KEF LS50 (tloo)

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KEFLS50(tloo)
its5Othanniversary,
KEF
hasproduced
its
Incelebrating
a minimonitorreflecting
heritage
andwithdetails
flagship
audioengineering
trickleddownfromitsBlade
Review:
JohnBamfordLab:KeithHoward
hileKEF- togetherwith
- hasbeenowned
Celestion
bythe HongKong-based
Cold
group
Peakmultinational
since1993,andtodayhasa massive
plantin southernChina,CP
manufacturing
Acoustics
is rightlyproudof the brand's
Britishheritage.
lt maintains
UKroots
with officesbasedin Tovil,Maidstone- on
the siteof the originalKentEngineering
Foundrywherethe late RaymondCooke
first startedhisKEFElectronics
company.
KEFwasfoundedin the autumnof
1 9 6 1 .S ot h i sd i m i n u t i vLeS 5 0' b o o k s h e l f '
proudlysports50th Anniversary
Model
legendson its baffleand rearpanel.
Handsomely
finishedin pianoglossblack,
andwith KEFs logomarketchedsubtly
intothe top of the cabinet,it'sa compact
minimonitormeasuring
around300mm
in height.Theenclosure
is reflexloaded,
a flaredellipticalport ventingat the
rear.Befittingits pricethe enclosureis
sturdilyconstructedwith constrainedlayer
dampingbetweenitswalls,internalcrossbraceandfront baffle.The baffleis curved
bothto minimise
diffraction
andfurther
increasethe rigidityof the structure.
however.
the LS50bearsaboutasmuch
resemblance
to its suggested
forebear
asdoestoday'sBMW-era
Minito SirAlec
lssigonis's
iconicdesignintroduced
in 1959
by the BritishMotorCorporation.
.POII{T SOURCE'
To casualviewersthe LS50will looklikea
minimalist,
single-driver
loudspeaker.
Of
course,audiophiles
that
will appreciate
this singledriveris one of KEF's
two-way
Uni-Qcoincident
arrayswith itstweeter
mountedat the acousticcentreof the
mid/woofer's
voicecoil- pioneered
in the
1980sto providea nominally
idealpoint
source.Thislatest
iteration,coloured
rosegoldfor this
sumptuous
1S50,
featuresa 130mm
( 5 . 2 5 i nm
) idrange
coneformedof
a magnesium/
aluminium
alloy
with a ribbedlongthrowsurround
that
KEFdubs'Z-Flex'.
It crossesoverat
2.2kHzto its 25mm
BBC CONNECTION
ventedaluminium
'l
It was,of course,in 966 that KEF
dometweeter.
introduced
the world'sfirstcommercially In today'sUni-Q
available
driveunitthat featureda cone
designthe tweeter
formedof Bextrene:its famousB110 driver. sportsa 'tangerine'
Alongwith the company'sT27 tweeterthe waveguideto
B110 wasto be employedby the BBCin
maximise
dispersion.
just 12in
the LS3/5Monitor,a smallspeaker
Thanks
to modern
highthat wasusedin outsidebroadcast
computer-aided
vehicles.
Subsequently
the speaker
was
designmethods
refinedto becomethe BBCLS3/5a,
employedby KEFfor
manufactured
underlicenceandmade
ambitiousprojects
available
to consumers
worldwide[see
suchasits f 20k
boxout,oppositepagel.
Bladefloorstander.
'LS'nomenclature
In employing
in this
the LS50includes
Anniversary
Modelit'sclearthat KEFis keen somepatent-pending
to remindconsumers
of the importantrole
it playedin earlyaudioengineering
RIGIIT:Rosegold
and
the emergingdevelopment
of hi-fisound
colourcd130mm
reproduction,
implyingthat the LS50is an
UniQcoincidentarray
LS3/5a
for the 21stcentury.Otherthan
with 25mmtweeter
the fact that it's a verycompactmonitor,
mountedat the centre
52 | www.hifinews.co.uk
I tUlVZOtZ
Forexample,
designinnovation.
while
theremightbe littlenew in flaringa port
at both endsto avoid'chuffing',the fact
that the port'stube isformedof closed-cell
foam and is actuallyflexibleand porous
is indeednovel.KEFsaysit aidsclarityby
allowingmidrange
frequencies
to escape
intothe cabinetandprevents
longitudinal
resonances
causinQ
midbandcoloration.
A two-waysuchasthis,with a single
Uni-Qdriver,makesfor an idealfront-centre
- the 'dialoguechannel'in an AV
speaker
system something
that wasnot loston
KEFin the early1990swhenit introduced
Reference
SeriescentresDeakers
aimed
at videoohileswith LaserDisc-driven
multichannelsystems.Beingso ultracompact, five or more LS50swould make
for an ideal surroundsound set-upin many
homes.What'sthe betting that a cost'non-Anniversary'
LS50is alreadyon
down
the CADscreensof KEF'sdesiqnteam?
1&|, MINI MARVELS
KEFrecommendsplacementon 45-60cm
tall stands,positioned
a metre from side
wallsto enjoy the
speakers'abilityto
create wide, out-ofthe-box images,and
around 50cm from a
rear wall.
I listenedto the
1550sin their au naturel state in my largerthan-averagelisteningroom, although a
foam bung is providedto modify the port's
output if ideal placementis constrained
Actually,it's a
by room layout/dimensions.
'half restrict'
bung within a bung: you can
ports
or fully block them. Thereare
the
no protectivegrillesprovidedwith these
AnniversaryModel LS50s,by the way.
I had in residencea pair of TrackAudio's
exquisitely-made
speakersupportsthat
proved a lovelymatch with the LS50s
- albeit more costlythat the speakers
themselves!Giventhat I sit around five
metres away from compact standmounters
in my 7m-long listeningroom, the LS50s
made surprisinglyeasywork of loading
'Thethought"Where
is all thatbassweight
comingfrom?"
crossedmymind'
the room.And
theysounded
larger
substantially
than I expected.
It'ssomething
o f a c l i c h 6l ,k n o w ,
but the thought
'Whereis allthat
bassinformation
and
weight coming from?' crossedmy mind
time and time again as I put them through
their paces.
W i t h M a d o n n a ' sg r a n d i o s e ' F r o z e n '
from | 998's RayOf Light album [Maverick/
Warner 9362-46847-21the sound was
easy-on-the-ear
and commendably
The Iate RaymondCooke,OBE,
worked alongsideDudleyHarwood
(who later founded Harbeth! in
the BBC'sEngineeringDesign
Department in the 1950sbefore
joining Wharfedaleand later
forming KEF.His relationshipwith
Auntie Beebblossomedas KEF
pioneerednew technologies.It
was the first companyto begin
production of drivers with cones
made of materialsother than paper
and was first to apply FastFourier
Transformanalysisto the measuring
of speakers.As well as producing
finishedspeakersin its Maidstone
factory it was sellingdriversto
other companies: not least its
Bextrene-coned811Obass/midunit
and Melinex-domedT27 tweeter
tS3/5a,
for the BBC-designed
manufacturedunder licenceby the
likesof Rogers,Chartwell,Harbeth
and Spendor...to name but four.
More than 100,000LS3/5aswere
sold worldwide. At one point KEF
drivers
was making around lO,OOO
of various types per week and,
reportedly,half of the UK'sspeaker
makerswere using KEFdrivers.
luxurious,notwithstandingthe'electronic
edge' of the recordingcreated by the
artificialproductiontechniquesemployed
by William Orbit and PatrickLeonard.The
LS50created a wonderfullywide, deep
'open'
and
image of a musicalevent that
never reallyhappened(Orbit worked with
samples,synthesizersoundsand ProTools
r a t h e rt h a n l i v e m u s i c i a n s . . a. )n d t h e
speakerallowed explicitdetailsof myriad
sound-effectsto cut easilythrough the mix.
The presentationwas all-embracing- and
amazinglyrich and full-bodied.
Thereare thunderous,air-movingbass
'Frozen'that
effectsin
can create mayhem
when playedthrough huge floorstandersor
subwoofers.A mini monitor won't rattle the
rafters,of course.Nonetheless,
the little
LS50more than hinted at the scaleof the
track, servingup a cavernoussoundstage.
The bassend was terrific.lt was vivid
and concise,reasonablypunchy when
the occasiondemanded,and remarkably
weighty consideringthe LS50'ssize.
Thisspeaker'sabilityto showcase
transparentlythe superiorityof hi-res
sourcescomparedwith'standard' CD
resolution16-bitl44.|kHzfileswas e>
JULY2012i www.hifinews.co.uk
!53
KEF LS50(rgoo)
KEFclaims85dB sensitivity
for the 1550,only about 1dB
optimisticaccordingto our.measurements
which findsthe
pink noisefigure,averagedfor the reviewpair,at 84.1dB
(2O0Hz-20kHz).
Thisperformancerequiresthat the LS50be a
4ohm design,with a minimummeasuredmodulusof 3.8ohm.
KEFinexplicably
accordsthe LS50an Sohmnominalratiag
while claiminga minimummodulusof 3.2ohm- but at least
our resultsshowthat minimumfigureto be conservative.
lmpedancephaseanglesarequite large,as a resultof which
the EPDR(equivalentpeakdissipationresistance)
fallsto a
minimumof l.9ohm at 25H2,with a similardip at 132Hz..
The payofffor the LS50'sbelow averagesensitivityand
moderatelytestingload comesin the form of good bass
extensionfor so smalla cabinet,our diffraction-corrected
near-fieldmeasurementrecording42Hz (-6dB re. 200H2).In
the mannerof the new Q Series,
this roll-offis rapidwhen it
comes,so transientcapabilitymay havebeencompromisedto
achievethis.The near-fieldtestingconfirmedthat KEFs clever
flexiblereflextube justifiesthe claimsmadefor it by doing a
good job of preventingunwantedmidrangeoutput from the
port. The on-axisfrequencyresponse[Craph1, below]isn'tflat
but followsa mostlyflat trend,within error limitsof 13.6d8
and t3.5dB respectively,2OOHz-zOkHz.
Pairmatching, ovef the
samefrequencyrange,was in the verytop drawerat 10.6d8.
Thecumulativespectraldecaywaterfall[Graph2] showsfast
initialdecayand impliesthe low cabinetoutput you'd expect
of the LS50'sexactingconstruction,althoughsomelowlevel
upper-midrange/lower-treble
hashis,stillvisible.KH
RIGHT: At the rear isjust
one set of high quality input
terminalsfor singlewiring. Put
fingersgently insidethe port
and you'lf feel a flexibletube
more than evidentwhen
playedthe often-mentioned
recordingby ChannelClassics
of the BudaoestFestival
Orchestraperforming
Stravinsky'sFire b i rd Suite
( o u rJ u n ec l a s s i c aal l b u m
choice).'Test'samplesat
4 4 . ' 1 . 9 6a n d 1 9 2 k H zc a n b e
downloadedat no cost from
www. ch an n eIc Iassi cs.com.
Where with 44.1kHz
playbackthe sound was
clearlygood enough to
show that this is a splendid
recording,balancedto sound
open and spaciouswhile
possessing
sufficient'oomph'
to make the sound appear
large-scale(neverceasing
to causevisitorsto remark,'Wow
- this little speakerhas amazing
basscapability...')the marked
improvementwhen playingthe
96kHz versionof the piece was as
clear as night and day.The orchestra
soundedless'tight' and constricted,
the image scaleincreasedin width
and depth, and the stringsand
percussionbecame smoother,more
l i q u i d ,w i t h o u t t h e s o u n da p p e a r i n g
t o l o s el e a d i n g - e d g e ' b i t e ' .
MIDBAND SUPERIORIIY
Trulysurprising
wasthe
imorovementobservedwhen
'upgrading'to
t h e 1 9 2 k H zv e r s i o n
of the track. Via my monolithic
TownshendAudio Sir Calahad
speakersthe differencebetween
t h e 9 6 a n d - 19 2 k H zf i l e si s s u b t l ea t
best,while the improvementin tonal
colour was more readilyobviousvia
the diminutiveKEF- testamentto
the LS50'sfabulousmidband clarity.
PerhapsI shoulddescribethe
differencebetween the two source
files as more 'vital'via the 1S50.in
that it appearedto further open up
t h e i m a g ea n d h i g h l i g h t h i s b a b y
monitor'sabilityto sound wa-ay
bigger than it is.With top-drawer
recordingsit truly can sing.
I can't criticisethe voicing of
t h e 1 5 5 0 .R o g e rW a t e r ' s1 9 9 2
epic Amused To Death [Columbia
468761-21sounded nothing short
o f s u b l i m eo n t h i s K E Fm i n i a t u r e .
54 j www.hifinews.co.uk! JULY2012
FElroo
93
w i t h t h e a l b u m ' si n t i m a t e l y
recordedvocalsand space-creating
sound effectsmelding to deliver
a deliciouslyinvitingthreed i m e n s i o n a l ' a u d iaot m o s p h e r e ' .
It rs possibleto pushthe speaker
beyond its comfort zone, of course.
Duringthe cataclysmically
dynamic
crescendosof 'lt's A Miracle',late on
i n t h e a l b u m ( t h i sw a s a r o u n d9 5 d B
at the listeningseat),I detected the
LS50introducinga hardeningto
Waters'tortured declarationsand
valedictions,which he howls at the
top of his voice.
Publicaddressit will not do.
But the LS50did prove capableof
shockingme with its abilityto let rip
u p t o a p o i n t ,a l l t h e w h i l e s o u n d i n g
fresh,open and very very refined.O
Thisis a crackinglittle speaker
of whichKEF's
designengineers
mustbe mostproud.Sweetly
voicedyet highlyrevealingof
sourcequality,it surprises
and
delightsin equalmeasure.
And
boy doesit soundbig,defying
its compactdimensions.
lt
deservesto be a runawaysuccess
for KEFworldwide,especially
if
the companyfollowsup with a
cheaper,lesselaborately-f
inished
versionfor a wider market.
Sound
0uatity:
86%
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i.*i i:r::,,,= fOO
90
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€
200
1k
10k
Frequency>>
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ABOVE:On-axi3responseshowsa flat trend with fine
pair matching. Uni-Qnotch is pushedout to 30kHz
Frequenq in Hz >>
ABOVE:Solid cabinet construction ensureslow
coloration,while Uni-Qresonancesare well controlled
dB
s€n:::'v'ty{sPflln{rj.ui':,::"1lt.lt":l.l
84:7dBi84:1
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Impedance modulus min,/max (2oqz-2okHzl
lmpedancephase min/max (2oHz-20kHz)
3 . 8 o h m@ 19 5 H z
I 35.5ohm 90Hz
@
- 5 8 " @ 10 5 H z
?o:@76H1
r0.6dB
42Hz I >4okqzl>4jkHz
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302x200x278mm