The Cadillac Brougham rear deck lid accommodates a 6x9 inch speaker size across all listed model years. Full-range units are the compatible type for the audio system at that location. These specifications cover the years 1987 through 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 deck lid is a horizontal surface spanning the width of the trunk area, positioned at the base of the rear window, and speakers mounted there fire upward into the cabin through grilles or perforations in the deck surface.
The 6x9 inch oval format is among the largest standard speaker dimensions used in automotive applications, with the elongated shape allowing for a larger cone surface area compared to a circular speaker of similar installation depth.
Greater cone surface area in a 6x9 inch driver enables more air displacement, which contributes to stronger low-frequency reproduction in an enclosure-limited environment such as a rear deck panel.
The rear deck lid position places speakers at the rear of the passenger cabin, a location that tends to create a rear-biased soundstage when speakers in that position operate without front-stage reinforcement.
Full-range drivers are designed to reproduce the audible spectrum across low, mid, and high frequencies within a single driver unit, relying on cone material, surround compliance, and tweeter integration to handle the full bandwidth.
In the Cadillac Brougham rear deck lid, a full-range 6x9 inch speaker handles bass, midrange, and treble simultaneously, which is a function of the full-range type rather than a divided crossover network.
The rear deck lid mounting surface is typically rigid sheet metal, and the speaker's basket must interface directly with that surface, making the outer frame dimensions and bolt pattern of a 6x9 inch driver critical to fitment.
A 6x9 inch full-range speaker mounted on a rear deck fires toward the headliner and relies on reflected sound to reach front-seat occupants, meaning the high-frequency dispersion characteristics of the full-range driver affect how treble content travels through the cabin.
Full-range drivers in rear deck locations are subject to acoustic reinforcement from the trunk cavity below, which can act as a partially sealed enclosure that influences the low-frequency response of the 6x9 inch driver.