INFINITY ALPHA 403F - New Gen Alpha Series 4″ 2-Way Coaxial Speakers

Infinity Alpha 403F | 4″ Coaxial Car Speaker System | 40 W RMS | 88 dB SPL

The Infinity Alpha 403F is a compact yet powerful 4″ coaxial car speaker system, expertly engineered for clean mids and sparkling highs in space-constrained applications. Its advanced Plus One™ woofer cone architecture and PEI balanced dome tweeter deliver rich, full-spectrum sound with minimal distortion—perfect for upgrading stock systems in smaller doors, dashboards, or rear factory locations.

With 40 W RMS (320 W peak) power handling, a 4 Ω nominal impedance, and 88 dB sensitivity (@2.83V), the Alpha 403F is optimized for strong output from both stock and aftermarket head units. Designed to bring Infinity’s signature sound to tighter installation environments, this speaker delivers surprisingly full-bodied audio in a highly space-efficient format.

Product Highlights:

4″ (100 mm) coaxial car speaker system optimized for compact locations

Plus One™ polypropylene woofer cone for increased cone area and better bass

PEI balanced dome tweeter for crisp, detailed treble with low distortion

High-efficiency 88 dB sensitivity ideal for use with factory or low-power systems

Smooth frequency response from 80 Hz to 20 kHz for a natural listening experience

Easy-fit design for factory replacements or custom compact installs

Tech Specs:

Model: Alpha 403F

Type: 2-Way Coaxial Car Speaker System

Woofer: 100 mm (4″) Plus One™ polypropylene cone

Tweeter: PEI balanced dome tweeter

Power: 40 W RMS / 320 W peak

Sensitivity: 88 dB (@2.83V)

Impedance: 4 Ω

Frequency Response: 80 Hz – 20 kHz

Applications: Dash, door, or rear fill in compact vehicles; OEM upgrade or retrofit where space is limited

Infinity Quality in a Compact Form

Like the rest of the Alpha series, the 403F features Infinity’s acclaimed sound engineering and tuning, with performance that punches above its size. Whether you’re enhancing your vehicle’s factory system or building a discreet custom install, the Alpha 403F ensures clean, balanced audio—Infinity sound, scaled down, but never compromised.