Are Class D Amplifiers Good for Car Audio Systems?


When searching for a car audio amplifier, we will find that most of them are made in the D class. Are the class D amplifiers good for car audio and worth buying?

The class D amplifiers are the most efficient in the car audio industry. Amplifiers made in D class are able to provide most of the power to the speakers or subwoofer from all amplifier types available, and they are best to power strong subwoofers. However, they have a lot of internal distortions that make produced sounds of lower quality.

Therefore, even the best quality speakers when powered by D class amplifiers will sound worse in comparison to A, or AB class amplifiers.

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In the article below, you will find more information about the advantages of D class amplifiers and how to choose the best class D car audio amplifier.

What are the advantages of class D amplifiers?

The amplifiers produced in class D have the highest efficiency from all types, up to 90%. This high rate is a big plus, you do not have to buy a large amplifier to produce the energy you want, and class D amplifiers do not make a lot of heat compared to the A, or AB equivalents of the same power. The high efficiency is possible to achieve, thanks to constant switching on and off transistors, that do not consume any energy when they are off.

class d car amplifier

The high efficiency of the Class D amplifiers leads to more benefits like costs and space savings. With smaller transistors needed, these amplifiers need less cooling areas on the cover; therefore, they can be lighter, better packed, and in effect, cheaper.

The only disadvantage of the class D car amplifiers is a distortion of the signal they produce. Fortunately, this is happening only on the higher frequencies, and when amplifiers are not equipped with a noise reduction LC filters.

Should we use a D class amplifier to power car speakers?

Not long ago, class D amplifiers did not produce the expected sound quality. Although they were powerful, a few models were able to make sounds in standards tolerated by people who needed something more than just a noise. Even though I am seeing many cars with powerful amplifiers every day, not many owners can be truly proud of the music quality in their vehicles. A large portion of vehicles are not much more than rattling boomboxes.

Modern class D amplifiers have been significantly improved over the years, and producers make constant R & D to ensure they offer better quality. When choosing the right amp for the speakers, it is really worth considering the branded product. For example, great amplifiers are made by JL, JBL, or Rockford Fosgate, to name a few. Although class D amplifiers become standard in the car audio, you still can be disappointed in their quality, especially when choosing budget, mediocre quality models.

In many professional car audio systems, class D amplifiers, thanks to their efficiency, are used only to power demanding subwoofers. Bass sounds do not require as precise accuracy as higher frequencies. Therefore these amplifiers have a better fit for the lows, allowing A/B amplifiers to make hi-end sounds and supply power to the surrounding speakers.

How to choose the best class D car audio amplifier?

Purchasing the amplifier is straightforward, just place an order online and a day after you have it delivered to your door. But will it be the right amplifier for your car audio?

When searching for the right amplifier, we need to understand our system requirements, and what type is really needed. The amp must match speakers that you already have. A different approach will be for selecting an amplifier for the subwoofer, so you have to know exactly what type of speakers it will power.

There are a few main factors that have to be considered when searching for the best car amplifier, especially when you want to power your car audio with a D class amplifier, and these are:

  • Number of channels
  • Power
  • Impedance
  • Signal to noise ratio

Number of channels

The Monoblock class D amplifiers have one channel and are used to power subwoofers, or in small portion single speakers.

In the case of the subwoofers, the high wattage of the amplifier will allow you to create a large amount of strong bass, and because its smaller size will easily fit in the trunk. Amp of the same power but in class A/B is usually over twice as big.

Monoblock Class D amplifiers can also be used to power speakers, but this is rare. In this type of system, you will need a separate amplifier for each channel, so if you have speakers in each door and a subwoofer, you will need five Monoblock amplifiers, and that will take a lot of space.

However, there are benefits of using designated amplifiers per speaker, like reduced sound distortions and assigning each transistor to each channel. Still, this type of system is preferably used by audiophiles, but not with class D amplifiers. Often chosen amplifiers for specific speakers are A/b class that are producing sounds of higher quality.

More popular are multi-channel class D amplifiers, and these are either 2, 4, or even 6 channels. The benefit of the multi-channel amplifier is space-saving when connecting the whole car audio system to one power station. Another good point is that most class D amplifiers with two or more channels can connect a subwoofer to one bridged channel.

For example, when you have a 4 channel amplifier, you can power 4 speakers in a car or one pair of speakers and a powerful subwoofer.
2 channel class D amplifiers are used in simple car audio application to power one pair of speakers, or one subwoofer.

Power

When it comes to power, you should have more of it rather than not enough. Although there are two main power ratings in the car audio world: RMS power and Peak power, we will always talk about RMS power, which is sustainable and means how much continuous power and amplifier can produce, or speakers can handle.

Because it is worse for speakers when they are underpowered rather than overpowered, the amplifier should produce as a minimum speakers’ RMS. How much is the maximum, though? It is recommended to not exceed 150% of speakers’ power handling, so if you have speakers 100W RMS, an amplifier should be between 100W and 150W RMS. The higher ratio should go towards powering subwoofers.

Impedance

Impedance is critical when it comes to producing stable power, and simply speaking, it should be the same on the speakers and amplifier. When you have speakers 100W with 2 ohms, do not buy 100W amplifier with 4 ohms, unless you want to fry it.

In the case of standard speakers, when you connect just one speaker per channel, which is either a coaxial or component system, the impedance must match. While a 100W 4-ohm speaker will demand a 4-ohm amplifier to supply 100W, low impedance 2-ohm speaker will try to pull from the same amplifier 200W.

Signal to noise ratio

Signal-to-noise ratio is essential when defining how loud is amplifier itself in comparison to the sounds it produces. The last thing you want to hear after having a high-end audio system installed is background noise while trying to enjoy your music, therefore the higher value of the SNR, the better.

The typical signal-to-noise ratio for class D amplifiers you can find is around 80 dB for multi-channel amplifiers and approximately 75 dB for mono amplifiers. Remember, the higher the value, the fewer background noises you will hear, and the speakers’ sounds will be more precise.

Below are examples of signal to noise ratio in popular amplifiers:

  • Rockford Fosgate R2-500 X4 – 80 dB
  • Rockford Fosgate R2-750 X1 – 70 dB
  • JBL Club 704 – 85 dB
  • JBL Club 5501 – 80 dB

Summary

In the audiophile world, where every tone has to be precisely selected and reproduced, class D amplifiers have no life. They simply cannot compete with much more accurate A or A/B amplifiers. Also, they have internal sound distortions at higher frequencies, so if you want to hear ideal sounds in your favorite tracks, class D, although very efficient, is not the best choice.

They are, however, fantastic for powering subwoofers and supporting mid-bass frequencies, or any type of the system that hi-end high tones are either not required or not achievable. Class D amplifiers are also a good option for small cars, or convertibles, where even with a closed roof, there is a lot of noise when comparing to the vehicles with a hardtop.

Regardless of which type of car audio applications, you will use an amplifier, remember the speakers’ requirements, and choose the right model for the best music experience.

Martin

Welcome to ImproveCarAudio! I am Martin, and I love to write about everything related to car sound systems. I strive to provide the most accurate and helpful information about car audio through extensive research, as well as my experience with car audio installations.

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