and 100 db was 0.80%. This is in the region where the speaker's response showed some peakiness on the frequency response tests.
At 250 Hz and 100 db, the THD+N measurement is 0.33%. Not at all bad for a $300 speaker!
At 10 kHz and 100 db, the distortion was a very respectable 0.52%.
The KEF Q300 achieved 100 db at 80 Hz at less than 3% THD + N. This is just one of the speakers being driven.
For all-purpose real-life applications, the KEF Q300's are the bee's knees. When you compare them to much more expensive speakers, you may find that the soundstage is not quite as 3d, the imaging is not as pinpoint; they don't have quite the same dynamic capabilities or the high frequency extension. But the Q300's aren't old-fashioned hi fi speakers with a boom tizz signature, either.
So what do you get for your $600? You get a speaker with a smooth detailed sound, nice air around instruments and respectable bass output. They got the midrange right too. Take a look at the bench test results. The response and distortion of these speakers can rival speakers that cost more than a kilobuck each. The KEF Q300's have serious high end aspirations.
For my part, I think I'm going to hang on to the review samples. They are a good reference as to what is possible for under $600/pair. The competition should take note.