The BMW 735i rear door panel accommodates a 6x8 inch speaker size, with all listed configurations supporting 6x8 inch units. Full-range types represent the compatible audio system components for the rear door panel location. The specifications cover the years 1990 to 1992.
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 rear door panel location in the BMW 735i places speakers within the door cavity, where the speaker cone faces into the passenger cabin from a side-mounted position, directing sound laterally across the rear seating area.
Door panel installations involve mounting depth constraints imposed by the internal door structure, window mechanisms, and wiring harnesses occupying the cavity behind the mounting surface.
A 6x8 inch speaker features an oval or elliptical cone geometry, which allows a larger radiating surface area to fit within a mounting cutout that is shorter in one axis than a comparable round speaker, making the format suited to door panel cavities where vertical space is limited.
The greater radiating surface area of a 6x8 inch driver, relative to smaller round formats, supports stronger low-mid frequency output from within a door panel enclosure that lacks a dedicated subwoofer enclosure volume.
The BMW 735i rear door panel positions the speaker at a low height within the door, meaning bass and lower midrange frequencies, which are less directional by nature, project into the cabin more uniformly than higher frequencies would from the same position.
Full-range speakers are drivers designed to reproduce the entire audible frequency spectrum within a single unit, covering low-frequency bass through high-frequency treble without requiring a separate tweeter or woofer in the same location.
In a rear door panel location, a full-range driver handles both the ambient low-frequency reinforcement and the midrange vocal frequencies that contribute to rear cabin sound presence.
The 6x8 inch full-range format in the BMW 735i rear door panel is the sole compatible speaker type across the 1990, 1991, and 1992 model years covered in the specifications, indicating a consistent mounting cutout and depth clearance across that production period.
Door panel speaker mounts typically use a baffle or bracket system to secure the speaker frame against the door skin, with the speaker grille on the interior trim panel side facing the cabin occupants.
The elliptical shape of a 6x8 inch speaker requires orientation-specific installation, as the longer axis of the speaker must align with the longer axis of the mounting cutout in the door panel.