Headphone impedance is a concept that is often misunderstood. While impedance does indeed play a major role in determining whether a headphone can be hard to drive or not, there are other factors such as headphone sensitivity that must be understood to correctly determine how power-hungry a headphone is.
Understanding these two concepts enables you to have a better understanding of how the drivers on headphones work. This makes sure that you won’t be making mistakes when buying headphones and headphone amplifiers. In this guide, we will be talking about the technical definitions of impedance, and sensitivity, as well as how to accurately determine whether or not your headphones require an amplifier.
What Is Headphone Impedance?
Headphone Impedance refers to the amount of voltage that headphones require to be properly driven by a source. Along with the sensitivity, these two serve as the primary basis that determines whether or not a headphone requires a headphone amplifier.
Generally, the rule is that the higher the impedance of the headphones, the more voltage that it requires. It, however, does not necessarily mean that high impedance headphones become harder to drive and vice versa. This concept will later be expanded along with the concept of headphone sensitivity.
What is Headphone Sensitivity?
Headphone sensitivity refers to the number of current headphones require to be properly driven by a source. Along with the impedance, these two serve as the primary basis that determines whether or not a headphone requires a headphone amplifier.
Generally, the rule is that the lower the sensitivity a headphone has, the more current it requires. Again, having a lower sensitivity does not necessarily make a headphone harder to drive and vice versa, This concept will later be expanded along with the concept of headphone impedance.
Do I Need an Amplifier Based on Impedance Alone?
To tell whether or not headphones need a headphone amplifier, you must consider both the impedance and the sensitivity. Headphones with a high impedance and low sensitivity are hard to drive while headphones that have a low impedance and high sensitivity are easier to drive.
Harder-to-drive headphones will require an amplifier while easier-to-drive headphones can be driven by most modern-day sources. Having a higher sensitivity does not automatically mean a headphone no longer requires a headphone amplifier. The HD650, for example, has an impedance of 300 ohms but has a higher sensitivity than most hard-to-drive headphones. This means that it still requires an amplifier but it doesn’t necessarily need a lot of power. Most midrange amplifiers will be able to do the trick.
There is however a trend with headphone impedance. Headphones that have an impedance below 100 ohms generally do not need an amplifier. This is evident with portable headphones that are designed to be paired with a smartphone. Headphones between 100 and 300 can still be driven by most sources to a certain degree. Adding an amplifier usually improves the sound of these headphones.
And headphones that have an impedance above 300 ohms need an amplifier. There are cases where some low impedance headphones are harder to drive and vice versa but that is rare to see. This is not always the case but without looking at the sensitivity, you can tell if a headphone requires an amplifier.
Once you determine if a headphone requires a headphone amplifier, look at the sensitivity and compare it with the specs of the headphone amplifier to properly determine if they are a good match. Here is a useful tool for calculating the amount of power needed by your headphones as well as common headphone amplifiers that may support it.
Are Higher Impedance Headphones Better?
Having a high impedance is usually a trait of the more expensive headphones. However, it does not always make them superior over lower impedance counterparts. Other factors need to be considered when comparing high and low impedance headphones.
For example, the Beyerdynamic DT770 Pro has four variants. There is the 16-ohms, 32-ohms, 80-ohms, and 250-ohms version. The 16-ohms version is the easiest to drive while the 250 ohms is the hardest to drive.
In this case, all three versions share the same characteristics with the higher impedance versions being slightly more detailed. The higher impedance 250-ohms version is technically superior when compared to the other variants. However, when compared with the 80-ohm version, the differences aren’t big. The 80-ohm version can be a better fit for most users as it represents a sweet spot in the three models.
The 16 and 32-ohm version has little to no benefit from using an amplifier. The 250-ohm, on the other hand, requires an amplifier. The 80-ohm version sits in the middle. It doesn’t need an amplifier for optimum performance but it still benefits from a good amplifier.
Another example is the Sennheiser HD 600 or HD650 / HD6xx and the newer Sennheiser HD660s. The older models in the HD 6XX series have an impedance of 300-ohms as compared to the 660s which only has an impedance of 150-ohms. However, this does not mean that they are superior to the new HD660s.
The Sennheiser HD660s uses a different driver that is more efficient. It still requires an amplifier but is generally easier to drive than its 300-ohm siblings. This new driver is technically superior to the rest of the 600 series. It still has the signature mid-centric sound but fixes a lot of the issues such as the infamous Sennheiser veil. It also adds more highs and a bit more soundstage.
Finally, another example is the Sennheiser HD800s and the Beyerdynamic T1. The HD800s have an impedance of 300-ohms while the Beyerdynamic T1 has an impedance of 600 ohms. Despite having double the impedance of the HD800s, the T1 is priced less than the HD800s. The T1 is also regarded as a similar-sounding headphone due to the similarities in their sound signatures. It is generally regarded as an equal or ranked below the HD800s.
We take a closer look here at good DAC/Amps for the Beyerdynamic T1 and here we offer a similar list of recommendations for the Sennheiser HDs if you’re looking to pair your high impedance headphones.
We could go on and on about models such as the Focal Elegia that only has 80 ohms but is widely considered as a superior headphone to a lot of higher impedance models. The point is, the impedance should not be the basis of whether or not a headphone is technically competent.
Instead, take a look at the quality and type of the driver that was used for the headphone. Consider if the headphone utilizes a dynamic driver, planar magnetic, electrostatic, or other types of drivers. This largely influences what kind of sound reproduction these headphones can do.
You should also consider the sound signature of the headphones. Some tend to be more bassy and fun while some tend to be more analytical. These factors play a bigger role in determining if a headphone sounds good.
Higher Impedance Headphones Advantages
One advantage of higher impedance headphones is that they are not overloaded easily. Headphones with an impedance above 100 ohms can generally take in more power from sources without getting too loud and damaging the drivers. Also, the sound that they produce does not easily distort.
Another advantage of high impedance headphones is that they can be paired with different kinds of amplifiers. Unlike lower impedance headphones that do not have a significant change nor improve when paired with an amplifier, the sound of higher impedance headphones can be slightly altered or improved when paired with a headphone amplifier.
An example of this is the Beyerdynamic T1. This is an analytical headphone that has a flat sound signature. Its accurate sound may not be what some consumers are looking for since this kind of sound signature tends to be too flat or dead sounding,
With amplifiers, this sound can slightly be altered or even enhanced. With a tube amplifier, due to its distortion, the sound can become warmer, less analytical, and overall more fun. Alternatively, using the Beyerdynamic A20 (an amplifier designed to be paired with the Beyerdynamic T1) can enhance the detail retrieval and analytical sound of the Beyerdynamic T1 which could be useful for critical listening.
Not all high impedance headphones react well to amplifiers but for flagship models such as the Beyerdynamic T1 and Sennheiser HD800s, you have a variety of options that can tailor to the sound unlike with lower impedance headphone where you tend to get stuck with the sound that they produce.
Higher Impedance Headphones Disadvantages
The main disadvantage of high impedance headphones is the fact that most of them need an amplifier to be properly driven. This is not ideal since they will have fewer use case scenarios as compared to low impedance headphones.
This means that most higher impedance headphones cannot be used in a portable setting since they cannot be properly driven by consumer portable devices such as smartphones. Professionals such as musicians also cannot readily use these kinds of headphones in their workplace since digital mixers, interfaces, and wireless receivers do not typically have a powerful output for high impedance headphones.
Another disadvantage of higher impedance headphones is they may not sound good when not properly driven. Some sources can make headphones loud enough but if these sources do not meet the optimal requirements of the headphone, then some aspects of the headphone may not come out. Examples of these are congested soundstage or middy highs, and lack of bass. The HD6xx series of headphones are examples of this where bass becomes less present if not properly driven.
Lastly, high impedance headphones are critical to the source. This can be a disadvantage for you if you want to upgrade your headphones but do not necessarily want to upgrade your source. If you were using an entry-level or a lower quality headphone amplifier then you suddenly decide to upgrade to a flagship pair of headphones, then you may hear that your source is not very good.
You may hear that your source is producing various artifacts such as electronic noise. This is a problem that devices that are not optimized for high fidelity sound reproduction such as smartphones or Personal Computers face.
Lower Impedance Headphones Advantages
The main advantage of low impedance headphones is that they can be easily driven by most sources. This is ideal for beginners who might only have a smartphone or a Personal Computer/Macbook as their source.
Headphones such as the Philips SHP9500 or Grado SR60E are great choices for beginners since they can be used with basic setups and can achieve very good results. Another reason why low impedance headphones are a great choice for beginners is that their sound is not altered too much by the source.
You can often hear issues about matching amplifiers or DAC/Amps with high impedance headphones. Users complain that the sound of the headphone and DAC/Amp combo do not fit their preferences. For low impedance headphones, the sound is not drastically affected by the source. Of course, there are exceptions for some headphones, but the general trend is that low impedance headphones have a more consistent sound regardless of the source.
This can also be ideal for live performers who do not have control over the equipment used in the venue and thus do not have the luxury of carrying around headphone amplifiers. Most performers use IEMs or custom IEMs (which have a low impedance) but some musicians still prefer to use headphones and for those who do, low impedance headphones would suit them better.
For studio use, the Audio Technica ATH M50X, for example, is a popular choice. It can be used with almost any source without any problems in getting an acceptable volume level.
Lower Impedance Headphones Disadvantages
The main disadvantage of low impedance headphones is the fact that they can be easily overloaded. What this means is that the drivers of these kinds of headphones are susceptible to damage or distortion if they are fed with too much volume. This means that they are not recommended to be used with headphone amplifiers.
Adding to the previous point, another disadvantage of low impedance headphones is that they have little to no improvement when paired with a headphone amplifier or DAC/Amp combo. As mentioned earlier, the main advantage of low impedance headphones is that they do not require an amplifier. However, this can be a downside for more advanced users who own multiple sources.
Headphone amplifiers can influence the sound of headphones. This can help in modifying or changing the sound of headphones. If you like the qualities of specific headphones except for the spiky treble area, then a headphone amplifier can help tame the high end. With low impedance headphones, you do not get this effect. You are stuck with the sound that you get and there is very little that you can do if you dislike that sound.
Another disadvantage of low impedance headphones is that most of these headphones, especially in the lower price bracket, have a driver that is technically inferior to high impedance headphones. This is the reason why it is hard to tell apart different sources and it is hard to tell whether or not a source has a bad or noisy output because the drivers found in most low impedance headphones cannot catch these little details.
Popular Low Impedance Headphones
The following are the types of headphones/earphones along with examples of models that usually have a low impedance:
- Studio monitoring headphones (Audio Technica ATH M50X)
- Portable over the ear headphones (Audio Technica MSR7)
- Portable on-ear headphones (Audio Technica ES770H)
- In-ear monitors (IEMs) (Shure SE 846)
- Earbuds (Venture Electronics Monk)
- Open-back headphones (Grado SR60E)
Popular High Impedance Headphones
The following are the types of headphones/earphones along with examples of models that usually have a high impedance and requires an amplifier:
- Open-back headphones (Beyerdynamic T1)
- Open-back planar magnetic headphones (Hifiman Arya)
- Closed-back planar magnetic headphones (Mr. Speakers/Dan Clark Audio Aeon Flow 2 Closed-Back)
Stephen is a musician, cinematographer, and headphone enthusiast who is passionate about reviewing audio equipment. He has been playing guitar for at least a decade, which introduced him to professional recording equipment such as headphones and in-ear monitors. With the help of reviews and online content, he was able to learn the ins and outs of the hobby. His goal is to give back to the community by providing quality content to help others enjoy the beautiful (and expensive) world of audio.
Favorite Headphones: Sennheiser HD660s