I became interested in hi-fi well before the stereo era, at a time when DIY was a significant part of the hobby. In store catalogs of the time, as much or more space was devoted to raw speaker drivers and enclosures than to complete speaker systems. Those of us who wanted or needed to save some money built our own speaker enclosures from kits or plans or from articles in magazines like Radio-Electronics, Audiocraft, and Audio.
In those early days, the popular choices were corner horns and bass reflex speakers, but everyone was welcome to put drivers into any box they would fit in. Then, in 1956, came Ed Villchur’s patent (footnote 1) for acoustic-suspension loudspeaker systems, marketed under the brand name Acoustic Research, and then, in 1961, the groundbreaking study by A. N. Thiele, “Loudspeakers in Vented Boxes” (footnote 2), which defined a series of sealed-box and vented alignments that related low-frequency performance characteristics (frequency response, power handling, cone excursion, and so on) to enclosure design and electromechanical driver parameters.
In a well-known corollary, known as Hofmann’s Iron Law, Josef Anton Hofmann (an audio engineer who worked at Acoustic Research—the H in KLH) posited that three parameters cannot all be had at the same time: low bass, small (enclosure) size, and high sensitivity. You can have any two of these, but not all three. These seminal works underlie most mainstream loudspeaker design to this day.
Most, but not all. Neither Hofmann, Thiele, nor Villchur anticipated KEF’s employment of active digital signal processing (DSP) to mate the driver, its enclosure, and the room. The KEF LS60 Wireless loudspeaker system ($6999.98/pair) is an end run around Hofmann’s Iron Law.
Planned for KEF’s 60th anniversary, much as the LS50 was planned for the company’s 50th, the LS60 Wireless is a statement product that encompasses the premise of company founder Raymond Cooke that loudspeaker performance could be improved through the application of new materials and new technologies. Improvements in recent KEF designs include the refinement of the Uni-Q coaxial driver, Metamaterial Absorption Technology (MAT), force-canceling Uni-Core woofers with P-Flex surrounds, cabinets shaped to reduce diffraction, and the configuration and arrangement of drivers to create what KEF calls a Single Apparent Source.
All those features except Uni-Core and P-Flex were incorporated in the Blade Two Meta, whichStereophile‘s editors selected as the 2022 Loudspeaker of the Year. The LS60 goes a few steps further, adding built-in amplification and electronics for wired or wireless streaming and, as already noted, DSP. That’s also true of the LS60’s smaller wireless siblings, the LS50 Wireless and the LSX, the latter reviewed in 2019 by Herb Reichert. KEF’s successful integration of these technologies in a trim, attractive, high-performance floorstanding loudspeaker makes the LS60 a landmark product.
KEF delivers
The team from KEF in New Jersey delivered and installed the LS60s, just as they did last year with the Blade Two Metas. Locating the speakers in the room progressed just as swiftly as before, but extra time was needed to link them to my local network so that I could control them and stream music to them. Ben Hagens, KEF’s product training manager, got me up and running in a few minutes. All seemed well, and the guys picked up the shipping cartons and departed.
The LS60’s matte-finished MDF cabinets are striking in appearance: Clean rectangular columns with radiused vertical edges, they are a petite 41″ high, 5.1″ wide, and 12.6″ deep. Each cabinet has three internal compartments. The lower compartment holds the electronics; the port on the back above the connection panel is a hot-air exhaust and serves no acoustical purpose; a small opening at the bottom of the cabinet is the cool air intake. An upper compartment holds the transducers, within which the Uni-Q has its own subcompartment. The upper compartments are sealed. The cabinets sit on flat bases that, though only slightly larger, are heavier and provide stability. Even in striking Royal Blue with bright copper Uni-Q drivers, they blended well with our mixed traditional/contemporary decor.
The 4″ Uni-Q driver is mounted to the 5″-wide front. The cabinet’s curve begins at the edge of its Shadowed Flare surround, which also acts as a waveguide for the tweeter. The cabinet’s curved edge minimizes diffraction. The Uni-Q is positioned a considerable distance from the top edge of the cabinet, so the impact of that transition on the radiated sound is minimal. The four low-frequency drivers are positioned in pairs on the cabinet’s sides, symmetrically just above and below the Uni-Q driver. The members of each pair share a common magnetic structure, their individual voice-coils mounted coaxially. Electrically, they operate in phase, their cones facing the world in opposite directions. This force-canceling configuration, which KEF calls a Uni-Core LF, permits—indeed, requires—the LS60 to maintain a narrow profile, which is key to the speaker’s operation as a Single Apparent Source.
While the above describes both speakers, the two speakers differ in that one, the “Primary” speaker, manages inputs and outputs and serves as the user interface. Starting at the bottom of this speaker’s back panel are five rows of connectors, from top to bottom, reset, speaker pairing, and Bluetooth pairing buttons; HDMI, TosLink, and RCA S/PDIF connectors; analog inputs on RCA, USB service port, and a subwoofer connection; RJ45 jacks for wired internet and interspeaker linkage; and a connector for AC power. The Secondary speaker has five rows, too, but each row has just one item: a button for pairing to the primary speaker, a USB service port, a subwoofer connection, an RJ45 jack for pairing, and an IEC connector for AC power.
After connecting both speakers to power, basic setup consists of loading the KEF Connect app from the Apple Store or (for Android devices) Google Play to a smartphone or tablet, pairing the app and tablet to the Primary speaker via Bluetooth, and following the onscreen instructions to connect the LS60 to your LAN. Then you pair the Primary speaker with the Secondary speaker and access your choice of an impressive array of music sources.
As is obvious from its name, the LS60 Wireless is designed to stream via Wi-Fi, and that includes the interspeaker link. My apartment does have Wi-Fi, but coverage dwindles at the speaker end of my living room. Consequently, upon setting the system up wirelessly, I quickly found myself dealing with dropouts and disconnections. There were two possible cures: to wire the LS60s to my LAN with an Ethernet cable or add a Wi-Fi extender. I did both. I have since encountered no problems with the system with either the wireless or wired connections.
Footnote 1: US Patent 2,775,309.
Footnote 2: Thiele, A. Neville (1961). “Loudspeakers in Vented Boxes,” Proceedings of the Institute of Radio Engineers, Australia, 22 (8), pp. 487–508.
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