The Plymouth Reliant dashboard accommodates a 3.5 inch speaker size in that location. Full-range units represent the compatible audio system replacement types. These specifications cover the years 1981 through 1989.
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 dashboard location in the Plymouth Reliant positions speakers at the front of the cabin, near the windshield, which places sound output at roughly instrument-panel height and directs audio toward the occupants from a forward angle.
Dashboard enclosures are typically shallow and space-constrained, limiting the depth and diameter of any speaker that can be mounted without conflict from the panel structure beneath.
A 3.5 inch driver is a compact size well suited to shallow-depth dashboard cavities, as the small cone diameter requires less rear clearance than larger drivers and fits within the narrow vertical space common to instrument panels.
At 3.5 inches, the cone area is sufficient to reproduce midrange frequencies clearly but is physically limited in its ability to move the air volume needed for strong low-frequency output, which is a natural consequence of a small radiating surface.
The Plymouth Reliant dashboard speaker position, with a 3.5 inch full-range driver, relies on the driver to handle the entire audible spectrum from a single point source, since no separate tweeter or woofer is specified for the location.
Full-range drivers are designed to reproduce low, mid, and high frequencies from a single cone and voice coil assembly, making them the functional requirement for a single-speaker dashboard position with no crossover network.
Because full-range drivers must balance frequency response across the entire spectrum, cone material and suspension stiffness in a 3.5 inch unit are tuned to avoid the resonance peaks that would arise if the driver were optimized for only one frequency band.
The dashboard mounting plane is generally horizontal or slightly angled toward the occupants, which affects the directional dispersion of high frequencies, as tweeters and full-range drivers both exhibit narrowing dispersion at higher frequencies relative to the listening axis.
A 3.5 inch full-range driver at the dashboard position is at a relatively close distance to front-seat occupants, which influences the perceived imaging and tonal balance compared to door or rear-deck mounted speakers farther from the listener.