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Think about the future: an *active* KEF LS50 loudspeaker?

  • When KEF introduced the LS50 monitor – a modern day re-imagining of the legendary LS3/5a – it was intended as limited production run. KEF’s Hong Kong production facility would make enough to satisfy demand throughout 2012, not un-coincidentally KEF’s 50th anniversary in the loudspeaker manufacturing game, but once it was gone, it was gone.

    With the global audiophile community – from forum dweller to semi-pro reviewers to print-mag journalists – unable to hone in on any rival US$1500 standmount bettering the sound of the LS50, it sold by the veritable truckload and recognising they were onto a good thing, KEF extended production indefinitely (with the “50th Anniversary Model” assignation quietly disappearing from the front baffle).

    It’s easy to see why: the Uni-Q coaxial driver array does something special with imaging, especially in conveying the illusion of soundstage depth.

    Or perhaps the LS50’s strikingly modern look, rumoured to have been implemented at the behest of the GP Acoustics mothership despite some reservations from the Kent engineering facility, delivered just the right amount of KEF’s (traditional?) house sound in a future-facing box? Being priced within the reach of mortals didn’t hurt.


    In June of this year I pitted Rogers’ “65th Anniversary” take on the BBC LS3/5a against the LS50. The old timer still has it over the LS50 on treble sizzle and ambient detail but its restraint with dynamics means it just can’t rock out. The LS3/5a is without doubt far better suited to a simpler, gentler musical programme; it nails voices like no other bookshelf box, not even the LS50.

    For the modern audiophile though, the LS50 is emphatically where it’s at – better dynamics, deeper soundstage, greater low end authority. The LS50 is an all-rounder for those whose musical taste takes in contemporary indie rock, dub reggae and electronica.

    More importantly, the LS50’s pole position in the sub-$2k standmount loudspeaker sector has been hard won over a relatively short period of time; it has yet to benefit/suffer (your choice) from the reputation elevation of misty-eyed, vaseline-lensed nostalgia.

    And despite 2014’s blue and white variant being greeted with a mixed reception, it did nothing to dent KEF’s reputation as holder of the entry-level speaker cards. Me? I’m hanging out for the possibility of a Ferrari Red cabinet with a gold-bullion-coloured driver.

    On a DAR level: 1) I receive more emails about the LS50 than any other speaker and 2) even though a full two years have passed since publication my piece on three amplifier choices for the LS50 has maintained its position as one of the most read articles on this site.

    Subsequent to penning those thoughts, I extracted maximum cleanliness and drive from the LS50 with a trio of separates from Wyred4Sound. The mPRE pre-amplifier pushing into a pair of mAMP monoblocks bested even the junior mINT and even the high-current provision of the REDGUM RGi60. The mINT is the way to go for those eyeing the LS50 as a desktop option. And why not? With the listener sitting in such close proximity to the loudspeaker, the LS50’s coaxial driver array ensures the woofer and tweeter’s air displacement coalesce more readily before reaching the ear.


    However, the ‘which amplifier?’ conundrum surrounding the LS50 (like ANY passive loudspeaker) can sometimes lead the consumer facing myriad options to make no choice at all; the whole shebang gets filed in the too hard basket.

    BUT…what if having to choose an outboard amplifier were removed entirely? I’ve been pondering this since giving numerous hours to KEF’s more affordable X300A and X300A Wireless solutions: a DAC, twin class A/B amplifiers and loudspeaker loaded into each box and joined via USB. If there’s a better all-in-one system available for less than US$1000, I’ve not heard (about) it.

    The X300A are proof positive that KEF are hip to modern city living, that not everyone wanting good sound lives in a space capable of accommodating the physical intrusion of separate DAC, amplifier and loudspeakers. In short, box count matters.

    Out in the room on speaker stands, swapping out an LS50 + mINT combo for the X300A saw the active option surrender a little on transparency and frequency extension but – take note – layer separation acuity went up a few clicks. The upshot? Once activated, the technically inferior/cheaper driver – a Uni-Q from KEF’s Q100 passive – did some things better than a pair of LS50 powered by outboard amplification.


    On value, the X300A nail the LS50 to the wall. I’d concluded as much back in 2013. Reaffirmation came after I’d covered the Wireless iteration of the X300A in July 2014.

    Twelve months on and the mental presence of active loudspeakers looms larger than ever for this writer. Srajan’s KIH piece on the re-activation planted the seed. A seed that had begun to sprout by the time I hit Munich in May. Spying towering monoliths powered by trunk-sized monoblocks just doesn’t excite me. Is the future of high-end audio really tied up in so many boxes? I doubt it. With component matching taken care of by the manufacturer, active speakers are plainly more relatable.

    Since May, I’ve acquired a pair of Audioengine’s 5+ – a most splendid entry point – as well as a pair of Adam Tensor Deltas (as a direct result of what follows below).  A pair of Genelecs with room-correcting DSP are also on their way.

    Not only do active loudspeakers forestall the tyranny of amplifier choice and lower the box count but they strip loudspeaker cables from the equation. Ditto analogue interconnects if a DAC comes along for the ride.

    The theoretical advantages of internalising amplification are numerous: amplification housed in each loudspeaker brings mono-block-grade channel separation; an active crossover can be tailored to accommodate driver impedance swings; sitting post-crossover, each driver can be assigned its own amplifier; each amplifier talks directly to the the driver’s voice coil where it need only juice a specified frequency band (and not the entire range); amplifier classes can be mixed as/when required. Oh, suits you, Sir.

    Furthermore, designers taking crossover network execution into the digital domain can stir DSP-enabled room-correction into the mix.


    Compare this to the passive-driving outboard amplifier which must be brought to life without knowing what it will be powering. Consequently, the amplifier must be (over)-engineered to accommodate myriad impedance swing possibilities and for full bandwidth operation. Its signal passes through a (potentially) power-sapping filter crossover network comprising passive components – resistors, inductors and capacitors – so implemented to divvy up the signal between drivers and smooth any frequency response anomalies.

    The pick-n-mix approach to matching amplifier to loudspeaker leads to a higher probability of disagreeability – power shortfall, driver overdamping, tonal balance shifts etc. – more often than not determined by the end user after money has been committed.

    Worse still, an amplifier manufacturer’s claim that their design is “stable down to 2 Ohms” is sometimes UNconfirmed the hard way – an expensive lesson to learn whose bill is too easily footed by the consumer.

    One must therefore ask: why do so many audiophiles continue to shoulder the responsibility of matching off-the-shelf amplifier to passive loudspeaker when the technical superiority of a bespoke solution is all but guaranteed?

    Actives are also, pound for pound, less costly to make: is an amplifier’s chassis not its most costly ingredient?


    Of course, the recording studios wised up to active loudspeakers years ago. Ditto the pro audio and DJ worlds. Take a peek at any pro audio store’s loudspeaker section and you’ll see actives (and nothing but).

    I did precisely that a few weeks back. I dropped into Store DJ’s Sydney branch not once but twice. The questions burned on each occasion: could I source an active loudspeaker that would rival the sound provided by a pair of KEF LS50 driven by Vinnie Rossi’s LIO?

    The short and most emphatic answer is YES.

    Before we get to dishing the details, a little background is required.

    Store DJ’s sales staff were gracious enough to allow injection of my Pono Player’s line-out to feed a switchbox that would call any of their shelf-mounted monitors to life. As an interesting aside, 80% of Store DJ’s loudspeaker range comes in at under AU$1000. Talk about keeping it honest!

    Running favourites, the home-grown Event Opal 2, were M.I.A. due to “supply issues”. At AU$3599 they are by far the most deluxe active monitor offered by the Store DJ chain.

    On dollar value alone, the next model down were the Presonus Sceptre S6 (AU$1799) and Adam Audio A7X (AU$1899). Having heard a pal’s Adam Audio Tensor Delta, I already had the German manufacturer’s X-ART ribbon tweeter mentally pegged as a contender. Next to the smooth-sounding A7X the Sceptre S6 had the theoretical benefit of coaxial driver alignment but in reality their horn-loaded tweeters sounded several clicks too insistent.


    Maintaining Adam Audio focus, the difference between their A7X and the more affordable F5 isn’t just 2” of driver diameter and AU$1000; the former is considerably more transparent, readily discernible in-store despite the wall-o’-speakers approach to demos.

    I dropped by the Store DJ a second time to confirm findings before dropping my own hard-earned on a pair of A7X (no review loaner here) and sneaking a few smartphone snaps for good measure.

    Setup at home, the 7” driver sees soundstaging come on that bit too large for long-term desktop deployment – the 5” A5X would be more appropriate here – but those extra inches really come good once the A7X were placed on the Atacama Nexus 6 stands previously occupied by the LS50. For maximum consistency, pre-amplification came from the variable output of the LIO.

    What is it that keeps audiophiles away from monitors whose pro-sector marketing makes more of a play neutrality? Why is the N word entirely acceptable when pitched by their own kind but tainted by the notion of a divorced emotional quotient when heard from over the fence?

    Powered internally, the A7X’s tonal balance isn’t too far removed from that of the LS50 + LIO MOSFET amplifier combo. Room drive proved to be comparable. Ditto soundstage height and width. The A7X demonstrates a little more fluidity (and less grain) in the treble than the KEF setup. The latter show slightly more eloquent midrange expression. Where the Adams come up short is on soundstage depth, an entirely forgivable shortcoming in the context of the Stateside asking price where a pair arrives for the same as a pair of LS50 sans juicebox.

    I missed the KEFs not one jot once the Adam A7X had been serving main-rig duties for a few days.


    I’ve taken the long way ’round to arrive at the punchline: that the audiophile world desperately needs an active LS50. The British manufacturer are already fully across such wishes from your truly. I’ve been at them about it for well over a year.

    The X300A prove KEF have the chops bring it to market. But more importantly, the LS50’s near universal praise, combined with its comparative affordability, might be just the ticket to overcome the audiophile world’s reluctance to head down the active route.

    As buried in my coverage of the Eversound Essence, living spaces for millions aren’t what you’d call spacious; just ask anyone living in Tokyo. Fewer boxes not only make for superior aesthetic agreeability, but active solutions take away the guessing game of amplifier matching – they remove a layer of complexity. Not every audiophile prioritises the flexibility of amplifier switch ups over having those same electronics tailored for an optimal match.

    Moreover, simplicity and convenience move in lockstep with one another. Either will attract some much needed fresh blood to this ‘ere audio malarkey.

    By activating their iconic standmount, KEF would further increase the LS50’s relevance beyond that of traditional hi-fi stores. Done right (with optional DAC board) it’d have the potential to go toe-to-toe with Devialet’s Phantom and emerge victorious.

    Whilst I’m on a predictive tip, I’ll go one further: the future of high/er audio for this British manufacturer doesn’t so much rest with Blade or Blade 2 but with an active LS50. (I’ll take mine in red and gold, please).

    Your move, KEF.

    Further information: KEF | Adam Audio | Store DJ


    Written by John

    John currently lives in Berlin where he creates videos and podcasts for Darko.Audio. He has previously contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

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