Helix Compose i3 Ci3 C100.2FM-S3 MK2 Coaxial 4 Inch FlexMount Speakers 80w RMS

The HELIX Ci3 C100.2FM-S3 MK2 is a 4 inch / 100 mm two-way coaxial speaker pair from the COMPOSE i3 range, rated at 80 W RMS at 3 ohms. It is a drop-in upgrade for tight factory door and dash locations, with FlexMount100 rings and FlexConnect terminals supplied.

This listing is the coaxial version. The HELIX COMPOSE i3 4-inch FlexMount speaker is also available as a Ci3 K100.2FM-S3 component set.

Key specifications

• Size: 4" / 100 mm coaxial, two-way
• Power handling: 80 W RMS / 120 W max
• Impedance: 3 ohms
• Frequency response: 100 Hz to 25 kHz
• Sensitivity: 91 dB @ 2.83 V / 1 m (87 dB @ 1 W / 1 m)
• Mounting depth: 30.0 mm
• Tweeter: 0.75" / 20 mm aluminium dome, neodymium magnet
• Crossover: Integrated, 6 dB highpass
• Includes: FlexMount100 adaptor rings and FlexConnect terminals

HELIX COMPOSE. The perfect speaker for any composition.

The HELIX COMPOSE platform was developed to combine the flexibility of universal speakers with the fit and acoustic advantages of vehicle-specific systems. Innovative materials and smart engineering deliver high efficiency, strong dynamics and excellent sound quality across a wide range of vehicles.

Performance highlight

The i3 coaxial systems deliver a first-class two-way sound experience using high-quality materials and practical engineering. All components are designed to work in harmony, and pair ideally with HELIX and MATCH amplifiers for maximum performance and power output.

High efficiency

The COMPOSE i3 uses 3 ohm technology, which harmonises with all HELIX and MATCH amplifiers and delivers a clear improvement in efficiency and maximum sound pressure over standard 4 ohm designs.

Cenosphere paper cone

The cone uses a "Cenosphere" coating — hollow spheres incorporated into a polyamide layer applied to the cone surface. This increases stiffness and improves internal damping, producing a lightweight yet exceptionally stable cone for precise sound reproduction.

High-tech polymer basket

The basket is made from a glass-sphere-reinforced high-tech polymer composite. This provides maximum stability with minimal self-resonance, eliminates flux modulation of the magnetic system, and resists thermal influences — while keeping overall dimensions compact for easier installation in tight spaces.

Stunning highs and outstanding stability

The 0.75" / 20 mm tweeter features a black aluminium dome, balancing low weight with high rigidity. Combined with a neodymium magnet system, it delivers precise, detailed high-frequency response with natural brilliance and impressive dynamics.

FlexMount100 – Universal meets car-specific

FlexMount100 adaptor rings allow COMPOSE speakers to be installed in the original factory location across a wide range of vehicles. The twist-lock design secures the speaker in an acoustically optimised position without modification to the vehicle.

FlexConnect – One terminal for all cases

The FlexConnect terminal allows direct connection to the vehicle's original wiring harness, maintaining the automotive-standard plug connection and providing built-in reverse polarity protection. Vehicle-specific adaptors are available to extend compatibility further.

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