HELIX Ci3 K165.2FM-S3 MK2 6.5" 2-Way Component Speakers 3Ohm

High-Efficiency 6.5" Component Speakers Built for the Vehicle Cenosphere Paper Cone, Aluminium Dome Tweeter COMPOSE Platform Product Overview The HELIX Ci3 K165.2FM-S3 MK2 is a 2-way component speaker kit from the HELIX COMPOSE platform a system designed from the outset for clean, non-destructive integration into factory vehicle audio positions. The kit pairs a 6.5" Cenosphere-coated paper cone midbass with a 0.75" aluminium dome neodymium tweeter through a compact, extensively tuned crossover, delivering 100W RMS / 150W max at 3 Ohm impedance. The MK2 revision introduces updated basket construction, COMPOSE Connect smart connectors (no soldering or polarity errors), and full compatibility with HELIX's FlexMount adaptor ring system allowing these universal speakers to install into factory speaker positions across a wide range of vehicles with vehicle-specific FlexMount20 (tweeter) and FlexMount165 (midbass) adaptor rings, both sold separately. The Ci3 FX-UNI.2 crossover features a 6-stage tweeter level adjustment with 12dB slope and integrated tweeter protection, allowing installation position compensation without separate components. The 3 Ohm design is engineered to extract maximum output from HELIX and MATCH amplifiers; the kit is rated for 92 dB sensitivity at 2.83V/1m. Features & Benefits HELIX COMPOSE platform — engineered specifically for vehicle integration, combining universal speaker dimensions with vehicle-specific installation options via FlexMount and WireKit accessories Cenosphere paper cone (midbass) — hollow ceramic microspheres are incorporated into a polyamide layer applied to the cone; this increases stiffness while optimising internal damping, resulting in a lightweight yet rigid cone with precise, controlled sound reproduction 0.75" / 20mm aluminium dome tweeter — black aluminium dome with neodymium magnet system; combines low weight with high rigidity for accurate, detailed high-frequency response and natural brilliance 3 Ohm high-efficiency design — engineered to maximise output from HELIX and MATCH amplifiers; the lower impedance draws more current, increasing real-world sensitivity and dynamics High-tech polymer basket reinforced with glass beads — minimises basket resonance, eliminates flux modulation of the magnetic system, and resists thermal influences; more compact than traditional cast frames for easier installation in constrained spaces Ci3 FX-UNI.2 crossover — 6-stage tweeter level adjustment with 12dB highpass slope and integrated tweeter protection; tuned for optimal frequency band distribution; compact dimensions for tight spaces; COMPOSE Connect and WireKit compatible COMPOSE Connect — proprietary automotive-grade push-in connectors that accept standard flat plugs and couplings with physical polarity lock; eliminates soldering and prevents connection errors during installation FlexMount compatible (FlexMount20 tweeter + FlexMount165 midbass) — adaptor rings sold separately allow vehicle-specific installation in factory mounting positions across a wide range of vehicles WireKit compatible — optional vehicle-specific wiring harnesses (sold separately) enable non-destructive, plug-and-play connection to factory wiring Separate crossover — crossover is a dedicated physical unit rather than in-line, allowing optimised placement independent of the drivers Tweeter mounting accessories included — flush mount and angle mount pods included for tweeter placement flexibility Technical Specs Specification Detail System Configuration 2-way component (midbass + tweeter + crossover) Power handling RMS / Max 100W / 150W Frequency response 60Hz – 25,000Hz System impedance 3Ω Sensitivity (2.83V/1m) 92 dB Sensitivity (1W/1m) 88 dB Midbass (Ci3 W165FM-S3) Size 6.5" / 165mm Outer diameter 165.0mm / 6.50" Installation diameter 142.0mm / 5.59" Installation depth 60.7mm / 2.39" Impedance 3Ω DC resistance (Re) 3.0Ω Resonance frequency (Fs) 70Hz Qms (mechanical Q) 4.17 Qes (electrical Q) 1.05 Qts (total Q) 0.84 Compliance (Cms) 454 μm/N Equivalent air volume (Vas) 11.2L Force factor (Bl) 4.0 Tm Cone area (Sd) 133 cm² Moving mass (Mms) 11.3g Mechanical resistance (Rms) 1.18 kg/s Voice coil diameter 25mm Voice coil winding height 10.5mm Max linear excursion (Xmax) ±3.2mm Cone material Paper with Cenosphere coating Basket High-tech polymer composite + glass bead reinforcement Terminal ProConnect Mount compatibility FlexMount165 Tweeter (Ci3 T20FM-AL MK2) Size 0.75" / 20mm Outer diameter 32.0mm / 1.26" Installation diameter 32.0mm / 1.26" Installation depth 9.8mm / 0.39" Impedance 4Ω Resonance frequency (Fs) 1,800Hz Voice coil diameter 20mm Dome material Black aluminium Magnet Neodymium Mount compatibility FlexMount20 Crossover (Ci3 FX-UNI.2) Dimensions 103.3 × 50.4 × 25.0mm / 4.07 × 1.98 × 0.98" Tweeter filter 12dB highpass + protection + 6-stage level adjustment Midbass filter 6dB lowpass COMPOSE Connect compatible Yes WireKit compatible Yes Compatible With / Goes Well With HELIX and MATCH amplifiers — the 3 Ohm design is optimised for HELIX and MATCH amplifier output stages FlexMount165 adaptor rings (sold separately) — vehicle-specific midbass installation in factory mounting positions FlexMount20 adaptor rings (sold separately) — vehicle-specific tweeter installation in factory positions WireKits (sold separately) — vehicle-specific plug-and-play wiring harnesses for non-destructive factory wiring connection COMPOSE Connect Kit (2 included) — automotive-grade connectors for safe, polarised connection Weight Not specified Frequently Asked Questions What is the HELIX COMPOSE platform and why does it matter for installation? COMPOSE is HELIX's approach to universal speakers that can also integrate into vehicle-specific positions. The system uses the FlexMount adaptor ring ecosystem — vehicle-specific rings (sold separately) that bolt to the midbass and tweeter and allow direct installation into factory speaker locations. Without FlexMount rings, the speakers install as standard universals into any appropriately sized opening. COMPOSE also standardises the COMPOSE Connect wiring interface for clean, automotive-grade connections throughout the system. What is the Cenosphere paper cone and what does it do sonically? Cenosphere refers to hollow ceramic microspheres derived from industrial processes, incorporated into a polyamide coating applied to the paper cone surface. The spheres increase cone rigidity (resisting flexion at higher output levels) while their hollow structure maintains low mass and adds internal damping (reducing stored energy and breakup artefacts). The practical result is a cone that stays controlled and accurate at higher volumes without the colouration typical of heavier, stiffer materials. Why is this speaker 3 Ohm and does it require a special amplifier? 3 Ohm speakers are not a special standard — they sit between the conventional 4 Ohm and 2 Ohm ratings. HELIX designed the COMPOSE i3 range to 3 Ohms because it allows HELIX and MATCH amplifiers to deliver measurably more power than into 4 Ohm loads, while remaining within safe operating range for virtually all amplifiers rated down to 2 Ohms. Standard 4 Ohm and 2 Ohm amplifiers are compatible; the 3 Ohm load simply extracts more performance from them. Are FlexMount adaptor rings and WireKits included? No — FlexMount165 midbass adaptor rings, FlexMount20 tweeter adaptor rings, and WireKits are all sold separately. The kit includes the speakers, crossovers, COMPOSE Connect kits, tweeter mounting accessories, and general mounting hardware, but the vehicle-specific integration accessories require a separate purchase matched to your specific vehicle. What is COMPOSE Connect and how does it simplify installation? COMPOSE Connect is HELIX's automotive-grade plug-in connector system. Standard flat plugs and couplings snap into proprietary plastic housings with a physical polarity lock that prevents reversed connections — eliminating the need for soldering, electrical tape, or self-made terminal joins. The connection is secure, automotive-rated for vibration and moisture, and fully removable without cutting wires.