How to Hook Up a 4-Channel AMP to Front and Rear Speakers

Hooking up an amplifier with new speakers will give you the best possible music system for your car. It may seem mechanical and tough, but it is very simple if you have all the tools and the right instruction manual.

Why Should You Upgrade The Amp?

The pre-installed sound system will not give you the best quality of sound volume or power, and that is why you must upgrade the car’s amplifier with the new speakers; it will help you get the best quality sound with reduced distortion.

4 Channel Amp

A 4-channel amplifier converts the weak audio input into 4 channels or speakers. The channels are the connectors at the back of amplifiers that power the speakers. One channel connects with one speaker, and a bridged channel can double the power output.  

Can You Hook Up Many Speakers To A 4 Channel Amp?

If you have a 4-channel amp, you can use two extra channels for two more speakers by bridging them. You can use this double or bridged power for a subwoofer. So, you can use a4 channel app for 4 speakers or a subwoofer along with two speakers. You will also need another RCA cable to connect the amp.

The amp and speakers hooking up is simple, and you must first make a list of the material you need for the entire process. The wiring kit must have a good quality remote wire, a ground wire, 2 RCA cables (18 inches each), crimp rings for terminals, a positive wire, a fuse, and a fuse holder.

For the wiring process, you need a lot of speaker wire- more than 10 feet, crimp connectors, crimper tool, pliers to cut the wires, a meter to measure the voltage, and plenty of wire ties. 

Hooking Up A Factory Radio Without RCA Inputs

Some built-in stereos do not have RCA inputs and may need line-level converters. This converter converts the signal from the stereo so that the amp can send the right signal via the RCA cables. Buy the best quality line converter so that the output leads to the best sound quality. 

If your car system has speaker level inputs, you do not even need to buy the line level converter. You can hook up the amp with the speakers taking care of each channel’s positive and negative wires. These are mentioned in the harnesses, and then you can pluck them back into the speaker and the amplifier. 

Hooking up speakers with RCA connections

RCA connections or line-level connections provide the best sound quality, and they are very easy to install. The RCA cables come with two channels connecting the front speakers and the rear ones. 

The speakers must be connected properly to ensure that the amplified signal is clear. 

You can keep all the wires around the hardness in the back of the stereo. But remember that the wires are connected through the amplifier and not directly to the stereo. 

Use an adequate length of wires and crimp connectors to ensure that the connections are secure. Use the color-coded wiring of the system. The RCA cable and the line level converters can be simply connected to the front and rear speakers and mark them as front or rear to differentiate.

If your existing stereo has only two channels to connect with your 4-channel amp, you need an additional adaptor cable that would be Y-shaped. Install a Remote-On Amp Wire By connecting the wire to the radio and bundle with the other wires. 

The Amplifier

Most people prefer to keep the amp in the trunk or the car’s rear side. The positive battery wire goes the car to the engine compartment through a small hole or gap. The wire must be connected using a crimping terminal to secure it.

Place the fuse holder near the battery and prevent a short circuit. The positive wire must be connected to the battery after ensuring that the area is clean and kept in place.

It would help if you connected the ground wire from the amp to the metal near where you want to mount it again using a crimping terminal. Now bundle all the wires and cables and bring them back to your amplifier in the back of the car. 

Mounting the amplifier.

You can either mount the amplifier to the subwoofer box itself or have another board attached to the car. The board is usually preferred as the subwoofer vibrations do not reach the amp.

You can make a mounting board using cardboard and carpet fabric or ask a mechanic to make it for you and mount the amp on brackets or stereo straps.

Connect the wires to the amp.

Switch off the power and remove the fuse before connecting any electrical wires. Check the current before connecting the wires to the terminals of the amplifier. Then secure all the wires. Use zip ties and crimp ring terminals to secure each wire to the amplifier.

Now it is time to check the functioning of the amplifier. Put back the power fuse and turn on the car and stereo. You can use a digital meter to check the power in the amp and the wires if the sound is distorted or not clear. Check the grounding wire connections, fuse, and voltage if you cannot find any issue. 

We also need to set up crossovers that will help to reduce distortion properly. The crossovers need a control between 50 to 60Hz so that the quality of the sound is good and there is no distortion even at higher volumes.

Test the amp system and reset the controls in a way that you like. The bass, treble, and gain settings must be exactly how you want to hear those sounds. 


A 4-channel amp is essential to get the best quality sound in the car. If you are a music aficionado, then you know that the slightest distortion can make the music sound unpleasant. Hook up the 4-channel amplifier to the speakers and subwoofers correctly and securely and enjoy the music. 

Liam Dare

As CEO of, my passion for the automotive world motivates me to build online businesses that provide information and entertainment to users. I am proud to contribute in a positive way to the automotive community.