The Ford F-150 behind seat location accommodates a 6x8 inch speaker size. Full-range units represent the compatible audio system type for the installation. These specifications apply to the 1999 model year.
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 Ford F-150 positions speakers within the rear wall of the cab, typically in an enclosed or semi-enclosed cavity behind the seating row, which affects both airflow around the driver and rear-facing sound projection into the cabin.
A 6x8 inch speaker occupies a notably larger surface area than a round 6.5 inch driver, with the oval shape allowing a greater cone area within a constrained vertical space - a practical fit for the shallower cavities often found in truck cab rear panels.
The extended cone area of a 6x8 inch driver supports stronger low-to-mid frequency output compared to smaller oval formats, allowing the behind-seat placement to contribute meaningfully to the lower portion of the audible range without a dedicated subwoofer.
Behind-seat placement directs speaker output forward into the cab at roughly ear level for rear passengers and at a low angle relative to front-seat occupants, creating a diffuse rather than direct listening axis for the driver.
The Ford F-150 behind-seat location for the 1999 model year accepts a 6x8 inch full-range driver, which is a compatibility constraint determined by the factory mounting cutout dimensions and the depth clearance available behind the seat panel.
Full-range drivers are designed to reproduce the entire audible frequency spectrum - typically from approximately 60 Hz to 20 kHz - from a single cone, which suits behind-seat positions where running separate crossover networks or component speaker wiring may not be practical.
The behind-seat position in a truck cab places the speaker in close physical proximity to seat-back foam and structural cab components, which can affect rear-wave dispersion and alter the effective acoustic loading on the driver cone.
A 6x8 inch full-range driver in a behind-seat enclosure benefits from the partial acoustic boundary created by the cab rear wall, which can reinforce bass frequencies that a smaller driver in an open-back mount would otherwise lose to cancellation.