how to bridge a 4 channel amp to 1 sub

Steps That Show You How To Bridge a 4 Channel Amp To 1 Sub

Have you been wondering if it is possible to connect a four-channel amp into just one subwoofer? In this article, we show you the best way to bridge a 4 channel amp to 1 sub.

A 4-channel amplifier has been designed to produce mids and highs in the speakers of a car’s doors.

It is possible for you to connect a 4-channel amp to one subwoofer. But to do this, you’ll need a low pass filter for your amplifier.

If you haven’t come across the concept of bridging before, let us briefly explain what this means.

When it comes to bridging, you take two different channels and connect them to each other. This allows you to add the power of each channel’s output on both sides together.

How To Go About Bridging A Car Amplifier

Most car amplifiers will come with a feature known as “bridging” or “bridge mode.” This enables you to combine two channels to make one with much greater power output.

How To Bridge A 4 Channel Amplifier To 1 Sub

Bridging any amp may at first seem quite challenging. However, it becomes a lot easier once you understand the process. Anyone with little or no DIY skills can carry out this task no matter what number of channels their amp has.

This is because the primary process for this task is the same for each channel. Once you have learned how to bridge an amp with two channels, you’ll be able to bridge a four-channel one.

If you’ve got a four-channel amp, you will find that the power output will double after the bridging has been completed. As a result, you’ll be able to drive more power to the speakers in your vehicle.

Even with basic knowledge of the wiring of your vehicle’s audio system, you will find that you can easily bridge an amp with four channels to one subwoofer.

What You Will Need Before You Begin

Black 4 Channel Amp

Before you start this task, there are a few materials and tools you’ll need to carry it out. Below is a list required items:

  1. Four-Channel Amp – You must check that the one in your vehicle comes with a bridging option.
  2. Screwdriver – This is a crucial tool as it will help remove and replace the screws that are attached to the amp.
  3. Wire Strippers – These are another crucial tool as you need them to separate the edge of the wire connected to the sub before you can put it into the amplifier channel.
  4. Speaker Wire – You need this to connect the sub to the terminals of the amplifier.

We suggest you acquire a good amp wiring kit and all the necessary tools before you begin.

Things You Need To Know First Before You Start

There are a few things you need to know before you begin work on bridging a 4-channel amp to a single subwoofer. In order to drive four speakers along with a sub, using a 4-channel amp means you’ll need to make some compromises.

Let’s explain what we mean here: 

You will likely have to give up the car’s front-rear fader control ability as you will not be able to use the two channels for the vehicle’s rear speakers to drive a sub.

However, you may find this next bit helpful when giving up the front-reader fader control in your car.

You can add some inline resistors to the rear speakers to avoid this problem. These will then allow you to drop the volume of these speakers as it will act as a fader.

Also, most car amps can handle speaker loads that go down to 2 ohms per channel. If yours cannot, you’ll need to find another way to do this. It also may mean you will have to buy some additional materials.

Steps You Need To Take To Bridge A 4-Channel Amp To 1-Sub

Step 1 – Find The Speaker Wire Terminals

Before doing anything, you must first find the terminals for the wire that will connect to the speaker on the amp. On a 4-channel amp, there are four connections (we refer to them here as terminals) to which you then connect wire for the speakers. Each terminal on the amp has a positive and negative connection.

Step 2 – Connect The Positive Terminal Of Channel 1 To Sub

Begin by using the wire strippers to remove about 1/2 inch of the insulation covering the wire from its end. You need to take the speaker cable and run it from Channel 1’s positive terminal to the positive terminal on the first subwoofer.

Using the screwdriver, ensure that the speaker wire is clamped securely to the amp’s terminal.

Step 3 – Now Connect Channel 2’s Negative Terminal To Sub

Again, take the wire strippers and remove around 1/2 inch of the insulation covering the end of the speaker wire. Then run this from the negative terminal from the second channel on the amp to the subwoofer’s negative terminal.

Again, you must ensure that the wire is connected securely to Channel 2’s negative terminal by tightening the clamp using the screwdriver.

Step 4 – Repeat Steps One Through to Three Again for Channels 3 and 4

Now you need to carry out steps 1, 2, and 3 again, but this time for Channel 3 and Channel 4 on the amp.

Begin by running a speaker wire from channel 3’s positive terminal to the positive terminal of sub-two.

After this, run the speaker wire from Channel 4’s negative terminal through to sub-two’s negative terminal.

A Word Of Warning

You must be very careful when you bridge an amp with four channels to one sub. If you aren’t careful, you could put a lot of strain on the car’s speakers or alternator.

How Does Bridging Work?

Black Amp

Now, you might be wondering where all this additional power is coming from?

Well, when you combine the negative signal from one channel with the positive signal of another, it effectively helps double the amount that each channel can do on its own when before it only could provide a load of 2 ohm.

Normally, you would find that the maximum wattage amplifiers are able to produce is just 2 ohm. But when you bridge an amplifier, you are helping to optimize the power potential of this system.

What To Do If Amp Cannot Be Bridged

While most amps with any power output can be bridged from two or four channels to one subwoofer can provide more power, some you may find cannot. This is especially the case with much older amps.

It is worth looking through your car’s amplifier manual to see whether it comes with a bridging amp feature or not.

If not, then you have a couple of options available to you:

You can get a new amp that will connect to the subwoofer.

Or, you can wire up one small sub to each of the rear channels. The problem with this option is that the subs will need more power to drive them, and they may not sound as good.

Will Bridging An Amp Change The OHM Load?

When you bridge an amplifier, you cut each channel in half, as only one load is being driven to each instead of two.

The OHMs per channel load will not change. It remains the same. What changes are related to the power output from each channel? This will be less as the wattage between the channels is split up before being put together again to drive the subwoofer.

Let’s Wrap Things Up

When it comes to carrying out the task of how to bridge a 4 channel amp to 1 sub, it is crucial to start off on the right foot. Have your tools ready and close at hand before you get to work.

Also, before you even think about doing this kind of work on your vehicle, you should first check if there is even an option that allows you to bridge the amplifier. You don’t want to waste time and money if this is not possible.

As long as you keep the points discussed above in mind, you should be able to carry out this work quickly and easily. Of course, you could always arrange for a trained mechanic to complete this task, but it might be more cost-effective to do it yourself.

Why not let us know what you thought of this article and how helpful it was if you decide to try out these tips for yourself. Simply leave us your comments below.