KEF LS50 Review

The LS3/5a was used as a their go-to monitor by the BBC for decades. Since its sound quality was exceptionally good, countless of copies of this speaker was made by other manufacturers - but the reference was always the BBC LS3/5a Monitor. If KEF was ever to launch a new project based on this legend, one must assume that the end result is a very special speaker indeed. The LS50 bookshelf speaker is a completely new design, with technical similarities to the current KEF Blade flagship floorstander. Add to that a good deal of brain power and sophisticated design solutions.

The elliptically shaped bass reflex tube is flared generously at both ends, which handles and controls the flow behavior of the air exiting, thus avoiding flow noise and 'chuffing'. Another special feature distinguishing the bass reflex tube from being ordinary; in the middle of the tube sits a flexible section allowing the tube to expand, like a balloon or bicycle tube. The flexible port helps to eliminate long-stroke resonances that would otherwise cause discoloration in the midrange.

High and mid frequencies are filtered at about 2,200 hertz, and the minimum impedance is, according to KEF, at 3.2 Ohms. Our impedance measurements showed that the impedance dropped to a minimum of 3.8 Ohms in the lowest bass frequencies, which is why we would identify the LS50 as a 6-ohm speakers. The impedance curve indicates that it won´t cause any trouble, so even lower powered amplifiers should have no problem driving a pair of KEF LS50's. Amplifiers are connected to the anniversary speaker using the well dimensioned single-wiring terminals to which, depending on personal preference, banana plugs or stripped cable ends can be connected.

Build Quality & Finish

The KEF LS50 monitors are a perfect example of excellent workmanship and are technically absolutely up-to-date. The internal stiffening and the curved baffle make for a very stable and sturdy cabinet, which is insensitive to resonances. Weighing in at 15.8lbs each and finished with a high-gloss lacquer in either black or white it oozes quality, and the finish is flawless. Add to that no visible screws in the curved baffle as icing on the cake.

The resolution of depth and width is extraordinary, voices sound natural and have exactly the right size and volume. Despite its small dimensions, the LS50 fills the listening room very convincingly with music. KEF's monitor speaker have an amazing stability to the sound and certainly has floorstander qualities - for a compact speaker with a 5.25 inch driver, this is more than remarkable. It can obviously not play really low bass, but down to 60-70 Hertz the LS50 sounds crisp and precise, without artificially adding anything. It sounds even larger when positioned near a wall while still looking great.

KEF monitors inspire with their plasticity, spatial acuity and their firm and clean sound image with excellent detail resolution. A real loudspeaker super star which time after time can give you spine-tingling experiences, particularly with vocal performances. KEF LS50 pairs accuracy with enthusiasm - they are the ideal speakers to make any type of music into an event.

Measurements

The KEF LS50 gave their best in our 'Measurement Lab'. Although the frequency response is generally slightly uneven, overall everything was very well balanced and without any disturbing dips or peaks. The fairly compact monitor reached quite deep down into the bass frequencies, and easily reached our upper measurement limit at about 25,000 hertz. The 0-, 15- and 30-degree measurement showed a more or less straight line, which impressively demonstrate its phenomenal omnidirectional characteristics. The waterfall diagram shows the excellent decay and the THD chart confirmed the good-natured distortion behavior of the speaker.