Does A Subwoofer Need An Amp? All Things You Need To Know

As a matter of fact, you can’t leave out a subwoofer in your audio setup if you want a quality listening experience. However, this unit cannot reproduce the deepest and most powerful bass. It needs a supporting device called an amplifier. Does a subwoofer need an amp?

Technically, a subwoofer is also a speaker, and all speakers need amplifier support. Otherwise, you will not hear the sound. However, depending on the type of gadget, support will be provided in a variety of ways.

This article will help you learn more about these two types of subs and why amps are such an integral part of any sound system.

​​Does A Subwoofer Need An Amp?

Sound system for car stereo - Does a subwoofer need an amp

Sound system for car stereo

The answer is yes. Subwoofers are inherently a form of speakers, so they all need an amplifier. Some get support from the external amp, while a few subs integrate with the internal amp.

The construction of the subs is to produce sound at low frequencies. This regeneration process takes a lot of energy.

If you’re equipping the subwoofer as part of a massive audio system, the system will automatically distribute power between the settings, so there won’t be any hiccups.

However, in the case of a standalone woofer, there is always a risk that it consumes more power than the receiver and the rest of the audio system.

So, the device will not be able to deliver deep bass clearly and resonantly.

The subwoofers that integrate with the amp are called active or powered subs. Also, devices that need the support of an external amplifier are passive subs.

What Does An Amplifier Do?

Amplifiers are really important to your audio system, especially in a car, RV or boat. It will take the weaker signal and amplify it.

A simple example is when you talk into a microphone connected to the source, the voice coming out through the speaker will be louder.

The amplifier acts as a microphone to turn the weak input signal into stronger and louder. As a result, output devices such as speakers and subwoofers can capture and output that audio signal.

Typically, the head unit will provide a low power signal (RCA output) compatible with the amp to power your woofer.

This weak power cannot provide enough for the subs to work without an amplifier. Many large subs will even require a separate amp to support them.

Amps are an integral part of any audio system. You can find it as a standalone unit or integrated into your car stereo.

When choosing audio equipment for your car or RV, you often come across the outputs. Often they will come with numbers like 4 x 50W Peak.

This number means that the head unit’s amp has an output power of 50W per channel, and it can output up to four channels.

What Is Sub And Amp Matching?

Black guitar amplifier with jack plugged in - Does a subwoofer need an amp

Black guitar amplifier with jack plugged in

When you look at subwoofers’ specifications, you may notice impedance in units of “ohm.” This number is the load that the amp has to bear from the sub.

Since the power of the amplifiers depends on the load attached, you need to make sure they are compatible with each other.

Two notable metrics are output impedance and power. The output power, in this case, is in the form of watts root mean square (RMS).

Watt RMS for subs means the amount of power the device can handle without damaging or distorting the sound. For amps, it refers to the device’s output power level.

With that knowledge, you can combine a sub and an amp with the following basic steps:

  • Determine the RMS watts RMS of your standalone woofer or subsystem.
  • Determine the impedance of the subwoofer.
  • At the right impedance, choose an amp that can produce between 75 and 150% of the RMS watts the sub can handle.

If you already have an amplifier, follow these steps to find the best subwoofer:

  • Determine the output power of amps at different impedance values. Use units of watts RMS.
  • Divide the output power by the number of subs you have. You will get the optimal RMS value for the device. The number of subs usually fluctuates at 75-150% of the RMS.
  • You should pay attention if using different woofers. Different devices will have different voice coils and wiring methods that affect impedance.
  • Select a sub that matches the parameters and criteria above.

If you want a more visual and detailed guide, check out the video below.

What Are Passive Subwoofers?

Black speaker car audio music system - Does a subwoofer need an amp

Black speaker car audio music system

Passive subwoofers are devices that cannot function without receiving power from external amplifiers.

Technically, they are speakers that can output sound at low frequencies. It needs the support of a suitable amp to receive the right amount of power to produce a bass effect.

If you do the wrong combination, the device will show incompatibility. The most common signs are dim lights and unstable sounds.

The factors that affect the power level of the subs are the specs of the device, the size of the space, and the amount of bass you want.

Those who install a custom sound system often use this device because they don’t want to have additional connection problems.

When paired with a matching amplifier, the passive subwoofer produces excellent bass. Therefore, it is also the top choice of audiophiles.

What Are Powered Or Active Subwoofers?

Man's hand adjusting volume knob -Does a subwoofer need an amp

Man’s hand adjusting volume knob

Active subwoofers are devices with built-in amps. As a result, they do not need to draw power from other system parts.

Instead, you must connect this device to an external power source.

The first advantage is that users can tune this unit to output bass at higher levels without placing a higher power load on the amp or audio source.

Better yet, you can connect powered subs to external amps to share audio data. This action will be necessary if you also own passive subs simultaneously.

Equipping many subs in one space is no longer a strange thing. Many people do this to ensure that the bass is evenly distributed to different corners or nooks and crannies.

Since this device does not need the help of an additional amplifier, its popularity in the market is quite large. Convenience is the key point that consumers prefer.

You don’t have to worry about matching and finding the right amp. Powered subs usually come with buttons on the back for you to customize the crossovers and other parameters.

Why Don’t You Need An Amplifier For Active Subwoofers?

Active subwoofers do not need the support of an external amp to operate. Instead, you need to connect them to an audio source and a power source.

When installing, users only need to link this device directly to the subwoofer preamp output (LFE input) or audio/video receiver.

Many people call them “Pre Out” and “Line Out,” respectively. You can find these parts on the back of the woofer.

Passive Or Active: Which Sub Should You Choose?

Most consumers opt for active subwoofers. They are extremely convenient and flexible when they have built-in amplifiers and do not need the support of external devices.

It is an affordable choice for the average home theater receiver or audio system.

Home audio receivers often come with one- or two-line preamp line outputs. The manufacturer designed this unit to connect to powered woofers straight out of the box.

Some people choose passive subwoofers to get better sound quality. However, the cost you need to spend on a matching amp can be more than the subs.

Is this investment worth it? It is a question worth thinking about for those on a tight budget.

Power options are not the only factor affecting the quality of woofers. Active or passive is no longer a problem if it can’t bring out the deep bass you want.


Please find the answers below if you have any questions regarding subwoofers and amplifiers.

FAQs - Does a subwoofer need an amp


1. What Are The Benefits Of An External Amplifier For The Car Stereo?

The main effect of an amplification amplifier is to help improve the clarity and reverberation of music. As a result, it will not blend in with road noise.

It gives your sound system more headroom to deliver powerful, dynamic music without distortion.

2. Does A Subwoofer Have A Built-In Amplifier?

There is a type of subwoofer with a built-in amplifier that is powered or active subs. Many people use this device because it doesn’t depend on any other amp or receiver gain limits.

However, using active or passive woofers is entirely up to you. It does not affect product quality.

3. How Many Watts Do You Need For A Sub?

You should look for equipment with an RMS of 200 to 300 watts.

250 to 500 watts of power output for amplifiers is a good start. You will need about 50 watts per channel.

For systems that require 100 watts RMS per channel, you should look for a power rating of around 1000 watts. However, this level is quite rare in the market.


Every subwoofer needs an amplifier. However, depending on the type of device, it will receive support in different ways.

With that in mind, many people choose powered subs because they are more flexible and convenient. You can also avoid the hassle around finding the right power amplifier.

Passive subs are still an interesting choice for those who really want to invest in their sound system.

What is your decision? Don’t hesitate to share it with us on My Car Gears! All of your comments help build our growing community of audiophiles.

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