Evaluating Headphones: All You Need To Know

how we rate headphones

Our expertise comes from conducting thousands of headphone reviews over two decades.

We work hard to help you find the best headphones. Every pair of headphones sold on headphones.com must go through an extensive testing and evaluation procedure by our expert sales team:

Reading: Build a graph headphone

we used and handled all the headsets, comparing their features & sound to similar models.
test them with various equipment and in the field if they are designed for specific activities.
hold group training sessions and complete evaluation forms.
most headphones undergo a rigorous measurement test. we believe that one pair of ears and real-time use are ultimately the best ways to test headphones, but measurements are a useful tool for providing objective data for comparison purposes.

learn more about headphone measurements from headphones.com

Our measurement data is directly out of scope, so to speak. Unless you’re an engineer, you probably don’t understand the full meaning of spikes and dips on charts. The important thing to know in general is that the less, the better. headphones are notoriously difficult to measure, and even the best headphones have complex graphs. so look for simple results, but don’t be surprised by a lot of movement, they are normal. and take it all with a fairly large grain of salt.

You can compare headset performance and create your own headset charts with our chart creation tool.

frequency response

What it means: Frequency response is a measure of the headphones’ ability to reproduce all frequencies equally. theoretically this plot should be a flat line at 0db. the left side of the line is bass, the right side is treble. if the line is high on the left and low on the right, the headphones are considered heavy. if the line is low on the left and high on the right, the headphones are likely to have a “bright” sound with an emphasis on the highs and lean bass response.

How we test frequency response: To perform this test, we drive the headphones through a series of 200 tones at the same voltage and increasing frequency. we then measure the output at each frequency through the ears of the highly specialized (and expensive!) acoustic headworn microphone. after that, we apply an audio correction curve that removes the head-related transfer function and accurately produces the data for display.

how to interpret the line: a “natural sounding” headphone should have slightly higher bass (about 3 or 4 db) between 40hz and 500hz. this makes up for the fact that headphones don’t give you the physical punch or “bump” that sound waves from a room speaker have; so a slight offset is needed for more bass response for a natural sound.

The headphones should also be turned down on the treble to compensate for the drivers being so close to the ear; a flat line with a gentle slope of 1khz at about 8-10db down to 20khz is about right. you’ll notice that all headphone measurements have a lot of irregular ups and downs. lows (peaks and valleys) in the high frequencies; this is normal and is mainly due to reflection cancellations in the folds and ridges on the outside of the ear. ideally, however, the rises and falls of the frequency response should be fairly small and average out to a flat line. large peaks or valleys greater than 3 kHz in width generally indicate poor headphone response and should be seen as coloration of the sound. some small dips in the highs can be really desirable and should exist in the 2khz to 8khz region.

harmonic distortion

what it means: when you put a single tone, let’s say 500 hertz, into headphones, you should only put out a single tone. but if the headphones are “non-linear” you will get extra power at other frequencies. these are called “distortion products” and occur at multiples of the fundamental test tone. in the case of a 500hz tone, the 2nd harmonic would be at 1000hz; the third harmonic at 1500hz; the fourth at 2000hz, etc.

How to interpret the line: In theory, perfectly linear headphones would have no harmonic peaks of any kind; in practice, this is rarely the case. the full discussion of pointexter is complex, but the general wisdom is that distortion is less annoying when each peak gets smaller as frequency increases and that the second harmonic is not as annoying as the third.

In general, in our experience, tight, clean, articulate-sounding headphones have little harmonic distortion product. headphones that sound lush (believed to be the even harmonics) or harsh and/or grainy (believed to be the odd harmonics) are likely to have much more harmonic distortion. however, in our experience, some great-sounding headphones have a significant amount of harmonic distortion, so it would be a mistake to assume that just because there are so many distortion products, headphones sound bad. it just isn’t the case. ears have to be the guide here!

impedance measurement

what it means: the headphone impedance graph is a measure of the headphone’s dynamic resistance in ohms over the entire audible frequency range.

How We Measure: This measurement is achieved by measuring the voltage drop before and after the output impedance resistor of our audio precision tester and doing a simple voltage divider calculation on each frequency.

How to interpret the line: The first large spike on the graph usually represents the location of the controller resonance. the total height above zero is the headphone impedance. the general trend in headphones over the last decade is a gradual reduction in impedance. In general, the lower the impedance of the headphones, the easier it is to get a louder volume. but, once a headphone drops below 20 ohms, it starts to draw a lot of current and can become unwieldy again. the best measure of how easy a headphone is to drive is our required voltage to get a 90 db measurement.

isolation measure

What it means: This is a measure of a headset’s ability to isolate the listener from external ambient noise. if there is no attenuation the line will be flat. if the headphones attenuate outside sound, the data on the graph will begin to decrease, representing a reduction in sound level at those frequencies.

How we measure: In this case, we measured the acoustic response of the head to pink noise generated by a loudspeaker mounted one meter from the head. then we simply put the headphones on the head and measure the spectrum of sound that the head “hears”. we then calculate the difference between the two measurements to calculate how much noise attenuation the headphones provide over the entire audible frequency range.

even open-back headphones remove a moderate amount of noise above 3khz. most sealed headphones will provide significant amounts of attenuation down to a few hundred hertz. noise-cancelling headphones sometimes extend this attenuation to just below 100hz. in-ear headphones, and in particular shure and etymotic, have by far the best isolation.

500hz square wave response

While the frequency response graphs will tell you about the headphones’ amplitude response at various frequencies, they will not tell you about the headphones’ ability to keep all the different frequency components aligned over time. For an audio signal to sound coherent and natural, the high-speed edges of the signal must travel through the system at the same speed as the low-frequency components.

When the phase fades, the square wave starts to look quite jagged as all of its components become misaligned. for the high and high mid frequencies, the 500hz square wave is very sensitive to phase errors.

50hz square wave test

what it means: the principles are very similar to the high frequency test, but the lower 50hz square wave test gives you more insight into the bass and midrange performance. mid-low.

How to interpret the line: The ability of the headphones to maintain constant pressure along the flat top and bottom is a measure of how well they can reproduce low-frequency notes. this is very difficult as the driver is small with limited excursion and the earphone is quite leaky and releases pressure easily. in no case have we observed that a headset has been able to maintain a truly flat line; ear canal hearing aids come the closest as they only have a small sealed volume of air in the ear canal to compress. but the headphones’ ability to create a straight line at the top and bottom, even if it’s tilted, will indicate consistent bass performance. edge noise is less important in this plot, as it is more observable with the 500hz square wave test.