Kerr Acoustic

K200 Standmount Loudspeakers

£19,995 RRP

Let's be honest here. Most of us will never own a pair of speakers costing as much as the Kerr Acoustic K200 or its immediate rivals from the likes of PMC and ATC. This is partly because nearly all audiophiles simply don't have the money to buy a pair but also because this sort of product is so large as to be intrusive into your living space. For those lucky enough to have separate 'music rooms', that might not be an issue – but for more average families, it most certainly is.

So for many of us, the K200 falls at the first hurdle – it's too expensive and not domestically acceptable from a practical point of view. Then there's the so-called style or aesthetic element to it. In the eyes of dyed-in-the-grain audiophiles, this huge standmounting speaker is a thing of pure, unalloyed beauty. Why? Because it's absolutely a case of form following function - this hasn't been 'styled' as such; it just is what it is because it does what it does.

Yet many people with this sort of money ready to lavish on a pair of speakers want them to look like some kind of abstract art piece – a talking point for their room's interior design. Without a doubt, spouses are partly to blame – but not entirely, in my experience. The K200 doesn't do this – it's no KEF Muon; it's simply old-school hi-fi built to do a job exceptionally well. This speaker is beautifully built and finished but still far from being beautiful to some eyes.

So, the 775x310x460mm [HxWxD], 43kg K200 is selling to a tiny subset of music fans and an even smaller subset of audiophiles within this pre-existing group. But there's more because this speaker uses transmission line (TL) loading to achieve a deeper and faster bass response than a conventional reflex-ported type. Some people love TLs. Still, others don't and worry about how the bass integrates with the rest of the drive units and cabinet as if standard reflex-ported types never had anything to worry about on this score.

Okay, given that we've excluded most people on the planet from ever owning a pair of K200s, let's look at why a tiny minority of audiophiles, along with myself, might be highly interested in the design. In a nutshell, this is a massive, wide baffle standmounter with excellent, innovative and carefully matched drive units in a 3-way configuration. Oh, and it has pro audio ambitions too. As a longtime Yamaha NS-1000M owner, then, it is just my kind of thing!

Loudspeaker designers have nowhere to hide. A great speaker must look a certain way, be of a certain size, and have a particular cabinet design to deliver top-notch results – at least if we're talking conventional types. That's because it has to move large amounts of air as fast as possible around a room without the former interacting with the latter. The K200 is designed to do just this.

First and foremost, its transmission line loading gives it a considerable advantage over bass reflex designs. Designer Jes Kerr says: “This confers a more time-coherent response throughout the lower octaves, compared to the majority of more commonly found bass-loading principles. The output from the line terminus works together in synergy with the output from the front of the cone to form a phase-coherent wavefront within a wider operating range than can be achieved with a reflex design.”

Translating this into human from audio engineer-speak, this makes for a faster, smoother and deeper bass from any given cabinet size than both a ported, bass-reflex (BR) design and a sealed box, infinite baffle (IB) type. Compared to BRs, you get less bass roll-off below the cabinet/port tuning frequency, and compared to IBs, you get great sensitivity and/or more linear electrical load characteristics, so amps have an easier time of it. Jess adds: “Another bonus is that a lack of internal reflections within the cabinet results in lower distortion, as the rearward energy from the cone is being channelled away and out through the tapering line, with the higher frequencies being absorbed along the way.”

So if TLs are so clever, why are so few loudspeakers using this kind of design? “Because it can take significant trial-and-error to get right, and there is no easy and accurate way to effectively model the behaviour of a given driver in a TL using software. Consequently, the design process is very time-consuming and new products can be costly to develop”, says Jes. What he's alluding to here is cost – it's hard to design a transmission line speaker to work properly, and then when you do, the complex internal structure is also more expensive than BRs or IBs.

For many speakers, TL loading would be enough to mark them out as special, but that's only part of the design of the K200. The other eyebrow-raiser is the drive unit complement, which, to my knowledge, is unique. The foundation is a brand new 250mm Volt Radial bass driver; no other speaker on sale currently uses this unit at the time of writing. It's a radical take on conventional moving coil drivers and features double rear suspension for long-throw stability and a four-layer 50mm voice coil, in addition to the iconic Radial intercooler front chassis. Jess says the speaker cabinet was “built around” this driver due to its excellent power handling, speed and efficiency. It's also very resistant to power compression thanks to the advanced cooling system.

Working in tandem with this is a 75mm Volt midrange dome that is proving popular on various big monitors with studio/pro audio inclinations. It's said to have a wide frequency response, excellent dispersion and very low distortion; in this application, it takes over from the woofer at 370Hz. “It features a short front-mounted horn to aid efficiency and dispersion,” says Jess, “and uses a single-layer 75mm voice coil and a 155mm ceramic magnet. The low-mass diaphragm is supported by front and rear suspension units for optimal stability over a wide operating range.”

Last but not least is the true ribbon tweeter, which kicks in at 3.6kHz and above. It's a 60mm design with an ultra-thin planar aluminium diaphragm; the total moving mass of just 0.027g is far less than that of a conventional metal or fabric dome tweeter. It's said to go all the way up to 45kHz. This unit is one of the few non-UK-sourced components in the K200; it comes from a particular supplier and is carefully modified to suit Jes Kerr's specifications, so it cannot be bought 'off the shelf' as is.

Marrying all this together is a 3-way, fifteen-element crossover circuit, with second-order filters on the midrange and tweeter and a third-order filter on the bass. This bolts to the inside of the rear terminal block and sports proprietary low-impedance air-cored inductors, which are hand-wound in-house, extremely high-grade polyester film capacitors, and carbon film resistors. Jes says: “Great care and attention to detail is invested to ensure that the filters are sonically transparent and as low-loss as possible and that the crossover points are chosen for maximum phase coherence between drive units.”

“The cabinet itself is constructed exclusively from high-grade 24mm Baltic Birch plywood and produced for me by Timberworx in Sheffield”, explains Jes. “The internal baffles forming the TL provide exceptionally strong bracing in the centre of the cabinet, which is a welcome by-product of the design. This material is very rigid and acoustically inert and far more costly to implement and machine than the more commonly-seen MDF variants. However, it results in significantly lower levels of resonance and cabinet colouration thanks to its rigidity and self-damping properties.”

The overall product is quite striking in the flesh and extremely well-finished in a conventional sense – it seems like an assembled kit of exceedingly high-quality bits. Jes makes no bones about the intended buyer: “It's somebody with a dedicated medium-to-large size listening space, who favours a natural and uncoloured voicing and isn't prepared to compromise on speed, dynamics and detail.”

You will need a powerful amplifier, ideally of around 150W RMS per channel or higher. It's not that a lower-powered design can't drive the K200; instead, it may not dynamically get the best out of it. Nominal impedance is an amp-friendly 8 ohms, and sensitivity is claimed to be 91dB (2.83V/1m). Frequency response is 22Hz to 45kHz. My review system comprised of a Sony TAE-86B preamplifier and Sony TAN-86B power amp (18W RMS per channel in Class A mode, 2x 90W RMS in Class AB), and also an MF Audio Silver Passive Preamplifier driving a World Audio K5881 valve power amplifier. Sources were a Chord Hugo TT2/M Scaler DAC and Marantz TT-1000/SME V/Lyra Delos turntable compliment.

THE LISTENING

Think of the Kerr Acoustics K200 as a large JBL, ATC or PMC in an expensive suit. It has all the physicality and clout of the aforementioned old-school 'professional monitors' – big bangers, as I call them – but with added polish and sophistication. It's quite an intoxicating combination, as classic wide baffle monitors have two things I love about them. First is a sense of effortlessness when delivering vast tracts of bass at high listening levels – and an associated lack of compression further up the frequency range. Secondly is their sort of devil-may-care attitude; they're a sort of 'Hell's Angels' of the loudspeaker world and wouldn't be seen dead fraternising with fancy, perfumed and polished B&W 800 Series types!

The K200 somehow bridges these two categories, thanks to the superb ribbon tweeter plus the excellent drive unit matching achieved by the designer. There are no spots where the speaker screams out at you. The combination of that Volt dome midrange – with its excellent accuracy and dispersion – plus the ribbon high-frequency unit – its incredible delicacy thanks to its superbly light diaphragm – is quite a thing to hear. Factor in one of the best big bass drivers in the business, working very well in tandem with a properly implemented transmission line, and you've got big audio dynamite.

That's not to say the K200 is perfect, but still, the combination of all its many positives overwhelms its few flaws, at least in my mind. Indeed, this speaker is far more than the sum of its excellent parts – and it has that aforementioned 'attitude' in spades. It certainly brought out the worst in me – causing me to rattle through certain aspects of my record collection like I was fifteen years old and my parents had gone away for the weekend! Heavy rock, classic electronica and reggae became my staple diet – because this big banger made such a great job of them.

And so to specifics. The most distinctive characteristic of the K200 is its physicality; anyone used to listening to a narrow-baffle floorstander of the same height as this speaker when on its matching stands may be shocked to discover the vast soundstage it delivers. This skill is allied to huge tracts of effortless bass and a general relaxedness that makes most modern speakers sound like they're squeezing the music out of a toothpaste tube. I'm just about old enough to remember how speakers used to be when back in the seventies, they were designed primarily around acoustics rather than domestic acceptability…

Cue up the southern rock of Midnight Rider by The Allman Brothers Band, and you instantly understand what is possible. By modern standards, this early seventies recording sounds ancient, yet it has a wonderfully infectious guitar and bass groove with a sweeping chorus that really takes you places. The sheer power, speed and transparency of the K200 let this emotion shine through as if the listener was in the studio on the day it was recorded, enjoying the vibe. The trick that this speaker performs is to deliver music to you almost intravenously; it bypasses your brain and goes straight to your heart. You don't care about the tape hiss, the curious production and mixing decisions, the softness and colour of what was quite possibly a valve-powered mixing desk, etc. All this becomes irrelevant as you get lost in the music.

Yet give the K200 a seriously well-recorded piece of music, and it flies. It's not a speaker that flatters poor recordings due to its innate colouration; quite the reverse, in fact, as its consummate clarity lets you get the best out of flawed recordings. Yet it's ready to shine the spotlight on great ones, as Kraftwerk's Techno Pop showed. This track is a pristine slice of electronica from the mid-eighties, one that was to my ears – when first realised in 1986 – from the best-sounding album I had ever heard. One listen to it via this Kerr Acoustics speaker instantly reminded me why I had thought that, as it's still jaw-dropping by today's standards.

The album took many years to complete, as the band went hunting the world for samples and rejigged their equipment and their own Kling Klang recording studios to make them state-of-the-art. This track has a thumping but bouncy electronic bass line that only great loudspeakers can properly handle, and the K200 had a ball. Low frequencies were rock-solid, full of power and punch, yet much cleaner than you'd expect from a ported speaker. That transmission line did its stuff, delivering huge amounts of bottom-end heft while keeping the music tight and tuneful. The result was a super-firm underpinning to the rest of the frequency range, which was rendered in a glass-clear way, with tremendous timbral accuracy to the digital synthesiser sounds and a deliciously sparkling top end with immense delicacy. Indeed, some might think the treble to be 'soft' because it completely lacks the artificial 'zing' that lesser dome tweeter designs usually add to the sound. The music had a great bite, but due to the purity and resolution of the high-frequency driver, not in spite of it.

So what we have here, then, is a combination of classic big monitor air moving ability alongside the delicacy and insight that you'd expect from a modern design. Loudspeaker fans will know this to be a preciously rare combination and quite a thing to hear. Power and punch allied to transparency and refinement is a special brew, whichever way you look at it. Its natural insight meant that the K200 worked great with any genre of music, even classical. Boccherini's String Quintet in D minor with La Magnifica Comunità and Enrico Casazza was a delight. The speakers set up a vast, almost walk-around soundstage inside which the musicians were precisely located. The instruments had a beautiful timbre and an eerily realistic presence in my listening room, resulting in a wonderfully tactile sound that felt like I could reach out and touch.

Whilst the K200 impresses hugely from a hi-fi point of view, its real party trick is its natural musicality. Just as the strings shimmered around my listening room with the Boccherini piece, delivering a wonderfully beguiling and pulchritudinous sound, so this big speaker also bashed out the indie rock of REM's Texarkana with gusto. Here was another chance for it to display its subterranean bottom-end power, capturing as it did Mike Mills' walking bass guitar line brilliantly. At the same time, the satisfying raunch of Peter Buck's jangling Rickenbacker guitar knitted the song together beautifully, perfectly syncopating with Mills' own lead vocals. Behind this, the soaring violins played rousingly, giving the song fantastic fluidity and motion. Having seen the band play live at Wembley Stadium around the time this album track came out, it recreated some magic memories.

Is the K200 the perfect loudspeaker? Not entirely, as no such thing has yet been invented. In absolute terms, compared to my reference Yamaha NS-1000Ms, there were times when the Kerr showed a slight sweet spot in the low bass, an idiosyncrasy you're always going to get with transmission line designs – and more so, of course, with bass reflex speakers. My infinite baffle Yams sounded tighter and crisper in my room, even though the Kerrs were still excellent in this respect. The NS-1000Ms were more linear low down, although they clearly lacked the Kerr's sheer physical punch and turbofan air moving ability.

I would say that my listening room played a slight part in this, as its 'issues' become more apparent the larger the speaker being used. Yet I still think infinite baffle loading done right delivers the most accurate low-end possible – whilst introducing its own problems, of course, which we don't have space to go into here. All things considered, though, playing the classic early eighties reggae of Smiley Culture's Police Officer at high volumes via the K200 was one of the most satisfying listening experiences I've had in a long time. Its epic and seismic sound reminded me in no uncertain terms why I love both music and hi-fi. This speaker is, first and foremost, immense fun.

THE VERDICT

At this price level, loudspeaker designers generally have a clear idea of what they're trying to achieve – and there's little sense in them developing a speaker to cater for all tastes. Yet still, the Kerr Acoustics K200 proved to be remarkably capable across a wide range of programme material and was less flawed to my ears than many similarly exotically priced, high-performance designs. It serves up a vast, physically moving (quite literally) sound that reminds you every second what real, live music is like. It does this through sheer ability, and at the same time, it has precious few vices to get in the way. For best results, you'll need an appropriately large listening room, a highly capable front end and an amplifier with large swathes of power, grip and detail. If you're lucky to have all of the above, then this big banger really is very hard not to love.

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