KEF Ci3160RLb-THX In-Wall Subwoofer

The KEF Ci3160RLb-THX is the in-wall subwoofer at the heart of KEF's Extreme Theatre system — a suite of architectural speakers engineered to deliver certified THX performance entirely within the fabric of a room. Sitting within the R Series tier of KEF's Ci custom install range, the Ci3160RLb-THX is designed to pair with the KEF KASA500 system amplifier, which handles all crossover duties and powers up to two Ci3160RLb-THX units simultaneously for the most demanding home cinema installations.

Design and Construction

The Ci3160RLb-THX uses three 160mm (6.5-inch) long-throw sub-bass drivers arranged vertically on a substantial aluminium baffle. The aluminium construction serves a structural purpose: it provides a rigid, non-resonant front surface that resists the mechanical forces generated by the drivers at high output levels, preventing cabinet colouration that a pressed-steel or plastic baffle would introduce. The unit is designed to be installed in a stud wall cavity, with the aluminium face plate flush-mounted to the wall surface for an entirely hidden installation.

Because the Ci3160RLb-THX operates exclusively with the KASA500 amplifier — which incorporates its own active crossover — the driver array has no internal passive crossover network. The KASA500 handles all low-pass filtering; the recommended low-pass filter range is 50Hz–120Hz, with a recommended high-pass filter on the main speakers of 80Hz to meet THX specification.

Performance and THX Certification

The Ci3160RLb-THX carries both THX Ultra and THX Select certification, which require compliance with stringent output, distortion, and frequency response standards defined for large-room and medium-room home cinema respectively. The unit achieves a sensitivity of 92dB (2.83V/1m), a frequency response of 20Hz–140Hz (±6dB, open-backed), and a maximum SPL of 112dB — output levels comparable to conventional freestanding subwoofers of significantly larger cabinet volume. The frequency range extends to 25Hz (−10dB), with the upper limit set by the KASA500 crossover.

An 80-litre rear volume behind each unit is ideal; 40 litres is the specified minimum. The installer must provision this cavity space during construction. An optional rough-in frame (RIF3160L) is available to simplify precise cut-out preparation before plastering.

The Extreme Theatre System

The Ci3160RLb-THX is one component within KEF's Extreme Theatre architectural system, which covers the full surround and subwoofer requirements for a large home cinema. The system spans three series tiers: the Reference Series (Ci5160REF-THX and Ci3160REF-THX in-wall LCR speakers), the R Series (Ci5160RL-THX and Ci3160RL-THX in-wall LCR speakers, plus the Ci3160RLb-THX subwoofer and the Ci200RR-THX in-ceiling speaker), and the Q Series (Ci4100QL-THX in-wall LCR and Ci200QSb-THX in-ceiling subwoofer). All models within the range have been sonically matched by KEF, ensuring consistent tonal character across LCR and surround channels regardless of which tier is used.

Installation

The Ci3160RLb-THX requires a cut-out of 660 × 209mm (H × W) in the wall surface and a mounting depth of 88.5mm from the surface. Wall material thickness must be between 6mm and 40mm. The overall unit dimensions are 680 × 230 × 96mm (H × W × D) and the net weight is 10.9kg. KEF recommends consulting a qualified installer and, where required by building regulations, fitting an appropriate fire hood and using low-smoke zero-halogen specification speaker cable within wall cavities.