How to Match Car Subwoofers and Amplifiers

With a plethora of subwoofers and amplifiers on the market, making the decision on how to match your subwoofers and amplifiers can be a pain.

However, taking a few factors into consideration, you can easily buy the best amp which goes perfectly with your subwoofer setup. Your top car subwoofer choices and your amplifier choices must be matched, otherwise you’ll be stuck with subpar audio.

The major factors which you should consider include the RMS power rating, the impedance of the amp, the number of channels your subwoofer has, and the enclosure of the amp. Let’s start with the first, and we’ll make our way down the list to help you make the right choice.

RMS Power Rating

The root mean square (RMS) power rating of an amplifier is a factor which lets you know how much power it can sustain. This is the power generated in the form of heat and vibration. The maximum value is the one which can be sustained without damaging the voice coil.

This should not be confused with maximum power, which sounds like a more useful figure – though it only really tells you the maximum resilience to a burst of power, not power figures which can be sustained over a long period of time.

The rule of thumb for matching your subwoofer and your amplifier is to calculate the power range of the amplifier, that is, the approximate range of power of the subwoofer that the amplifier should be able to sustain. This is between 0.9 times the subwoofer power and 1.2 times the subwoofer power.

If you have a subwoofer setup which consumes 1400W as a total, your power range is between 1260W and 1680W. You should ideally go in for an amplifier which has more power than the calculated maximum power (1800W is a good estimate), to give you what’s called headroom. This will help your amplifier work for longer, since it reduces heat exposure.

Underpowering your amplifier will give you subpar audio quality. It also causes distortion which heats up your voice coil, and this can lead to irreparable damage to your subwoofer system.


The impedance of any electrical element is defined as the electrical resistance offered by the element to the flow of current across its electrical terminals.

The key takeaway here is that the impedance of the amplifier and your subwoofer setup should be matched. Now, one might be inclined to think that “match” here means that the amplifier and the subwoofer should have the same impedance.

Unfortunately, this only applies to situations where there is a single subwoofer.

Most car audio equipment manufacturers give you the option of 2 ohm or 4 ohm subwoofers. This changes in case of dual voice coil subwoofers, where your amplifier needs to have twice the impedance of the subwoofer. This is because of the dual input/output connections which dual voice coil subwoofers have.

Also, for multiple subwoofers, your amplifier must accommodate the impedance needs for each subwoofer. Hence, make this calculation before you buy the amplifier.

If you try to use a low impedance amplifier with a higher impedance subwoofer system, you’ll have excessive heating which leads to poor audio quality and long term damage to the subwoofer system and the amplifier. Most subwoofer systems shut themselves off for protection; there’s no point in taking the risk though.

In case you’re confused about matching the impedance, check out this helpful article.


A car amplifier can have as many as 6 channels. The most recommended ones, however, are monoblock or single channel amplifiers. This implies that the amplifier processes one audio signal through a single channel connected to the subwoofer.

Multiple subwoofers can be connected to the single channel – however, each subwoofer receives the same frequency. The lower range of frequencies aren’t heard as much as the medium-range and high-range frequencies that car speakers generally produce, hence the single channel is more than sufficient for your audio needs.

Using multiple channel amplifiers limits your power output and impedance.


Enclosures are probably the most underrated part of the sound system as a whole. The enclosure quality can influence the audio output to a large extent. Bear in mind that sealed enclosures have better amplifiers. There are basically two kinds of enclosures – sealed and ported. The difference is mainly in the kind of audio they produce, with a few physical differences.

The sealed enclosures which give you a tight and crisp bass sound, are smaller in size but require more power for louder bass. Ported enclosures, on the other hand, give you a very boomy and loud, but less accurate bass sound. Ported enclosures tend to be larger and don’t require as much power.

Some other things you should keep in mind are:

  1. CEA compliance for audio products is a necessity. Make sure your amplifier satisfies this requirement.
  2. As a general rule, if your car is less than 5 metres long, and you do not listen to music at very loud volumes, an amplifier with 400 watts is more than likely to suffice. Only go in for more if you have more complicated setups.

If you’re planning on installing the subwoofer on your own, do check out our detailed guide.


Making sure your amplifier and subwoofer match not only affects the longevity of the system, but goes a long way in making sure you get the best audio experience possible. The most important factors which you have to keep in mind include the power output in RMS terms, the impedance of the amplifier, the number of channels in the amplifier and the enclosure.

Keeping these factors will make sure your systems lasts longer, plays better, and keeps the costs in check at the same time! Happy listening!

About the Author Roger

Roger is a mechanical engineer by day and grease monkey by night, who spends all his free time tweaking things in his car. His love for car audio equipment is only matched by his desire to help others find the best products suited to their needs.

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