The BMW 524td rear deck lid accommodates a 4x6 inch speaker size, with both years in the specifications supporting identical 4x6 inch units. Compatible types for the audio system are limited to full-range replacement speakers. The specifications cover the years 1985 to 1986.
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 top of the trunk compartment, behind the rear passenger seating area, which places speakers in a rearward-facing or upward-radiating orientation relative to the cabin.
A 4x6 inch oval speaker format is the specified size for the BMW 524td rear deck lid across both listed model years.
The 4x6 inch oval driver has a cone surface area larger than a round 4 inch driver but smaller than a round 6.5 inch driver, making the format a compromise between bass extension and spatial efficiency in shallow or constrained mounting cavities.
Oval speaker formats like the 4x6 inch are commonly used in deck lid and door locations where rectangular or irregular cutouts limit the use of standard round drivers.
The rear deck lid position places the speaker baffle facing upward toward the rear window glass, a surface that can reflect and diffuse sound forward into the passenger cabin.
The mounting depth available in a deck lid is typically shallow due to the structural panel and trunk space below, which constrains the maximum excursion and magnet size of compatible drivers.
Full-range is the only compatible speaker type specified for the BMW 524td rear deck lid, meaning a single driver at the location handles the entire reproduced frequency spectrum without a dedicated crossover network directing separate bands to separate drivers.
A full-range driver reproduces low, mid, and high frequencies from a single cone and tweeter or whizzer cone assembly, relying on the driver's natural rolloff characteristics rather than a passive crossover to manage frequency distribution.
In a rear deck lid position, a full-range driver handling high frequencies benefits from the reflective surface of the rear window, which can help distribute treble content toward the front of the cabin.
The bass output of a 4x6 inch full-range driver at a rear deck location is limited by the small cone area and shallow mounting environment, which restricts low-frequency excursion and acoustic output below approximately 80 to 100 Hz.