KEF
KEF Ci4100QL-THX
KEF Ci4100QL-THX
In stock
KEF Ci4100QL-THX
The KEF Ci4100QL-THX is a THX Ultra2 certified in-ceiling loudspeaker from KEF's Ci-R Series — a range that brings the acoustic engineering principles of KEF's celebrated Reference floorstanding loudspeakers to the demands of custom installation. Where lesser in-ceiling designs treat architectural integration as a compromise, the Ci4100QL-THX treats it as a design constraint to be overcome — delivering a level of sonic performance that challenges the assumptions of what a ceiling-mounted loudspeaker can achieve, and setting a new standard for custom installed home theatre.
Uni-Q Driver Array with Tangerine Waveguide
At the heart of the Ci4100QL-THX sits KEF's Uni-Q driver array — a concentric arrangement placing a 25 mm vented aluminium dome tweeter at the acoustic centre of a 100 mm aluminium cone midrange unit. This coincident point-source geometry ensures that high and mid-range frequencies radiate from precisely the same point in space, producing a soundstage of exceptional width and stability — a quality that is particularly valuable in a ceiling-mounted application, where the speaker's position relative to the listening area is fixed. KEF's patented tangerine waveguide manages high-frequency airflow, ensuring even, controlled dispersion throughout the room below.
THX Ultra2 Certification
The Ci4100QL-THX carries THX Ultra2 certification — the highest level of THX certification available for home cinema loudspeakers. THX Ultra2 certification demands that a loudspeaker meet stringent performance criteria across frequency response, output capability, and imaging quality — criteria derived from a deep understanding of the professional studio monitoring environment in which film soundtracks are created and mixed. A THX Ultra2 certified system recreates the tonal balance of the filmmaker's final mix in the listening room, ensuring that action sequences carry genuine impact and that dialogue-driven moments are natural and intelligible. The Ci4100QL-THX delivers this standard from a ceiling-flush enclosure, combining the performance of a traditional box speaker with the aesthetic freedom of architectural installation.
Aluminium Baffle and Precision Engineering
The Ci4100QL-THX is built around a precision-machined aluminium baffle — a construction choice that eliminates the resonance and vibration that plastic or composite baffles introduce into the signal chain. The aluminium baffle provides the mechanically inert platform that KEF's Uni-Q array demands, ensuring that the driver's output is uncoloured by the enclosure to which it is mounted. Four 100 mm aluminium cone bass drivers complete the driver complement, delivering the low-frequency extension and dynamic headroom that a THX Ultra2 certified installation demands. The speaker supports bi-wire and bi-amplifier connections for those wishing to maximise system performance.
Installation and Finish
The Ci4100QL-THX ships with a paintable magnetic metal grille, a cutout template, gaskets, and all hardware required for installation — accommodating a broad range of wall cavity depths. The grille can be painted to match any décor, and an optional black cloth grille is available separately for those who prefer a more discreet finish.
Technical Specifications
| Specification | Detail |
|---|---|
| Type | 3-way in-ceiling, THX Ultra2 certified |
| HF Driver | 25 mm vented aluminium dome (Uni-Q) |
| MF Driver | 100 mm aluminium cone (Uni-Q) |
| LF Drivers | 4 × 100 mm aluminium cone |
| THX Certification | THX Ultra2 |
| Frequency Response (±6dB, open-backed) | 50 Hz – 28 kHz |
| Nominal Impedance | 4 Ω |
| Sensitivity (2.83V/1m) | 88 dB |
| Recommended Amplifier Power | 40 – 150 W |
| Connections | Bi-wire / bi-amplifier |
| Dimensions H×W (overall) | 890 × 190 mm |
| Cutout Dimensions H×W | 872 × 167 mm |
| Mounting Depth | 99 mm |
| Baffle | Precision-machined aluminium |
| Grille | Paintable magnetic metal (included) |
Who Is It For?
The Ci4100QL-THX is the correct choice for a custom installation home cinema where ceiling-mounted surround or overhead channels are required to meet THX Ultra2 standards — whether as part of a Dolby Atmos overhead configuration or as surround channels in a 5.1 or 7.1 system. It pairs naturally with the in-wall designs from the same Ci-R Series, including the KEF Ci3160RL-THX and the KEF Ci5160RL-THX. For the ultimate in custom installed front-stage performance, the KEF Ci5160REF-THX represents the pinnacle of KEF's architectural loudspeaker range.
Buying from Martins Hi-Fi
Martins Hi-Fi has been in Norwich since 1968. Elizabeth Gould runs the business today, and we stock only brands we have heard properly and stand behind.
We can advise on the full Ci-R Series installation at our Norwich showroom, including system design, amplification, and room planning for custom home cinema projects. When you get in touch, you'll be speaking with Dave, Chris and Tim — experienced specialists who can advise on this product and your whole system.
Contact us at info@martinshifi.co.uk, call 01603 627010, or WhatsApp on 07554 687137. You can read more about how we work on our Why Martins Hi-Fi page. We are at 85–91 Ber Street, Norwich, NR1 3EY.
