BMW 135i Rear Side Panel Speaker Size
The BMW 135i rear side panel accommodates 0.75 inch speakers, 1 inch speakers, and a 4 inch speaker size across the model's production years. Compatible types for these locations include tweeters and midrange units. The specifications cover a range from 2009 to 2013.
| Year | Type | Size (inch) |
|---|---|---|
| 2013 | Tweeter | 1 |
| 2013 | Midrange | 4 |
| 2012 | Tweeter | 1 |
| 2012 | Midrange | 4 |
| 2011 | Tweeter | 1 |
| 2011 | Midrange | 4 |
| 2010 | Tweeter | 0.75 |
| 2010 | Midrange | 4 |
| 2009 | Tweeter | 0.75 |
| 2009 | Midrange | 4 |
Speaker Types
| Type | Description |
|---|---|
| Tweeter | A small driver built for high frequencies, typically from about 2,000 Hz to 20,000 Hz. It adds treble detail and clarity and is usually mounted near ear level or aimed at the listener. |
| Midrange | A driver for the middle of the audible range, typically from about 300 Hz to 5,000 Hz, where vocals and most instruments sit. It is often paired with a tweeter and a woofer. |
Additional Notes
- The rear side panel location in the BMW 135i accommodates 2 distinct speaker sizes simultaneously, indicating a multi-driver configuration within the same mounting zone.
- The 4 inch midrange driver appears across all listed model years at the rear side panel, occupying a fixed mounting position sized for a relatively compact cone driver in an enclosed or semi-enclosed panel cavity.
- A 4 inch driver in a midrange role handles the middle portion of the audible frequency spectrum, roughly covering vocal clarity and instrument body, where cone area is sufficient for output without requiring the depth of a full woofer enclosure.
- The tweeter mounting at the rear side panel is a secondary, smaller position alongside the midrange, a placement that localizes high-frequency dispersion toward the rear cabin occupants.
- The BMW 135i rear side panel accepts a 1 inch tweeter for the 2011, 2012, and 2013 model years, while the 2009 and 2010 model years use a 0.75 inch tweeter in the same position.
- A 1 inch tweeter dome has a larger radiating surface than a 0.75 inch unit, which affects high-frequency dispersion angle and the lower crossover point at which the driver can operate without distortion.
- A 0.75 inch tweeter, being a smaller dome, is typically crossed over at a higher frequency than a 1 inch unit, concentrating output toward the uppermost treble range with a narrower effective bandwidth in the high-frequency region.
- The rear side panel is a structural body panel rather than a door, meaning the speaker baffle depth and rigidity characteristics differ from door-mounted installations, which influences resonance behavior of both the midrange and tweeter drivers.
- Tweeters reproduce high frequencies, generally above 2,000 to 3,500 Hz, and in a rear side panel position, the 1 inch and 0.75 inch variants contribute high-frequency energy into the rear seating area from a fixed, non-moving surface.
- The pairing of a midrange and a tweeter at the rear side panel, rather than a full-range or coaxial driver, indicates a dedicated split configuration where each driver handles a distinct frequency band independently.