Note: Measurements taken in the anechoic chamber at Canada's National Research Council can be found through this link.

I first heard KEF’s R Series R11 speakers, however briefly, when reporting on the Montréal Audio Fest for SoundStage! Access. Show demos being inconsistent at best, I wasn’t sure what to make of the R11s, which sounded a bit bright. Then again, the exhibitor was playing them way too loud -- I wondered what they’d sound like in my own listening room.

KEF’s goal for the R Series has always been to deliver high sound quality for what many enthusiasts consider affordable prices -- and when the line debuted, in 2011, it won critical acclaim for doing just that. It took KEF seven years to come up with what they say are improved versions of the R models, but when they did, I got my hands on a pair of the line’s new flagship, a three-way tower: the R11 ($4999.98). (All prices USD; all speaker prices per pair, except as noted.)

Description

The redesigned R Series comprises six models, each of which includes the most current iteration of KEF’s Uni-Q driver: a 1” tweeter coaxially mounted at the center of a 5” midrange driver. The only stand-mount model, the R3 ($1999.98), is a compact three-way speaker that adds a single 6.5” woofer to the Uni-Q driver. The R5 ($2799.98), the smallest of the three floorstanders, has two 5.25” woofers, one above and one below the Uni-Q. The R7 ($3799.98) has the same driver arrangement as the R5, but with two 6.5” woofers. The biggest floorstander is the R11, with a pair of 6.5” woofers above the Uni-Q and a second pair below it. There are also the R2c ($1199.99 each), a three-way, sealed-box center-channel speaker with a pair of 5.25” woofers flanking the Uni-Q; and the R8a ($2799.98), a small, two-way, closed-box surround speaker with only a single Uni-Q driver, to be placed atop a conventional speaker to serve as a Dolby Atmos upfiring speaker module. Complementing the R Series is the R400b active subwoofer ($1699.99), each of its two, opposed 9” woofers driven by a 250W class-D amp. As KEF explains in a 20-page white paper, “R Series 2018,” the new R models contain several technical refinements; here, I provide only the highlights.

The Uni-Q driver array, a KEF trademark, is now in its 12th generation, and the version in the R models contains three major new improvements. There’s a new motor system with a shaped and undercut pole, and symmetrical aluminum demodulation rings to significantly reduce inductance in the lower midrange. The midrange cone, surround, and decoupler have also all been refined. KEF has also developed a tweeter-gap damper, to mitigate the negative acoustic effects of the small channel of air between the coaxially mounted midrange cone and tweeter: Soundwaves radiated by the tweeter and transmitted by the air in this gap can excite resonances. KEF claims that their damper fully absorbs these soundwaves.

Also new in the Uni-Q is what KEF calls its Shadow Flare diffraction control. Rather than use a typical trim ring around the edge of the driver, KEF has shaped the surfaces to blend the driver diaphragm into the front baffle. This results in the tweeter having no direct line of sight to the edges, which, KEF claims, dramatically reduces edge diffraction, which mostly affects the higher frequencies.

KEF has also revamped the internal bracing of the R models’ cabinets. Instead of rigidly affixing the braces to the cabinet walls, a highly lossy material is used between the two. When the cabinet walls vibrate and change shape due to sound pressure, the layer of lossy material converts that vibrational energy into heat more effectively than do traditional braces. The positions of the two ports on the rear panel have also been optimized with computer simulations, as slight changes in their positions can greatly affect how much midrange energy will leak out. These ports are not centered but on the right side of the rear panel. Also, the flexible inner port lining that KEF introduced in the LS50 minimonitor has now found its way into the R models. The company claims that this unique design greatly reduces unwanted noise from air rushing through the ports.

The woofers have been overhauled to reduce distortion. These changes include an undercut central pole, to provide a magnetic field more accurately focused on the driver’s voice-coil. To match the improvements in the motor system, the suspension has been redesigned, for linear cone excursions twice as long as before. Finally, the woofer diaphragms are now stiffer. In fact, these cones are now hybrids, with a paper rear part and a large aluminum disc at the front.

The R11’s cabinet is a conventional-looking box. Slim and tall at 49.2”H x 7.9”W x 15.1”D, it weighs 83.1 pounds. On the rear panel are the two flexible ports and two pairs of high-quality five-way binding posts. Instead of removable metal jumpers for single-wiring, between the binding posts are two small knobs; these can be turned to electrically disconnect the pairs of terminals from each other, for biwiring or biamping; or to connect them via jumper wires inside the cabinet. The R11’s six drivers are made of aluminum (or, in the case of the woofers, aluminum and paper), and the specified crossover frequencies are 400Hz and 2.9kHz. The claimed frequency response is 46Hz-28kHz, ±3dB, with a typical -6dB point of 26Hz in-room. The specified maximum output is 113dB, the sensitivity 90dB/2.83V/m, the nominal impedance 8 ohms, and the minimum impedance 3.2 ohms.

The finishes available are Gloss Black, Gloss White, or the retro-looking Walnut of my review samples. I’m no longer a fan of wood grain on speakers -- give me gloss black every time -- but the fit’n’finish of my review samples was top-notch. No seams or mitered joins were visible, and the real-wood veneer was smooth and flawless. In a nice touch, the entire speaker is color-coordinated: My Walnut samples had copper-colored drivers and Shadow Flare trim pieces, and brown metal for the outrigger feet on which the speakers sit.

Those feet are more than mere afterthoughts. All the metal hardware for these perches comes carefully packed in a separate box: four big feet to bolt to the bottom of the speaker; four adjustable metal spikes to screw into the feet; felt-bottomed metal discs for hard floors; and a tool for adjusting the level of the speakers once they’re standing upright. The metal feet form a base much wider than that of the cabinet itself, which is quite slim, and thus provide a welcome increase in stability for those with big dogs, acrobatic cats, and/or rambunctious kids.

Setup

Unpacking the R11s took some doing. Not only did I have no help from a friend, but the speakers are tall enough, and my basement room’s ceiling low enough, that I couldn’t follow KEF’s instructions and lift each R11’s box straight up and out of the way. A bit of awkward maneuvering later, I’d unboxed the speakers without incident.

In each box is an instruction manual, two port plugs, a magnetically attached grille, and the footer hardware. I installed the hardware and spikes (my room has carpet over concrete slab), then righted the R11s and put them where speakers usually end up in my room: 16” from the wall behind them and toed in toward my ears 18°, the speakers and my high-backed listening recliner describing a 9’ equilateral triangle. My relatively small (15’L x 12’W) listening room is isolated, insulated, and quiet, with bass traps in the front corners, and the front and side walls treated with broadband absorption. The wall behind me has a variety of diffusion treatments.

After the R11s were set up, I took a good look at them. Their height made them somewhat imposing in my small space, but nonetheless I was struck by their beauty, an impression at least partially attributable to their slim front baffles -- a slimness that also provides sonic benefits.

I connected the R11s to the 8-ohm output taps of my McIntosh Laboratory MC302 power amp with generic speaker cables. The source was a Bluesound Node streamer, connected via optical digital link to my miniDSP DDRC-22 processor, its digital output in turn connected via TosLink optical link to the DAC in my McIntosh C47 preamplifier-DAC. The C47 was connected to the MC302 with balanced (XLR) interconnects. When the DDRC-22 is in the signal chain with Dirac Live’s room-correction filters turned off, as I used it, all it does is upsample all incoming PCM data to 24-bit/96kHz. I always leave the DDRC-22’s digital volume control set to maximum. I used the Node as a Roon endpoint, and controlled it with Roon’s remote app installed on a Samsung Galaxy Tab S.

When reviewing floorstanding speakers, I usually stick with what I feel is the most appropriate and informative comparison: my Bowers & Wilkins 705 S2 minimonitors run full-range, their output below 50Hz reinforced by two SVS SB-4000 subwoofers, without Dirac Live room correction. These speakers and subwoofers are part of my reference system. I matched the speakers’ levels using a 1kHz warble tone, and found the R11s to be 2dB more efficient than the 705 S2s. Each time I switched between speaker pairs, I adjusted the volume on my C47 preamp accordingly. And before doing any serious listening, I played music at a decent volume through the R11s for a few days to ensure that they were broken in.

Sound

Getting the KEF R Series R11s’ bass right required a bit of trial and error. My first impression was favorable: the bass was tight, ample, extended, very fast, and rhythmic, but somewhat boomy. The boom didn’t surprise me -- the R11s are a lot of speaker for my small room. Luckily, KEF provides remedies. I reached for the port plugs, set up my miniDSP UMIK-1 calibrated microphone, and began to measure and listen. Ultimately, I got the best results by plugging the top port of each R11 and leaving both bottom ports open. This significantly reduced a big peak at 50Hz that was present with all four ports open, but still left me with, on average, a pleasing 5-6dB of bass boost from 35 to 80Hz relative to 1kHz.

In my room, the R11s managed a very respectable 27Hz, -3dB, with the top port of each speaker plugged; 26Hz with all ports open; and 32Hz with all ports plugged. With one port plugged, the R11s’ overall in-room frequency response was equally impressive -- as textbook as my room will allow without equalization. Above the Schroeder frequency, around 200Hz (below the Schroeder frequency, most rooms exhibit bass nulls and peaks, and my room is no exception), I saw a relatively smooth and gently downsloping response, about 2-3dB down (relative to 1kHz) at 16kHz. This almost perfectly follows Harman International’s emulated target response curve, which I use when Dirac Live is correcting the sound of my room, and which Harman’s research has found sounds best to most people, including me. As I said -- textbook response, without room correction.

Once I had the R11s’ bass response dialed in, I played “Nothing At All,” from Santana’s Shaman (16-bit/44.1kHz FLAC, Arista), which has seriously deep, powerful bass. When the bass notes dropped, I liked what I heard -- my room was filled with deep, punchy lows. The R11s generated enough sound pressure in the lower octaves to thump my chest, and enough low-frequency extension to let me physically feel each note in the lower half of my body. Still, the R11s weren’t the last word in low-end extension -- after all, I’m used to dual subs that play flat down to 16Hz -- but they were outstanding in this regard for their size and price. What most astounded me about the R11’s bass was its speed. The pace and rhythm of bass notes were fantastic. It felt as if the R11s’ eight woofers were starting and stopping on a dime in lock step. Throughout my weeks of listening to them, the R11s always got my toes tapping.

The opening brushed cymbal to left of center in “Locked in the Trunk of a Car,” from the Tragically Hip’s Yer Favourites (16/44.1 FLAC, Universal), seemed to appear from nowhere, and was delivered with perfect delicacy and extension as it gently grew in volume and spread into the right half of the soundstage. The R11s again provided a foundation of strong, punchy bass with fast pace and drive. The rhythm guitars, imaged hard right and left, and the lead guitar at center right, came through with grunt and plenty of texture. Lead singer Gordon Downey’s voice was smooth, with convincing presence, its image dead center on the soundstage, clearly above the Uni-Q driver and just behind the plane described by the speakers’ frontmost vertical edges. The R11s could also play very loud while their sound remained composed. I pushed up the volume to the limit of my hearing (close to 100dB) but heard no obvious compression or edginess. The R11s just kept rockin’, with exceedingly clear sound even at very loud volumes.

“My Skin,” from Natalie Merchant’s Ophelia (16/44.1 FLAC, Elektra), has a lovely, simple arrangement and is well recorded. It opens with Merchant’s haunting wail, accompanied by piano. The R11s conveyed the plunk of the keystrokes with perfect weight, leading edges, and decay. Imaging was first-rate, the piano notes clearly delineated below, to the right, and slightly in front of Merchant’s equally well-defined voice. The character of her voice was smooth, delicate, and detailed, never irritating. The bass drum had appropriate amounts of weight, slam, and extension. The violin prominent toward the end of the track, when Merchant stops singing, was also reproduced skillfully -- I could easily “see” its image behind the piano, as I could the delicately brushed cymbal to the left -- never over-accentuated, it had just the right amounts of shimmer and detail. The KEFs didn’t draw special attention to any part of the audioband. With this and other tracks, their sound seemed perfectly balanced from the low bass all the way up through the upper treble. Nor did they draw attention to themselves -- they were very transparent, providing that treasured illusion of a pair of speakers “disappearing” from the room to leave behind only the music.

In “Here We Go Again,” from his Genius Loves Company (16/44.1 FLAC, Concord), Ray Charles sings a duet with Norah Jones. Again, the R11s sounded great. Jones’s voice imaged dead center, high above the Uni-Qs, surrounded by plenty of air and space. When Charles enters, I could easily “see” his voice on the soundstage, to the left of Jones’s. And when they sang together, it was easy to continue to make out the voices of both singers -- they seemed to stand next to each other with space between them, every detail of intonation and pitch laid bare. The cymbals were reproduced with delicacy and sparkle, never overstated -- and again, the foundation of bass laid by the KEFs was strong, solid, fast, and punchy.

KEF R11 vs. Bowers & Wilkins 705 S2 + two SVS SB-4000 subwoofers

For this comparison I used my Bowers & Wilkins 705 S2s ($2500/pair) run full-range, and reinforced below 50Hz by two SVS SB-4000 subwoofers ($1499.99 each) -- total price $5499.98. There’s just no way the KEF R11s ($4999.98/pair) could provide as much low-frequency extension as those two SVS subs, let alone more, and they didn’t. With Santana’s “Nothing At All,” the subs dug deeper than the R11s, letting me feel more bass in the seat of my chair -- no surprise. But in every other aspect of bass quality I give the nod to the KEFs. With the R11s I could feel in my chest more punch and slam, and the sense of speed, pace, and rhythm was better. Bottom line (so to speak): The R11s produced fast, exhilarating bass.

Through the midrange, the 705 S2s’ tipped-up treble made the B&W-SVS combo sound more forward, typically surrounding voices with more presence and air. This can at first easily be perceived as better sound, especially at lower volumes -- but turn up a bright or sibilant recording and most listeners, I believe, would opt for the more neutral-sounding R11s. With “Here We Go Again,” there was no question that the voices of Ray Charles and Norah Jones had more presence, intimacy, and detail through the B&W-SVS combo -- based on their voices alone, this combo gets my vote for this cut -- but the B&Ws’ forward treble also made the snare drum sound too “snappy,” bordering on irritating at loud volumes. Through the KEFs, that snare sounded just right.

Gord Downey’s voice in “Locked in the Trunk of a Car” also sounded more forward through the B&W-SVS rig, but had more body through the KEFs -- the R11s’ neutrality made them my choice for this track. Although the B&W-SVS quartet surrounded Natalie Merchant’s voice in “My Skin” with more air and ambience, the extra sibilance -- nonexistent with the R11s -- had me again choosing the KEFs. The R11s’ reproduction of the violins and piano in this track was also superior -- they sounded rounder and fuller, but a bit thin through my reference speakers and subs. And the soundstage reproduced by the R11s was a bit bigger than the B&W-SVS combo could muster.

The recordings themselves dictated which speakers sounded better at the top of the audioband. The cymbal crashes in “Feeling Good,” from Michael Bublé’s It’s Time (16/44.1 FLAC, Reprise), had more presence and longer decays through the B&W-SVS rig, which made them more prominent in the mix. Was this good or bad? Well, it sounded good with this track -- but we know from frequency-response measurements that in this regard the R11s are truer to the source. This comes down to personal preference, of course; nonetheless, I believe that neutrality and accuracy ultimately win the long game of owner satisfaction.

Case in point: Although B&W’s hot tweeter may have been partly responsible for convincing me to buy the 705 S2s in the first place, what at first seemed a boon can become an irritation with some recordings played at higher volumes -- even as, conversely, with other recordings, the B&Ws’ midrange and top end can make magic. Since buying the 705 S2s, I’ve applied Dirac Live room correction to the sound of my system and room, using a target FR curve that looks very much like my measurements of the KEF R11s’ in that same room. Draw your own conclusions.

What most amazed me in these comparisons was the R11s’ imaging and transparency. With respect to transparency, I found the two setups on an equal footing. Both sets of speakers were able to “disappear” from the room, never hinting that the sounds I was hearing were coming from two or four boxes. I never heard any cabinet colorations, and always felt I could “see” into all of a recording’s layers and details.

It was the R11s’ imaging that blew me away. With or without the assistance of subwoofers, the 705 S2 minimonitors are imaging monsters that can chisel out aural images on a soundstage with laser precision. Not everyone likes or wants this, but I do. Because the R11s are large tower speakers, I didn’t expect that level of imaging definition. Then I listened to “Give Me One Reason,” from Tracy Chapman’s New Beginning (16/44.1 FLAC, Elektra), a track I often play to test a speaker’s imaging abilities. It begins with plucked guitar to left of center, then Chapman’s voice dead center, then Andy Stoller’s bass drum, including his subtle cymbal work just to the right of and behind the first guitar, then a second guitar far to the right of Chapman’s voice. Then two background singers enter, behind and to the right and left of Chapman’s lead vocal. As I listened to the R11s re-create each of these images with exquisite precision, sometimes down to what seemed the size of a tennis ball floating between the speakers, I knew they’d give up nothing to the much smaller B&Ws with SVS subs. Even when instruments were panned hard right or left, their sounds didn’t seem to emerge from the R11s’ baffles, but to hover just around the edges of the speakers -- just as I’m used to with my reference setup.

When I swapped the B&W-SVS combo back in and listened again, my suspicion was confirmed: The KEFs’ imaging was the equal of the B&W-SVS system’s. I attribute this to KEF’s Uni-Q driver, which puts the tweeter smack in the middle of the midrange driver, to constitute an effective point source for all frequencies above 400Hz -- and to the speaker’s very narrow front baffle, which minimizes the surface area that might interfere with the soundwaves launched from it.

Conclusion

KEF’s R Series R11 speaker impressed the heck out of me. First, it’s nice to look at -- a pretty speaker of first-class fit and finish, and color-coordinated from top to bottom. Second, it’s chock full of cutting-edge technological innovation: e.g., the 12th generation of KEF’s Uni-Q driver, Shadow Flare diffraction control, and flexible port linings. But none of that would matter without the third thing: the R11 sounds even better than it looks.

The R11s provides a textbook-accurate frequency response, with punchy, extended, fast bass. Its midrange transparency and reproduction of detail are beyond reproach -- always smooth, never edgy, yet not recessed. Nor was the R11’s treble response ever etched or overaccentuated or sibilant, but always clear and extended. And their imaging abilities were outstanding for large floorstanders, equaling what my reference two-way minimonitors can do.

The $4999.98 KEF asks for a pair of R11s makes them a steal -- you’d be hard-pressed to find a better speaker at the price. Were I in the market for a pair of floorstanders, I’d buy KEF R11s.

. . . Diego Estan
diego@soundstagenetwork.com

Associated Equipment

• Speakers -- Bower & Wilkins 705 S2, SVS SB-4000 subwoofers (2)
• Power amplifier -- McIntosh Laboratory MC302
• Crossover -- Marchand Electronics XM446XLR-A custom balanced passive line-level 120Hz high-pass filter (between preamp and amp)
• Preamplifier-DAC -- McIntosh Laboratory C47
• Room correction -- miniDSP DDRC-22 with Dirac Live (between digital sources and DAC)
• Digital Sources -- Rotel RCD-991 CD player, Bluesound Node streamer, Windows 10 laptop running Roon Core
• Analog source -- Pro-Ject Debut Carbon Esprit turntable with Ortofon 2M Red cartridge
• Speaker cables -- 12-gauge oxygen-free copper (generic), terminated with locking banana plugs
• Analog interconnects -- AmazonBasics unbalanced (RCA), Monoprice Premier balanced (XLR)
• Digital link -- AmazonBasics TosLink (optical)

KEF R Series R11 Loudspeakers
Price: $4999.98 USD per pair.
Warranty: Five years parts and labor.

KEF North America
10 Timber Lane
Marlboro, NJ 07746
Phone: (877) 271-9355

E-mail: info.us@kef.com
Website: www.kef.com