Best Car Amplifier – Boost your stereo’s power today

If you are looking to improve the quality of your car stereo system, you will quickly find yourself comparing different types of car amplifiers. However, unless you have experience with car stereo systems, this can be an intimidating task, with many acronyms and unfamiliar terms to learn. In this article, we will go over some common terminology to help you know what to look for when finding the best car amplifier.

Our Top Pick of Car Amplifiers

Top Pick
Rockford Fosgate P400X4 Punch 4-Channel Amplifier

Best Car Amplifier Reviews

Rockford Fosgate P400X4 Punch 4-Channel Car Amplifier

Rockford Fosgate makes a world-class car amplifier. Users are extremely impressed by this Punch 4 channel amp. Whether you need 50 watts, 100 watts or 200 watts, this amplifier has you covered. Of course, it depends on your particular setup, but this amp is more than enough to run two components and a pair of 6x9s.

The Punch 4 channel amp from Rockford Fosgate has a nice compact size that will make it easy to fit under a seat or easy to bolt down to a speaker box. It weighs just over 11 lbs and sizes in at nine inches by 5 inches. It is constructed with a cast aluminum heatsink. The control panel is discreetly hidden on the top so as not to interfere with the connections or detract from its sleek look.

This car amp will work with aftermarket and stock (factory installed) head units. Many users were happy with the ease of install on their systems. Some also commented that spending a little more for a higher quality amp was well worth it because they were tired of purchasing cheap car amps. Rockford Fosgate has been in the audio industry for a long time, and they certainly nailed it with this amp. The Punch 4-channel amp is one of the highest rated car amplifiers.

Why It Made The List: We really liked that this car amp was constructed with quality. We also loved the cast aluminum heatsink that it's built around.

Rockford Fosgate P400X4 Punch 4-Channel Amplifier

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Alpine MRV-F300 4-Channel Car Amplifier, 50 Watts RMS x 4

Alpine is a great audio company. They make speakers, car stereo head units, amplifiers and more. You get nothing but greatness with this little 4 channel amp. Alpine offers the same power as most top end amps but in a 40 percent smaller chassis. In fact, this amp weighs less than 5 lbs.

Users absolutely love this car amplifier. It got a near-perfect rating on Amazon with more than 350 individual reviews. Users reported that they were using this amp to run everything from 12” subwoofers to three sets of speakers throughout their car. Some even stated that they were using one Alpine amp, and loved it so much they bought a second one.

Aside from being an excellent 4-channel amplifier, this unit looks fantastic. It has a high-end, premium feel to it. One feature is that this amp dissipates heat very well. It barely gets warm when the system is cranked up. This is important if you plan on hiding it under a car seat or surrounding it in the trunk. You really can't go wrong with Alpine, and you won't be disappointed if you pick up one (or two) of these bad boys.

Why It Made The List: This amp is a boss when it comes to spreading and dissipating heat. It keeps cool under extreme usage.

Alpine MRV-F300 4-Channel Car Amplifier, 50 Watts RMS x 4

Kenwood KAC-8406 900W 4-Channel Car Amplifier

Kenwood is one of the leading car audio manufacturers, dating back to 1946. Their amplifier technology coming to life in the late 70s and early 80s. This 4 channel amp is an excellent testament to Kenwood’s manufacturing ability. At a peak/MAX wattage of 900w, it’s going to be more than enough to run a few speakers. This Kenwood amplifier is going to pack a punch, especially for the price.

This amp is loaded with all the features that you would need. Whether it is boosting the bass on a couple of 10” subwoofers or a few component speakers. It has a bass boost control built in. It also has a variable high-pass filter and a variable low-pass filter.

Kenwood makes sure you are going to be happy with your purchase. They offer a 1-year warranty on this amp to back up their quality. You probably won't need to use it, but it’s nice to know you’re covered. Users are generally satisfied with this amp. The main issue is that it doesn't have a line out. This means you can't daisy-chain multiple amps together, you’ll have to do it another way. Other than that, this Kenwood amp got pretty solid marks.

Why It Made The List: It comes with a manufacturer's one year warranty.

Kenwood KAC-8406 900W 4-Channel Amplifier

Kenwood KAC-M3004 Compact 4 Channel Digital Car Amplifier

Because Kenwood is a reliable car audio company, it’s only natural that another Kenwood amp made it to our list. This amp is going to have a max/peak power of 600 watts. The watts might be a little lower, but when connected right, it will still provide high power and clarity to almost any sound system. As a side note to this, one user actually crunched some numbers and ran some setup tests and found surprising results. He concluded that this amp was actually underrated and would provide 731 watts of “Dynamic RMS Power at 2 ohms (bridged).”

This tiny little guy really does perform well. We say tiny because it measures in at just under 6”x7”. It's about 3” thick as well. This thing is like a mighty mouse. Tons of power in a small container. Something only Kenwood could pull off. The other great thing about this unit being so small is that it can be used in your car, boat or even ATV. And for the price, you might as well buy one for each. This thing rocks.

Why It Made The List: Individual user tests confirmed that this amp was extremely underrated and it would perform much better than expected.

Kenwood KAC-M3004 Compact 4 Channel Digital Amplifier

Precision Power P900.4 900-Watt Phantom Series Class D Full Range 4-Channel Car Amplifier

With this amp, Precision Power is back in the amplifier business. Users were extremely pleased with the amount of power this little guy put out. One user reported using it in his sound competition car. If you trust an amp enough to be used in a competition, then the price and power must be spot on.

This amp has a Mosfet power supply and a heavy duty heatsink made of aluminum alloy. This amp needs it because it gets hot. That’s because there is no fan or vent. You could consider this a blessing in disguise because you won't have to worry about dust getting inside. The Precision Power P900.4 is just under 11”x7” so finding a spot to hide it might be slightly tricky depending on your car. It is only 2 inches thick, so that's a plus.

Overall, you won’t be upset with this amp. It’s going to provide you with enough power to run any modest setup. Or you can even use it to enter competitions.

Why It Made The List: It is competition grade and will surely provide the everyday user with more than enough power.

Precision Power P900.4 900-Watt Phantom Series Class D Full Range 4-Channel Amplifier

JL Audio JX400/4D 4-channel Car Amplifier — 70 watts RMS x 4

Last but not least is the JL Audio 4-channel amplifier. It came with nearly perfect reviews. In our opinion, it should be a perfect 5 stars because the one lower rating was because one of the channels wasn’t functioning out of the box. Should have been an easy replacement. JL Audio has a fantastic reputation, and I’m sure they would have taken care of it. That being said, JL Audio hit a home run with this amplifier.

They have provided a protection system that is unmatched. This unit protects 3 ways from speaker shorts, overload, and thermal issues. You are wise to choose this amp for your car stereo needs. It is just a bit larger than some of the other amps we’ve reviewed, measuring in at 12”x9.5”x4”. It does have some weight to it as well. This amp is made with quality components. JL Audio JX400 rounds out our list of car amps.

Why It Made The List: The additional protection from speaker shorts is a huge plus. It should prevent you from needing to replace your speakers in the event of an electrical surge.

JL Audio JX400/4D 4-channel car amplifier — 70 watts RMS x 4

Car Amplifier - What is it?

In any type of speaker system, from the public address system at a stadium to the small speaker in your phone, an amplifier is what makes a speaker work. Amplifiers send electrical signals that interact with the magnet on a speaker, causing the speaker cone to vibrate and produce sound. In the simplest car stereo systems, the car radio head unit (the box behind the radio controls on your dashboard) has a small amplifier contained within it that powers a modest array of speakers.

The type of car amplifier (or car amp) we will be addressing in this article is a separate box you can install in your car stereo system.

But if the stereo head unit already HAS an amplifier built in,

The Best Car Amp

why would you need to buy one?

Adding a separate amplifier to your car stereo system can be used to make it more powerful, increase the number of speakers, improve the sound quality, or all three. Car amps take the signal from the head unit, amplify it, and send it out to the speakers in your stereo system.

Common Car Amplifier Terminology

Pre-amp input

In car audio terminology, pre-amp refers to things in the signal chain that comes before the signal reaches the amplifier. The input jack on a car amplifier is called the pre-amp input and will get its signal from the pre-amp output on the radio head unit. Many car amps also have pre-amp outputs as well, allowing you to daisy-chain more than one amp together. The pre-amp output on a car amplifier will not amplify or “boost” the signal, but merely pass it on to another amp.

Car Amp Channels

Car amps send signals directly to the speakers in the stereo system. These outputs are called channels (not to be confused with the channel presets on a car radio). Car amps typically have between one and six channels, although the 5 channel amp, 4 channel amp, and 2 channel amp are some of the most common. An amp with a single channel is typically referred to as a “monoblock,” and is usually used to supplement a car’s built-in stereo system by powering a subwoofer.

Filters & Crossovers: Your car amplifier should have these...

A filter is a circuit in an amplifier that allows only signals of a specific frequency to pass through. Filters are used to send sounds of certain frequencies through some channels and not through others. The human ear can detect frequencies from about 20Hz - 20,000Hz (or 20kHz), but not all of these frequencies will sound good coming through your car’s stereo system.

A filter is a circuit in an amplifier that allows only signals of a specific frequency to pass through. Filters are used to send sounds of certain frequencies through some channels and not through others. The human ear can detect frequencies from about 20Hz - 20,000Hz (or 20kHz), but not all of these frequencies will sound good coming through your car’s stereo system.

First, the extreme high and low ends of the spectrum are not useful. Sounds close to 20Hz are so low that they become subsonic, and sounds close to 20kHz are perceptible only as a ringing in your ears.

The best car amplifier

Second, stereo systems can produce more precise, better quality sound when the individual speakers put out audio at narrower frequency ranges. In the simplest stereo systems, a few speakers are responsible for outputting the full range of frequencies, and the result is a middle-of-the-road mix that lacks clarity. In more advanced sound systems, different frequency ranges get delegated between low-range, mid-range, and high-range speakers, resulting in a clear-sounding, more enjoyable listening experience.

A high-pass filter will cut out low frequencies (perhaps anything below 100Hz) and allow any frequencies higher than 100Hz to “pass” through.

A low-pass filter does the opposite, cutting our higher range frequencies and allowing anything lower to pass through.

A crossover is a particular type of filter used to separate the bass channel from the rest of the signal, usually at about 100Hz as the cutoff point. A crossover can take a signal from a stereo head unit and send all of the frequencies at 100Hz and below to an amp powering a subwoofer, and the rest of the frequencies to a different amp power the rest of the speakers.

Decibels (dB) & Sensitivity: Good car amplifiers help regulate these...

The Decibel, or dB, is a unit of measure used to quantify amplitude or loudness. This unit of measurement is most commonly used to describe Sound Pressure Level (SPL). A source of sound with an SPL of 0dB is undetectable by the human ear. Sounds with an SPL of 120dB can cause instantaneous noise-induced hearing loss. For a few points of reference, a normal conversation usually has an SPL of 40-60 dB from three feet away, while a jet engine from three feet away would register an SPL of about 150dB.

Another place you will see dB used is to measure the sensitivity of speakers in a stereo system. A speaker’s sensitivity as measured in decibels is the SPL from 1 meter away, with 1 watt of power sent to the speaker. For example, a speaker with a sensitivity of 84dB would produce a sound of 84dB with a 1 watt signal from 1 meter away. Wattage must be increased exponentially to make the speaker louder. For every additional 3dB, the wattage must double, meaning that same speaker would produce a signal of 87dB at 2 watts, 90dB at 4 watts, and 110dB at 200 watts.

Watts & Ohms

The output power of a car amplifier is measured in watts. While it is not necessary to have an extensive understanding of how wattage is measured to know your way around a car stereo system, it is essential to understand the two different ways that wattage is measured for car amps, which we will discuss below.

The Ohm is a unit of electrical resistance. Again, it is not necessary to have an extensive understanding of how electrical resistance works to understand car stereo systems. The critical thing to know is that, when matching power ratings of speakers to the power ratings of amplifiers, you should use the resistance rating of the speaker (usually 2 or 4 ohms) when pairing it with the power rating of the amp.

RMS Power & Peak Power: Important numbers when rating car amps

Car Amplifier

Your car doesn't need a fancy head to sound good. Adding a car amplifier is an easy way to boost the power to your speakers and get an extra kick out of them.

RMS Power (short for “Root Mean Square”) is an estimate of the continuous power output (in wattage) of an amp channel. This number is essential to know when choosing an amp for your speaker system, or vice versa. A good rule of thumb is that the RMS power rating of a speaker should be between 0.8-1.5 times the RMS power rating of the amp channel powering it.

For example, if an amp has an RMS power rating of 50 watts per channel, you could safely connect a speaker with an RMS power rating of anywhere between 40-75 watts. Use a speaker with a higher RMS and the amp will not have enough power to make the speaker sound loud and clear. Use a speaker with a lower RMS, and you risk distortion, or even blowing the speaker during a sharp peak from the amp.

Unfortunately, the power rating listed on the front of most car amplifier brands is not the RMS power but the amp’s Peak Power. This is the peak power output on all channels combined that the amp is able to put out. While this number is more massive and looks impressive, it is almost useless for designing your stereo system. When choosing car amps, you should pay attention only to the RMS power ratings.

Here are a few actual examples of power ratings taken from aftermarket car amplifiers:

  • A 2000 watt amp (max power) with 1 channel has an RMS power output of 1500 watts at 2 ohms or 750 watts at 4 ohms.
  • A 1000 watt amp (max power) with 2 channels has a per-channel RMS power output of 375 watts at 2 ohms or 188 watts at 4 ohms.
  • A monoblock amp listed as a 500-watt amp has an RMS power rating of 500 watts at 2 ohms.

As you can see, the max power wattage of an amp is reported inconsistently across different car amplifier brands and is meaningless without taking into the number of channels and the resistance per channel. Always make sure to look for the RMS power rating to pair the right amp with the right speakers.

Car Amplifiers -
Complete Comparison Chart

Rockford Fosgate P400X4 Punch 4-Channel Amplifier
Alpine MRV-F300 4-Channel Car Amplifier, 50 Watts RMS x 4
Kenwood KAC-M3004 Compact 4 Channel Digital Amplifier
Kenwood KAC-8406 900W 4-Channel Amplifier
JL Audio JX400/4D 4-channel car amplifier — 70 watts RMS x 4
Precision Power P900.4 900-Watt Phantom Series Class D Full Range 4-Channel Amplifier

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