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4 Channel Amps: Bring On The Power

Four channel amplifiers are used to power your car’s speakers. The most common setup is to power 4 speakers, one off of each channel. However, depending on your speakers and the amplifier, you can power up to 8 speakers, or you can power a pair of component speakers with one channel dedicated to the woofer and the other channel dedicated to the tweeter. But what is special about 4 channel amplifiers?

4 channel amps are very popular. The advantage of the four-channel amplifier vs. your radio is that the amplifier provides significantly more power. The amplifier’s power is cleaner than the output from your radio, and the amp has better crossover and filter controls. 

If you want great sound from your car’s speakers, adding a 4 channel amplifier is one of your best options. In this guide, we are going to take an in-depth look at 4 channel amps. We will explore what they do, what they are used for, as well as what the best model 4 channel amp currently is. 

What Does a 4 Channel Amp Do?

4 channel amps, as you may have already guessed, are extremely similar to 2 and 5 channel models. They do share a few differences, however. They too use a single power supply to provide a higher output voltage, stepped-up from 12V, to drive the speakers with more power than is possible with only 12V like factory systems.

Following this, they contain 4 independent audio amplifier sections which these days are normally designed in such a way that each channel pair can be bridged for additional power if desired. Some have features such as a bass boost control that may be used only for 2 of the 4. 

This varies from brand to brand and model to model, so it’s important to be sure before buying.

A 4 channel amplifier is basically the same as a 2 channel amplifier with 2 additional audio channels in a more compact design. It’s important to note that some, however, do have special features (such as a bass boost option) available only on 2 of the 4. 

A 4 channel class A/B amp has quite a few transistors on the left-hand side to drive the outputs. That’s one reason it’s longer than a 2-channel amp alone.

4 channel amps are very flexible and offer a number of advantages over other models. You can configure (and easily reconfigure) many different types of sound systems in your car.

For example:

  • A 4 speaker system (front/rear)
  • Front full-range (2 ch.) + bridged subwoofer
  • High pass/low pass component speaker setup, with tweeters on channels 1-2 and woofers on 3-4
  • Front speakers with a high-pass crossover and front woofers on low-pass channels

When adding a 2nd amp, the possibilities are even more extensive! Remember that it’s ok if you don’t use all channels present in an amp – there’s no harm in having a speaker output disconnected.

There are a number of basic features that although are very common in modern amplifiers you should always verify they’re present before purchasing, rather than assume.

I recommend an amplifier with built-in high and low-pass crossovers. The best ones are adjustable although that’s not a big deal in everyday use. But it does make it easier to tailor the sound to your liking and it’s especially true when using the high-pass feature to block lower end bass from speakers that can’t handle it in order to prevent distortion and get more clean high volume sound.

Ideally you’ll also have an amplifier with good terminals that are easy to connect power and speaker wire too but stay nice and tight after installation.

When choosing an amplifier, you should also consider the power unit you have. The two main types of power ratings that amps use are peak power and Root Mean Square Power (RMS). RMS measures the continuous amount of power that a car amplifier uses to deliver power to your speakers. When using RMS, you should ensure that the power of your subwoofer and speakers equals the power of your amplifier. 

If your amp’s RMS power is very powerful, it can damage your speaker.

For example, if the amp features 60 watts of power per channel. In that case, every channel of the amp can be able to support or power up a standard subwoofer. On the other hand, if the sub cannot stand 60 watts, you may still get some music, but it may start getting distorted and eventually damage the sub.

Your amp’s RMD depends on your speaker’s highest RMS output rating. For example, a 50 watts speaker needs a 50 watts output RMS capacity channel. However, if you have a big car and need more volume, you should ensure you get 75 watts RMS per speaker.

Peak power is higher than RMS power. It shows how many watts the amp has for short and abrupt increases in volume. Whether you choose a 2 channel amp or a 4 channel amp, it would be best to choose one that can deliver power equal to twice your speaker’s continuous power rating. You should also consider testing the amplifier to ensure that it has the proper voltage. 

4 channel amp in a car

2 Channel Amp Vs. 4 Channel Amp: Which One Is Better?

Car stereo systems deliver about 10 watts RMS power channel or output, which is very low. To convert this to some rocking music, you will need to upgrade your system by adding quality after-market speakers or subwoofers and a powerful amp to power them.

The number of channels an amp has is one of the major factors you should consider when buying an amp. Several cars use either a 2 channel or a 4 channel amp. It is important to note that the difference between 2 channel vs. 4 channel amp is the number of the channels they have and the number of subwoofers or speakers they can be connected to.

A 2 channel amp can connect to fewer subs and speakers when compared to a 4 channel amp. Both these amps are in the class A or B category. They are designed to power up tweeters and mid-bass amps. To help you determine which amp is better for you, here is what you need to know about 2 channel vs. 4 channel amp. 

When it comes to 2 channel vs. 4 channel amps, the ideal amplifier for your car depends on the number of subwoofers and speakers you have and their wattage. Each channel on the amplifier acts as a separate power source for each after-market device. This means that each channel on your amp can connect to one subwoofer and one speaker.

If you have two high-output front speakers, a 2 channel amp may be the perfect choice for you. However, if you have an additional pair of speakers on the rear, you will have to add two additional channels to your amp; hence a 4 channel amp would be more applicable. 

This way, you can use both rear and front speakers and subs and get good sound quality. If you are a rock lover and want to achieve a boom-blasted explosion in your car, you can install both the 2 channel and 4 channel amps.

How To Bridge a 4 Channel Amp

When installing a car amplifier, you need to install power, ground, and remote turn-on wires. The onboard gain and tone controls function the same as in unbridged mode, and need to be adjusted properly. You should note that in this bridging scenario, the amp’s left positive and right negative terminals are used for the output. A different amp may use the left negative and the right positive outputs instead.

Another common amp-bridging scenario is to power a pair of high-performance component speakers for the front only and we’re using an aftermarket receiver. You can run rear speakers off of the stereo’s power, and to keep our example simple, there’s no subwoofer.

You can get a 4-channel amplifier that normally puts out a mere 30 watts RMS per channel, but can deliver two channels of 125 watts RMS when bridged. You run a dual RCA cable from the receiver’s front left and right RCA outputs. Then at the amp end of the cable, you attach a Y-adapter to each RCA connector, so you end up with four RCA connectors to plug into the amp’s four RCA inputs.

For the outputs, connect the amp’s front right negative output terminal to the left speaker’s negative terminal, and the amp’s front left positive terminal to the left speaker’s positive terminal (well, these connections are made to the crossover box, actually). The same connection scheme applies for the rear amp channels going to the right speaker.

For convenience, I refer to the pairs of channels in a 4-channel amp as the front pair and the rear pair. As I see it, in this set-up, the roles of the channel pairs have been changed from powering front and rear speakers to powering a left and a right speaker.

How does bridging work?

Where does all this extra power come from? Using the negative signal of one channel with the positive signal of the other channel effectively doubles what each channel alone could put out through a 2-ohm load. 

Usually, this is the maximum wattage the amp can put out. So, when you bridge your amplifier, you’re also optimizing your system’s power potential. And that’s a good thing. This is essentially how the bridging process works. 

Skar Audio RP-150.4AB

The Skar Audio RP-150.4AB is a powerful, efficient, and highly reliable four channel class A/B full-range car amplifier. Ideal for powering an entire aftermarket sound stage in a vehicle, this amplifier packs some serious punch with its conservative RMS power rating of 250W x 4 channels. It packs the power that will allow you to get loud and let your speakers come alive. 

Featuring a high speed MOSFET power supply, premium grade internal components, as well as 4-way protection circuitry, the amplifier will operate at the highest levels of performance for hours on end safely. With a depth of adjustable user controls such as the gain, lpf, hpf, crossover, and bass eq, this amplifier is extremely versatile and can be used in so many applications. 

These advanced user controls will allow you to dial your sound in exactly as you want for perfect clarity, whether running active components or speakers with in-line crossover networks. The class A/B circuitry design of this model allows it to amplify your audio signal with maximum clarity and sound excellence, all while being extremely efficient. This model also features large 4 gauge power and ground input terminal connections for maximum current flow.


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