The BMW 535is rear deck lid accommodates a 4x6 inch speaker size. Full-range units represent the compatible audio type for the system. These specifications cover the 1988 model year.
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 location in the 1988 BMW 535is positions speakers within the horizontal shelf behind the rear seating, a surface that typically places drivers at an angle aimed toward the cabin interior and headliner.
Deck lid installations are generally flush-mounted into a flat panel, requiring speakers with a mounting depth shallow enough to clear any structural bracing or trunk cavity beneath the panel.
A 4x6 inch oval speaker, as specified for the BMW 535is rear deck lid, produces a cone surface area larger than a 4 inch round but in an elongated footprint, allowing a wider mounting profile to fit within the lateral dimensions of a rear deck without requiring the depth clearance of a larger round driver.
The oval geometry of a 4x6 inch driver distributes cone excursion across a non-circular surface, which affects how the driver reproduces midrange frequencies compared to a circular cone of equivalent area.
Full-range speaker types are designed to reproduce the entire audible frequency spectrum from a single driver, covering bass, midrange, and treble frequencies without the need for a dedicated crossover network or supplemental tweeters.
In a rear deck lid position, full-range drivers handle ambient and spatial sound reinforcement for the cabin, as the location disperses audio energy toward the rear headliner and reflects it into the passenger compartment.
The 4x6 inch size at the rear deck of the 1988 BMW 535is is compatible exclusively with full-range type speakers according to the specifications, meaning no component or coaxial multi-driver configurations are listed for that position.
A 4x6 inch full-range driver in a deck lid mounting relies on the enclosure effect of the trunk cavity below the panel, which can influence low-frequency output depending on the volume and seal of that cavity relative to the driver.