How To – Installing a Car Amplifier

How To's

If you want to improve how way music sounds in your car a new amplifier is essential. You could pay someone to install this for you, but it's not a particularly difficult project for anyone even slightly familiar with auto electrics. Why not do it yourself and put the money saved towards new speakers or that subwoofer you've been thinking about?

We're going to talk you through the main steps in installing a car amplifier. Each make and model of car is different, so we can't provide precise instructions for your specific vehicle but we will take you through what you need to do. In doing that we'll address:

  1. Amplifier types and integration
  2. What you'll need (tools and parts)
  3. Installing the amp
  4. Running power
  5. Speaker hookups
  6. Finishing up

1. Amplifier types and integration

If you've done your homework you'll understand how to size your amp for the speakers you intend using. You'll also know that amplifiers come with various numbers of channels and usually two speaker input options. (Our Top list will help you find the best car amplifier for your needs.)

Channels and speaker inputs have a large bearing on how long the install will take. A mono channel amp has only one output and that you'll use for driving a subwoofer. A two-channel amp will most likely be hooked to the front speakers, although you could bridge the outputs to drive the subwoofer.

Likewise, a four-channel amp works with either four speakers or the two fronts and a subwoofer. And if you haven't already figured this out, a five channel works with four speakers plus the subwoofer.

The speaker inputs you'll use depends on whether you're sticking with or replacing the factory head unit. Factory units rarely have pre-amp outputs, so you'll be tapping in to the speaker wires and feeding them to the speaker-level inputs on your amplifier. An aftermarket head unit will probably have pre-amp outputs that feed straight into the amplifier inputs.

However many channels on your new amplifier, and however you feed the signals to it, there's one other part of this project to remember: you will also be running wires from the amplifier out to all the speakers.

2. What you'll need (tools and parts)

In addition to the amplifier itself, go out and buy:

  • Amplifier wiring kit. (These come in various wire gauges. Check the instructions with your amp for the correct size.)
  • T-tap connectors (if that's your preferred wiring connection method.)
  • Zip ties or electrical tape.
  • As for tools, you should have:
  • Pry tools for removing trim pieces.
  • Crosshead and flat-bladed screwdrivers.
  • Pliers
  • Wire strippers
  • Soldering iron (if you prefer the security of soldered joins.)
  • Electric drill
  • Utility knife
  • Socket set

3. Installing the amp

Start by deciding where you want this mounted. An important aspect to consider is airflow for cooling. Amplifiers can get warm and heat is no friend of electronics. Bear this in mind when installing an amp.

The most popular places are:

Passenger side firewall (keeps the wire runs short but access may be difficult.)

In the trunk, against one of the side panels (or the back seat, if that's fixed.)

Under one of the front seats. (This will mean taking the seat out. If it has airbags built-in be very careful how you do this.)

Having settled on a location, remove any trim, mark where you want the holes to go, then drill. (Be careful to check what's on the other side of the panel!) Secure the amp with the screws provided. (From here on we will assume you put your amp in the trunk.)

4. Running power

This section covers installing the power, ground and amp turn-on wires. First, disconnect the battery.

The amp draws currently directly from the battery through a large diameter red cable. Connect the wire to the battery, then install an in-line fuse. This is essential to protect your high-value system!

Thread the power cable through the firewall and into the cabin. You may need to drill a hole for this. If so, try to fit an appropriate grommet.

Remove the kick panel and door scuff panels and run the power wire through to the back seat. Lift out the seat cushion and thread the wire into the trunk.

The amp needs a turn-on wire so it powers-up when the head unit is turned on. This joins to the turn-on output at the back of the head unit, so that has to come out of the dash. Every vehicle is different but this generally means removing the trim pieces on each side of the center console, then unbolting and withdrawing the unit itself.

If the head unit doesn't have a turn-on output, connect to the ignition wire running to the head unit. This can lead to an audible thump as the amp turns on, so an alternative is to buy a line turn-on converter.

Run the turn-on wire back to the amplifier.

Connect one end of the ground wire to the amp and the other to a good chassis ground. Then connect the power and turn-on wires to the amp.

5. Speaker hookups

Run speaker wires from the amp out to the front and rear speakers plus any subwoofer. Disconnect the wires coming from the head unit and fit the new wires to the speakers.

If the head unit has pre-amp outputs, (usually RCA connectors,) connect wires to these and run them back to the amp. Run them down the opposite side of the car to the power and turn-on wires so as to avoid interference.

If the head unit lacks pre-amp outputs, which is usually the case with the factory installed system, you'll need to connect to the speaker wires. You can do this at the head unit itself or out at the individual speakers. (The former allows you to keep the wires away from the power.) Connect your wires using either T-taps or by stripping, splicing and soldering the joints.

At the amplifier plug in wires from the pre-amp outputs. If you're using the speaker wires themselves, these go into the speaker level terminals on the amp.

6. Finishing up

Before replacing all the trim you've removed check everything works. Reconnect the battery and turn the system on. Verify you're hearing sound from all the speakers and that the amp only turns on with the head unit. Set up your amp following the instructions supplied.

Re-install the head unit. Before putting trim back use zip ties or electrical tape to secure all the wires. You don't want them tapping or rattling while you drive! Finish by reinstalling all the trim.

Save money by installing a car amplifier yourself

When upgrading your car audio system you naturally want the best car amplifier you can afford. Why not save some money to put towards the amp by installing it yourself?

Installing an amp is a straightforward job, especially if you've had some previous experience with vehicle electrics. In just a few hours you'll be enjoying deeper, clearer and crisper music from your car's speakers.