When choosing an amplifier for car audio, there are a few different classes or types you can consider.
Some of the critical factors to consider when choosing an amplifier class include power output, cost, size, and efficiency, but which amplifier class is best for car audio? Let’s find out.
If you are looking for high power output or an amp just for the subwoofer, then a Class D amplifier is the best option. On the other hand, if you want the best sound quality from the speakers, then the Class AB amplifier is the better choice.
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Tip: When you are on the budget, it is better to look at a compact D class multichannel amplifier that will be good enough for the entire system without needed investments into the A/B amp for the speakers and a strong D class for the subwoofer.
An excellent example of the compact D class amp is the Rockville dB55, equipped with a 12 band equalizer and full bass control for the subwoofer channel.
In the article below, I will go into more detail about the different amplifier classes and how to choose the right one for your car audio.
What Are the Differences Between Amplifier Classes?
All three types of amplifier classes can be divided into two main groups:
- A, and AB, are amplifiers with constant energy consumption, even if there is no signal transferred to them
- D class amplifier consumes energy only when transmitting a signal to the speakers.
A Class Amplifiers
The pure class A car amplifier is “on” nonstop and consumes the whole supplied energy, transferring it to heat.
For example, when you have a 100W class “A” amplifier in a car, and while you drive, it runs at its full capacity and consumes 100W of energy all the time, and it does not matter if you are listening to the music or not.
This energy is transmitted to the heat. In an ideal situation, if this amplifier was 100% efficient, it would supply a 50W per channel, assuming this is a stereo (or two-channel) amplifier, but in this case, it is zero.
That means the “A” class amplifiers are inefficient unless when you drive your car, you are listening to the music nonstop, then efficiency is a little higher, but still very low due to the amount of heat produced.
When you turn your radio on, the output of 100W energy changes from the heat and goes immediately to the speakers. Now, this energy is transferred into a sound, which is what you want, and the sound quality from the A-class amplifiers is crystal clear.
The reason for constant energy consumption in an “A” class amplifier is to keep transistors, or any other output devices turned “ON” all the time. This is reducing the noise created by the transistors and makes the highest quality sounds.
Class A amplifiers produce the highest sound quality and, at the same time, a lot of heat.
Unfortunately, because they are so inefficient (in a range of around 25% if you are lucky), it cost a lot of money to produce a powerful “A” class amplifier. They are, therefore, the most expensive of all car amplifiers.
For example, a 2x100W Mosconi Dynamic A-Class Car Audio Amplifier costs over $2.200.
AB Class Amplifiers
Although class AB has the same principle as class A to keep an amplifier always on, a 100W AB class am amplifier will not consume a constant 100W of energy.
Continuous energy consumption depends on the model, ranging from 2W to 20W, so it is more like running on “stand-by” mode.
The great thing is, even if you do not listen to the music, the AB amplifier consumes this power and operates in class “A” mode. This energy is needed to keep all components powered and ready for any signal input.
When you turn the radio on, this energy is immediately transferred into a sound. However, when you listen to quiet music, it can happen that the AB amplifier will continue to consume this basic 20W and will never switch to the B class.
But, when you increase volume and start listening to loud music, the amplifier’s energy consumed will rise to the max, and it will drop down back to the minimum level when you turn the radio off.
This technology’s advantage is the lower signal distortion, which makes a music signal clear, and these amplifiers produce much less heat compared to the pure “A” class. They are also much cheaper than pure A-class models but still expensive.
The main disadvantage of the AB amplifiers is their efficiency which is also not too great. It is higher than A class amplifiers, and depending on the model, it varies between 50% and 70%.
The other disadvantage of the AB amplifiers is their size and weight.
D Class Amplifiers
Class D is a different way of generating energy and powering loudspeakers. The primary term for the class D amplifiers is a Pulse Width Modulation, but what is this?
According to Wikipedia, “Pulse width modulation (PWM), or pulse-duration modulation (PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts.”
In other words, these are signals at regular frequencies. For example, for 100Hz frequency, the D class amplifier will switch “on” and “off” every 1/100 of the second. With sounds of the 4000Hz frequency, the amplifier turns on and off 4000 times per second!!!
Because transistors in “D” class amplifiers are either on or off, they run at maximum efficiency close to 90% for the top models, creating very little heat at the same time and the biggest disadvantage of the D amplifiers at the same time.
The D class’s most significant disadvantage is that when transistors switch between “on” and “off” thousands of times per second, they create a lot of noise that has to be somehow eliminated.
Otherwise, the noise will be transmitted to the speakers, but I would rather listen to music than the buzzing sounds.
To eliminate these noises, “D” class amplifiers are equipped with a low pass filter made from many inductors and capacitors.
Another problem with class D amplifiers is their sound distortion that affects especially high-frequency sounds. This is the main reason why D class amplifiers are not the best choice when you value clear music more than anything else.
To sum up, D class amplifiers are the cheapest, smallest, and most efficient option creating the least heat. Still, their disadvantage is the sound quality and performance in comparison to A or AB class amplifiers.
Which Class Amplifier Should I Choose for My Car?
Choosing the right amplifier is not straightforward due to the number of their types.
When searching for the amplifier to power the speakers, the best choice, as I already mentioned, is the A/B amplifier that provides a high sound quality without distortions in high tones, and it does not matter if you will use it for coaxial or system speakers.
Car speakers usually do not need hundreds of watts per channel, so A/B is the best option if you want to listen to high-quality music.
For the subwoofer, the situation is a little different. Subwoofers need a lot of power, and while an A/B amplifier can still supply this, there is not much of a need for the sound quality in the frequencies produced by the subwoofer.
Subwoofers work at the lowest range of the tones, starting from around 20Hz up to 200Hz at the most, and for these frequencies, the class “D” amplifiers will be the best because they are powerful and efficient.
Many mono amplifiers are made in class D because of this reason. They are supplying subwoofers with a ton of power and are much cheaper than AB class amplifiers.
How to Balance The Power of Two Amplifiers in The Car?
When there is more than one amplifier in the car, for example, one for a subwoofer and another for the rest of the speakers, or when speakers are powered directly by the head unit, it is essential to create the right balance between these two sound systems in the car.
The ideal balance should be 50/50, or 60/40, which means the RMS power of the subwoofer amplifier should be close to the total RMS for the head unit.
For example, when a car radio has the power 4x30W RMS, ideally, if the amplifier for the subwoofer will produce a total of between 120W and 180W. Or, when you use a 4x200W amplifier for the speakers, the amplifier for the subwoofer should be between 800 and 1200W.
Do I Need an Amplifier for Door Speakers?
Absolutely. External amplifiers installed in the car have a positive impact on the music dynamic and sound quality. Amplifiers built-in head units have several weak points, which can be compensated by external amplifiers:
- With the external amplifier, you can listen to the music with better sound quality and without distortion, especially in the higher volumes.
- Many multichannel amplifiers allow you to connect both speakers and the subwoofers at the same time.
- New and more powerful than factory speakers, will need more power than the head unit can produce