The GMC Sonoma D-Pillar accommodates a 4x10 inch speaker size in that location. Full-range units represent the compatible speaker types available for that position. These specifications cover the years 1998 to 1999.
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 D-pillar location in the GMC Sonoma positions speakers at the rearmost structural column of the vehicle, placing audio output toward the back of the cabin.
A 4x10 inch speaker occupies a rectangular footprint, and the mounting cavity at the D-pillar must accommodate the elongated frame dimensions of that format rather than a standard circular cutout.
The 4x10 inch format produces a relatively large cone surface area despite the narrow width, which supports extended low-frequency and midrange reproduction compared to smaller rectangular formats.
The narrow 4-inch dimension of the 4x10 inch driver limits the depth of the mounting cavity required, a relevant factor given the typically shallow space available within a pillar enclosure.
Full-range speakers are designed to reproduce the entire audible frequency spectrum from a single driver, covering low, mid, and high frequencies without requiring a dedicated crossover network.
In a D-pillar position, a full-range driver handles all frequency content directed toward the rear listening zone without supplemental tweeters or woofers at that location.
The GMC Sonoma D-pillar accepts a 4x10 inch full-range speaker across both the 1998 and 1999 model years, indicating consistent cavity dimensions between those 2 model years.
The elongated cone geometry of a 4x10 inch driver distributes sound dispersion differently along its horizontal and vertical axes, affecting the stereo imaging characteristics perceived from rear-cabin seating positions.