The Pontiac Bonneville dashboard accommodates a 4x6 inch speaker size and 3.5 inch speakers across the model's production range. Full-range units are the compatible speaker types for all configurations. These specifications cover the 1985 to 1991 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 dashboard location in the Pontiac Bonneville places speakers at the forward edge of the cabin interior, near the base of the windshield, where the enclosure depth is shallow and the mounting footprint is constrained by the instrument panel structure.
Dashboard installations typically involve limited rear airspace behind the speaker cone, which affects bass extension and makes full-range drivers the practical choice for this position.
The 4x6 inch oval format, specified for the 1988 through 1991 model years, occupies a larger surface area than a round speaker of equivalent minor-axis diameter, allowing greater cone excursion within a shallow mounting cavity.
The wider cone area of a 4x6 inch driver enables more efficient low-frequency reproduction than a smaller round driver of comparable depth, which is acoustically relevant given the limited enclosure volume available beneath a dashboard panel.
The 3.5 inch round format, specified for the 1985 through 1987 model years, is a compact driver size whose small cone area and reduced mass favor upper-midrange and high-frequency output over low-frequency extension.
A 3.5 inch driver in a dashboard location reinforces midrange frequencies, roughly centered in the vocal intelligibility range of 500 Hz to 4 kHz, where dashboard placement near ear level contributes to direct sound projection toward the occupants.
Full-range drivers, the only compatible type listed across all specified model years, are single-driver units designed to reproduce the broadest audible frequency band a single cone can manage without the use of a passive crossover network.
The full-range designation in a dashboard context means the speaker handles the entire signal without frequency division, which is characteristic of factory-level installations where a dedicated crossover or separate tweeter is absent at that location.
The physical transition between the 3.5 inch specification and the 4x6 inch specification at the 1987 to 1988 model year boundary reflects a change in the mounting cutout dimensions within the Bonneville dashboard structure.
Dashboard speaker positions in vehicles of the late 1980s and early 1990s were typically designed for front-fill imaging, placing the sound stage at dashboard height to complement lower door or kick-panel mounted woofers when present in the system.