Car Amplifier Buying Guide

For experienced audiophiles, choosing an amplifier is a rewarding task. But for those of you new to aftermarket car audio, choosing an amplifier can be another headache. Your speakers and subwoofer all come with different specifications, not to mention that funky word impedance. Ultimately there are infinite possibilities when constructing your aftermarket system. But your friends at Sonic Electronix are here to eliminate the confusion and boil this topic down to just a handful of possibilities that will serve the large majority of our customers.

Section Description
1. Channel Configuration Choosing the number of channels needed is simpler than it seems. If you have four door speakers, you'll need four channels - one channel per speaker. If you want to add a sub you'll need an additional channel. There are other options available but that is recommended only for the experts.
2. Watts Decoded Matching the watts of your speakers/subs is an integral part of your aftermarket system. A general rule is that it is always better to have extra power (headroom) than too little power.
3. Wiring Subs There are two options when wiring a DVC sub. Series doubles the impedance lowering the power whereas parallel cuts the ohm load in half contributing more power.
4. Examples This section gives real life examples to help you better understand this blog.
5. Sonic's Secret There are many secrets to share with our amazing customers. Check out this section to get insider information from technicians with decades of experience.

One of the first things you need to consider when constructing an aftermarket system is what amplifier to use. Sure we all want louder sound and more bass but none of this is possible without an amplifier. Once you have your amp, all you have to do is match the power specifications of each speaker/woofer to the amp. But don’t worry this comprehensive guide will give you all the information you need.

1Channel Configuration

The first thing you should consider is how many channels you need. This topic will be answered throughout the following section.

Monoblock Amplifier

NVX JAD1200.1 True 1200W RMS, Class D Monoblock Amplifier with Bass Remote Included

Shop Monoblock Amps!

Typically a monoblock amplifier is for bass; your subwoofer(s). A monoblock amp can be used to run one or mulltiple subwoofers. The important thing is too never drop the ohm load below what is listed, typically 2 or 1 ohms. Also make sure you have the correct power at that ohm load.  If you don’t satisfy the demands of your woofer, it will sound awful and there is really no reason to invest. Never cheap out on your amplifier this will directly hinder the sound quality.  Two of my favorite brands are NVX and JL Audio. An amplifier from either manufacturer is gauranteed to give you years of reliability and utmost sound quality.

2 and 4 Channel Amplifier

NVX JAD800.4 True 800W RMS, Full Range Class D 4-Channel Amplifier (JAD-800.4)

Shop 4 Channel Amps!

2 and 4 channel amplifiers are typically used to power your door speakers. If you have four speakers it is advised you utilize a 4 channel amplifier rather than a 2 channel amplifier. Stacking speakers will cut the ohm load in half, running your amp unnecessarily hot, and directly affecting your sound quality. Assuming watts and impedance are matched the sound quality will be impeccable. However brands do matter, not all products are created equal! Again NVX and JL Audio are my personal favorites when it comes to amplifiers.

The power demand of your speakers are going to be significantly less than your subwoofer so it is recommended your sub is powered by a monoblock amp and your 4 door speakers powered by a 4 channel amp.

5+ Channel Amplifier

NVX JAD900.5 True 900W RMS, Full Range Class D 5-Channel Amplifier with Bass Remote

Shop 5+ Channel Amps!

A 5+ channel amplifier can be used for an entire system. 2 front speakers, 2 rear speaker and a sub all off one amazing amplifier. Again be conscious of the power demands/impedance of all the different components of your system.

Typically you can decipher what kind of amp it is by the model name and number. Often the numbers represent the wattage and total channels. For example NVX clearly labels all amplifiers so the customer can identify the wattage and channels almost instantly. The JAD1200.1D is a class D monoblock amplifier at 1200w whereas a JAD900.5 is a 5 channel amplifier at 900w. The same is true for other brands like JL Audio. The RD500/1 is a class D monoblock amplifier with 500 watts and the RD900/5 follows the same rule; 5 channel class D amp with a power handling of 900 watts. Ultimately this is true for most but not all products, there is never a universal truth when referring to car audio.

2Watts Decoded

Speakers and subwoofers love good clean power, you can never have too much power; we call this headroom. The positive side of this is that your amp will never run in distortion and flat-wave your speakers. This will help everything in your system sound better and last longer. It may sound counter-logical but one of the worst things you can do is under-power your speaker/sub.

  • What I am saying is if you have a 50 watt speaker, it will sound better and last longer if you run it off a 75 watt amp rather than a 25 watt amp.

Matching your system’s power requirement to your amplifier is actually much simpler than it seems. Always utilize the RMS power when determining which amplifier you will need. RMS stands for Root Mean Square, but what it means to you is the actual power demand you must fulfill. Peak power is never sustainable, our tech calls it JBIB (just before it blows).

  • Brands do matter, because another rating our tech calls unicorn watts exists among certain manufacturers. That 10,000 watt amp you bought for $99 does not actually have 10,000 watts.

Next you’ll want to consider impedance, which comes in the form of ohms. This determines the power output of an amp. It’s an inverse relationship because a lower impedance demands more power from the amplifier. Although the idea of more power is desirable an amplifier will have greater longevity if played at a higher impedance.

understanding watts and volts and impedance

When pairing your speaker/subwoofer with your amplifier, there are a couple things to keep in mind. You’ll want your amplifier to match the RMS rating of your speakers/sub between 75-150% of the power demand. A speaker with a power handling of 200 watts demands an amplifier with a power rating between 150 and 300 watts. Next you’ll need to match impedance. A 2 ohm woofer needs an amp stable down to 2 ohms or less. Bare in mind that the wire gauge can affect impedance, with that in mind use a good quality wire that is a proper gauge for the power you are running.

Generally for mids and highs (door speakers – driver and tweeter) you’ll run at 4 ohms. Be sure to use 1 channel per speaker and your sound quality will thank you. Broken down a bit more, two speakers need a 2 channel amp whereas 4 speakers need a four channel amp. If you are not a trained professional don’t try anything fancy, stick to the basics. Chances are you will need extra guidance and a blog with this information will only complicate matters. Rather call into our expert customer service department, ask for Weber, and refer to this blog.

ohm explained

General info use Watt’s law: Volts x Amps = Watts (subtract for efficiency). Now that you understand the power output of your amplifier; next you’ll have to decide how you will wire your subs.

3Wiring Subs

If you have a DVC sub, you have two wiring options; series or parallel. The easiest way to identify whether your sub is a DVC or SVC, is to simply count the terminals. A subwoofer with 4 wiring terminals is a Dual Voice Coil and a sub with 2 wiring terminals is a Single Voice Coil. Depending on how you utilize these coils will directly affect the impedance level.

Kicker Comp C124 (10C124) SVC and NVX NSW124v2 DVC

The left features Kicker’s 12″ Comp C124 (SVC) and on the right we have NVX’s 12″ NSW124v2 (DVC). Note the difference in terminals.

Series

Series wiring will double the ohm load making your woofers demand less power. This will increase the longevity of your subwoofer. A couple example to better understand this concept:

  • A dual two ohm woofer wired in series will give you four ohms
  • A dual four ohm woofer wired in series will give you eight ohms

Series Wiring

Parallel

Parallel wiring will cut the ohm load in half, giving you more power from the amplifier. Although more power is desirable, keep in mind the harder you work your speaker/sub the shorter the lifespan. An example to better understand this concept:

  • A dual two ohm woofer in parallel will give you one ohm.
  • A dual four ohm woofer in parallel will give you two ohms.

Parallel Wiring

Next I will give you some real life examples to better understand the concepts listed in this blog.

4Examples

This section gives you examples with actual products and specs. This will help you better understand the blog and apply these concepts to your own system.

  1. If you have two 6.5″ NVX XSP component speakers in the front and two 6.5″ NVX VSP coaxial speakers in the rear just look at the recommended watts when choosing an amplifier. You can match these speakers with an NVX JAD 800.4 amp. It is as if the cats over at NVX had a plan for these products to be used together. Please note you should adjust this system with the fader on your stereo rather than the gain knob on your amp.
  2. With NVX’s JAD 900.5 amp, you can wire all four speakers and a subwoofer off this single amplifier! For this example you can utilize the same 6.5″ XSP component speakers with the same 6.5″ VSP coaxial speakers. With the addition of the NVX VSW104v2 10″ woofer, your system has been completely transformed without having to invest thousands of dollars. For this specific example you’ll run 4 channels at 4 ohms for the speakers and the fifth channel at 2 ohms for the woofer.
    1. This type of system is recommended for those that want quality sound without dominating bass.

5Sonic’s Secret

  1. Keep it simple: You should always follow the KISS rule. Keep it simple stupid is something to live by if you are not experienced in the field. Those experienced in car audio installation can tinker with the rules because they are trained professionals. If you are not;  KISS!!Don’t try to get too fancy. Use an amp that fits your application and make sure the power handling matches your speakers and woofers. You won’t be disappointed!
  2. Don’t worry about AB vs D amps: This distinction was a concern when your father was purchasing aftermarket amplifiers. It used to be that AB was much cleaner and warmer offering fuller sound whereas a class D amplifier was more efficient in regards to power output. In today’s world, there is an insignificant difference between the two classes. The lines have blurred and the distinction has little meaning.
  3. Never trust unicorn watts: Always use a name brand amplifier that is compliant with CEA standards. Certain manufacturers base their power rating off unicorn watts which are essentially made up and not tested. The majority of phone calls we receive are from distraught customers because they trusted unicorn watts when construing their system.

Born in a subwoofer box, music has always been my passion. At the proud age of 9 I began driving. The two eventually met and led to my career at Sonic Electronix.

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