Buyers guide

The Best 4 Channel Car Amplifier – Buyer’s Guide and 5 Excellent Choices

I love 4 channel amplifiers! As an installer and a car audio fanatic I’ve installed, tested, and tried many over the years. In my opinion 4 channel amps are some of the most flexible and the best value. However, finding the best 4 channel car amplifier can be tough!

In order to help you find the best for your money I wrote a helpful buyers guide. I’ve also provided 5 excellent models with reviews to help you get an amp you’ll enjoy.

If you’re short on time click here to jump right to the reviews and best 4 channel car amps list.

What is a 4 channel amp?

4 channel amps, as you may have already guessed, are extremely similar to 2 and 5 channel models. They do share a few differences however. They too use a single power supply to provide a higher output voltage, stepped-up from 12V, to drive the speakers with more power than is possible with only 12V like factory systems.

Following this, they contain 4 independent audio amplifier sections which these days are normally designed in such a way that each channel pair can be bridged for additional power if desired. Some have features such as a bass boost control that may be used only for 2 of the 4. This varies from brand to brand and model to model, so it’s important to be sure before buying.

Internal image of a 4 ch. amp

A 4 channel amplifier is basically the same as a 2 channel amplifier with 2 additional audio channels in a more compact design. It’s important to note that some, however, do have special features (such as a bass boost option) available only on 2 of the 4. This 4 channel class A/B amp (show here) has quite a few transistors on the left-hand side to drive the outputs. That’s one reason it’s longer than a 2-channel amp alone.

System flexibility and advantages

4 channel amps are very flexible and offer a number of advantages over other models. You can configure (and easily reconfigure) many different types of sound systems in your car.

For example:

  • A 4 speaker system (front/rear)
  • Front full-range (2 ch.) + bridged subwoofer
  • High pass/low pass component speaker setup, with tweeters on channels 1-2 and woofers on 3-4
  • Front speakers with a high-pass crossover and front woofers on low-pass channels

When adding a 2nd amp, the possibilities are even more extensive! Remember that it’s ok if you don’t use all channels present in an amp – there’s no harm in having a speaker output disconnected.

What to look for in a car amp

There are a number of basic features that although are very common in modern amplifiers you should always verify they’re present before purchasing, rather than assume.

I recommend an amplifier with built-in high and low-pass crossovers. Ideally these would be adjustable although that’s not a primary concern. But it does make it easier to tailor the sound to your liking and it’s especially true when using the high-pass feature to block lower end bass from speakers that can’t handle it in order to prevent distortion and get more clean high volume sound.

Ideally you’ll also have an amplifiers with good terminals which are easy to connect power and speaker wire too, but remain secure and well-connected after installation.

Class A/B vs class D amplifiers

Technology has improved a lot in the last several years when it comes to car amplifiers. Although the traditional designs that have been around for decades, class A/B amps, still remain. Whereas as traditional A/B amplifiers are based of a design in which driving transistors largely remain on during use (even when no audio is present) and are only near 65% efficient, class D amplifiers are nearly 90% efficient and can be designed to fit into much smaller chassis. A class D amp works by switching the transistors that create an audio waveform incredibly fast, saving energy and bringing heat levels down to an incredibly low level.

Class D amplifier sound quality

Class D amps do have one drawback: because of how they operate, the noise floor is somewhat higher than that of A/B amps, which you can hear as a slight hiss if you listen closely and especially if the gain is turned up high. It’s critical to buy a well-designed brand name amp to get the best sound and lowest noise as lower-end amps aren’t as well designed. 

Today’s brand name 4 channel class D amps have reduced noise levels and generally overall better sound than others, and proven by the many happy customers who’ve said the same.

The good news is that a well-designed amplifier of this type can have great sound quality. Highs are crisp and bass is tight and punchy, just like older designs. Again, it’s really important to shop carefully to get the best sound.

Class A amps are low-noise designs somewhat similar to A/B, but even less efficient and generally not as common. They’re often much more expensive, too.

Image of Alpine KPA-445U mini amplifier controls

Class D amps use relatively recent design to produce efficient power and can be incredibly compact as they don’t waste large amounts of energy as heat like older amplifiers. This excellent Alpine KTP-445U 45W x 4 mini-amp. for example, measures only 7 7/16 x 1.5 x 2.5″ (189 x 38.2 x 64.5 mm) in size!

Why choosing a class D may be the best choice

Because they’re so small, this type of amplifiers opens new possibilities for installation and can fit in areas previously completely unavailable! That’s a fantastic advantage as you can do things like the following:

  • Place an amplifier under a seat (or 2 for a multi-amp system)
  • Install them in storage containers in your vehicle’s interior
  • For trucks, they can be placed under the normally limited space under the rear folding seat
  • Hide them from thieves looking in your vehicle to avoid theft

Because they’re so efficient you can actually get away with smaller size power wire. Remember that while they have great power output, very similar to traditional amps, they use almost 1/2 of the power draw of older amps!

That means they draw a lot less amperage and can you won’t need as large a power wire. As the price of copper wire has risen over the years, that’s a big advantage!

However is having the lowest noise level possible is a concern for you, then perhaps A/B is the best choice. I’ll list some models below that are great choices.

How much power do I need?

As an installer I generally recommend a minimum of 50W RMS per channel into 4 ohms. If you’ll be driving subwoofers and are likely to want very heavy, high-powered bass you should select a model with much higher bridged power instead.

For most people a 50W RMS x 4 amplifier is fine, as it provides sufficient volume and bridging the amp generally provides around 150W into 4 ohms, which is sufficient to drive a subwoofer well for great bass sound.

For great sound with additional high-volume ability, I would choose a 75W per channel or higher model.


The best 4 channel car amplifier choices

1. Alpine FRV-F300 – Great sound in a small package – one of the best values available today!

Image of MRV-F300 amplifier end

This is one of the most compact and best sounding 4 channel car amps today. It features end caps that snap on and off for a cleaner-looking installation, great sound, 50W x 4 (4 ohm) / 75W x 4 (2 ohm) power, and is the next evolution in car class D technology. It measures only 7 7/8″ W x 6.5″ D x 2 3/16″ H (200 x 165 x 55 mm) and is so small it easily fits under seats too. It’s bridgeable to 150W into 4 ohms.

Alpine has done additional engineering work to reduce noise in the model, and it shows…or should I say it can be heard! Few class D amps can say the same.

Alpine MRV-F300 4 channel amp end view

Full crossovers as expected and a bass boost is available on channels 3/4 as well. Speaker level inputs are provided, too, in case you have a factory system you’re looking to upgrade. I’m so impressed with it that I did a full review you can read here. This is a fantastic and great sounding powerhouse you shouldn’t miss! It sells for close to $150, depending on the retailer.

It’s a very cool amp that’s affordable and one of the best all-around buys. Don’t waste any more time if you’re looking for a fantastic-sounding way to power system – head over to check out the amazing reviews at Amazon now.

2. Rockford Fosgate Punch P400X4 – Powerful, all-out fantastic sound and bonus setup features

Punch P400X4 top view

If your budget allows you to spend a little more, the P400X4 is one of the best on the market today. Rockford Fosgate has used class A/B design with their own Trans-ANA circuitry to deliver lower noise and some of the best sound quality available in this price range (around $200).

The company’s legendary expertise in car audio design makes it possible to get all of this in an 11-1/8 x 2-7/16 x 8-13/16″ size. That’s because the company uses the latest and best electronic components available –not the cheapest like competitors!

Punch P400X4 controls view

The high and low pass crossovers are adjustable to 250Hz, while the Punch EQ2 is unique from other brands in that it’s adjustable for both bass and treble with 0-18 dB level possible at 45Hz and 12.5KHz.

A Punch EQ remote control knob (sold separately) can be added for adjusting the sound while driving. It doesn’t support speaker level inputs, but a 2/4 way input switch is provided for the RCA inputs.

What I really love – and what definitely sets it aside from others, is the C.L.E.A.N. gain setup system feature which, when used with the included test tone CD, actually allows the amp to indicate signal levels to aid in setting up the amp gain. It allows you to the lowest-noise and best optimization for your amp.

The amp is conservatively rated (will actually exceed its rated specs) at 50W x 4 into 4 ohms (100W x 4 into 2 ohms) and 200W x 2 when bridged to 4 ohms. A certificate of performance verification is included, too!

It seems like so many online retailers are charging way too much for it, so take my advice and check out the lower price I've found at Amazon.

3. MTX Audio Thunder 75.4 – 75W x 4 of clean, reliable MTX quality power in a smaller package

MTX Thunder 75.4 side view

If you’re wanting the absolute lowest noise in your music but still want something affordable, the Thunder 75.4 can give you that – and more power in a smaller package than other similar amps!

MTX has managed to fit 75W x 4 (@ 4 ohm) channels of crisp, powerful musical reproduction into a package that’s only 12-5/8″W x 2-1/4″H x 6-5/16″D in size thanks to using surface mount technology (SMT). It can also deliver 100W x 4 @ 2 ohms and 200W x 2 bridged to 4 ohms.

MTX Thunder 75.4 end 1

The high-pass crossover is adjustable and reaches as high as 750Hz while the low pass is adjustable to 200Hz. 4 gauge-capable power connection terminals and well-made, secure speaker wire terminals round out a great design you’ll love. However it doesn’t provide speaker level inputs.

It’s a fantastic and powerful compromise between cost, size, and power, selling for less than $200.

Head over to check out the fantastic reviews and current price at Amazon today.

4. Alpine KTP-445U Mini Amplifier – One of the smallest but best sounding mini amps available today. Truly a great amp that fits nearly anywhere.Image of Alpine KPA-445U mini amplifier controls

As I wrote about in my extensive review, the KTP-445U is a marvel of Alpine’s expertise in compact audio based on class D technology. As not all of us have room for a standard sized amplifier (even the compact ones listed here) it solves the problem of having very limited installation space while still providing up to 45W of clean sounding power into 4 channels! And it even handles 2 ohm speaker loads.

The amp measures an astounding 7 7/16 x 1.5 x 2.5″ (189 x 38.2 x 64.5 mm) in size. That’s smaller than pretty much any comparable amplifier available anywhere in the world today! It can be installed using the included brackets or even using zip ties if you’re working with a more difficult installation challenge like putting it inside a dashboard opening.

Image of Alpine KPA-445U with accessories

Even better is that it features built-in high and low-pass crossovers which are enabled by switches on the bottom. You can also use all 4 channels with only a 2-channel input source thanks the the built-in “Y” adapter function. Both RCA and speaker-level inputs are provided.

Alpine has taken great care with a fresh design of their own in order to minimize noise and keep the sound quality great, responsive, and crisp, with excellent high-end response you’ll love. It sells for somewhere around $160.

Head over to check out the amazing reviews from others and the best price at Amazon.

5. Planet Audio Anarchy AC1200.4 – 4 channels of good budget power and sound that works

PLanet Audio AC1200.4 amp top

Have less than $100 to spend? You’re in luck, as you can still get a good buy and plenty of good, powerful musical sound that’s easy to use and looks good too. It can also be used with factory speaker level systems. Thanks to the AB traditional design you can spend less and still get better sound quality than some of the low-end competing products out there today.

Power is 113W RMS x 4 into 4 ohms (225W x 4 into 2 ohms) and bridged 450W x 2 into 4 ohms. It features high/low pass 12dB crossovers and an adjustable 0-18dB bass boost on channels 3/4. It also has thermal and speaker short protection circuitry.

lanet Audio AC1600.4 amp end view

The Planet Audio amp shares the same basic design as the parent Boss company brand, just so you know. It’s not on the level of the models I’ve listed above, but offers decent quality and isn’t short on having enough power to let you enjoy a great system in your vehicle.

It’s a good deal and budget priced. You can check out the current price and the many happy reviews before buying.

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