How To Bridge A 4 Channel Amp To 1 Subwoofer

Norvan Martin
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If you have a four-channel amp and just one subwoofer and wondering if you will be able to have the connection, do not worry. In this article, we explain how to wire a 4-channel amp to one subwoofer.

If you have 2 subwoofers, check out our guide on how to bridge a 4 channel amplifier to 2 subwoofers

Normally, 4 channel amplifiers are designed to produce mids and highs for door speakers for the front and rear of the car. Connecting a 4 channel amp to a 1 subwoofer is possible, however, you will need a Low Pass Filter on your amplifier. Remember, your subwoofer uses frequencies passed by the low pass filter.

Bridging The Amplifier: In looking at how to connect a 4 channel amplifier to 1 sub, you may have come across the concept of bridging. Basically, bridging means that you take two channels and connect them together to add together the power outputs from both sides.

Example of Bridging: As an example, let’s say you have a 4 channel amp that has 2 channels front rated at 150 RMS each. If you bridge them together, you will end up with 300 watts RMS per channel after being jumped (connected together). It’s similar to how you would wire two amplifier channels to one speaker. If your subwoofer is rated at 300 watts, then this will be sufficient to power it. However, 150 watts would not power it.

How To Bridge A 4 Channel Amp To 1 Sub

Bridging any kind of amp may first seem critical and tough. However, once you know the accurate process, it becomes very easy and anyone can DIY no matter how many channels your amp comes with.

This is because the main process is the same for every channel and once you learn how to bridge a two-channel amp, you will be able to bridge a four-channel amp too.

If you have a four-channel amp, you can easily double its power output by bridging it. This way, you will be able to drive much more power to your speakers.

With the basic knowledge of car audio wiring, you can easily bridge a four-channel amp.

How To Bridge A 4 Channel Amp To One Sub

What You Need

Before you begin the process, you need to have some materials to work with. Here’s a list of what you need:

  • Four-channel amp: check if your four-channel amp has a bridging option.
  • Screwdriver: this will help with hooking up the screws attached to the amp as you have seen in the procedures above.
  • Wire stripper: this will be used to separate the edge of the wire before putting it into the amplifier channel.
  • Speaker wires: the speaker wires will be needed for connecting to the terminals of the amplifier.
  • Manual: before you well understand the connection process, you will need to go through the manual to understand whether the amp can be bridged or not.

The most common way to have your amp bridged is to connect it to a pair of 4-ohm subwoofers. Follow the procedure below to bridge the amp:

Step 1: Locate The Speaker Wire Terminals

Locate the terminals of the speaker wires on the amp. You should be able to see four-speaker wire terminals or channels. The terminals consist of both positive and negative terminals. Locate The Speaker Wire Terminals on an amplifier

Each of the terminals has a screw-down clamping system that helps to hold the speaker wire in place.

Bridge A 4 Channel Amp To 1 Sub

Step 2: Connect The Positive Terminal Of Channel One To The Subwoofer

Use a wire stripper to strip about ½ inch of insulation from the ends of the wire. Run the speaker wire from the positive terminal of channel one to the positive terminal of the first subwoofer.

Run the speaker wires from the positive terminal of the first channel to the positive terminal of the first subwoofer.

Ensure the speaker wire is securely clamped down using a screwdriver in the amp’s terminal.

Step 3: Connect The Negative Terminal Of Channel Two To The Subwoofer

Again, use a wire stripper to strip about ½ inch of insulation from the ends of the wire. Run the speaker wire from channel two’s negative terminal to the first subwoofer’s negative terminal.

Clamp down the speaker wire and ensure the connection is secure by tightening the terminal screw-down clamp.

Step 4: Repeat Steps One And Two For Channels Three And Four

Now repeat steps two and step three for channels three and four.

Run a speaker wire from the positive terminal of channel three to the positive terminal of subwoofer two. Finally, run the speaker wire from channel four’s negative terminal to subwoofer two’s negative terminal.

Here is a guide on how to connect your amplifier to your subwoofer if you don’t know how.

How To Wire A 4 Channel Amp To 4 Speakers And A Sub

Although a four-channel amp provides greater flexibility for your audio connections, they are mainly used with four-speaker or two speakers and a subwoofer, not both.

However, you can still wire a 4-channel amp to four speakers and a sub. Fortunately, you can do this with three methods.

Method 1: Using A Four Channel Amp Rated 2 Ohms Stereo, 4 Ohms Bridged

This is the most common setup. Each front amplifier channel is wired with two speakers in parallel for 2 ohms per channel.

The subwoofer is then connected to the two rear channels. Remember to check the amp’s bridged wiring instructions as not all amps use the same bridged wiring.

Method 2: Using A Fourfour Channel Amp Rated For 2 Ohms Stereo, 2 Ohms Bridged

In this method, each front amp channel is wired with two speakers in parallel for 2 ohms per channel. The subwoofer can be either 2 or 4 ohms.

Method 3: Using A 4-Channel Amp Rated For 4 Ohms Minimum Speaker Load

Each of the front amp channels is connected in parallel to 2 speakers for 4 ohms per channel. You will need resistors to keep the total speaker load at 4 ohms per channel.

4 Channel Amp Wiring Sub And 2 Speakers

You can wire two speakers and a subwoofer to a four-channel amplifier. You will, however, need to bridge two of the channels to power the sub while the two speakers are connected to the other two channels.

How To Bridge A 4-Channel Amp To 2 Speakers And 1 Sub

This is an easy connection. Wire the two speakers to the front channels of the amp. Then, wire the subwoofer to the rear channels by bridging the channels to the sub. The channels can, however, be used interchangeably with the speakers going to the rear channels and the sub to the front ones.

Can You Use A 4 Channel Amp For 1 Sub

As we already said, you can easily bridge two outputs to the sub and leave the other two channels for the front speakers.

How To Bridge A 4 Channel Amp To 2 Subs

Bridging a four-channel amp to two subwoofers is an easy process. Just like we have discussed above, you can bridge your four-channel amplifier to two subs easily by following the process we have outlined below.

Step 1: Strip The Wire

Remove about ½ inch of insulation from the wire with the wire stripper.

Step 2: Fix The Positive Wire

Put the red wire into terminal one, to the positive option of the first channel.

Step 3: Fix The Negative Wire

Put the black wire into terminal four, to the negative option of the second channel to complete the connection of the first speaker.

Step 4: Connect Speaker Two

Repeat steps 1 and 2 to connect speaker two through terminal five and terminal eight of the third and fourth channels.

Tighten the screws and check the connection. Ensure the connection is secure and there are no loose wires.

To learn more, check out our complete guide on how to bridge a 4 channel amplifier to 2 subwoofers

What Happens if You Bridge a Non-Bridgable Amp?

You can’t bridge a non-bridgable amp. You’ll need to make sure the amps you purchase and install are compatible with your stereo system, as well as each other.

If they aren’t bridgable, you won’t be able to do anything but replace them both.

You can also look into buying an aftermarket receiver that offers additional channels of amplification for subwoofers (or “satellite speakers”).

When Should I Bridge My Amp?

When you bridge the channels, this increases the power output.

To power a subwoofer, most amplifiers are bridged to combine two channels into one subwoofer or four channels into two subwoofers.

Therefore, this is usually the best time for you to consider bridging your amp.

Does Bridging an Amp Change the OHM Load?

When you bridge an amplifier, you are essentially using it as a mono amp.

That means the impedance on each channel is cut in half because there’s only one load being driven instead of two.

You won’t change your OHM load when bridging – that stays the same at four ohms per channel (two channels x two ohms = eight total).

What changes with this setup is maximum power output by splitting up the wattage between both channels and putting them together to drive one speaker or subwoofer.

At the end of the day, however, note that the best option for a subwoofer is to get a monoblock amplifier. A monobock amp is better for a suwboofer than a 2 channel or 4 channel amplifier

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Norvan Martin is the founder of He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin