KEF Ci Series — Premium Custom Install
The KEF Ci4100QL-THX sits at the top of KEF's Ci (Custom Install) series, a range engineered specifically for discreet architectural installation without compromising on the performance standards KEF sets across its entire loudspeaker portfolio. THX Certified SELECT, it meets the exacting output and distortion thresholds required for genuine cinema-grade playback in rooms up to 80m³, making it equally at home as a dedicated home cinema speaker or as a high-quality zone in a whole-home audio system.
Uni-Q Driver Array
At the heart of the Ci4100QL-THX is KEF's patented Uni-Q driver array, in which the 19mm aluminium dome tweeter is positioned at the acoustic centre of the 100mm midrange cone. By co-locating both drivers at a single point source, Uni-Q ensures that high and mid frequencies radiate from exactly the same origin, resulting in an exceptionally wide and consistent dispersion pattern. Listeners anywhere in the room — on-axis or well off to the side — hear the same balanced sound with accurate stereo imaging and natural tonality, a significant advantage in typical living and cinema environments where seating is rarely perfectly aligned.
Three-Way Design
Flanking the Uni-Q unit are three 100mm bass drivers arranged vertically, sharing the load of reproducing lower frequencies. The three-way configuration cleanly divides the audio spectrum: bass duties handled by the three woofers (crossed over at 2.2kHz), midrange handled by the 100mm driver within the Uni-Q array, and high-frequency detail delivered by the co-axial tweeter. The result is a frequency response extending from 55Hz to 28kHz (±6dB, open-backed), with a nominal impedance of 4Ω and sensitivity of 89dB (2.83V/1m) — ensuring compatibility with a wide range of custom-install amplifiers running 10–150W per channel.
Rectangular Form Factor and Ultra Thin Bezel
The long rectangular baffle — 490mm tall by 128mm wide — suits rooms and installations where a round speaker would be architecturally incongruous. It can be orientated vertically in a wall for a discrete, almost invisible installation, or positioned horizontally as a wide-dispersion centre channel above or below a display. The Ultra Thin Bezel (UTB) design minimises the visual footprint, and once painted the same colour as the surrounding wall or ceiling, the speaker becomes effectively invisible. A matching white grille is included. An optional RIF4100L rough-in frame is available for new-build projects where the cutout must be prepared before plasterwork is completed.
Applications
The Ci4100QL-THX is ideally suited to dedicated home cinema rooms requiring THX-compliant main or surround channels, prestige residential installations where acoustic performance and visual discretion are equally important, and distributed whole-home audio systems where zone speakers must deliver genuine hi-fi quality rather than background-audio performance. It is sold individually, allowing flexibility in system design — single, stereo pair, or multi-channel array as required.