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Are Class AB Amplifiers Good for Car Audio?

If you’re a car audio enthusiast, then you know that the quality of your sound system is a big deal.

But is it worth investing in a class AB amplifier for the car audio? Let’s find out.

Class AB amplifiers are perfect for car audio systems because they combine Class A and Class B to achieve an amplifier with more efficiency than Class A but lower distortion than class B. All packed in the compact box make the AB amplifiers the perfect choice for anyone who values the quality of the car audio system.

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Tip: AB class amplifiers can be used for speakers or subwoofers if you aim for outstanding bass quality.

The one I would choose for the subwoofer is the Planet Audio PL1500.1M (link to Amazon) because its frequency response starts at 9Hz, which is enough to support even the most demanding subwoofers.

In this article, I will explore the pros and cons of using class AB amplifiers in your car audio. I will also provide some tips on how to choose a suitable amplifier for your needs.

What Does Class AB Mean for Amplifier?

Class AB amplifiers are audio amplifiers that combine the best features of class A and class B amplifiers. They are more efficient than class A amplifiers but still provide excellent sound quality.

Class AB amplifiers are often used in car audio systems because they offer a good balance between sound quality and power efficiency.

In other words, the AB class amplifiers are designed to overcome and eliminate the disadvantage of low efficiency in class A amplifiers and distortion in class B amplifiers and utilize the advantages of both the amplifier classes.

This is achieved by biasing both transistor types, so they conduct when the signal is close to zero in two scenarios:

#1. For large excursions, only one transistor is active for each half of the waveform, acting like a class B amplifier.

#2. For small signals, both transistors are active and act like a class A amplifier.

What Are Class AB Amplifiers Used For?

Because of the elimination of crossover distortion, AB amplifiers are preferred for radios, audio systems in homes or cars, and TV receivers.

In this article, I focus on car audio applications. The AB amplifiers have their place in many systems, often used as multi-channel applications to power car speakers or monoblocks used to power the most demanding subwoofers.

This is because the mid and higher frequencies have to be reproduced with very low distortion for the high-quality systems, and sounds created by lower class amplifiers do not guarantee such a low distortion level.

Thanks to the low distortion of the sounds created by AB class amplifiers, you can connect to them component speakers in an active way.

Active connection means that instead of connecting the amplifier with the speakers through the crossover, you connect each separate speaker directly to a dedicated channel from the amplifier.

This allows separating the control of the gain and volume for mid-woofers and the tweeters, which is impossible when connecting the component speakers in a standard way through the passive crossover.

If I were to install an AB amplifier with the speakers in my car today, I would choose the 6 channel Focal FDP6.900 for two way set Focal ES 165KX2 or three-way components system KX3 (links to Amazon).

Focal ES 165 KX3 K2 Power 6-1/2" 3-Way Component Speakers

The only disadvantage of such a connection is that you have to use all four channels (or six) for one pair of speakers, so if you have speakers in the front and the rear of the car, you need two amplifiers.

It is a more expensive installation, but the sound quality is well worth it, especially if you use top-class elements like the above from Focal.

Are Class AB Amps Good for Subs?

The AB class amplifiers are also used to power car subwoofers because they reproduce low-frequency signals with high fidelity and power efficiency.

Especially if you have a car audio system with sealed subwoofers, where the sound quality is a top priority.

An excellent example of the AB class monoblock amplifier that works great with the subwoofer is the Planet Audio AC1500.1M or higher from the AC series (link to Amazon).

It has an adjustable low pass filter from 45 Hz to 90 Hz, variable bass boost between 0 and 18 dB, and a frequency response from 20 Hz to 20 kHz ±1 dB.

Those parameters combined with the AB class transistors make it an excellent choice for most of the subwoofers, but if your sub starts close to 20Hz like for example Skar Audio ZVX-18v2, I recommend using a similar Planet Audio PL1500.1M or higher from PL series (links to Amazon).

PL amplifiers start the frequency response at 9Hz, so you do not have to worry about cutting out the lowest tones.

Planet Audio PL1500.1M Monoblock Car Amplifier - 1500 Watts, 2/4 Ohm Stable, Class A/B, Mosfet Power Supply

For other enclosure types, especially for the ported ones where the created bass sound more “boomy”, the AB class amplifiers are not required, and many use for the loud subwoofers cheaper but more efficient D class amplifiers.

What Are the Pros and Cons of Class A/B Amplifiers?

There are a few things to consider before choosing a class A/B amplifier for your car audio system. Here are some pros and cons:

Pros:

#1. Class AB amplifiers offer an excellent balance between sound quality and power efficiency.

#2. Class AB amplifiers are less likely to overheat than class A amplifiers.

#3. Class AB amplifiers offer a wide variety of features and options.

Cons:

#1. Class AB amplifiers are more expensive than more popular D class amplifiers.

#2. Class AB amplifiers create more heat than D class amplifiers.

The above shows that the main benefits of having an AB class amplifier are sound quality and power efficiency.

However, there are a few drawbacks, such as the increased cost and heat output.

Ultimately, the decision of whether or not to use an AB class amplifier will come down to your specific needs, but more importantly, to the budget.

How to Choose the Right Class A/B Amplifier for Your Car Audio System?

When choosing a class A/B amplifier for your car audio system, you should keep a few things in mind. Here are a few tips:

#1. Make sure to match the amplifier’s wattage to your speakers’ wattage.

#2. Consider the size of the amplifier when choosing a location for it in your car.

#3. Make sure the amplifier has a low-pass filter if you’re planning on using it for subwoofers.

#4. Choose an amplifier with a wide variety of features and options to get the most out of your sound system.

When choosing an A or AB class amplifier, you must remember not to cut corners by picking the “you name me brand”.

As you know, the quality comes with the cost and to get the best quality amplifier, you have to choose a reputable brand that spends the money on the R&D.

Only by doing tests and improvements, you can be assured that the product was really developed over the years and not the technology was bought or “borrowed” by some factory that aims to be an “audio producer”.

Focal FDP6.900 6 Channel Amplifier 4 x 150 + 1 x 600 W

For me, when it comes to the AB class amplifiers, the absolute top is the FOCAL, especially the six-channel Focal FDP6.900 (link to Amazon).

Conclusion

If you’re looking for a balance between sound quality and power efficiency, then a class AB amplifier will not disappoint you.

Class A/B amplifiers offer a wide variety of features and options, making them an excellent choice for most car audio systems.

However, remember that class AB amplifiers are more expensive than more popular D-class models, so when you aim for the best, you need to consider the budget, well… unless you do not have to.