Sneak Peak: KEF LS50

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Sneak Peak: KEF LS50

Some speakers sure know how to make an entrance. I know that’s how I felt when I crossed paths with the KEF LS50 a few months ago. I’m just wrapping up a full review of this speaker  to appear in Issue 231 but here are a few of my forthcoming impressions.

Designed in celebration of KEF’s 50th anniversary the LS50 tips its hat to the KEF BBC monitor’s of the 70’s. But it’s not an exercise in nostalgia. It bears zero resemblance inside or out to the birch ply, two-way of that era–examples popularized by Spendor, Rogers, Harbeth and of course KEF.  

The pink-gold diaphragm of the Uni-Q driver is a pure KEF designed coaxial unit and the star of KEF’s current generation of speakers. It’s is positioned  dead center in a radically curved one-piece front baffle. According to the design team, the 5.25** magnesium-aluminum alloy midrange driver uses a mechanism to damp the diaphragm resonances, so the usual peak in response common to metal cones is ameliorated. Also KEF engineers installed aluminum magnet rings to reduce flux modulation, a source of midrange distortion. The vented aluminum dome tweeter driver is derived from no less than the statuesque Blade. The now-distinctive  “tangerine” waveguide uses radial air channels to produce spherical waves up to the highest frequencies­–and this allows a deeper “stiffened dome” diaphragm which raises the first resonance and permits a response that extends beyond 40kHz. The crossover point is 2.2kHz and impedance (nominally 8 Ohms) never dips beneath a reasonable 3.2 Ohms. Still this is an 85dB sensitive speaker and benefits from amplification with solid power reserves.

Sonically the LS50 doesn’t suggest the lighter, faster and edgier personality of the average compact with a five incher for a driver. This is an essentially neutral monitor  throughout the broader midrange. But there’s also a prevailing sweetness, a harmonic saturation that lends it a darker, velvety overall character. The mid and upper treble range is smooth, the sibilance region is controlled–crisp, clean but with some compliance.As I listened to a variety of symphonic music I noted image focus was excellent as I’d expected from the coincident. But it’s not hyper-foccussed in a mechanical sense. It’s a more spacious, open and in my view authentic representation of an orchestra. Yes, the LS50 has quick transient reflexes, but that is not what grabbed my attention.  Rather it’s the bloom and tonal weight that it imposes in the listening space. And heavens to Betsy, this little speaker has guts. But I’ll save that part for the full review            

One sonic key for me is how well it handles voices. As I listened to the Bryn Terfel and Renee Fleming duet of “Not While I’m Around” I immediately gleaned the physical presence of these superb singers, fully formed, their performances seamlessly expressed  and rooted in their frames, from diaphragm, throat, head. Ultimately, when pressed at higher volumes,  the LS50 will give up some of the finer lower level details­ but overall this little gem has me mightily impressed. I just wonder if KEF saved me a piece of anniversary cake? 

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