How To Bridge A 4 Channel Amp To 2 Subs

Norvan Martin
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If you have 2 subwoofers and want to get maximum power from your amplifier, bridging a four-channel amplifier is a good option. In this article, we look at how to bridge a 4-channel amplifier to 2 subs.

If you only have one subwoofer, check out our guide on how to bridge a 4 channel amplifier to 1 subwoofer

Bridging A 4 Channel Amp To 2 Channels For 2 Subs

Bridging any kind of amplifier may initially seem very difficult. However, once you learn the process, the process becomes seamlessly easy.Bridging A 4 Channel Amp To 2 Channels For 2 Subs

The bridging process is the same and applies to all types of amplifiers. If you learn to bridge a two-channel amp, bridging four-channel amplifiers becomes much easier.

Amplifiers may commonly have channels of up to four. If you intend to bridge a four-channel amplifier, you will follow the step-by-step procedure we have outlined below.

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:

The Bridging Process Of A Four-Channel Amplifier

Since you already have the right materials, you can begin the process. You must however understand the location of the positive and negative channels of the amp.

To avoid any doubts, see the clarification of the channels below.

Bridging A 4 Channel Amp To 2 Subs Circuitry

Channel 1

Channel 1 of the amplifier has two terminals – positive and negative. The first is the positive one, and the second is the negative one.

  • Terminal 1 – (+ve)
  • Terminal 2 – (-ve)

Channel 2

This channel has similar terminals as channel 1. The terminals are marked as:

  • Terminal 3 – (+ve)
  • Terminal 4 – (-ve)

Channel 3

This channel is also similar to channels 1 and 2. Besides, the terminals are the same.

  • Terminal 5 – (+ve)
  • Terminal 6 – (-ve)

Channel 4

Channel 4 is the last in your four-channel amp and has two terminals similar to the other channels. The positive and negative terminals are also positioned the same way as in the previous three channels.

  • Terminal 7 – (+ve)
  • Terminal 8 – (-ve)

From the description of the four channels above, it is now clear where to find the positive and negative terminals.

Step 1: Strip The Wire

To strip the wire, cut both the edge of the wire to remove about ½ inch of insulation of the wire with the wire stripper. This should expose the section of the wire to make the connection easy.

Step 2: Fix The Positive Wire

Now, move the screw of terminal 1, of channel 1 to the anticlockwise direction. 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 sub.

Step 4: Connect Speaker Two

Repeat steps 1 and 2 to connect subwoofer 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.

How To Bridge An Amp With 2 Subs

Most amplifiers when bridged, cannot provide enough power to drive a sub with an impedance of fewer than 4 ohms. To bridge an amp with 2 subs, you will need to run them in stereo which does no good for sub duty.

Wire the amplifier with each subwoofer on separate bridged channels and expect good results.

For the many amplifiers, the right negative and the left negative are the primary signal outputs. You will need to first locate the amp terminals before bridging a two-channel amp or a four-channel amp.

You should however avoid wiring the subs in series as that will not deliver much volume and power from the system.

What’s The Best Way To Bridge A Subwoofer

Generally, the term “bridging subwoofers” may be a bit misleading. In a good sense, the phrase refers to wiring a sub to a bridged amp to drive deeper bass to the sub. It is important to learn the ins and outs of the bridging circuit as any problem can easily damage your devices.

Step 1: Prepare To Wire The Subs To A Bridged Amp

  • Locate the specifications of your device such as the output power (watts), minimum impedance (ohms), terminal locations, and labels among other specifications. Although some car stereo amps work well at 2 ohms, the majority of amplifiers are more stable at 4 ohms when bridged.
  • Write down the necessary values such as the speaker power rating, amp bridged output power, speaker impedance, and the amp bridged minimum impedance.
  • Calculate the total impedance of all the speakers. To ensure that the total impedance value of your speakers is equal to or closer to the minimum impedance of your amp on each channel, add together the speaker impedance number for all the available speakers.
  • Calculate the power required by each speaker based on the total impedance together with the power output of your amplifier.
  • Verify that the amp has enough power to drive the subs. Check that the speakers are labeled in wattage and the output wattage of the amp should be equal to or more than the sum of all your speakers.
  • Do not wire the equipment while on the mains. Unplug them first or disconnect the battery terminals if you are working on the car stereo.

Step 2: Wiring Dual Subs To A Bridged Amp

  • Wire the amp to the first subwoofer in a similar way to wire a single sub.
  • Connect the two subs in series or parallel.
  • Wire the second subwoofer to the first sub. You can use series or parallel connections.
  • Connect the second sub’s coils similarly as you connected the first.
  • Complete the connection by running a wire to connect the negative terminal of the second sub to the negative bridged terminal of the amplifier.

How Do I Connect 2 DVC Subs to a 4 Channel Amp?

To connect two subwoofers to one amplifier, you will need three speaker cables.

Two of the speaker wires are for connecting your subs in mono while the third wire is used as a ground wire that connects both amps into an electrical system.

This type of setup works well if you have only one space on your amp for input and output connections because it requires less wiring than having separate inputs/outputs on each channel.

How to Bridge a 4 Channel Amp to 2 Subs at 4 ohms

The best way to bridge a 4-channel amp to 2 subs at 4 ohms is to use a single channel of an amplifier that can be bridged.

Next, connect the positive and negative wires from each sub to the corresponding speaker output on your amp.

Once this is done it will allow you to have more power being delivered to these two subs at once.

The only thing left would be connecting the ground wire for each sub.

This way, all four channels will power two subs at once but they will be sharing amps channels. So, don’t expect both of them to perform similarly because they won’t!

However, they’ll still bump harder than having just one running on its channel before doing the bridge process.

At the end of the day, however, note that the best option for a subwoofer is to get a monoblock amplifier. A monoblock amp is better for a subwoofer 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