ESR in Subwoofer Capacitors: What Is It?

Every audiophile knows that a subwoofer can make or break the audio experience, but have you ever wondered about the role of ESR (Equivalent Series Resistance) in these powerful bass machines?

In this article, we will discuss ESR and its importance in the subwoofer capacitors.

What is ESR in Subwoofer capacitors?

ESR refers to Equivalent Series Resistance, also known as internal resistance in subwoofer capacitors. It is simply, a value that represents the loss of usable energy in the electrical circuits of subwoofer amplifiers consisting of capacitors and resistors.

Every subwoofer capacitor has an equivalent series resistance (ESR), even if the resistance is too low.

When current passes through the device, some of the energy is lost as heat, which is common with any other kind of resistance.

The size of the ESR determines the amount of energy that dissipates or is lost.

Less energy is wasted in the form of heat with low ESR capacitors, which further helps in improving the efficiency of a power supply.

ESR or equivalent series resistance is affected by frequency whereas the capacitor’s performance depends on frequency, voltage, and temperature.

Moreover, the performance of the capacitor can change with the component’s age. Hence, considering ESR is important in choosing electrolytic capacitors.

Is a low ESR capacitor better for subwoofer?

Low voltage ripple is directly affected by ESR and most powered circuits in audio systems demand low ripple.

Hence electrolytic capacitors with sufficient output capacitance with the combination of low ESR are recommended in most audio systems.

Compared to high ESR capacitors, low ESR caps have less power losses and internal heating issues.

Furthermore, the lower ESR value allows a greater ripple current capacity to be achieved.

Can you measure ESR of audio capacitors?

ESR is typically an AC resistance, hence it is measured at specified frequencies.

For switched-mode power supply components, ESR is measured around 100 kHz. On the other hand, for linear power-supply components, ESR is usually measured around 120 Hz.

At 1000 Hz, audio components may report a “Q factor” that includes ESR among other things.

Note: In the equivalent series resistance the “Q factor” represents the ratio of energy stored in the capacitor to the energy dissipated.

In a voltage divider configuration, ESR can be measured by applying an alternating voltage at a specified frequency to the capacitor’s reactance level.

To get the accurate value you can use an improvised ESR meter comprising a square-wave generator and oscilloscope.

If you want to measure the ESR value of multiple capacitors in quick time you can use a professional ESR meter.

Additionally, standard measurement bridges, LCS, and Q meters are also used to measure accurate ESR values along with various circuit parameters.

However, a dedicated ESR meter is a perfect device to obtain accurate values and is relatively inexpensive.

Hence it is mainly used to identify capacitors with larger ESR including their low resistances.

Does ESR change with frequency?

ESR is typically large at low frequencies, as soon as the frequency is increased the ESR value decreases quickly.

If the frequency is on an increasing trend constantly, the ESR value will continue to decrease but at a much slower pace.

Additionally, ESR values are also lowered by applying a voltage to a capacitor and can be measured using ESR measuring meters.

How to measure ESR in audio capacitors?

You can use a meter specially designed to measure ESR in audio capacitors.

These devices usually come with instructions to follow and are relatively easy.

A capacitor’s ESR measurement meter first displays the ESR value followed by the capacitance in most cases.

The capacitors need to be attached to the meter or to its terminal ends and you will need to press the On button to get the value instantly.

Also Read: Replacing the Capacitor In Subwoofer

Final Thoughts

ESR is a term used to describe the loss of useful energy in subwoofer amplifier circuits, which are made up of capacitors and resistors.

The lower the ESR (Equivalent Series Resistance) value, the better the capacitor functions in audio circuits.

ESR values are lowered by applying a voltage to a capacitor and can be measured using ESR measuring meters.

It is very important to consider ESR when choosing a capacitor for your audio system.

Frequently Asked Questions

What is an ESR meter?

An ESR meter is used to measure the equivalent series resistance (ESR) value of capacitors. It is typically a two-terminal electronic measuring device that can be used to measure ESR without disconnecting the capacitor from the circuit.

How does a capacitor ESR meter work?

ESR meter discharges a real electrolytic capacitor followed by passing an electric current through it for a short time so that it is adequately charged in quick succession.

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!