- Table of Contents
- Intro
- Our Tests
- Conclusion
- Comments
Our Sound Quality Score And Tests
Headphones
Sound is a key component of a pair of headphones' performance. You'll want good-sounding headphones, whether you're listening to podcasts, team meetings, rock operas, or anything in between. That's where your preferences come into play. Some people may prefer more low-end so they can really feel the rumble of basslines, while others may want something more balanced and flat to focus on details like each pluck of a guitar string. It's not all about taste, though. Some elements of sound, like if the left and right drivers match one another, are performance-based—everyone can agree on what constitutes a good (or bad) result.
We evaluate sound using a mix of preference-based and performance-based tests. This article will give you a quick overview of these tests, but there's a link to more information if you want to know more.
Our Tests
Raw Frequency Response
Frequency response is a measure of the magnitude of the output of a system compared to its input, as a function of frequency. In other words, it describes how accurately a system reproduces each frequency of a piece of audio content in terms of amplitude. For example, for an input signal that has three frequencies of equal amplitude (say, 100Hz, 1kHz, and 10kHz, all at -6dB FS), a pair of headphones with a neutral frequency response would output a signal that, just like the input, has equal amplitudes at 100Hz, 1kHz, and 10kHz.
Raw frequency response is related to our Sound Profile test; it's the data before compensation. If you're an experienced user, you may prefer this test since you can more easily compare it to other targets or use it to apply your own target.
Sound Profile
Sound Profile is a similar test to Raw Frequency Response but with a twist. This test applies our target curve to the response, effectively turning the target curve into a straight line and letting you see how the frequency response deviates from the curve. This test is especially useful if you're just starting your audiophile journey and learning how to parse through the data, as you can see all the deviations from our target curve more easily.
Frequency Response Consistency
- 1.0% Avg. Std. Deviation
Frequency Response Consistency describes the variations in a pair of headphones' frequency response due to their fit, positioning, and seal on your head. Although most listeners naturally compensate for variations in frequency response caused by their unique features, like the shape and size of their heads, other factors, like their preferred placement of the headphones and how the ear cups' acoustics interact with their ears, may cause additional variations in the response. As a result, headphones may sound slightly different depending on the size and shape of your head, how they interact with your ears, and whether you wear glasses.
Inconsistent headphones may have a drastically different sound from listener to listener. For example, if you wear glasses or have thick hair, a pair of bass-heavy headphones could lack a lot of bass since something is disrupting the ear cup padding's seal. Ideally, headphones should consistently reproduce the same response regardless of positioning or head/ear shape.
This test is scored using the average standard deviation across five different passes with five different users.
Bass Profile: Target Compliance
- 90.0% RMS Deviation From Target
- 10.0% Low-Frequency Extension
Bass Profile: Target Compliance describes how closely the headphones reproduce the low-frequency region of the audible frequency spectrum in relation to our target curve. This range starts from 20Hz and goes up to 250Hz. It represents the low thump/rumble, punch/kick, and melodious basslines you can hear in tracks.
This test is scored using two factors: low-frequency extension, which tells you the lowest frequency response a pair of headphones can produce before significant roll-off, and how much the response deviates from our target curve.
Mid-Range Profile: Target Compliance
Mid-Range Profile: Target Compliance describes how a pair of headphones' mid-range frequency response deviates in relation to our target curve. The mid-range spans 250Hz to 2kHz. It represents the lower and higher harmonics of instruments and vocals and their comprehensibility and clarity; this is where the bulk of the audible audio frequencies reside.
This test is only scored by how much deviation exists in this range relative to our target curve.
Treble Profile: Target Compliance
Treble Profile: Target Compliance describes how a pair of headphones reproduce the high frequencies of the audible frequency spectrum. The treble ranges from 2KHz to 20KHz and represents the higher harmonics of lead instruments and vocals, cymbals, the sibilant tones (S and T sounds), and the airiness you can hear in tracks.
When treble is lacking, the higher harmonics of instruments and vocals lose detail and brilliance. This is significant, as the absence of good treble may make audio sound dark and lacking in detail and presence. In our frequency response score, treble is assigned the same weight as the mid-range and bass, even though very high frequencies are less audible to older listeners.
This test is only scored using how much deviation exists in this range relative to our target curve.
Peaks/Dips
Peaks/dips represent how well the headphones can follow their own sound profile. This test helps identify frequencies that are too emphasized/de-emphasized proportionally to their own sound profile. A flat profile is good because the headphones can accurately reproduce the sound profile they aim to achieve. Conversely, if there are a lot of peaks and dips, then it can indicate that the headphones struggle to control their sound. Sharp spikes can feel annoying or inconsistent, whereas larger, smoother peaks and dips are harder to notice.
Imaging
Imaging qualities are inherent to the audio content; the headphones have to 'reproduce' them rather than 'create' them. They determine how accurately the objects are positioned in the stereo image and how transparent the imaging is.
Having good matching between the left and right driver of the headphones in amplitude, phase, and frequency response helps accurately reproduce the positioning of objects/instruments in the stereo image that was designed or recorded without imbalances or holes. A low group delay can help you hear each layer of the audio content clearly and faithfully.
- 17.0% Weighted Group Delay
- 27.0% Weighted Phase Mismatch
- 28.0% Weighted Amplitude Mismatch
- 28.0% Weighted Frequency Mismatch
Imaging describes the accurate reproduction of location, stereo width/balance, and transparency of instruments/objects in the soundstage as intended by the audio source. Headphones with good imaging reproduce the slight time and amplitude differences between the audio's L/R channels, which are responsible for generating a stereo image.
However, some aspects of imaging are very hard to notice for the average listener, and therefore, imaging may not be as important for everyone. Imaging also varies between units. However, as a result, imaging can be used as an indicator of a manufacturer's quality control and ergonomics.
There are several components for this test:
- Group delay
- Phase response
- Amplitude mismatch
- Frequency mismatch
Passive Soundstage
- 15.0% PRTF Accuracy (Std. Dev.)
- 15.0% PRTF Size (Avg.)
- 20.0% PRTF Distance
- 20.0% Openness
- 30.0% Acoustic Space Excitation
Soundstage describes the perceived location, size, and environment where the music/sound is happening. Headphones that can reproduce this effect give the impression that sound is coming from outside, in a room, rather than inside a vacuum in your head. Headphones with a good soundstage will sound more like speakers in a room than headphones on your head.
Soundstage gives spaciousness to an audio reproduction, making it sound more natural and open. Thus, soundstage is an important component of sound quality.
There are a few different components to this test:
- PRTF (Pinna-Related Transfer Function) Accuracy (Std. Dev.)
- PRTF Size (Avg.)
- PRTF Distance
- Openness
- Acoustic Space Excitation
Weighted Harmonic Distortion
Weighted Harmonic Distortion is the amount of unwanted frequencies, otherwise known as harmonics, alongside desired frequencies. Distortion can affect the clarity and purity of your audio and is very important if you care about high-fidelity sound. However, it can be hard to hear if you don't know what you're listening for.
This test is done at 90 dB and 100 dB, as distortion can vary depending on your listening volume.
Conclusion
To understand a pair of headphones' sound, we evaluate both these performance-based and preference-based tests to give you a better picture of what you can expect with your own product. In the case of preference-based tests like Sound Profile and Frequency Response, there are no scores. Enjoying a sound other than our target curve is possible, and that's alright! You can use the data to make your own informed decision. Beyond this, other tests like Peaks/Dips and Weighted Harmonic Distortion are performance-based. For example, if there's a lot of distortion, all users will find this bad. These tests are scored.