The GMC Sonoma rear door panel accommodates a 4x6 inch speaker size across all listed model years. Full-range units are the compatible audio system replacement types for the location. These specifications cover the years 1998 to 2004.
A single driver that reproduces bass through treble without a separate crossover network. It is the simplest replacement option and is common in factory audio systems.
Additional Notes
The GMC Sonoma rear door panel speaker location accommodates a 4x6 inch driver, an oval format whose asymmetrical dimensions serve to maximize cone surface area within the constrained vertical and horizontal space typical of a door panel cavity.
Door panel speaker enclosures are generally shallow, with limited depth behind the mounting surface, which affects the excursion and low-frequency extension available to any driver installed in that position.
The 4x6 inch format produces a larger radiating area than a standard 4 inch round driver, which supports greater acoustic output across the midrange frequencies without requiring a deeper mounting pocket.
The oval geometry of a 4x6 inch speaker results in a somewhat directional dispersion pattern along its longer axis, a characteristic relevant to the horizontal orientation common in door panel installations where the driver faces the cabin laterally.
Full-range speakers are designed to reproduce the entire audible frequency spectrum, including low midrange, midrange, and high-frequency content, through a single driver unit, typically incorporating a cone for lower frequencies and an integrated tweeter or whizzer cone for upper frequencies.
In the rear door panel position of the GMC Sonoma, a full-range driver operates without acoustic reinforcement from a dedicated subwoofer or separate tweeter at that location, requiring the single driver to handle the complete frequency output assigned to that channel.
The 4x6 inch full-range driver in a door panel installation is subject to acoustic interference from road noise and mechanical vibration transmitted through the door structure, which can affect the clarity of mid and high-frequency reproduction.
Full-range drivers in the 4x6 inch size class generally handle frequencies from approximately 80 Hz to 20 kHz, though the lower end of that range is constrained by the shallow mounting depth and absence of a sealed rear enclosure in a door panel installation.
The rear door panel location places the speaker behind the seated passenger, a position that influences the spatial and stereo imaging characteristics of the rear channel audio within the cabin.