Our Sound Quality Score and Tests
Sound quality is how accurately audio is reproduced as intended by the producer/engineer. Our reference for headphones sound quality is the loudspeaker. The ideal headphone sounds like the ideal stereo speaker setup in the ideal room.
From music and movies to podcasts and spoken word, audio is arranged/mixed in a studio to have a distinct sound, and accurate headphones are able to reproduce that sound as intended. Though some listeners might prefer a more hyped bass or mid-range, in our tests, we consider an accurate and neutral reproduction to be more desirable.
For our sound quality score, we evaluate the bass, mid-range, and treble frequency response, as well as frequency response consistency, total harmonic distortion, soundstage, and imaging of the headphones we test.
Bass frequency response describes how accurately headphones reproduce the low-frequency region of the audible frequency spectrum. Bass ranges from 20Hz up to 250Hz and represents the low thump/rumble, punch/kick and melodious basslines you can hear in tracks.
Good bass does not overpower the presence of instruments and vocals and adds excitement to tracks that would otherwise sound weak or thinned out. In our frequency response score, bass is assigned the same weight as treble and the mid-range.
- 100% Std. Err.
Mid-range frequency response describes how accurately headphones reproduce the mid region of the audible spectrum. The mid-range spans 250Hz to 2KHz and represents the lower and higher harmonics of instruments and vocals, as well as their comprehensibility and clarity.
The mid-range is where the bulk of the audible audio frequencies reside, and when unbalanced, causes the instruments and vocals in music to sound thin, distant or muddy/cluttered. In our frequency response score, the mid-range is assigned the same weight as treble and bass.
- 100% Std. Err.
Treble frequency response describes how accurately headphones reproduce the high frequencies of the audible frequency spectrum. 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 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.
Frequency Response Consistency
- 100% Avg. Std. Deviation
Frequency Response Consistency describes the variations in a headphones' frequency response due to their fit on your head. Headphones will sound slightly different depending on the size and shape of your head, how they interact with your ears and whether you wear glasses.
Frequency response is the most important part of a good audio reproduction. Although most listeners naturally compensate for variations in frequency response caused by their unique features, such as the shape and size of their heads, other factors like their preferred headphone position, and how the ear cups' acoustics interact with their ears, may cause additional variations in the response. An inconsistent headphone may have a drastically different sound from listener to listener. This means a headphone that will sound bass-heavy for most could lack a lot of bass for listeners who wear glasses. The ideal headphone should consistently reproduce the same response regardless of positioning or head/ear shape.
Total Harmonic distortion
Total harmonic distortion is a flaw in audio reproduction that generates unintended frequencies that reduces the clarity of the intended sound. For examples, if a 100Hz signal is fed to a headphone with second order harmonic distortion, it will produce a 200Hz tone in addition to the intended 100Hz tone. The higher the amount of harmonic distortion, the higher the level of the 200Hz tone will be, relative to the 100Hz signal. At high levels of harmonic distortion, audio quality deteriorates because the unwanted frequencies make tracks sound unclear and fuzzy.
Luckily, harmonic distortion is hard to perceive by ear alone and although noticeable at higher amounts or by very sensitive ears, for most people it’s rarely audible. This is why we have not assigned much weight to this test.
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. A headphone with a good soundstage will sound more like speakers in a room compared to headphones on your head.
Soundstage gives spaciousness to an audio reproduction, which sounds more natural and open. This makes soundstage an important component of sound quality.
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 L/R channels of the audio, 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.
What is not included
A few elements that you could care about are not included in the score:
- Format of audio (Compression, bitrate, digital, analog, etc...)
- Source of audio output
- Impedance and Driveability (Coming soon)
- CSD (Cumulative Spectral Decay)
- Dynamic Range Compression
If you feel there is an item missing that should be included, please let us know in the Q&A section.
Sound quality is how accurately audio is reproduced compared to the original audio arrangement. An ideal headphone's audio reproduction sounds like a pair of loudspeakers in a room and is balanced and accurate to the source material as it was intended to be heard. For sound quality, we evaluate the bass mid and treble frequency response, as well as frequency response consistency, total harmonic distortion, soundstage, and imaging. Headphones that score highly for sound quality will sound great no matter what you are listening to.
Questions & Answers
Will you be reviewing more open-back headphones? What about some planars? I am curious about the following: HiFiMan HE400s, HE400i, HE560, Oppo PM-2, Audeze EL-8, and Audeze LC-2.In regards to dynamic open-back, a few headphones of great interest are: Sennheiser HD600, HD650, AKG 7xx (previous massdrop), and AKG 702 Anniversary edition (basis of current massdrop). And of course the Audeze Sine (closed planar).
It would be great to create some reference tests for soundstage. IMO, soundstage and imaging are what make music immersive, and it's quite difficult to engineer great sound with immersiveness. Drivability/matchability would be another good metric, with a subscore for phone/tablet pairing.
Thanks for your suggestions.
We are currently in the process of refining our soundstage and bass response tests. That's why we are holding off on more high-end open-back headphones until we can better measure the qualties that sets them apart from lower-end models. Planar headphones are especially interesting for our new sounstage and bass response tests, so it's likely that we will review some in the coming months.
Adding impedance and drivability-related tests are also on the agenda, as well as publishing articles on our testing methodology and philosophy. However, these are of a lower priority and will be added after sound-quality-related tests.
Before asking a question, make sure you use the search function of our website. The majority of the answers are already here.