Subwoofer Capacitors: Types and Functions

To deliver the deep thumping bass, the sub amps play an important role by transmitting low-frequency signals to these units.

Amps are the powering units that include multiple settings controlled by special circuitry to balance the power flow within the sound systems.

To handle most electrical tasks, capacitors sit on the amp’s circuit to manage the flow of electrical charge.

In this article, we will discuss about subwoofer audio capacitors, their functions, and types, along with the answers to a few frequently asked questions.

What are audio capacitors in Subwoofers?

Capacitors also known as condensers are among the electric components in most amplifier circuits. These components are capable of storing electrical charge in two different plates or electrodes.

The extra energy stored by capacitors works as an instant power available for the amp.

For example, if there’s not enough power available to handle a sudden increase in the bass level, capacitors lend their charged energy to power the speakers as a temporary fix.

They are passive components and typically store energy in the form of a magnetic field.

The strength or effects of capacitors are defined as Capacitance consisting of two conductors separated by a dielectric substance.

The electric charge (positive and negative) builds up on the plates as soon as they are linked to the power.

These plates or surfaces are typically metallic conductors that are separated by a dielectric media.

One of the conductors holds a positive charge while the other accumulates a negative electrical charge.

Additionally, capacitors couple the consistent DC signals with promptly fluctuating voltages in audio amplification systems.

This further helps in smoothly driving the subwoofers and speakers to output a balanced sound.

What are the types of audio capacitors?

There are different types of audio capacitors used in amplifier circuits such as electrolytic (or aluminum electrolytic), ceramic capacitors, and power film capacitors (such as metalized film and or film and foil).

Let us discuss the capacitors of different types and materials used in audio amplifier circuits.

Electrolytic capacitors in audio amps

Electrolytic capacitors are very linear, it uses an electrolyte to achieve a larger capacitance than their counterparts.

In simple words, an electrolyte is a liquid or a form of gel containing a high ion concentration.

Due to their liquid form, they are able to pack a lot of capacitance into a small space.

However, Electrolytic capacitors also pack a lot of dielectric absorption, prone to large leakage currents, value tolerances, and low ESR (Equivalent Series Resistance) hence, they need to be used with discretion in audio circuits.

Additionally, electrolytic capacitors may not resist excess heat and can melt under heating conditions.

The maximum temperature ratings range around 40°C for aluminum electrolyte capacitors. However, it can range from 85°C up to 105°C depending on their size and type.

Note: ESR is a value used in electronic circuits to define the loss of usable energy by resistors and capacitors.

Ceramic capacitors in audio amps

Ceramic capacitors are commonly used in electronic circuits as fixed-value capacitors which are made using ceramic materials that serve as the dielectric.

The electrical behavior is typically defined by the composition of ceramic materials in different applications.

They are mainly used for high-stability performances and low-loss devices to provide more accurate results.

Ceramic capacitors typically consist of a metallic layer along with two or more alternating layers of ceramic layers.

Additionally, the capacitance values of ceramic capacitors are stable with respect to temperature, the applied voltage, and frequency.

The temperature handling capacity of ceramic capacitors typically ranges between -50°C and 125°C. They can withstand extremely low to extremely high temperatures.

Although the capacitance of ceramic capacitors doesn’t vary much with rising temperatures, however, it also depends on their way of construction and sizes.

It may happen that there’s a dramatic increase in capacitance within lower temperature ranges and vice versa.

Film Capacitors in audio amps

Film capacitors or film caps are also referred to as plastic film capacitors, polymer film capacitors, film dielectric capacitors, or power film capacitors.

These are again electrical capacitors with insulating plastic and sometimes combined with paper film as the dielectric.

The combination of paper works as the carrier of electrodes.

Film capacitors can be expensive depending on their size and ratings compared to their counterparts.

Do large capacitors store more energy in Subwoofer?

Capacitors are designed to store short-term power, unlike batteries that can hold electrical power for an extended length of time.

The electrical energy stored by capacitors is typically measured in farads and the farad ratings are determined by the electrical demands of audio systems. 

In most cases, subwoofer capacitors can be physically larger and hold relatively high farad ratings.

The higher farad capacitors can store more electricity than units with lower numbers, however, oversized capacitors can cause unnecessary power drains and overload the circuits.

On the other hand, too small capacitors will fail to provide the required energy. 

Hence, the size and capacity of a subwoofer and speaker capacitor must correspond to their connected audio systems.

Final Thoughts

Capacitors and resistors are passive components of audio circuits that prevents electrical components in subwoofer or any electronic device where capacitor is installed.

Electrolytic capacitors are used to store some amount of energy in the amp’s circuitry of most audio systems.

When it comes to high-end audio systems, plastic film capacitors are used for a wide array of applications in their audio circuits.

The choice of the right audio capacitors greatly determines the quality of the audio signal, hence, it is important to choose the best ones to minimize the degradation of the audio signals.

Frequently Asked Questions

What does ESR mean in an electrolytic capacitor?

ESR refers to Equivalent series resistance and is also known as internal resistance. It defines the lost value of usable energy in electronic circuits consisting of resistors and capacitors.

What are capacitor conductors made of?

Sintered metal beads, foil, thin sheets, or electrolytes are commonly used as conductors in most audio capacitors.

What are dielectric materials in audio capacitors?

The most common materials used as dielectric materials are oxide layers, ceramics, plastic film, glass, mica, and paper. These nonconducting dielectric materials help increase the ability of the capacitor’s charge.

Armed with a Diploma in electrical engineering and a remarkable 12 years of expertise, he excels in rejuvenating music systems, washing machines, dryers, and laundry-related appliances. Manish's profound insights and practical know-how establish him as a credible authority in appliance and music system repairs. Contact: manish.singh (at) He's always ready to lend a helping hand!