Understanding Headphone Impedance

Impedance is one of the most important technical specifications to keep an eye out for when selecting a pair of headphones. But as with many other technical specifications, it can be a little confusing.

In this guide, we dive deeper into what headphone impedance is and why you should pay extra attention to this often-overlooked specification.

Table of Contents

Simple Technical Definition

Let’s start with a top-level technical definition that won’t require you to have a degree in audio engineering to understand!

Impedance is a measure of the resistance that headphones have to the flow of alternating current. It is measured in ohms (Ω) and determines how much power is required to drive the headphones.

Stylized Ohms Symbol.

Impedance is measured in ohms (Ω).

Impedance is essential when pairing headphones with audio sources because matching impedance ensures optimal performance. Mismatched impedance can result in poor audio quality.

Low-impedance headphones are easier to drive, while high-impedance headphones may require a headphone amplifier. The relationship between impedance and power is also significant, as higher-impedance headphones need more power to reach the same volume.

Impedance can also affect the frequency response of headphones, causing variations in sound characteristics.

How Does Impedance Impact Sound

Understanding how impedance affects sound can significantly enhance your audio experience. Impedance plays a crucial role in determining the overall sound quality of your headphones.

The impedance of your headphones affects factors such as frequency response, power requirements, and distortion levels.

Low-impedance headphones are easier to drive but may sacrifice some control and accuracy. On the other hand, high-impedance headphones require more power, but they offer better control and accuracy. Medium-impedance headphones strike a balance between the two.

Some other non-technical aspects can impact sound quality, like attaining a good fit which can sometimes be challenging. For example, if you wear glasses having an understanding of how to wear headphones with glasses can ensure you have a proper fit to achieve maximum isolation and tonal matching.

By considering the impedance of your headphones along with other factors, you can choose the right pair that matches your audio equipment and personal preferences while maintaining optimum sound quality.

How Dynamic Drivers Work

So you now know what impedance is and why it is essential. Fundamentally it is all about handling electrical currents to achieve optimum sound. But how does this play a role in headphones? It’s all about the driver. While there are various types of drivers, most headphones on the market will feature a Dynamic Driver.

When exploring the components of a dynamic driver in headphones, it’s like peeling back the layers of an onion to reveal the intricate inner workings that produce captivating sound.

Two dynamic headphone drivers.

Magnetic fields play a critical role in dynamic headphone drivers.

At the heart of the dynamic driver is a diaphragm, typically made of a lightweight material such as Mylar or titanium. This diaphragm is attached to a voice coil, surrounded by a magnetic field created by permanent magnets.

When an electrical signal is sent through the voice coil, it generates a magnetic field that interacts with the permanent magnets, causing the diaphragm to vibrate and produce sound waves.

The size and shape of the diaphragm and the magnetic field’s strength contribute to the headphones’ overall sound quality and characteristics.

Impedance Matching

With all that information up your sleeve, you’ll now want to go ahead and match the impedance of your headphones with the audio source so you can achieve optimal sound quality.

Impedance matching ensures that the power output from the source is compatible with the requirements of the headphones.

One of the most common questions I get asked regarding headphones is, do I need a headphone amp? By following the steps below, you’ll be able to determine if your headphones and source match and whether you’ll need to invest in a dedicated headphone amp.

Step 1: Identify the impedance rating of your headphones. You can find this in the user manual. If you no longer have the manual for your headphones, you can easily find this information with a quick Google search.

Step 2: Check the output impedance of your audio source. Refer to the device’s user manual or technical specifications. Once again, Google can be helpful here if you don’t have the user manual.

Step 3: Ideally, the source’s output impedance should be less than 1/8th of the headphone impedance. This ensures efficient power transfer and minimizes potential impedance mismatches.

Side view of the Beyerdynamic DT 1990 Pro headphones.

High-impedance headphones require a suitable headphone amp.

For example, for a pair of 250-ohm headphones like the Beyerdynamic DT 1990 Pro, it is recommended to use a headphone amplifier with an output impedance of less than 1/8th (31.25 ohms) of the headphone impedance. Therefore, a headphone amp with an impedance of 31.25 ohms or lower would be suitable for driving the 250-ohm headphones effectively.

If you require more power to drive your headphones, you’ll need to invest in a headphone amplifier that can provide the necessary power to your headphones. Some DACs also feature a built-in headphone amp.

By carefully considering the impedance of your headphones and matching it with the audio source using these basic steps, you’ll likely prevent any potential issues with sound quality.

The Rule Of Eights

I’ve touched on the rule of eights above, but it is worth diving into this further as it is among the most straightforward ways to ensure you get the most out of your headphones.

The Rule of Eights states that for optimal performance, the output impedance of your audio source should be no more than 1/8th the impedance of your headphones. This rule helps to minimize impedance mismatches and ensure proper power transfer.

Following the Rule of Eights ensures that your headphones are appropriately matched with your audio source, resulting in optimal sound quality and performance. Remember to check the output impedance of your audio source and select headphones accordingly to achieve the best audio experience.

Other Important Specifications

While headphone impedance is an important specification to be aware of, there are other specs to consider that also play a role in the audio performance of your headphones and directly relate to the impedance rating.

Sensitivity

Headphone sensitivity refers to how loud headphones can get for a given input level. It is measured in decibels per milliwatt (dB/mW).

Higher-sensitivity headphones can produce louder sounds with less power. This means you can achieve higher volume levels without straining your audio source or needing a powerful amplifier. But this doesn’t always correlate exactly based on the impedance of the headphones.

For example, the AKG K371 has an impedance of 32 ohms with a sensitivity of 114dB, while the Rode NTH-100 has the same impedance rating but a sensitivity of 110dB.

Understanding headphone sensitivity is crucial when choosing headphones, especially if you use them with portable devices or low-power sources.

High-sensitivity headphones are more efficient and can be driven by devices with lower power outputs, such as smartphones or laptops. On the other hand, low-sensitivity headphones may require more power to achieve the same volume level.

Total Harmonic Distortion

Now that you understand the concept of headphone sensitivity, let’s delve into another important aspect of audio quality: total harmonic distortion (THD).

THD refers to the amount of unwanted sound or distortion added to the original audio signal. It is measured as a percentage and represents the difference between the input audio signal and the output signal from the headphones.

Various factors impact THD, including the design and quality of the headphones, as well as the impedance and sensitivity of the drivers. High THD can result in a loss of clarity, detail, and accuracy in sound reproduction.

Stylized image of a pair of headphones with a distortion effect.

Mismatched impedance can lead to greater distortion.

Impedance affects total harmonic distortion by influencing the interaction between the source and load impedances. When the source and load impedances are mismatched, it can lead to reflections and distortions in the signal, resulting in higher total harmonic distortion. Matching impedances can minimize these distortions and improve overall signal quality.

When choosing headphones, it’s important to consider the THD specifications provided by manufacturers. Lower THD values indicate better audio quality, as they indicate less distortion.

Additionally, it’s worth noting that THD can vary at different volume levels, so it’s important to test headphones at different volume levels to ensure the desired audio quality.

Frequency Response

Impedance plays a crucial role in determining the frequency response of headphones.

When the impedance of headphones is high, it may decrease the overall loudness and affect the frequency response, especially in the low-frequency range. High impedance can cause the headphones to work less efficiently, resulting in a loss of power transfer and reduced bass response.

Due to this higher power requirement, it becomes critical to ensure you power high-impedance headphones correctly to achieve optimum frequency response as intended by the manufacturer. A high-quality headphone amplifier will ensure you get the most out of your headphones.

On the other hand, lower-impedance headphones tend to have a more consistent and accurate frequency response without the need for additional amplification.

Frequently Asked Questions (FAQ)

Do All Headphones Have The Same Impedance?

Headphones can have different impedance levels ranging from low to high. Low-impedance headphones are in the range of 18-32 ohms. High-impedance headphones can often range from 150-300 ohms.

Do High-Impedance Headphones Sound Better?

If matched correctly with an adequate power level, high-impedance headphones sound better. They have better control over the audio signal, resulting in improved clarity, detail, and overall sound quality.

Can I Use High-Impedance Headphones With My Smartphone?

Yes, but remember that high-impedance headphones may require more power to achieve the same volume level compared to low-impedance headphones.

Should I Use A Headphone Amplifier With Low Impedance Headphones?

Low-impedance headphones will work efficiently with portable devices and do not require additional amplification for optimal performance.

Enjoy Optimum Audio Quality

Understanding headphone impedance is like unlocking a hidden secret. By matching your headphones with the correct power level, you allow them to perform to their maximum potential.

The result is improved volume, dynamics, frequency response, and clarity. So the next time you are looking at buying headphones, take some extra time to ensure you’ll be able to drive them accordingly. If you already own a pair, double-check that you are giving your headphones the best chance to provide you with quality sound.

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Article by Robert Calabrese
Article by Robert Calabrese

Robert has over 15 years of experience working in the digital marketing industry. From a very young age he was influenced by music theory as part of his education and played a variety of instruments. From there, his passion moved into electronic music and the equipment used to create it. Using his education and experience, Robert started his own digital marketing company and successfully operates his business in the music industry.

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