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An amp is key to better sound in the car

One thing every music lover should discover

One of the best things you can do to improve your sound is to add an amplifier to your system. Whether you like it loud or soft, extra power will breathe life into your music, bringing out all of its emotional excitement, impact, and fine detail. The good news is, the compact design of many amps makes it possible for more cars than ever to have one. The kind of amp you need will depend on what you’re planning to power.

electric guitar player shredding

What does an amplifier do?

  • An amplifier boosts the sound to overcome road noise, improving your music’s clarity and intelligibility.
  • It’ll increase your system’s headroom — the ability to play sudden blasts of music with power and ease, without distortion.
  • Most aftermarket speakers sound better when powered by an amp than they would with just an in-dash stereo.
  • A subwoofer requires an amplifier — bass sound waves take up lots of air space and need lots of power to propagate.
Car amp under the front seat

4-channel amplifiers

If you’re looking simply for more power for your front and rear speakers, a 4-channel amplifier is the way to go.

Diagram of 4-channel amp

They basically come in four sizes:

  • 40 to 50 watts per channel compact power packs that conveniently connect to factory wiring and can often fit behind the dash for a stealthy installation.
  • 50 watts per channel amplifiers work well for most people, producing plenty of volume in most vehicles.
  • 75 watts per channel amplifiers are for those who like it a bit louder in their larger vehicles.
  • 100-up watts per channel amps are for when you want your music boosted to competition-level volume.

A 4-channel amplifier can also power two speakers with its front channels plus a subwoofer from bridged rear channels. Often, people build up their system piece by piece, and start with a 4-channel amp running front speakers and a sub while leaving the rear speakers powered by the receiver. Then later, they add a dedicated subwoofer amplifier and connect the rear speakers to the unbridged rear channels of the 4-channel amp.

Compact amp in hand

Compact power packs like this can often fit behind the dash near the stereo

Mono (1-channel) amplifiers

People who just want to add a subwoofer to an existing system should consider a mono amplifier with bass EQ and a low-pass filter to help reproduce bass notes that are loud and clear.

Diagram of mono subwoofer amp

When adding a subwoofer, you need to blend the bass to balance with the rest of your system. Here's a rule-of-thumb guide to sub power:

  • If you're using your car's factory stereo — about 100 watts RMS of power for the bass will do nicely.
  • An aftermarket receiver — you might want 200 to 300 watts RMS of power for your sub.
  • Amplified speakers with around 50 watts RMS per channel — plan on about 500 watts RMS for bass
  • A 75 watts RMS or higher per channel system — now you're looking at 750 to 1,000 watts RMS for your sub. Please thump responsibly.

It's true, you can use a multi-channel amplifier to run a subwoofer from bridged channels, but why bother?  Most multi-channel amps can't drive loads lower than 4 ohms when bridged, and don't have enough power to drive more than one sub. Mono, 1-channel amps are designed to work with a wider range of impedances, and have tone controls and filters specifically designed to help reproduce bass.

5-channel amplifiers

Planning to drive a full system — four speakers and a sub? In addition to conveniently centralizing all controls in one chassis, installing a 5-channel amplifier saves you from having to run two sets of power wires for separate speaker and subwoofer amps.

diagram of 5-channel amp

Many 5-channel amps can run and control a completely active 2-way front stage and subwoofer system all by themselves. Two channels drive the tweeters, two the midrange speakers, and the fifth channel powers the sub.

2-channel amplifiers

A lot of sports cars and trucks only have two speakers to begin with, so a 2-channel amplifier will be the most efficient way to power them. A 2-channel amp can also be used to run a subwoofer when in bridged, one-channel mode. Most people, however, choose a mono amplifier to drive their subs because higher amounts of power are available in those amps. This same is true for 4- and 5-channel amps — they're more versatile and powerful than most 2-channel amplifiers.

Diagram of a 2-channel amp

3-, 6-, and 8-channel amplifiers

For those who want to run multiple speakers and subwoofers, there're specialized amplifiers out there that can take care of custom-designed systems. A 3-channel amp can power two speakers and a sub, for a compact, one-chassis solution in a small vehicle. Many 6-channel amplifiers are designed to accommodate 3-way systems, with onboard signal processing necessary to power tweeters, midrange drivers, and subs. Crutchfield carries an 8-channel amplifier with sophisticated computer-controlled digital signal processing suitable for a large, high-fidelity 3- or 4-way audio system.

close-up of an 8-channel amp controls

JL Audio's 8-channel amp makes nearly anything possible

You love your music — give it an amplifier

The major boost in musical impact and power that an amplifier will give to your system will also bring joy and excitement to your life on the road. For more information about adding power, you can refer to our Car amplifiers FAQ, or check out our Car amplifier buying guide.

Ready to shop?

See our entire selection of car amplifiers if you're ready to add more power to your system.

For expert one-on-one advice, call, chat, or email us today. And remember, free lifetime tech support is included with your Crutchfield purchase. Our tech support team will answer questions about installation, setting up and tuning the amp, and will help out if something ever goes wrong. 

  • Buck Pomerantz from Crutchfield

    Posted on 12/15/2017

    Anthony, Those two amplifiers will perform identically. For help deciding, why don't you get in touch with a member of Crutchfield's Sales Advisor Team via phone or chat - just click on the Contact us link at the very top of this page for more information.

  • Anthony from Baltimore

    Posted on 12/13/2017

    Hey Buck, I have a '12 Ford Focus sedan with an integrated HU that I don't want to replace. Based on your articles, I've settled on getting a small 4 channel 50W amp with signal-sensing turn-on. Now I'm stuck between the Alpine MRV-F300 and the Kenwood Excelon X301-4. Same features, same price, within 1' size; and (for the aesthetically inclined) each company offers a matching 500W mono amp that I can get later on to add a sub. Do you have any insights to which of the two would be better for me? Or maybe a better third option (at that size and price) that i've overlooked? Thanks!

  • Buck Pomerantz from Crutchfield

    Posted on 7/31/2017

    Michael, MOSFET stands for "metal oxide semiconductor field-effect transistor" and is an electronic component that switches high voltage using low voltage triggers. MOSFETs are used in all Classes of amplifiers. An amplifier's Class is based on the architecture of its output circuit and how long the output transistors are powered.

  • Michael Moale from Detroit

    Posted on 7/29/2017

    Buck, Read the info on amplifier classes and surmised that the class D is the cat's meow but was wondering what class a MOSFET amp fits in and your professional opinion about its overall sound clarity and efficiency in comparison to the class D. Thanks, Mike

  • Buck Pomerantz from Crutchfield

    Posted on 7/10/2017

    Dro, Perhaps this diagram can be a basic guide. In your case you'd replace the 4-channel amp in the diagram with your 5-channel amp and add the second subwoofer.

  • DroAquin from Chicago

    Posted on 7/7/2017

    Looking to get a pdx-v9 for components/sub and a pdx-m12 to add more power to a sub. How do you recommend wiring?


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