Audi A4 S4 B9 Boot Trunk Subwoofer Rear Bass Speaker Audio Unit 8W9035382B

Visual condition of the part

The product shows signs of use visible in the photos.

Audi A4 S4 B9 Boot Trunk Subwoofer Rear Bass Speaker Audio Unit is an original audio component designed for installation in the rear of the vehicle, within the trunk area. This factory subwoofer has been engineered for precise low-frequency reproduction, ensuring a cohesive sound profile with the rest of the audio system speakers. Thanks to its design tailored to the Audi A4/S4 B9 body, it serves as a functional service solution when replacing a damaged or worn-out component.

Specifications and technical data

• SKU: 8W9035382B
• Mark: Audi
• Condition: Used
• OEM Part Number: 8W9035382B
• Substitutable numbers: 8W9035382B, 8W9 035 382 B, 900164B456
• Location on the vehicle: Rear
• Category: Other Starters, Alternators, ECUs & Wiring

Purpose and function in the audio system

The subwoofer mounted in the rear of the trunk is responsible for generating low tones that complement the frequency response of standard door speakers. In practice, this means:

• more distinct and controlled bass during daily driving,
• better music clarity at higher volume levels,
• maintaining the factory sound characteristics intended by the manufacturer.

By being matched to the specific Audi A4/S4 B9 platform, the subwoofer works seamlessly with the factory amplifier and wiring, allowing for the acoustic consistency of the entire system to be maintained.

Design tailored to the rear of the vehicle

Placement in the rear trunk zone allows for effective use of the vehicle's acoustic space. The speaker has been designed to:

• occupy as little usable space in the trunk as possible,
• operate stably even during prolonged use,
• limit unwanted resonances and vibrations of upholstery elements.

The factory design of the subwoofer promotes the preservation of the original trunk ergonomics, without the need for additional enclosures or interior modifications.

Characteristics of the used component

The offered speaker is a used component, which in practice means it has been removed from a vehicle and verified for its suitability for further use. This type of solution is beneficial when you want to:

• maintain the original audio system specification,
• reduce repair costs compared to purchasing a new sub-assembly,
• avoid issues with fitting non-factory aftermarket replacements.

A used subwoofer allows you to restore proper audio system operation without interfering with the factory electrical installation and without the need for adapting additional components.

Practical installation and operational tips

When replacing the subwoofer in the trunk, it is worth paying attention to several technical aspects:

• checking the condition of the wiring harness and connectors in the rear of the vehicle,
• proper seating of the speaker in the factory mount,
• checking the tightness of the enclosure for any unwanted vibrations.

Careful installation allows you to fully utilize the acoustic capabilities of the component and reduce the risk of subsequent failures resulting from mechanical looseness or improper connection.

If you are planning a comprehensive repair or upgrade of the rear zone in your Audi and need other elements from the same group, such as additional speakers, audio modules, or wiring, check out the available parts in the Other Audi category.

Support in selection and development of the Audi audio system

The trunk subwoofer is an important element in the context of expanding or restoring the factory sound system in Audi models. If you are interested in a broader look at the differences in design and equipment of the brand's sports versions, it is worth reading the material describing the characteristics of engines, brakes, and chassis – you will find it in the article Audi RS vs other models – what is hidden under the hood and chassis?.

When selecting used audio elements and other components, practical tips regarding verification of compatibility and manufacturer markings can also be helpful – they are discussed in more detail in the guide how to professionally select used car parts, based on the experience of specialists dealing with OEM components.