The CSS230 sits within Monitor Audio’s Super Slim range — a line of custom-install speakers engineered specifically for shallow ceiling voids where conventional in-ceiling designs cannot physically fit. With a mounting depth of just 50mm, the CSS230 is designed to install between 2-inch stud frames or in spaces where pipework, cabling, or structural constraints reduce the available cavity behind the ceiling panel.
Driver Array & Acoustic Design
Rather than using a single large bass-mid driver (which would demand a deeper enclosure), Monitor Audio employs three 3-inch C-CAM cone drivers arranged radially around a central 19mm C-CAM Gold Dome tweeter. This configuration allows the trio of smaller drivers to collectively match the bass output of a conventional 6½-inch unit while keeping the overall depth within the 50mm envelope. The C-CAM (Ceramic-Coated Aluminium/Magnesium) cone material is a long-established Monitor Audio technology, offering a rigid, lightweight diaphragm that resists breakup across its operating bandwidth.
The crossover network uses high-quality film capacitors and low-loss inductors to maintain signal integrity. Monitor Audio specifies a minimum external crossover point of 100 Hz at 12 dB/octave, with 24 dB/octave recommended for optimum integration when used with a subwoofer.
Hybrid Back-Box Construction
The CSS230’s hybrid back-box can be operated in two modes: sealed (enclosed) or open-back (ported). In sealed mode, the frequency response extends from 100 Hz to 30 kHz; in open-back mode, it reaches down to 85 Hz at the −6 dB point, trading some sound isolation for improved low-frequency extension. When operating in ported mode, a fine gauze protects the acoustic system from dust ingress. The ABS housing is UL94 rated and RoHS2 compliant.
Installation
The CSS230 uses Monitor Audio’s Tri-Grip II dog-leg fixing system for secure, tool-free mounting. The cut-out diameter is 211mm, and the overall diameter including the magnetically-attached round grille is 250mm. An optional square grille (249 × 249mm) is available for installations where a square aesthetic is preferred. Gold-plated sprung-push terminals accept bare wire up to 4mm². For new-build projects, the optional CB6 pre-construction bracket allows the speaker position to be fixed before the ceiling is finished.
| Speaker Type | In-Ceiling (Super Slim) |
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| Drive Units | 3 × 3” C-CAM cone (bass/mid), 1 × 19mm (3/4”) C-CAM Gold Dome tweeter |
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| Frequency Response (−6 dB) | 100 Hz – 30 kHz (sealed); 85 Hz – 30 kHz (open back) |
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| Nominal Impedance | 8 Ω |
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| Sensitivity | 86 dB (1W @ 1m) |
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| Maximum SPL | 103.8 dBA |
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| Power Handling | 40W (full range); 60W (with 100 Hz crossover at 12 dB/octave) |
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| Recommended Amplifier Power | 10 – 60W |
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| Crossover | Minimum 100 Hz at 12 dB/octave; 24 dB/octave recommended |
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| Mounting Depth | 50mm (2”) |
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| Overall Diameter | 250mm (9 13/16”) |
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| Overall Depth | 54mm (2 1/8”) |
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| Cut-Out Diameter | 211mm (8 1/4”) |
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| Square Grille Option | 249 × 249mm |
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| Weight | 2.88 kg (6 lb 5 oz) |
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| Terminals | Gold-plated sprung push (bare wire up to 4mm²) |
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| Enclosure Material | ABS (UL94, RoHS2 compliant) |
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| Grille | Painted steel, magnetically attached (round included; square optional) |
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| Fixing System | Tri-Grip II dog-leg |
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| Sold As | Single |
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