The Buick Regal rear deck lid accommodates a 6x9 inch speaker size in that location. Full-range units are the compatible audio types supported in the system. These specifications cover a range of years from 1973 to 2020.
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 of the Buick Regal positions speakers horizontally along the parcel shelf area at the base of the rear window, facing upward toward the cabin interior.
A speaker mounted in the rear deck lid fires sound forward and upward into the passenger compartment, with the rear window glass acting as a reflective surface that influences how sound reaches front and rear occupants.
The 6x9 inch oval format is a physically large driver, and the elongated cone geometry increases the radiating surface area compared to a round driver of similar minor-axis diameter, which contributes to greater low-frequency displacement in a shallow mounting cavity.
The rear deck lid mounting location typically accommodates limited depth behind the mounting surface, and the 6x9 inch format is commonly engineered with shallow mounting depth profiles to fit within such constraints.
A 6x9 inch driver placed at the rear of the cabin creates a significant physical distance between the speaker and front-seat listeners, which affects the perceived time alignment of sound arriving from the front versus rear of the vehicle.
The Buick Regal rear deck lid speaker opening is sized for a 6x9 inch driver, meaning the cutout dimensions, bolt pattern spacing, and available mounting depth correspond to that oval format across all listed model years.
Full-range is the sole compatible type specified for the Buick Regal rear deck lid, designating a single driver designed to reproduce low, mid, and high frequencies without requiring a separate crossover network or additional driver.
A full-range speaker in the rear deck lid position handles the entire audible frequency spectrum from that location, typically spanning from the upper bass region through to the high-frequency range within the limits of its cone and tweeter design.
Many 6x9 inch full-range designs incorporate a small whizzer cone or integrated tweeter element within the main cone to extend high-frequency reproduction, compensating for the natural roll-off of a large cone at upper frequencies.
Because the rear deck lid location places the driver behind and below the rear occupants, bass frequencies produced by the large 6x9 inch cone are more omnidirectional and tend to blend into the cabin, while higher frequencies from the same driver remain more directional and angle toward the headliner.