Infinity Primus 503F 5.25" 2-Way Car Speakers

The Infinity Primus 503F is a pair of 5.25-inch, 2-way coaxial car speakers designed to replace worn or basic factory speakers. Their compact format is intended for vehicles with limited mounting space, helping make an audio refresh possible without adding a separate tweeter assembly. Each speaker combines a polypropylene woofer and a centrally mounted silk-dome tweeter.

With 40 watts RMS power handling per speaker and a 3-ohm nominal impedance, the Primus 503F is suited to factory-radio upgrades as well as compatible aftermarket amplification. Its 91 dB sensitivity rating helps it produce useful output from modest power. Confirm that the vehicle, mounting location, and amplifier or radio support the speaker's physical and electrical requirements.

The 5-1/4-inch polypropylene woofer uses Infinity's Plus One cone architecture. This design increases the available cone area compared with conventional cones in its class, supporting stronger low-frequency output from a compact speaker size. A hi-roll rubber surround supports cone movement while the rigid basket structure supports the driver assembly.

A 1/2-inch edge-driven silk dome tweeter handles high frequencies, with a specified crossover point of 6 kHz at 6 dB per octave. The 75 Hz to 20 kHz frequency-response rating reflects a sound profile intended to cover vocal, instrument, and treble detail in a full-range door, dash, or rear-deck replacement application. For deeper bass, pair these speakers with a properly integrated subwoofer rather than expecting a 5.25-inch speaker to reproduce the lowest bass notes.

The Primus 503F is supplied as a stereo pair with mounting hardware, foam gaskets, and short pigtail cables. Its 5-1/8-inch cutout requirement and 1-13/16-inch top-mount depth should be checked against the vehicle before purchase. It can serve as a practical front or rear replacement where 5.25-inch coaxial speakers are specified and sufficient clearance is available.

Key Features

• 5.25-Inch Coaxial Design: Combines woofer and tweeter in each speaker for a straightforward full-range replacement.
• 40W RMS Per Speaker: Supports use with compatible factory radios or aftermarket amplifiers.
• Plus One Cone Architecture: Provides increased cone area for a compact 5.25-inch speaker.
• Silk Dome Tweeter: Handles upper-frequency detail with an edge-driven 1/2-inch dome design.
• 3-Ohm Nominal Impedance: Designed for compatible car-audio source units and amplifiers.
• Vented Basket Frame: Helps move heat away from the motor structure during operation.

Design & Installation

The Primus 503F uses a polypropylene woofer, hi-roll rubber surround, silk dome tweeter, ferrite motor structure, and vented basket frame. The all-black presentation is designed to blend into typical vehicle interiors, while the basket construction supports cooling around the voice-coil area. Infinity specifies a 2-way architecture with a 6 kHz crossover point.

Verify the vehicle's speaker opening, mounting-hole pattern, panel clearance, and wiring connection before installation. The specified cutout is 5-1/8 inches, and top-mount depth is 1-13/16 inches; spacers, vehicle-specific adapters, or harness adapters may be required depending on the vehicle. Use the supplied foam gasket and mounting hardware where appropriate, maintain correct speaker polarity, and ensure the connected amplifier is stable at 3 ohms.