The Pontiac Bonneville rear deck lid accommodates a 6x9 inch speaker size and also supports 4x10 inch units. Full-range types are the compatible audio system replacement options across all listed years. These specifications cover the 1985 to 2005 chart of 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 rear deck lid is a horizontal surface positioned at the base of the rear window, behind the rear passenger seating area, and above the trunk cavity in a sedan body style.
Speaker placement on the rear deck lid directs sound upward and forward into the cabin, using the rear window glass and headliner as acoustic reflective surfaces.
The 6x9 inch oval format occupies a larger cone area than standard circular drivers, which increases low-frequency displacement and allows fuller bass reproduction relative to the physical footprint of the mounting cutout.
The elongated oval geometry of a 6x9 inch driver distributes the mounting footprint across a wider but narrower horizontal span, which suits the lateral constraints of a rear deck panel where vertical depth is limited by trunk clearance beneath.
The 4x10 inch oval format shares the elongated oval geometry but extends along a longer horizontal axis, making the mounting width greater while keeping the short axis narrower than the 6x9 inch configuration.
The narrower short axis of the 4x10 inch driver relative to the 6x9 inch driver results in a reduced cone area, which affects low-frequency output capacity and requires the driver to work differently across the bass range.
Both the 4x10 inch and 6x9 inch mounting locations on the Pontiac Bonneville rear deck lid are oriented horizontally, meaning the driver fires upward toward the ceiling and rear window rather than directly toward the listening position.
Full-range drivers are single-unit speakers designed to reproduce low, midrange, and high frequencies without a passive crossover network, relying on the driver's own cone and dust cap geometry to distribute frequency response across the audible spectrum.
In a rear deck lid position, a full-range driver handles bass frequencies that reinforce the lower end of the soundstage from behind the passengers, midrange vocal content, and high-frequency detail that reflects off the rear window.
The rear deck location introduces proximity effects at the listening position because sound from rear-mounted full-range drivers arrives after a time delay relative to front speakers, which affects imaging and staging within the cabin.
The Pontiac Bonneville rear deck lid specifies full-range as the sole compatible type across all listed model years, meaning the mounting depth and baffle dimensions of the deck panel are matched to the profile of full-range oval drivers rather than component or coaxial multi-element systems requiring additional depth clearance.