Ford Sierra Rear Side Panel Speaker Size
The Ford Sierra rear side panel accommodates a 5.25 inch speaker size and 4x6 inch speakers, with each location supporting one of these 2 distinct sizes depending on the model year. Compatible types across the audio system include full-range units and midbass replacement drivers. These specifications cover the range of years from 1982 to 1990.
| Year | Type | Size (inch) |
|---|---|---|
| 1990 | Midbass / Full-Range | 5.25 |
| 1989 | Midbass / Full-Range | 5.25 |
| 1988 | Midbass / Full-Range | 5.25 |
| 1987 | Full-Range | 4x6 |
| 1986 | Full-Range | 4x6 |
| 1985 | Full-Range | 4x6 |
| 1984 | Full-Range | 4x6 |
| 1983 | Full-Range | 4x6 |
| 1982 | Full-Range | 4x6 |
Speaker Types
| Type | Description |
|---|---|
| Midbass | A driver tuned for upper bass and lower midrange, roughly from 80 Hz to 500 Hz. It has longer cone travel than a full-range unit, which supports stronger bass in doors and panels. |
| Full-Range | 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 Ford Sierra rear side panel location accommodates 2 distinct speaker sizes across its model years: 5.25 inch (round) and 4x6 inch (oval).
- The rear side panel is a fixed structural cavity within the vehicle's C-pillar or quarter panel area, meaning available depth and baffle dimensions are determined by the body panel itself rather than by adjustable mounting hardware.
- A 5.25 inch round speaker occupies a circular mounting footprint, and the rear side panel cutout in the Ford Sierra accommodates this diameter for the 1988-1990 model years.
- The 4x6 inch oval format fitted in the 1982-1987 model years reflects a wider but shallower footprint than a 5.25 inch round unit, suited to panel cavities where horizontal space exceeds vertical or radial depth.
- Oval speaker formats such as 4x6 inch produce a slightly asymmetric dispersion pattern compared to round drivers, which affects how sound radiates within the rear cabin area.
- A 5.25 inch round driver, when used as a midbass speaker in the Ford Sierra rear side panel, handles lower midrange and upper bass frequencies - typically spanning approximately 80 Hz to 500 Hz - while offloading high-frequency reproduction to a separate tweeter elsewhere in the system.
- When a 5.25 inch driver is configured as a full-range speaker in the rear side panel, a single driver handles a broad frequency span from bass through treble, often achieved through a cone and whizzer cone or a coaxial tweeter integrated into the driver itself.
- The 4x6 inch format in the rear side panel is listed exclusively as full-range, meaning a single driver is responsible for the entire audible frequency output from that location across all years where that size applies.
- Full-range speakers installed in a rear side panel position radiate sound toward the cabin interior from a rearward and lateral angle, which influences how direct and reflected sound reach front and rear seat occupants.
- The rear side panel placement positions drivers away from the primary listening axis of front-seat occupants, making the location more relevant to ambient and rear-seat audio reproduction than to direct high-frequency delivery at ear level.