KEF LS50 Wireless: La bomba inglesa

Todo tipos de noticias y actualidad sobre Audio.

por Nico » 29 Dic 2016, 16:20

La gente de KEF le dió una vuelta de tuerca a sus monitores estrella, los LS50, proponiendo un setup all in one, sin perder todo lo logrado anteriormente.









How transportable is your hifi system? My latest rig flew as a single piece of checked baggage from Hong Kong to Australia and then to the UK before being couriered to Germany. Landing at my door in Berlin however was not a palette but a single cardboard box. Inside, a pair of standmount loudspeakers, dual mono amplifiers, a D/A converter and wifi/Ethernet streamer.

We’ve seen this kind of thing before from KEF but not even their superb X300A and X300A Wireless models can compete with what we have here.

This is the loudspeaker system that I’ve been hankering for. This is the loudspeaker system that I first caught sight of during a visit to GP Acoustics’ Hong Kong HQ in August (and was asked not to film). This is the loudspeaker system formally introduced by KEF on the coattails of RMAF in October; that’s your primer.

This is the LS50 but not as we know it. Jack Ocklee-Brown and his team of Kent-based engineers have activated this super-popular standmount with bespoke fit amplification, DAC and network streamer and installed the whole lot inside the speaker enclosures.

Inside each speaker sit two amplifiers and two DACs. Digital inputs arrive at the right hand unit with incoming digital signal upsampled to 24bit/192kHz and handed off to the left channel via Ethernet cable.

Cast a casual eye over any audio show coverage: how many rooms full of racked-up separates do we see? And how many rooms feature active loudspeakers? Yup – thought so. “They’ll have to pry my ten box system, cabling and rack from my cold, dead hand!” says the audiophile world nervously.

Another question: how quickly can you unbox your hifi system, piece it together and have it play music? If it’s the LS50 Wireless system, it goes like this: place each speaker on a speaker stand (or credenza), tie ‘em together with the (supplied) Ethernet cable, connect each speaker to a mains power socket and tap the power button on the righthand speaker’s OLED touchscreen. This 21st Century hifi system comes to life with a four-note start-up sound and we are ready to play music in under five minutes.

The fastest and easiest way to get tunes to spill from the LS50 Wireless is from its Bluetooth (4.0) input. Pair and play – anyone can do it, even your Mom. aptX-capable sources like Macbooks, (some) Windows phones and selected Android phones will deliver slightly better sound quality than those that fall back to Bluetooth audio’s more vanilla SBC: iPhones and iPads. Presumably KEF specified this input for convenience and inclusivity. Audiophiles will demand better source quality. Let’s move on up the food chain…

A TOSLINK input means the LS50 Wireless make an ideal choice for elevating a TV’s sound quality; not just to the next level but all the way to the top floor. Rubber feet will keep them secure. Spotify too – many modern Smart TVs have the streaming service baked into their operating system.

If your TV is more Plain Jane – of if you prefer Tidal or Qobuz – consider Apple’s Airplay by setting aside the TOSLINK input for an Apple TV (3rd Gen) or an Airport Express.

Alternatively, go for the best of both worlds: connect a 4th Gen Apple TV to the TV with HDMI and then the TV’s digital audio output to the LS50 Wireless’ TOSLINK socket. Easy.

Computer audiophiles or those with more sophisticated digital audio streamers will likely peg the LS50 Wireless’ USB input (that KEF have labelled ‘PC’) as their preferred hookup point.

Turntablists should feed their phono stage’s output into the LS50’s auxiliary input. Purists should be made aware that all incoming analogue signals are instantly digitised to 24bit/192kHz PCM; how else would the signal be split and the left channel handed over to the other loudspeaker via Ethernet?

Don’t trust the transparency of an ADC? I’d invite you to hear for yourself how even the most basic converter easily captures the differences between cartridges, surface noise and more.

Whatever your source preference, the KEF LS50 Wireless is a complete high-end audio system-in-a-box; one that thumbs its nose at the trial and error of separates compilation. Experience tells us that hooking up different amplifiers to the passive LS50 is a lottery that many audiophiles enjoy in all but expense: assuming we hit the jackpot from the first hand dealt, amplification satisfaction will invariably take our credit cards a long way north of ~US$700 – the delta between the original passive LS50 and its new active cousin.

Designing an amplifier for a passive loudspeaker where impedance swings and sensitivity vary wildly from model to model means a one size fits all approach must account for all manner of downstream unknowns.

By activating the LS50, each internal amplifier’s output has been tailored to precisely fit the driver’s impedance curve.

The KEF LS50 Wireless gives us the equivalent of a dual mono configuration but with a separate amplifier applied to each driver in KEF’s 5.25” concentric (Uni-Q) array: 200wpc of Class D for the mid/bass and 30wpc Class A/B for the tweeter.

Piling on another active advantage, the LS50’s Wireless crossover is stitched together via digital signal processing (DSP), thus side-stepping the potential for phase shift and/or distortion introduced by capacitors and resistors found in passive networks – like that of the standard LS50. This DSP coding has reportedly allowed KEF to juice every last drop of performance from the LS50’s drivers, their elliptical reflex port, the curved front baffle as well as the constrained-layer damped braced cabinet in which the whole shooting match comes together.

In my listening tests, comparing the LS50 Wireless to its passive forerunner dressed in red and juiced by a Peachtree nova300 (with internal DAC) over AudioQuest Rocket 88 loudspeaker cable, the active LS50 takes Jah Wobble’s bass notes lower with more abundant textural information and renders the cymbal work found parked at the back Bowie’s Blackstar as altogether smoother. Voices pop with a little more clarity. Furthermore, the LS50 Wireless give us a cleaner window from which to ‘view’ inner detail and layer separation.

This Peachtree powerhouse is a superb amplifier but it’s an off the shelf solution designed to meets the needs of many varied loudspeaker designs: electrostats, planars, high efficiency widebanders, low efficiency sealed boxes – the list goes on. Those tucked away inside the KEF cabinets aren’t so much ‘better’ as they are a better (read: precise) fit for the each driver’s load impedance.

The LS50 Wireless are for listeners who are happy to surrender amplification flexibility in the name of better sound…

…and to wipe away the expense of loudspeaker cable. As point of reference, this reviewer’s 6m pair of AudioQuest’s Rocket 88 sell for around a thousand bucks.

Also erased from the LS50 Wireless scene is the hifi rack – more effective and more handsome models often sell for as much as the LS50 Wireless themselves – US$2199 (+ sales tax) in the USA, €2298 inclusive of VAT in Europe, £2000 inclusive of VAT in the UK.

The LS50 Wireless are therefore for listeners who demand lower physical intrusion from their hi-fi system.

From the outset, the only additional purchase required by those of a more audiophile bent is a pair of loudspeaker stands. I use Atacama’s Nexus 6i. If I were to place them on a sideboard or IKEA Kallax, I’d opt for something from Canada’s ISOAcoustics – yes, they’ll make a big difference.

For even greater placement flexibility, a pair of switches on the master speaker’s rear panel allows us to DSP-tailor the LS50 Wireless’ output according to room placement: desktop or stands, free space or close to a wall. Such audible customisation recalls Dynaudio’s Xeo 2 but the KEFs are a far bigger sounding, more dynamic loudspeaker.

KEF’s Kent-based engineering team have also taken room tuning to the next level – much, much further than the Danes – with a corresponding smartphone app, available for iOS and Android.

Basic mode applies DSP customisation according to a real world multiple choice Q&A: about the LS50’s location (desk or stands); about the room size; about its acoustic make-up. Expert mode takes this DSP tweaking a step further and talks to audiophiles in terms of adding or subtracting decibel amounts to and from treble and lower frequencies.

Don’t worry about stuffing it up. A single button press returns us to factory default settings.

In my tests, I found different DSP settings preferable depending on placement: atop Atacama Nexus 6i stands or flanking a Samsung TV atop an IKEA Kallax unit. That makes the LS50 Wireless one of the few standmounts for which front wall proximity isn’t so much of an issue and for which proper stands are rendered less essential.

The smartphone app is also where we configure the crossover point/s and gain for a subwoofer attached to the back of the right hand speaker (should we have one) and where we turn off/on the DSP crossover phase correction (should we wish to).

The KEF LS50 Wireless are for people who live in the real world where listening rooms are often lounge rooms shared with others (and the TV); where loudspeakers can’t always be positioned well clear of front or side walls; where a parquet floor adds a zippy liveliness to sound; where heavy furnishings might over damp the vibe; where bass traps and acoustic panels would be an unwelcome visual intrusion (and expense).

Sat on the couch, a slim line remote control, colour matched to the speaker’s own two-tone scheme, takes the OLED touchscreen’s functionality – input selection, volume up/down – and adds play/pause and forward/next for UPnP LAN streaming.

Those who choose to translate KEF’s ‘Wireless’ nomenclature literally will be disappointed to learn that electricity still requires cables. Friendly jibe aside, KEF’s chosen name is confusing and perhaps runs the risk of customers misperceiving their new baby as some do Devialet’s Phantom: a fancy pair of Bluetooth speakers. These active LS50 are more front foot with vocals, better extended up top and less low slung and heavy in the bass than their more costly French rival. Not to mention a whole lot less expensive.

The ‘W’ word here refers to the aptX Bluetooth input but also to the WiFi LAN streaming input which, upon first use, requires the aforementioned smartphone app to hook the speakers into your wireless network. KEF call this process ‘onboarding’: essentially, your smartphone (or tablet) temporarily connects directly over WiFi to the LS50 Wireless in order to feed the speakers details of your home or office’s WiFi network, specifically SSID and password.

If that all sounds like too much hard work – or if your wifi network lacks the robustness, stability or bandwidth called for by lossless Redbook or hi-res LAN streaming – the option to hardwire the LS50 Wireless into a network over Ethernet also presents. Got drop-outs? Go Ethernet.

At time of writing, LAN streaming is UPnP only. Use the KEF app, or one of your choice, to control playback.

Let’s exemplify: I have my music stored on a hard-drive which is USB-connected to an Intel NUC. The Intel NUC is connected to my LAN via Ethernet. Plex is my UPnP server app of choice. The NUC’s role is to serve content from its kitchen location, over the network, to the KEF LS50 Wireless’ internal streamer. The LS50 Wireless sit in the lounge room. In case it is not already obvious, there is no direct connection between the UPnP server (the Intel NUC) and the UPnP endpoint (the LS50 Wireless). Completing this digital audio streaming triangle is the smartphone app – it tells the server what to send to the speakers and when.

Alas – black mark incoming – KEF have done little to elevate my enthusiasm for UPnP streaming despite its application to less conventional servers/sources. Like several other UPnP devices out in the wild, network streaming on the LS50 Wireless isn’t gapless.

End users will either find workarounds (try Bubble UPnP for Android or JRiver) or do as I did and just move to Roon. Sometimes, it makes more sense to spend money more than it does time.

The triangular nature of our network audio configuration still applies to Roon: Roon runs on the Intel NUC as the Core (server) and sends audio over the network to a third party Roon Ready endpoint – one that’s connected directly to one of the LS50 Wireless’ digital inputs – as is instructed by the Roon smartphone/desktop app.

Roon Ready endpoints are available at different price points. Sonore microRendu (US$640) will feed the KEFs over USB. Others will prefer the financial prudence of the SonicOrbiter SE at US$299. For frugalphiles, a Gen 3 Apple TV or Airport Express provides Redbook-limited Roon Readiness but via TOSLINK for under US$100. In terms of sound quality, you get what you pay for – if you can afford it, get the microRendu. Add a linear power supply (to it) as funds allow.

Is the passive LS50’s amplifier lottery not why we hear some complain that they are too eager in the upper mids? Or too laid back? Or that you need to spend US$x000 on an amplifier to really make them sing. If nothing else, and to borrow from modern marketing parlance, this new active version allows us to the hear the LS50 as its engineers intended; and for a price that sits well below the cost of many amplifiers juicing the passive version out in the field.

Professional musicians and bedroom bangers cottoned onto active speakers years ago. You’d have to hunt seriously hard to locate a passive loudspeaker and an amplifier in your local DJ store.

That we also get smartphone app-based DSP customisation, Bluetooth, a network streamer and D/A conversion thrown into the bargain makes the LS50 Wireless a contender for bargain of the decade.

Hardware upgrades are limited to cables and loudspeaker stands. If you simply must have the flexibility to mix n’ match amplifiers and DACs at will, nothing stands in your way but your bank account.

Sure, the network streaming could be better (i.e. gapless) but even once the additional cost of a third party streamer is factored into the total cost of LS50 Wireless ownership, we’re still a long way ahead: no speaker cables or hifi rack required.

If we’ve learnt anything from companies like AURALiC, OPPO Digital and Devialet, we know that the software evolves over time. I’d urge KEF to talk to the guys at Roon at the earliest possible opportunity – the LS50 Wireless are screaming out to be Roon Readied. For more casual listeners, the addition of Spotify Connect would also be a terrific bonus.

Something for audiophiles, something for mainstreamers – after all, it’s in the LS50 Wireless’ DNA. As a straddler of worlds, the KEFs walk away not only with a Knockout Award but also DAR’s Product of the Year award for 2016. If this product doesn’t convince audiophiles of the legitimacy of active loudspeakers, nothing will. ... year-2016/
Copland CSA 8 > Analysis Plus Chocolate Oval 12/2 > Kef LS50 Limited Red Racing Edition
Mac Mini > LMS 7.8.1 > Slim Devices Transporter
Playstation 4 > Tritton Pro+ 5.1
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