Buying an amplifier for a car audio system can be a daunting task. It can be a challenge for someone new to the industry to select the perfect amplifier for their application, so we’ve put together this guide to help you find out what type of amplifier you need for your new system. Remember – you should either choose an amplifier first and build your system around it, or you choose the other components first and choose an amplifier (or amplifiers) to power the components. This guide assumes you have an idea of what type of system you want without any idea about the amplifier.
Let’s get started!
Selecting a Channel Configuration
All amplifiers are designed to output power into different “channels”. This helps pair the amplifier to the application it’s being used in. The most common amplifiers are 2-channel, 4-channel, and monoblock. Now, just because an amplifier is branded as “2-channel” doesn’t mean it’s only capable of powering 2 speakers. In theory, it’s possible to have as many speakers as you want paired with a 2-channel amp, it will just change the impedance (ohms) and change how the power is distributed between the speakers. Even though it’s possible to wire many additional speakers, it’s most common to use a 4-channel amplifier for 4 speakers, a 2-channel for 2 speakers, and so on.
Here’s a list that helps identify each different amplifier channel configuration and more information about each one.
- Can be used to power one set of speakers (2 total speakers)
- Most commonly used to power a subwoofer, or multiple subwoofers
- Usually has Class A/B Circuitry, but can also have full-range Class D as well
Perhaps one of the most popular selections, 2-channel amplifiers are great for multiple purposes. Two channel amplifiers output dedicated power to two separate channels, great for powering one set of car speakers (2 total speakers). The two channels can also be combined, or bridged together to provide more output to one dedicated channel, and is commonly done to power a subwoofer or subwoofers. 2-Channel amplifiers are stereo, meaning they have a Left and Right output. This is important for staging, and tuning. These amplifiers are capable of playing what is considered the full spectrum of sound that humans can hear, usually around 20-20,000 Hz.
- Bridgeable (most of the time)
- Usually used to power two sets of speakers (4 total speakers)
- Also able to be used in other configurations, however this is not as common
- Usually has Class A/B Circuitry, but can also have full-range Class D as well
Another popular option, 4-channels, are commonly used to power an entire set of door speakers (4 total speakers). 4-Channel amplifiers are also bridgeable, allowing for a ton of configurations, but the most popular application we find these amplifiers in is powering door speakers.
- Mono (one channel, no Left/Right differentiation)
- High-powered car amplifier
- Not full-range since subwoofers do not play higher frequencies
- Usually used to power one or more subwoofer
- Commonly has Class D circuitry, however can also have Class A/B as well
Monoblock amplifiers are designed primarily for subwoofers. Subwoofers require a lot more power than standard speakers, and the signal does not need to be as clean as the signal going to a full-range amplifier. Bass doesn’t need to be processed as much for high quality sound, like a really nice full-range amplifier does. Monoblocks are also not usually full-range capable, because higher frequencies are not played by subwoofers. Having these amplifiers capable of playing high frequencies would be a huge waste in efficiency. Because subwoofers require much more power than smaller tweeters or door speakers, monoblock amps are designed for maximum efficiency and power output first.
- Hybrid amplifier
- Front 4-channels are stereo/1 channel is mono
- Basically a 4-channel amp and a monoblock amp combined
- Allows an entire system to be powered from one amplifier (4 speakers, 1 or more subwoofer)
- Good for those who don’t want multiple amplifiers powering their entire system
5-Channel amplifiers are basically a mixture of a 4-channel amplifier and a monoblock amplifier, built into the same chassis. This helps eliminate the need for multiple amplifiers and elaborate wiring scenarios. These amplifiers are a great, simple solution for those looking to power 4 speakers and a subwoofer. They’re a bit more difficult to use for high powered audio applications, since 5-channels are usually only capable of running around 600-1000W RMS. This amount of power is perfect for mid-tier audio systems though.
- Hybrid Amplifier
- Front 2-channels are stereo/1 channel is mono
- Basically a 2-channel amp and a monoblock amp combined
- Most commonly allows an entire truck system to be powered from one amplifier (2 speakers, 1 or more subwofer)
3-Channel amplifiers are a smaller version of a 5-channel. They’re basically a 2-channel amplifier and a monoblock combined. They’re most commonly used to power an entire audio system in 2-door truck, or other small vehicles similar to this. You’ll also find 3-channel amps used to power just the front speakers and a subwoofer in a budget system.
- Similar to a 4-channel amplifier, but with 2-extra channels
- Allows powering of a center channel, or two additional sets of speakers
- Usually for specific audiophile applications
6-Channel amplifiers are usually reserved for audio enthusiasts or those with specific audio applications in mind. These amplifiers are most commonly used in vans, SUVs, and boats where you may require more than the traditional 4-speaker setup. They can be used in a lot of installations, but usually they’re bought with a certain application in mind.
Determining Power Requirements
Trying to match up your system’s power requirements with an amplifier can look confusing, but really it’s easier than it seems. The first thing to always remember is to only look at RMS power. Looking at peak or max power without a deeper understanding of it, will only confuse you. Secondly, impedance (or ohms) is a way to measure resistance. All speakers have an ohm rating, or impedance that tells the amplifier how much power to output. Lower impedance means more wattage from the amplifier. At 4 ohms an amplifier will output less power than at 2 ohms; however, an amplifier is more comfortable running at higher impedance and will tend to run cooler. For example, an amplifier at 4 ohms may put out 75 watts RMS, and at 2 ohms this same amplifier will output 100 watts RMS. Finally, you’re going to want to match up the impedance and RMS wattage of the speaker and amplifier. For example, if the manufacturer specifies that each speaker will require 100 watts RMS at 4 ohms, you will want to find an amp which pushes between 70-130 watts RMS at 4 ohms.
For more information regarding impedance, check out this video on matching subwoofers and amplifiers:
You may also want to check out our subwoofer wiring diagram:
Subwoofer Wiring Guide
Although you will get sound from a speaker even if you’re powering it with less than 70% of the rated RMS power, it’s usually not advised. When underpowering a speaker or subwoofer there’s a problem you’ll run into called “clipping”. This occurs when the amplifier tries to push more power to the subwoofer or speaker than the amplifier is safely capable of reproducing. For more on clipping, check out this video.
Determine if Auxiliary Battery is Required
Batteries are underused in car audio, when in reality they should be overestimated and overused. It’s understandable, considering that adding an additional battery is a bit of an investment to an already expensive complete system build, however the investment can be put to exceptional use in moderate and higher powered systems. Personally, I agree with the rule of thumb that systems running over 1000 watts of total RMS power should ALWAYS have at least an upgraded starting battery. An auxiliary battery should also be highly considered in these types of systems. The reason for this is, car audio systems are very demanding when it comes to using power. Your vehicle has a battery used to start your car, but also power things like your head unit, air conditioner, power windows, illumination on the dash, and, perhaps most importantly, headlights.
A common symptom you’ll see when adding a higher powered car audio system (600W RMS and up) is that when the bass hits, you’ll see your headlights dimming. This is because bass is very demanding, and every time it’s hitting it’s pulling a ton of voltage from your battery. In order to combat this, I’d personally recommend any system over 600 watts of RMS power (or fuses that add up to 60 amps or more) should highly consider either upgrading their starting battery to one more capable of keeping up with their system, or adding an auxiliary battery.
Determining Wire Gauge
Now, you’ve picked out your amplifier, you’ve picked out the speakers and subwoofer(s). You’re reading to get this system ordered and installed. Hold up. One last final thing to mention is wiring. Now, we’ve stressed before the differences between Copper Clad Aluminum(CCA) and Oxygen-Free Copper (OFC) wiring before in some of our videos and blogs. This is important to consider, but mainly we’re going to assume you went with OFC and are curious about the gauge of wire to choose.
The fuses on your amplifier (if your amplifier has them, lately more manufacturers have been opting out of external MIDI fuses and relying on your main fuse near the battery to protect your amplifier) are a good place to start to determine what wire gauge to choose. The reason for looking at fuses instead of rated power, is because power ratings with amplifiers can be very misleading. Reliable manufacturers in the industry who follow CEA compliant power ratings are much easier to determine wire gauge for than manufacturers who just list peak power or over-inflate their RMS power ratings.
Looking at total RMS power for your amplifier(s) is the way to determine the main run from your battery to your amplifier area. Another factor to consider is the length of the wire run. If you have your amplifiers under your front seat, you may be able to get away with a small gauge then if you’re running it to a trunk. Consider the RMS power, the length of the run, and the quality of wire that you’re choosing to find out if you’re using large enough wire to allow for proper system requirements.
Now that we’ve talked about some of the main points to consider when purchasing your next car audio system, get to building out that system! If this seems like a bit too much info for you, and you just want that sound in your car, give us a call! We have experts on the line who are complete car audio enthusiasts who will be happy to help you get exactly what you’re looking for!