How to Bridge an Amplifier

Have you ever wondered why some people bridge car amplifiers? Or have you ever tried to figure out the whole process explaining how to bridge an amplifier? Well, if these have been your questions, let me give you some untold answers. Firstly, car amplifiers are bridged so as to increase power. Bridged amplifiers give out more power as compared to the non-bridged channels. For example, a typical amplifier, which is designed to put out an A watts directly into a B impedance in each of the two channels, when singularly bridged, it will put out a 4A watts into that B impedance.

If this happens, it permits you to run effectively a mono signal. That said, it is pertinent to understand that amplifier bridging is importance since it increases the power of the amp output. This then powers your subwoofer; hence, it gives you that perfect sound you need to hear as you drive.

Read our review of best 1-ohm stable amps.

How to Bridge a Two-Channel Amp

Typically, when it comes to bridging a two-channel amp, you will need to utilize the left positive terminal, and also the right negative terminal on that amp. However, you have to pay attention to the manufacturer’s installation, since some manufacturers do it differently. The following image represents an Audison amp, which is designed not to use the outside terminals; however, it can still make use of the left positive to the right negative when it comes to bridging.

What you need to remember always when bridging a two-channel amp, is that the amp will have to split and then share the impedance between the given two channels. This means that a two-channel amp bridged to a 4-ohm load will make the amp recognize only 2ohm, meaning it splits the 4ohms into halves.

Suppose you want an output of almost 600 watts RMS when you bridge to 4-ohm subs load, what would be the best way to go about it? It is simple, for this to work; you need to buy a couple of single voice coil, which are 2-ohms subs. These two, when paralleled, they will give 1-ohm load. One won’t work in our case; therefore you will need to wire them in series and then go ahead to bridge the amp. In this case, your amp will give out 600 watts RMS just as you wanted it to, and it will have been bridged to a 4-ohm load.

The good thing is, in most cases the manufacturers usually provide power ratings, which acts as a revelation to you, to understand the capability of the amp to the subject. To further summarize this, it should be noted that when the amount of power RMS is rated as A, it means the amp will put out RMS x 2 @ say 4-ohms if you successfully bridge to a 4-ohm subs or speaker. Each speaker or sub will be connected to one channel either right or left. If you do this well, you will be successful, and your amp will automatically play a stereo signal.

Bridging a Four-Channel Amp

There is no bigger difference, whether you are bridging a two-channel or a four-channel amp. That means if you master the whole art of how to bridge an amplifier, say a two-channel amp, you can as well get it right when you are given a four-channel amp. However, some caution needs to be observed. For instance, before attempting to bridge your four-channel amp, ensure the amp is bridgeable. This will tell us is there a possibility that other amps are not automatically bridgeable. Nonetheless, it is very easy to understand whether your amp is bridgeable or not. You only need to read you user’s guide.

Generally, this is a hint to keep you going.

If your amp is a four-channel amp, you will notice eight terminals on it; the 1st channel through 4th will always have a positive as well as negative terminals.


Consider those wires coming out of your speaker; at this terminal, connect the positive terminal to the positive speaker lead in channel one. Do the same thing to the negative terminal; connect it to the negative speaker lead in channel two. In the same process, do it to the wires coming from the second speaker. Connect the positive terminal, to the positive speaker lead in channel three; do the same for the negative part; here, you need to connect the speaker to the negative terminal 4.

In the same process, you did when bridging the two-channel amp, apply the same principles here. Connect the wires from speaker to the amp, simply by screwing the wires in between the bottom and top portions of the terminal. Ensure the screws are tightly screwed, this will keep it secure. The image below should explain the whole process;

If you first consult you amp manual, or do some research on how to bridge a four-channel amp, you will always get the revelation of how the whole process occurs. Some specifics to put into consideration is to understand the whole layout of your equipment. This will tell you where the first channel is, both the positive and negative part. Another good way of doing this is to master the steps; like how to first connect the amp to the speaker. This might sound very mild; however, some people fail to get what they want when it comes to bridging because either they don’t know how to connect an amp to the speaker, or even they are just afraid doing it themselves.


Vincent Talbot