What Size Amp Do I Need for 2 400 Watt Subs?

For two 400 watt subs, you will need an amplifier that can produce at least 800 watts rms of power. Getting the right size amp for your subs is crucial for getting the maximum power and sound output.

If you have two 400 watt subs, you will need an amplifier that can deliver at least 800 watts rms of power to drive the subs. The rms power rating is what indicates the continuous power the amplifier can deliver to the subs.

What Size Amp Do I Need for 2 400 Watt Subs

Rms Wattage Explained And Impedance

When it comes to picking the right amp for your subs, understanding rms wattage and impedance is crucial.

Here’s what you need to know about rms wattage and how it affects your sub’s performance:

  • Rms (root mean square) wattage is a measure of the continuous power output your amp can provide to your subs.
  • It is important to match the rms wattage of your amp and subs to prevent damage to your equipment.
  • Overpowering your subs may cause damage or even burn out the voice coils, while underpowering them can lead to distorted and weak sound.

Impedance Explained

Impedance is another important factor to consider. Here are the key points regarding impedance:

  • Impedance determines how much electrical resistance your subs offer to the amp’s output.
  • Measured in ohms (ω), subs can have an impedance of either 2, 4, or 8 ohms.
  • Lower impedance means more power can be delivered to the subs, but they may also require more power to produce the same volume.
  • Most amps are built to handle a range of impedance, so it’s important to check that your amp can handle the impedance of your subs.

The Relationship Between Rms Wattage And Impedance

The relationship between rms wattage and impedance is essential to understand when building your sound system. Here’s why:

  • Higher impedance subs require more power to produce the same volume as lower impedance subs.
  • Lower impedance subs demand more power from the amp and can handle more power input.
  • The impedance of your subs will affect the amount of power your amp will deliver to them.
  • Match your subs’ impedance and rms wattage with the amp’s output to ensure optimal performance and prevent damage.

Remember to keep these factors in mind when choosing the right amp for your subs. Proper matching of rms wattage and impedance will result in higher quality and longer-lasting sound performance.

Calculating The Ideal Amp Wattage

If you’re a bass lover, you know that getting the right amp is crucial. You’ve got a pair of 400-watt subs, but what size amp should you get? Don’t worry; we’re here to help you calculate the ideal amp wattage.

Keep reading to find out how to get the most out of your subs.

Determining The Total Wattage Output Of Subs

Before you can determine what size amp you need, you need to know the total wattage output of your subs. Here’s how to calculate it:

  • Find the nominal impedance of your subs.
  • Multiply the nominal impedance by the number of subs you have.
  • Find the rms power rating of your subs.
  • Multiply the rms power rating by the number of subs you have.
  • Add these two numbers together to get your total wattage output.

Matching The Amp Wattage To The Subs

Now that you know the total wattage output of your subs, you can match it to the amp wattage. Here are some things to consider:

  • Make sure the amp wattage matches or exceeds the total wattage output of your subs. This will ensure that you get the most out of your subs without damaging them.
  • Look for an amp with a high signal-to-noise ratio (snr). This will ensure that you get clean, distortion-free sound.
  • Consider the class of the amp. Class a, ab, and d amps are commonly used for subs, but each has its advantages and disadvantages.
  • Make sure the amp is compatible with the impedance of your subs.

Factoring In Other Components

Finally, you need to factor in other components. Here are some things to keep in mind:

  • Check the wiring of your subs. Make sure they’re wired correctly for the amp you’re using.
  • Consider the type of enclosure you’re using. Different enclosures will affect the way the sub sounds.
  • Think about the music you’re listening to. If you listen to music with a lot of bass, you might need a more powerful amp than if you listen to other genres.

With these factors in mind, you’ll be able to find the perfect amp size for your 400-watt subs. Enjoy the bass!

Options For Types Of Amps

When it comes to powering your two 400 watt subs, having the right amplifier is key. But with so many different types of amps out there, it can be overwhelming to decide which one is the best fit for your setup.

Don’t worry, we’ve got you covered! Below are some of the most popular types of amps for subs along with their key features to help you make an informed decision.

Monoblock Amplifiers

Monoblock amplifiers, also known as single-channel amps, are designed specifically for subs. The key benefits of monoblock amps include their ability to efficiently deliver power to your subs, minimize distortion, and avoid interference with other car components. Here are some things to keep in mind if you opt for a monoblock amp:

  • Choose an amp that delivers around 200-300 watts per sub for optimal performance.
  • Look for an amp with high efficiency and a low thd (total harmonic distortion) rating- less than 1% is ideal.
  • Match the ohm rating of your subs with the ohm rating of your amp.

Two Channel Amplifiers

Two channel amps are a good choice if you have a limited budget or if you plan on powering a set of full range speakers in addition to your subs. Here are some of the key things to consider if you choose a two channel amp:

  • Choose an amp that delivers around 150-200 watts per sub for optimal performance.
  • Make sure that the amp has a built-in crossover to separate the frequencies going to your sub from those going to your other speakers.
  • Match the ohm rating of your subs with the ohm rating of your amp.

Multi-Channel Amplifiers

Multi-channel amps are a good option if you want to power more than just subs and full-range speakers. They’re versatile and can be used to power your whole car audio system. Here are some things to keep in mind if you choose a multi-channel amp:

  • Make sure to choose an amp that is rated for the correct power output for your subs- around 150-200 watts per sub is recommended.
  • Look for an amp with high efficiency and a low thd rating- less than 1% is ideal.
  • Match the ohm rating of your subs with the ohm rating of your amp.

Amplifier Wiring Kits

No matter which type of amp you choose, it’s important to make sure that you have the right wiring kit to connect your amp to your subs and power source. Here are some things to keep in mind when choosing an amp wiring kit:

  • Make sure the kit is designed for your amp’s power rating and the ohm rating of your subs.
  • Choose a kit with high quality cables and connectors for maximum performance and durability.
  • Make sure the kit includes all necessary components- power cables, ground wires, rca cables, and fuses.

Choosing The Best Amplifier For Your Setup

If you’re planning to install 2 400 watt subs in your car, choosing the right amplifier is essential to maximize their potential. This blog post will give you some insights on what to consider when purchasing an amp for your subs.

Subwoofer And Amplifier Compatibility

Your subwoofers’ specifications should match your amplifier’s capabilities. Here are some factors to ensure compatibility:

  • Amplifiers rms power rating should match (or exceed) subwoofers rms power rating
  • Impedance (measured in ohms) should match between the subwoofers and the amplifier
  • Wiring should be correctly set up and secure
  • The amplifier’s crossover and equalizer settings should complement the subwoofers’ frequency range

Amplifier Class Options

The amplifier class defines the way it processes the audio signal. Here are the most common amplifier classes and their advantages and disadvantages:

  • Class a: Most desirable in terms of audio quality, but highly inefficient and expensive
  • Class b: More efficient than class a but can produce distortion at low volumes and require more complex circuitry to eliminate it
  • Class ab: Combine the advantages of both previous classes and are the most popular choice on the market
  • Class d: Most efficient in terms of power consumption, but can produce distortion at high frequencies

The Importance Of Brand And Performance

Brand reputation and performance are a crucial factor in choosing the right amplifier. Here are some of the best brands in the car audio industry:

  • Jl audio
  • Rockford fosgate
  • Kicker
  • Alpine
  • Kenwood

Make sure to consider an amplifiers’ performance in terms of power, distortion levels, frequency response, and signal-to-noise ratio.

By following these guidelines, you’re on your way to choosing the perfect amplifier for your setup. Keep in mind that while buying a high-quality amplifier can cost you more up-front, it is a one-time investment that can significantly upgrade your overall sound experience.

Installing Your Amplifier

Installing a powerful amplifier can help you enhance your car stereo system’s bass. When it comes to managing two 400-watt subs, you need to ensure that the amplifier’s size is compatible with your subwoofers. Installing your amplifier consists of four crucial steps, which are as follows:

Preparing Your Vehicle

Before you start installing your amplifier, make sure you have all the necessary tools to prevent any hassles. Here are some of the essential items that you will need to prepare your vehicle:

  • Power drill
  • Screwdriver set
  • Socket set
  • Cable ties
  • Crimping tool
  • Wire cutter/stripper

Mounting The Amplifier

The next step is to mount your car amplifier correctly. You must pick an appropriate spot to avoid interfering with other car parts. Here are some tips to help you mount the car amplifier:

  • Choose an area that is free from dust and moisture.
  • Check the space behind the chosen location to make sure no obstructions are present.
  • Use a drill to screw the amplifier in position.

Wiring Your Amplifier

When it comes to wiring your amplifier, you need to be extra cautious. Failing to wire your amplifier correctly can cause electrical damage to your car. Here is a step-by-step guide about wiring your amplifier:

  • Use the wiring diagram that comes with your amplifier to complete the installation.
  • Connect the power cable from the car battery to the amplifier’s positive terminal.
  • Join the ground wire from the amplifier to the car’s metal body to enable a safe electrical connection.

Testing Your Setup

After wiring your amplifier, it’s time to check if everything is in order. Testing your setup ensures that your amplifier is working correctly, and you can enjoy your music without any interruptions. Here are some troubleshooting tips to help you test your set up:

  • Check if the output power is enough and provides the required bass.
  • Ensure that the subwoofers are not overheating or vibrating excessively.
  • Make sure all other car sound devices are working correctly.

Installing your amplifier for two 400-watt subs requires some technical know-how. However, by following the steps mentioned above, you can enjoy the high-quality sound from your car subwoofers without any issues.

Frequently Asked Questions

What Size Amp Is Best For 2 400 Watt Subs?

To power two 400 watt subs, you’ll need an amplifier that can output at least 800 watts rms at the speaker’s impedance. A good rule of thumb is to have an amplifier that is capable of producing as much power as the subwoofers rms rating.

How Many Channels Do I Need For 2 Subs?

You will need at least 2 or 4 channels for driving 2 subs, 1 or 2 subs per channel, respectively. If you have dual voice coil subs, you can wire the coils in series or parallel to produce and match rms impedance with the amp channels.

What Is Rms Power And How Many Watts Do I Need?

Rms stands for root mean square and measures a speaker’s continuous power handling ability. It’s essential to match the amp’s rms power output with the subwoofers. Ideally, you want an amplifier capable of producing power equal to the total rms power of all subs combined.

How Do I Wire Two Subs To An Amplifier?

First, check the impedance of the subs and the amplifier’s capability to handle the impedance. Next, if you have two subs with single voice coil, wire them in parallel to the amp channel. If you have two subs with dual voice coil, wire them in series or parallel to match the amp’s impedance.

Can I Use A Car Stereo To Power 2 Subs?

Most car stereos don’t have enough wattage to power subs, so you’ll need a separate amplifier. You also need to check if the head unit has preamp outputs necessary for connecting to the amplifier, or if it has speaker-level outputs that run directly to the subs.


After considering the factors such as speaker sensitivity, amplifier power rating, and your own preferences, determining the ideal amp size for a pair of 400-watt subs can be tricky. However, the general rule of thumb is to match the amplifier power rating with the combined rms power handling of both subs to achieve optimum performance without causing any damage to the equipment.

Additionally, it’s advisable to use a high-quality amplifier with efficient heat dissipation and adjustable gain levels to manage the power output. Selecting the right amp size for your subs plays a crucial role in enhancing your audio experience while avoiding potential equipment damage.

With proper research and understanding of the technical specifications, you can select a suitable amplifier that delivers excellent sound quality, reliability, and durability. So set up your system, crank up those tunes, and enjoy the incredible bass that your new subs & amplifier combination delivers!

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