The GMC Sonoma behind seat location accommodates a 4x10 inch speaker size, with all positions supporting 4x10 inch units. Full-range audio components are the compatible system types for the replacement. These specifications cover the 1991 to 1993 model years.
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 behind-seat location in the GMC Sonoma is a rear-facing or side-facing enclosure integrated into the cab structure, a position typically constrained by the shallow depth of the cab wall and the proximity of the seat back.
A 4x10 inch speaker occupies an elongated rectangular footprint, a non-standard shape that requires a dedicated mounting cutout sized specifically to that dimension rather than a universal round opening.
The 4x10 inch format distributes its cone surface area across an oblong plane, which suits the low-profile, horizontally oriented cavities found behind seats in compact trucks of the GMC Sonoma's class.
At 4 inches in the narrow axis, the cone excursion and low-frequency extension are limited compared to larger drivers, placing the effective bass reproduction in the upper bass and lower midrange region.
The 10-inch length of the cone provides additional radiating surface area, which partially compensates for the narrow width by increasing overall cone area and supporting fuller midrange output within the behind-seat enclosure.
Full-range drivers are single-unit speakers designed to reproduce a wide portion of the audible spectrum, from bass through treble, without the need for a crossover network or supplementary tweeters.
In the behind-seat position of the GMC Sonoma, a full-range driver handles the entire frequency responsibility for that location, as no crossover-dependent multi-driver system is specified for that mounting point.
The behind-seat location places the speaker at a low height relative to the seated listener's ear level, which influences the directional projection of high-frequency content, since tweeters and upper-range drivers are more directional and benefit from ear-level alignment.
The 1991, 1992, and 1993 GMC Sonoma models share the same 4x10 inch behind-seat specification, indicating a consistent cab interior dimension and mounting structure across those model years.