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KEF LS50 Loudspeaker Review Print E-mail
Thursday, 07 November 2013
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KEF LS50 Loudspeaker Review
Set Up and Listening

ImageKEF, based in the U.K., enjoys status as one of the most respected, and long-lived, speaker manufacturers in high-end audio. The company has designed and sold some of the best-known speakers in the history of the hobby. They have multiple lines they sell direct and through an extensive worldwide dealer network. Their products range from statement, reference level speakers, to more modest home theater applications. Their economies of scale and engineering resources allow them to cover all bases.

KEF is famously associated with the development of the British Broadcasting Corporations’ iconic LS3/5a two-way mini monitor. The BBC used KEF drivers to develop a compact speaker for location monitoring that could stand the rigors of professional use. The design was later licensed to a number of manufacturers including Rogers, Spendor, Harbeth, and others. I owned two pairs of Rogers LS3/5As; I currently own a pair Spendor S3/5Rs. Variations of the design are still manufactured by a few companies, including Stirling Broadcast, Harbeth, Spendor, and My Audio Design.

KEF decided to commemorate their 50th anniversary with the LS50 monitors, which sell for $1500 a pair. They were designed in the U.K. and are manufactured in their own group factory in Asia. According to KEF, “the LS50 is a two-way loudspeaker system, inspired by the LS3/5A and conceived to celebrate the 50th anniversary of KEF. Like the LS3/5A, the LS50 has been developed with the extensive application of the latest engineering techniques, along with meticulous attention to detail. It uses KEF's latest 5” mid-range and 1” high-frequency driver units in a compact two-way system. Extensive listening tests were performed to ensure the right engineering choices were made to achieve the best possible balance. Both systems could be described as “Engineers loudspeakers”, where the design has been determined by engineering parameters and sonic performance, rather than marketing requirements.”

KEF says they used all of their engineering muscle to develop the LS50 as a “statement” product, despite its affordable price. Starting from the ground up, they paid attention to very specific parameters such as enclosure design, bracing and resonance control, front baffle diffraction, and port design.

In KEF’s own words, “the development of the LS50 was based on a highly technological approach. Simulation and measurement is used wherever possible to identify, quantify and resolve performance shortcomings. This philosophy is classic KEF and is one which has been consistently applied over the company’s 50 year history. The recent maturity of numerical techniques, such as FEA and BEA, make the approach more effective than ever – especially when guided by critical listening and engineering intuition. Recent products such as the Blade, the R-series and now the LS50 are testament to the efficacy of this process.

The LS50 uses a central driver position and computer optimised acoustical damping to avoid
exciting resonances due to standing waves. A combination of bracing on the symmetry planes and constrained layer damping within the enclosure construction is extremely effective at absorbing the driver vibration and effectively eliminates cabinet colouration due to wall radiation. The baffle design provides a smooth response over the entire forward region, reducing tonal variation in different listener positions and ensuring the most spacious sound with precise stereo imaging. The port design has a profile optimised to avoid turbulence with the accompanying distortion and bass compression. A flexible section in the port reduces resonant midrange output from the port

The LS50s secret weapon is KEF’s proprietary Uni-Q driver. Variations on this coaxial driver design are used throughout KEF’s lines, including on their flagship, $30,000 Blade floorstanders. I am a big fan of speakers with coaxial drivers, which includes Thiel and the recently reviewed Bogdan Audio Creations Art Deco. This type of design brings an unmistakable coherence and singular voice to the table. The KS50 uses a 5.25” Uni-Q driver, finished in a very distinctive orange-gold melange. KEF hyper-engineered the Uni-Q driver to address linearity, distortion, and dispersion. This allows the driver to essentially act as a point source. 


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