Where is the factory amplifier located in a vehicle?

This blog will answer the following questions: where is the factory amplifier located? What is the function of an amplifier? How to bypass a factory amplifier? 

Where is the factory amplifier located in a vehicle?

The factory amplifier that is used to power the speakers or subwoofer in the vehicle is usually located in the following locations in a vehicle:

  • Under the rear seats
  • In the luggage compartment or trunk
  • Built into the audio head unit

Depending on the car manufacturer and the type of audio system in the car, there can be more than 2 amplifiers. The amplifier is located in the above-mentioned places because there is sufficient space and ventilation. Let’s take a closer look at each location

Under the rear seats

The factory amplifier under the rear seats is easy to access and the amplifiers can be easily cooled thanks to the air conditioning system in the passenger cabin. Usually, the factory amplifier is located on the passenger side of the rear seats.

There are also additional components like the rear compartment fuse and relay box located near the amplifier so it is easy to install any aftermarket electrical harness for a bigger amplifier. All the factory amplifiers come with a built-in cooling fan with a heat sink.

The factory amplifier is mounted in a bracket, and the bracket then fits into the compartment under the rear seats. This location is very common in old cars because the fuel tank was located behind the rear seat backrest or under the luggage compartment.

Factory amplifiers located under the rear seats also stay in good condition for a long duration as they are isolated from any moisture. Replacing the factory amplifiers does not need any major disassembly, only the rear seat bench is removed to replace the stock amplifier.

In the luggage compartment or Trunk of the vehicle

This is the most common place for the factory amplifier. The luggage compartment has panels covering the left and right quarter panel area. Many manufacturers use the area behind these panels to mount the amplifiers along with some of the other control units.

The size of the amplifiers can also be big as the luggage compartment offers more space compared to under the seat. The optical lines connecting the amplifier to the head unit are routed from one side of the rear quarter panel. All the speakers are connected to the amplifiers so there are fewer wires going into the head unit located in the dashboard.

Manufacturers can also use the same amplifier to power a subwoofer along with more speakers. One of the downsides of mounting the amplifier in the trunk area is the risk of water entry into the amplifier.

There are rubber seals and plastic rivets that cover the area between the quarter panel and the trunk gate. These seals get weak and hard as the vehicle ages and water falls directly behind the quarter panel through the cracks developed in the seals, damaging the factory amplifier.

Amplifiers can also get hot in the luggage compartment as there can be a lack of ventilation. If the cooling fan malfunctions due to dust build-up, the heat sink cannot dissipate the heat quickly in the luggage compartment.

Built into the audio head unit

If the vehicle is small and consists of 4 to 6 speakers then there is no requirement for a large amplifier. A small amplifier can be integrated into the audio head unit and all the speakers are connected directly to the head unit.

The electrical wiring harness for this setup is simple and inexpensive. There is no need for the optical fiber line connecting the head unit to the amplifier. The head unit is also well ventilated as there are plastic pipes connecting the air conditioning vents to the evaporator housing.

The disassembly of the amplifier that is built not the head unit can be difficult as the center console of part of the dashboard is removed to gain access to the head unit.

The amplifier can only be replaced with the head unit. It is not possible to open the head unit and replace the amplifier or even repair it. 

What is the function of an amplifier in a vehicle’s audio system?

The function of an amplifier in a vehicle’s audio system is to boost or amplify a low-level audio signal generated by the audio head unit. The amplified signal can then be transmitted to the speakers or subwoofers.

If the vehicle is fitted with a premium or high-end sound system then the subwoofer has a separate sound amplifier. A pre-amplifier is also used in some of the aftermarket setups, pre amplifier or preamp is a device that prepares the input signal for amplification and improves the overall sound quality.

It cannot work as a stand-alone amplifier as the only voltage is provided by the pre-amplifier. The power required for the speakers comes from the main amplifier. The amplifiers are distinguished based on a class.

Class A, A/B, and D are some of the different classes in car audio amplifiers. The A/B class amplifier is very popular because of its low power consumption and good sound quality. There are also two different channels in the car audio amplifiers, it is independent audio paths that are used to produce sound output from the amplifier.

The RMS or root mean square of the amplifier refers to the power an amplifier is able to produce that will be supplied to the subwoofer and speakers. If the number of speakers is high then an amplifier with a higher RMS rating is needed. Speakers in the car should not be underpowered.

How to bypass a factory amplifier?

A factory amplifier is not capable of producing high RMS, if you want to add a subwoofer or add a few additional speakers then the factory amplifier will need a bypass. The following procedure can be used to bypass the factory amplifier.

  • Locate the factory amplifier and disconnect the couplers, identifying positive and negative speaker lines from the original coupler.
  • Remove the original speaker lines from the coupler and mark the positive and negative lines, and connect them to a new amplifier.
  • Install the new amplifier and connect it to the audio head unit.

The new amplifier should be mounted in a ventilated space otherwise it overheats and becomes irreparable. 


This blog explained the various positions used for mounting factory amplifiers. Amplifiers can last a long time but due to overheating or moisture penetration, they can stop working resulting in expensive repairs. If an amplifier does not work then no sound will come from the audio system of the vehicle.