What Does a Capacitor Do for Subs?

Hey there, it’s great to have you here for the Ultimate Guide to the Functions of Subwoofer Capacitors!

As someone who loves music and has a passion for car audio systems, I know how frustrating it can be when your subwoofers don’t perform as expected. That’s why I’ve spent countless hours researching and testing capacitors to bring you this comprehensive guide.

In this article, we’ll dive into what capacitors are and how they work with your subwoofers. We’ll also explore common pain points that come with using subs without capacitors, such as power depletion and electrical system issues. By the end of this guide, you’ll have a clear understanding of whether or not a capacitor is right for your setup.

What Does a Capacitor Do for Subs?

So sit back, relax, and let’s get started on our journey towards better bass!

But beware: after reading this article, you might just become an expert in all things subwoofer-related.

What is a Subwoofer Capacitor?

A capacitor is an electrical device that transmits appropriate electric power from a power source to another device. Unlike a battery, it holds no electrical power of its own.

The low bass frequency of subwoofers is essential for a rich audio performance of your car’s sound system.

However, the sub might need extra power boosts when it activates, and this is where a capacitor comes in handy.

A subwoofer capacitor retains power from your car battery to transmit to your subwoofer when the sub requires a burst of power.

What Does a Capacitor Do for Subwoofers?

The capacitor helps keep fluctuations and sound disturbances at bay. Their construction consists of two metal plates with a dielectric material separating them.

When there is a potential difference between the two plates, an electric field is created in the dielectric material.

Most cars have a stiffening capacitor that keeps your car’s headlights from dimming during heavy bass plays.

In such moments of high-power demands, the capacitor swiftly transmits stored electrical charge to the amplifier to keep your lights from dimming.

However, in some cases, a capacitor may do more harm than good. Due to the limitations of your car’s electrical system, the capacitor might drain your alternator and battery.

Thus, it’s crucial to install the right capacitor for your car, and also determine if your car’s audio system really needs a capacitor.

How Do I Know if My Subs Need a Capacitor?

Dimming headlights are an indicator that you may need a Capacitor.

When your car’s electric system cannot handle the heavy bass of your music, it draws power from your car’s power supply, thereby producing a not-so-great sound experience and dimmer lights.

Some other instances necessitate installing a capacitor for your subs. If…

  • Your car’s audio system has large amplifiers and subwoofers that require large currents to function efficiently. In this situation, a capacitor will be a good investment.
  • Your car’s sound system does not have an inbuilt reserve capacity. A capacitor will help support your car’s audio system.
  • You’re into bass-heavy music. Such types of music utilize your car’s subwoofers, thereby increasing power demand, especially at high volumes.

How to Connect a Capacitor

Disconnect your battery’s ground cable, and take out the in-line fuse of your amplifier’s wire. Then, install the capacitor securely near the sub-amplifier with short wires.

Next, run power cables from the battery to the capacitor, matching the positive and negative terminals.

Then run a shorter cable to the positive and negative terminals of the amplifier.

Scrape off all the paint on a portion of the chassis ground and connect the cap’s negative terminal to it.

Charge your capacitor slowly until it’s full and ready for use. Note that capacitors can be dangerous, and can melt metal when charged.

Thus, you’d likely see a wired light bulb in the pack of your new cap, and wiring this bulb right slowly and safely discharges the cap.

Frequently Asked Questions

  • Do capacitors improve sound quality?

In essence, the capacitor cannot “improve” the sound quality of your system.

It only helps the sound to not deteriorate due to voltage dips during your subs’ peak performance.

If you’re wondering, “what does a capacitor do in car audio?” The simple answer is that it essentially stays on guard as a buffer to prevent unanticipated power dips from affecting the equilibrium of your audio signals.

The capacitor simply helps your subwoofer perform more efficiently.

  • Does a capacitor increase bass?

If an appropriate capacitor is installed correctly, it can potentially boost the bass of your music.

Since bass-frequency audio has a high electrical energy demand, a battery might simply not be sufficient to meet its energy demands.

However, installing the right capacitor (in close contact with the subwoofer) will provide the necessary power to give you the rich bass experience you love.

Installing it close will ensure that the bass plays efficiently during a voltage drop.

  • Will a capacitor drain my battery?

Simply put, a capacitor is not likely to drain your car’s battery prematurely.

Remember, capacitors cannot store power long-term, but act as buffers to temporarily keep and distribute energy quickly.

Thus, they cannot drain your car’s battery. Although small leakage currents can discharge your battery, the discharge is negligible and much less critical than your battery’s self-draining.

  • Should I add a capacitor to my subs?

Installing a capacitor for your subs should be a matter of need and not just a fancy.

If your car audio system is not fitted with a stiffening capacitor, you will observe serious power issues when you play bass-heavy music loudly.

If you also tend to play such bass-heavy music, a capacitor might help you enjoy a smoother audio experience.

If you are not certain if you need a capacitor or not, it’s best to involve a professional car electrician to seek advice about installing a capacitor for your subwoofers.

  • What alternatives can I use instead of a capacitor?

A secondary battery might be better suited for your car’s issues than a capacitor. Get a professional to install a secondary battery in your car if need be.

Alternatively, you can use a hybrid device that yields a power supply for longer.

These devices combine electrolyte-type and carbon capacitors and act almost like a battery-capacitor combo to meet your sound system’s high power demands.


Capacitors do a great job of temporarily holding and releasing power when your subwoofers are activated, to ensure peak performance.

As for the type of capacitor to get, a basic capacitance of 1 Farad is sufficient for 1,000 watts RMS of total system power. However, a higher capacitance will not harm your system.

Note that even though capacitors can help when the voltage drops, there are some instances where capacitors will not serve any significant function for some cars’ audio systems.

It’s best to consult a professional to ascertain if a capacitor is an ideal choice for your situation, and to install one if need be.

Last Updated on April 6, 2024 by Brian Beasley

Written by Danny Reid

Hey, I'm Danny, and I know how hard it can be to find the perfect audio gear. Need a new stereo, amp, speakers, or subs? Don't worry – my blog is here to help you cut through the noise! My mission is to give you the best reviews, so you can make the right decision for your audio needs. And if you ever get stuck thinking, "Where does this blue wire go?" don't worry – I've got tons of cool tips to help you out of any jam. So come along with me on this fun, sound-filled adventure, and let's find the perfect audio setup to make your tunes really sing!