SoundXtreme ST-603 6" 3-Way Coaxial Car Speakers

The SoundXtreme ST-603 is a pair of 6-inch, 3-way coaxial car speakers designed as a direct replacement or basic upgrade for compatible factory speaker locations. Their coaxial construction places multiple drivers within each speaker assembly, helping keep installation straightforward where a conventional round speaker fits. They are intended for wired vehicle-audio systems using 4-ohm speaker outputs.

These speakers are suited to drivers replacing worn or damaged factory speakers, as well as listeners who want a full-range coaxial speaker without adding separate tweeters. The ST-603 uses an injection-cone woofer and a PEI dome tweeter arrangement to cover bass, midrange, and high-frequency content from a single mounting location. Published sensitivity is 89 dB.

The speaker design is listed with a 30 mm PEI dome tweeter, a 25 mm voice coil, and a 10-ounce magnet. A rubber surround and steel basket are also listed in marketplace specifications. These elements support the speaker's compact, vehicle-oriented coaxial design.

SoundXtreme lists the ST-603 as a 350-watt maximum-power speaker, while some marketplace copy separately states a 320-watt peak-power figure. An RMS power rating has not been verified, so amplifier matching should not be based on an assumed RMS value. The published frequency-response figure most consistently reported in technical listings is 65 Hz to 20 kHz.

With a listed mounting depth of 2-3/4 inches, the ST-603 should be measured against the available depth and mounting diameter in the intended vehicle before purchase. It can be used with a factory head unit or a compatible external amplifier, provided the installation supports 4-ohm speakers. The pair format makes it practical for replacing two matching speakers in a vehicle audio system.

Key Features

• 3-Way Coaxial Design: Combines multiple driver elements in each speaker assembly.
• 6-Inch Round Format: Intended for compatible standard round speaker locations.
• 4-Ohm Impedance: Matches many conventional vehicle speaker circuits.
• PEI Dome Tweeter: Uses a listed 30 mm PEI dome high-frequency driver.
• Injection-Cone Woofer: Provides the primary low- and mid-frequency driver section.
• 89 dB Sensitivity: Published sensitivity specification for the ST-603.

Design & Installation

The ST-603 is built around a steel basket, injection-cone woofer, rubber surround, 25 mm voice coil, and 10-ounce magnet. Product listings also identify a rubber magnet boot cover and a PEI dome tweeter assembly. The speakers use a round coaxial layout rather than separate component woofer and tweeter installations.

Confirm that the vehicle accepts a 6-inch round speaker and provides at least 2-3/4 inches of mounting depth before installation. The speakers are listed with spade terminals, so use secure, correctly polarized speaker-wire connections and appropriate vehicle-specific mounting hardware or adapters when required. A pair of ST-603 speakers is included; verify all supplied accessories upon delivery because package-content descriptions vary by seller.