KEF LS50 Wire­less

FOR Im­pres­sive clar­ity; ex­cel­lent build; neat pack­age AGAINST Some mi­nor us­abil­ity is­sues

What Hi-Fi (UK) - - Contents -

Imag­ine a pair of ac­tive speak­ers with preamp func­tion­al­ity, in­clud­ing dig­i­tal and ana­logue in­puts, Blue­tooth and stream­ing ser­vices such as Tidal built in. Now you have that in mind, wouldn't it also be nice to in­clude a streamer to re­play mu­sic stored on a NAS unit or com­puter con­nected to your home net­work?

Such well-equipped ac­tive speak­ers would not only get rid of the clut­ter of tra­di­tional hi-fi, but could po­ten­tially de­liver a per­for­mance broadly equiv­a­lent to a sim­i­larly priced sep­a­rates rig. The good news is that such a prod­uct does now ex­ist – in the form of KEF’S LS50 Wire­less.

Not fully wire­less

These are two fully ac­tive speaker boxes, ar­ranged in mas­ter and slave con­fig­u­ra­tion. All sources con­nect to the right (mas­ter) speaker, which is then linked to the left by means of a sup­plied eth­er­net cable.

As is usu­ally the case, wire­less doesn’t ac­tu­ally mean wire­less. There are two mains leads – one for each speaker – and the con­nect­ing lead be­tween them. Still, it's a neater so­lu­tion than tra­di­tional sep­a­rates.

It should come as no sur­prise that the Award-win­ning pas­sive LS50S are the ba­sis for this de­sign, with the drive units re­main­ing un­changed. The LS50S use a Uni-q ar­ray with the 25mm alu­minium dome tweeter in the mid­dle of a 13cm mag­ne­siu­ma­lu­minium mid/bass cone.

This ar­range­ment helps to pro­duce an even dis­per­sion of sound and im­proves in­te­gra­tion be­tween the two driv­ers. What looks like a grille in front of the tweeter is in fact a wave­guide that im­proves its per­for­mance.

That beau­ti­fully built and fin­ished en­clo­sure is the same as the pas­sive ver­sion too bar a cou­ple of cen­time­tres of ad­di­tional depth to ac­com­mo­date the elec­tron­ics and heatsink­ing. There are three cab­i­net op­tions: the Ti­ta­nium of our re­view sam­ples, gloss black and gloss white – each op­tion com­ing with a con­trast­ing colour on the UNI­Q driver ar­ray.

That un­usual-look­ing curved front panel is made of Dough Mould­ing Com­pound, a polyester resin com­bined with glass fi­bre and cal­cium car­bon­ate, cho­sen for its in­ert­ness and flex­i­bil­ity. The rest of the en­clo­sure is made from MDF. It’s heav­ily braced and strongly damped to min­imise any res­o­nances. The port here is flex­i­ble in a bid to re­duce dis­tor­tion.

Fine-tuned per­for­mance

These are true ac­tive speak­ers where each drive unit has a ded­i­cated power am­pli­fier. A 30W Class A/B cir­cuit feeds the tweeter while a 200W Class D mod­ule pow­ers the mid/bass unit. The Class D de­sign was cho­sen for its com­bi­na­tion of high power and low heat out­put.

KEF has taken ad­van­tage of the in­ter­nal DSP by phase cor­rect­ing the cross­over and us­ing the soft­ware to al­low the speak­ers to play loud and true while min­imis­ing dis­tor­tion. The dig­i­tal sig­nal path is 24-bit/192khz ca­pa­ble and there’s a ded­i­cated DAC for each drive unit. Only the op­ti­cal in­put is lim­ited to 96khz sig­nals, but that’s not un­usual.

At the back of the right speaker you’ll find stereo ana­logue, op­ti­cal and USB Type B con­nec­tors. There’s also a sub­woofer con­nec­tion, in case you want to add more low fre­quency out­put, and an eth­er­net socket for con­nect­ing to your net­work.

Nor­mally we’d rec­om­mend stick­ing to the wired net­work op­tion for greater sta­bil­ity, but we use the twin-band (2.4ghz/5ghz) wire­less op­tion for most of our test with­out is­sue.

There are also con­trols for ad­just­ing the sound for dif­fer­ent speaker place­ments with op­tions for close-to-wall or free space po­si­tion­ing as well as the choice be­tween desk or stand sup­ports.

The ios/an­droid app looks nice, is well laid out and easy to use. It con­trols the stream­ing (DLNA as well as Tidal) func­tion­al­ity and al­lows plenty of scope to fine-tune the speaker’s per­for­mance in a given en­vi­ron­ment. There is room for im­prove­ment, though. It’s a lit­tle glitchy and feels un­re­spon­sive at times.

Dig­ging up de­tail

The slid­ing vol­ume con­trol doesn’t change the vol­ume until you lift your fin­ger, so you don’t know how loud it’s go­ing to be until you hear it. It can be a shock. It’s im­por­tant to note that the app doesn’t switch be­tween phys­i­cal in­puts, as it op­er­ates the KEFS only in stream­ing mode. To change in­puts, you need to use the sup­plied re­mote or the touch con­trols on the mas­ter speaker. This swap­ping around of con­trollers is an­noy­ing if you switch sources a lot, par­tic­u­larly as the app has to re­con­nect with the LS50S ev­ery time you switch back. It would also be nice to see an in­di­ca­tion of the in­put cho­sen when sit­ting at the lis­ten­ing po­si­tion – the only in­di­ca­tor is out of sight on the right

speaker’s top panel. So if you’re us­ing the re­mote to change in­put there’s no way (apart from count­ing clicks) to know what in­put the LS50 has set­tled on. None of these things is serious enough to be a deal breaker, but they make us­ing the speak­ers a fussier ex­pe­ri­ence than it should be.

We start off with Arvo Pärt’s Tab­ula Rasa and are deeply im­pressed by what we hear. The LS50 Wire­lesses sound clean and pre­cise, dig­ging up de­tail and de­liv­er­ing it in an or­gan­ised and sta­ble man­ner. We’re struck by the KEFS’ abil­ity to gen­er­ate strong dy­namic shifts with­out stress. To our ears they sound at least as good as the best com­pa­ra­bly fea­tured sep­a­rates com­bi­na­tions avail­able for sim­i­lar money.

These are small speak­ers but they man­age to fill our medium-sized lis­ten­ing room with high vol­ume lev­els. KEF claims a max­i­mum sound pres­sure level of 106db, which should be loud enough for most peo­ple in most cir­cum­stances.

Po­si­tioned with care, a lit­tle away from the rear wall and with a touch of toe-in to­wards the lis­ten­ing po­si­tion, they ren­der a lovely, ex­pan­sive sound­stage that’s neatly lay­ered and nicely de­fined. Even with the LS50S in less op­ti­mised po­si­tions, the app makes the re­sults sound bal­anced.

Mov­ing on to Mas­sive At­tack’s An­gel shows the LS50S’ im­pres­sive bass per­for­mance. These aren’t big speak­ers so you won’t get floor-shak­ing bass, but they gen­er­ate low fre­quen­cies that are taut, ar­tic­u­late and punchy. For a speaker that stands 30cm tall and has a mid/bass unit that’s just 13cm in di­am­e­ter, it’s im­pres­sive. The good news con­tin­ues higher up the range with a trans­par­ent and fluid midrange and in­sight­ful highs. Vo­cals are de­liv­ered with pas­sion while per­cus­sion comes through with bite and com­po­sure.

Broad range of tal­ents

Over­all, these speak­ers have the in­sight to un­ravel a record­ing yet never tear the mu­sic apart. They’re in­for­ma­tive, but musical too.

We play a range of mu­sic from the heart­felt grit of Bruce Spring­steen’s Terry’s

Song and sparse elec­tron­ica of xx’s Stars through to large scale sym­phonies by Stravin­sky and Beethoven. These speak­ers take it all in stride – and it takes a broad range of tal­ents for this to hap­pen.

KEF has done a ter­rific job in tak­ing the Award-win­ning LS50S and mak­ing them an even bet­ter propo­si­tion. That £2000 price tag looks hefty for such com­pact speak­ers, but remember: that money also buys you a ded­i­cated streamer, a Blue­tooth mod­ule, 24-bit/192khz DAC, preamp and four power am­pli­fiers with a to­tal of 460W of out­put. Is this what the hi-fi sys­tem of the fu­ture should look like? We cer­tainly hope so.

“To our ears, these KEFS sound at least as good as the best com­pa­ra­bly fea­tured sep­a­rates com­bi­na­tions avail­able for sim­i­lar money”

The con­nec­tions, in­clud­ing one for a sub­woofer, are on the right speaker

They might be small speak­ers, but the KEFS have a max­i­mum sound level of 106db

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