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Positive Feedback ISSUE 68
LS50 50th Anniversary Loudspeakers - The Little Truth Tellers
as reviewed by Mark Pearson
In order to celebrate their 50th anniversary of building loudspeakers, KEF developed the LS50 Reference speaker. The purpose of bringing the LS50 to market was two-fold; KEF wanted to ‘best' the world-renown LS3/5a monitors that were used by the BBC for recording monitors for many years and they wanted to showcase their UNI-Q driver technology found in the KEF Blade reference speaker which sells for a cool $29,900 per pair. The amount of technology that is packed into this speaker is fairly incredible. It starts from the curved front baffle and carries over to the rest of the enclosure which includes the internal bracing and the constrained layer dampening. This is one stiff non-resonant enclosure. For all of the background on the LS50 including all of the pertinent specifications and the engineering that went into the design, I refer you to the following link.
The LS50s retail for $1500 which includes shipping to your door. However, since the LS50s are mini-monitors, you will need a pair of dedicated stands to place the LS50s on which ups the ante by the cost of the stands you use. I ordered a pair of custom stands from Sound Anchor which are 30" high so the center of the tweeter would be at ear height while sitting in my listening chair. These Sound Anchor stands added another $800 to the total purchase price of the LS50s. The LS50s weigh 15 lbs each and the Sound Anchor stands weigh 75 lbs each which provides a very solid and stable platform for the LS50s to work their magic.
Now, I have to tell you that my reference speakers are the Definitive Technology BP7000SC speakers which are the former top of the line speakers for Definitive Technology. The BP7000SC speakers are full range speakers with built in 14" subwoofers powered by a built in 1800 watt amp and they also have two 14" passive radiators. In combination with the BP7000SC speakers, I also use a pair of Definitive Technology Reference subs which use the same 14" driver and two 14" passive radiators as found in the BP7000SC speakers. They also contain an 1800 watt amp, but the amps built into the Reference subs have more controls to match the subs with the main speakers and blend into the room.
As my listening room is fairly large (15'W X 23'L x 9'H) and I'm used to listening to full range speakers and subs as described above, I made the decision to run the LS50s with my subs because there is no way a pair of 5¼" drivers is going to provide the bass depth and impact that I am used to. If you have a small room and you don't care about the last 1½ octaves of bass information, you may just find the LS50s by themselves are all you need. I have the LS50s set up so they are about 9' center to center, 34" from the side walls and 82" from the rear wall. Because I have the LS50s so far out from the rear wall, the foam plugs were not installed in the ports per the instruction manual.
So how do the LS50s sound? In a word, stunning. I call these speakers the little "truth tellers" because that is exactly what they do. The midrange and highs are so pure you could be fooled into thinking you were listening to a pair of electrostatic speakers. The LS50s truly speak with a single voice. They also throw a very wide and deep soundstage where every instrument and singer is placed with precision upon the soundstage. Voices have to be heard to be believed and appreciated through these little gems.
I have been a proud owner of the Beatles BC-13 EMI Parlaphone LP collection for over 30 years (sometimes referred to as the Blue Box collection) and I can tell you that Beatles have never sounded better than when played through the LS50s. The voices of John, Paul, George, and Ringo just sound incredibly right. You also can quickly zero in on all of the studio tricks that were used by George Martin, especially with the very early LPs. There was lots of double-tracking of the voices to make the sound fuller and it all becomes more readily apparent when heard through the LS50s. Since I installed the LS50s in my system, I have gone through the entire BC-13 collection with a big smile on my face.
Outside of classic rock, my favorite genre of music is jazz. The LS50s bring out the best with all of my jazz recordings whether they are LPs, 15ips 2 track tapes, or DSD recordings. If you want some chills to run up and down your spine, play the Ray Charles duet "You Give Me Fever" from the Ray Charles album Genius Loves Company. Ray is accompanied on this song by Natalie Cole and the sounds of their voices are just stunning and the backing music was extremely well-recorded.
The tweeters used in the UNI-Q driver are quite special and don't have any break-up modes until you hit 40kHz which keeps the break-up point well outside of the audio band. These tweeters are very sweet and delicate sounding while still retaining all of the dynamic characteristics that makes the upper partials of drums and cymbals sound so exciting and real. If you have recordings that have captured the sound of air coming off cymbals as they are struck and the resulting shimmer and decay, the LS50s will give it all back to you.
So where do the LS50s fall short? Again, they won't give you the last 1½ octaves of bass. You will need subs for that. They do have a dynamic envelope they can't be pushed past, but I can tell you that envelope will satisfy all but those who love to listen at constant sound pressure levels north of 100dB. Even in my fairly large room, I rarely wish for more SPLs than the LS50s can deliver and I like my music to be played back at realistic levels. You can pay far more money than the cost of the KEF LS50 speakers, but you may not buy the quality of sound that these speakers are capable of delivering at anywhere near their price point including a suitable pair of stands. With a sensitivity of 85dB and 8 ohm impedance, I recommend that you hook them up to some muscle in order to extract the sound from them that they are capable of delivering to you. And by "muscle," I mean an amp that is capable of putting out a very solid 100 watts into 8 ohms.
In closing, I want to make it clear that I highly recommend the LS50s. Whether you are buying your first system or your last system, the LS50s are faithful to the music and they will shine a light on the upstream components. The better your source material and your preamp/amp or integrated amp are, the better the LS50s will sound. Even at the full retail price of $1500, these are an incredible bargain. Highly recommended. Mark Pearson