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  1. Table of Contents
  2. Intro
  3. Design
    1. Style
    2. Comfort
    3. Controls
    4. Stability
    5. Portability
    6. Case
    7. Build Quality
    8. Breathability
    9. Cable
    10. Front
    11. Angled
    12. Side
    13. Rear
    14. Top
  4. Sound
    1. Bass
    2. Mid
    3. Treble
    4. Frequency Response Consistency
    5. Raw Frequency Response
    6. Soundstage
    7. Imaging
    8. Total Harmonic Distortion
  5. Isolation
    1. Noise Isolation
    2. Leakage
  6. Microphone
    1. Recording Quality
    2. Noise Handling
  7. Active Features
    1. Wireless Range
    2. Latency
    3. Battery
    4. App Support
  8. In the box
  9. Conclusion
  10. Q&A
Reviewed on May 26, 2017 , Marc Henney, Yannick Khong

Superlux HD 668B
HEADPHONES REVIEW

Usage Ratings - Version 1.1
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Test Benches:

  • 1.1: Summer 2017
  • 1.0: Winter 2017
  • 0.9: Winter 2016
5.8
Mixed Usage
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What it is This is the combination of the different use cases to evaluate how versatile the headphones are. Therefore an everyday headphone should be well-rounded enough to adapt to most situations and environments without significant losses in sound quality, design ergonomics or isolation.
Score components:
7.5
Critical Listening
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What it is The level of audio fidelity a headphone can reproduce. Therefore a balanced and true representation of bass, mids, treble, soundstage and imaging, as well as a comfortable listening experience, is essential for critical listening.
Score components:
4.8
Commute/Travel
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What it is How well the headphones handle the loud environments involved in commuting or traveling. Therefore your listening experience should be comfortable, hassle-free and as isolated from noise as possible.
5.3
Sports/Fitness
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What it is How well-adapted the headphones are, to use while doing sports or strenuous exercise. Therefore the headphones should not be too cumbersome and deliver a stable and comfortable listening experience.
5.2
Office
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What it is How well the headphones can deliver a comfortable and isolated listening experience in an office-like environment. They should not leak much and should block the noise of a busy office.
Score components:
Type : Over-ear
Enclosure : Semi-Open
Wireless : No
Noise-Cancelling : No
Mic : No
Transducer : Dynamic

The Superlux HD 668B are great-sounding and affordable critical listening headphones. They let in a lot of ambient noise and leak enough to be distracting to those around you, so they won't perform as well for other use cases. They're also a bit bulky and cumbersome to carry around. However, when it comes to sound, they deliver an almost unmatched audio reproduction at this price range.

See our recommendations for the best Critical Listening Headphones.
Test Results
Design 5.6
Sound 7.9
Isolation 3.9
Microphone 0
Active Features 2.7
Pros
  • Great sound quality.
  • Lightweight design.
Cons
  • Sensitive to noisy environments.
  • Plasticky build quality.
  • Uncomfortably tight for some listeners.
Update 8/10/2017: Converted to Test Bench 1.1. Learn more about our new versioned test bench system here.

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5.6

Design

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Score components:
Superlux HD 668B Design Picture

The Superlux HD 668 look like a budget version of the AKG K240, with minor changes to the headband design. They have the same semi-open ear cups that make them a bit cumbersome to carry around since they don't fold or lay flat. They're also not the best headphones to use outdoors as they're a bit bulky and not stable enough for sports. On the upside they're lightweight, they have a detachable cable, and they can be comfortable depending on your head size.

Style
Superlux HD 668B Design Picture 2

The HD 668B look very similar to the AKG K240. They have paddles instead of a fabric strap to cushion the headband and an odd-looking male audio jack in place of a more traditional female port for the detachable cable. However, the rest of the HD 668's design, including the large semi-open ear cups, look like a cheaper version of the K240s. Overall, they have an understated and utilitarian appeal but they're not headphones you would use outdoors for their style.

6.0 Comfort
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What it is: Adjustability and degrees of freedom, pressure, stiffness and weight.
When it matters: When the headphones are going to be used for long durations.
Score components: Subjectively assigned
Superlux HD 668B Comfort Picture
Weight : 0.51 lbs
Clamping Force
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What it is: The force that the headphones exert on your head, once you have them on. This is purely a measurement of the force applied, which does not take into account the earpad's surface area and the resulting pressure you will feel, on or around your ears.
When it matters: The tighter the headphones, the more force they put on your head. This can get uncomfortable or cause pain and soreness during long listening sessions.
:
1.2 lbs

The Superlux HD 668 are decently well-padded but a bit too tight on the head. They're lightweight and the ear cups are large and fit well around most listeners ears. Unfortunately, the headband doesn't extend to accommodate different head sizes, so they tend to feel a bit tight. That and the paddles that act as a cushion for the headband put quite a bit of pressure, which will get fatiguing after a long listening session.

0 Controls
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What it is: The control scheme of the headphones, the number of functions provided, button layout and ergonomics as well as the quality of tactile feedback.
When it matters: If you want to control volume, pause your music or make phone calls without directly interacting with your audio device.
Ease of use : N/A
Feedback : N/A
Call/Music Control : No
Volume Control : No
Microphone Control : N/A
Noise Canceling Control : N/A
Talk-Through : N/A
Additional Buttons : N/A

6.5 Stability
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What it is: How the headphones are designed to prevent them from slipping off your ears or falling off your head.
When it matters: If you plan on using the headphones while doing sports or other physical activities that requires a lot of movement.
Score components: Subjectively assigned
Superlux HD 668B Stability Picture

The HD 668B are tight on the head which make them decently stable. They won't fall during casual listening sessions and may even be tight enough for a light jog but they are not sports headphones. The earcups are a bit bulky and move a lot under physical activity so they won't be the ideal headphones to go running with. On the upside, the detachable audio cable will disconnect if it gets hook on anything

5.2 Portability
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What it is: The volume of space occupied by the headphones when folded into their most compact format.
When it matters: If you're often on the move and need to carry your headphones in a bag, purse , or pocket.
Score components:
Superlux HD 668B Portability Picture
L : 9 "
W : 7.1 "
H : 4.1 "
Volume : 262 Cu. Inches
Stand required : N/A

The Superlux are lightweight but too bulky and cumbersome to be portable. The ear cups do not fold or lay flat, so unless you have a bag, they will be a hassle to carry around on your person.

5.5 Case
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What it is: The provided carrying options to protect your headphones when transporting them.
When it matters: To prevent damaging your headphones, if you often carry them in your bag or pocket.
Score components: Subjectively assigned
Superlux HD 668B Case Picture
Type : Pouch
L : N/A
W : N/A
H : N/A
Volume : N/A

Comes with a somewhat, rugged pouch that will shield the headphones from scratches and minor water exposure. However, it will not protect your headphones against drops and impacts.

5.5 Build Quality
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What it is: Durability, material quality, cheap/expensive feel.
When it matters: When the headphones are going to be used by multiple users (classes/studios), by children, in tough conditions, on a daily basis, or for exercise.
Score components: Subjectively assigned
Superlux HD 668B Build Quality Picture

The Superlux HD 668 are cheaply made and plasticky. They feel like a budget version of the AKG K240, which shows in their build quality. They have a plastic design with no metal parts, and all the materials used in their build quality feel slightly low grade. They won't break if they accidentally fall once or twice, but they don't feel like durable headphones. The paddles, especially, are weak points that will wear over time.

6.7 Breathability
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What it is: How hot the headphones get when you wear them for an extended period of time.
When it matters: If you often have long listening sessions or use your headphones while doing physical activities like running or working out.
Score components:
Superlux HD 668B Breathability Before Picture Superlux HD 668B Breathability After Picture
Avg.Temp.Difference : 4.8 C

Cable
Superlux HD 668B Cable Picture
Detachable : Yes
Length : 10 ft
Connection : 1/8" TRS

Comes with 2 audio cables: a female to male 1/8" TRS cable and an another, shorter female to male 1/8" TRS cord.

Front
Angled
Side
Rear
Top
7.9

Sound

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What it is: How accurately the audio is reproduced. The tests are performed with the headphones' most commonly used features enabled (noise-cancelling, wireless, etc.)
Superlux HD 668B Frequency Response

The Superlux HD 668B are a great sounding pair of headphones with a balanced Bass, excellent Mids and good Treble. They perform quite consistently on most people and have good Imaging and Distortion performance. However, they lack a bit of thump in Bass, and the Treble could sound a bit sharp on overly bright tracks. Also, they don't have the most open and immersive Soundstage due to their relatively closed and shallow earcups.

8.6 Bass
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What it is: Frequency Response from 20Hz-250Hz
When it matters: When the material is heavy on bass frequencies, such as those of kick drums and bass guitar.
Score components:
Superlux HD 668B Bass
Std. Err.
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What it is: The amount of deviation (weighted standard error) in bass frequency response (20Hz-250Hz) as compared to a target response that would sound perfectly balanced to most people.
When it matters: When a balanced and neutral (reference) bass performance is desired.
Good value: <4dB
Noticeable difference: 0.1dB
:
1.89 dB
Low-Frequency Extension
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What it is: The lowest frequency at which the frequency response reaches -3dB of the target response.
When it matters: Shows how extended the bass is.
Good value: <40Hz
Noticeable difference: 5Hz
:
33.15 Hz
Low-Bass
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What it is: The average amount of over/under-emphasis in frequency response from 20Hz-60Hz.
When it matters: Kick drums and low frequency effects get their 'thump' from this range. Mostly felt than heard.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
-3.09 dB
Mid-Bass
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What it is: The average amount of over/under-emphasis in frequency response from 60Hz-120Hz.
When it matters: Melodic bass instruments have most of their fundamental frequencies in this range. This is where the 'body' and 'punch' of the bass sits.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
1.49 dB
High-Bass
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What it is: The average amount of over/under-emphasis in frequency response from 120Hz-250Hz.
When it matters: Most instruments get their warmth and full-ness from this range. When over-emphasized, mixes tend to get muddy and boomy.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
0.82 dB

Very good Bass Range performance. Low-bass which is responsible for low-end thump and rumble is slightly lacking, but the rest of the Range is virtually flawless.

9.0 Mid
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What it is: Frequency Response from 250Hz-2KHz
When it matters: When the material is heavy on mid-range frequencies. This is the case for the majority of audio content.
Score components:
Superlux HD 668B Mid
Std. Err.
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What it is: The amount of deviation (weighted standard error) in mid frequency response (250Hz-2.5KHz) as compared to a target response that would sound perfectly balanced to most people.
When it matters: When a balanced and neutral (reference) mid performance is desired.
Good value: <4dB
Noticeable difference: 0.1dB
:
1.38 dB
Low-Mid
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What it is: The average amount of over/under-emphasis in frequency response from 250Hz-500Hz.
When it matters: Most instruments have their fundamentals or low harmonics in this range. Over-emphasis in this range sounds muddy and cluttered. Under-emphasis, thins out the vocals and lead instruments.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
0.03 dB
Mid-Mid
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What it is: The average amount of over/under-emphasis in frequency response from 500Hz-1KHz.
When it matters: This range is occupied mostly by upper harmonics. Over-emphasis sounds forward and boxy. Under-emphasis pushes instruments to the back of the mix.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
-1.31 dB
High-Mid
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What it is: The average amount of over/under-emphasis in frequency response from 1KHz-2KHz.
When it matters: Most instruments, especially vocals, get their intensity and clarity from this range. Over-emphasis sounds honky and harsh, under-emphasis sounds weak and distant.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
-0.77 dB

Excellent Mid-Range performance. Low-mid is reproduced flawlessly. There is a small but broad dip surrounding 1KHz, which tends to push vocals/leads to the back of the mix. However, at about 1dB this effect will be very subtle.

7.8 Treble
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What it is: Frequency Response from 2KHz-20KHz
When it matters: When the material is heavy on high-range frequencies, such as voice, cymbals, and any other material where brightness, brilliance and airiness is desired.
Score components:
Superlux HD 668B Treble
Std. Err.
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What it is: The amount of deviation (weighted standard error) in treble frequency response (2.5KHz-20KHz) as compared to a target response that would sound perfectly balanced to most people.
When it matters: When a balanced and neutral (reference) treble performance is desired.
Good value: <4dB
Noticeable difference: 0.1dB
:
3.64 dB
Low-Treble
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What it is: The average amount of over/under-emphasis in frequency response from 2KHz-5KHz.
When it matters: Almost all instruments rely on this range for their presence, detail, and articulation. Over-emphasis can sound harsh and painful. Under-emphasis hurts the comprehensibility of vocals and lead instruments.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
-0.68 dB
Mid-Treble
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What it is: The average amount of over/under emphasis in frequency response from 5KHz-10KHz.
When it matters: This is the sibilance range. Cymbals, vocals, and lead instruments rely on this range for brightness and presence. Over-emphasis sounds piercing and painful, under-emphasis sounds dull and lispy.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
3.48 dB
High-Treble
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What it is: The average amount of over/under-emphasis in frequency response from 10KHz-20KHz.
When it matters: This range gives brilliance and airiness to the sound. Over-emphasis sounds hissy, under-emphasis sounds closed-up and lifeless.
Good value: +/-3dB
Noticeable difference: 0.1dB
:
2.09 dB

Good Treble Range performance. Low-treble and treble are a bit inconsistent. Additionally, treble and high-treble are overemphasized by a couple of dBs, making these headphones a bit bright and sharp on certain tracks.

7.5 Frequency Response Consistency
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What it is: The amount of deviation of each frequency response pass, from the average frequency response.
When it matters: Shows how consistently the headphones perform after re-positioning them.
Score components:
Superlux HD 668B Consistency L Superlux HD 668B Consistency R
Avg. Std. Deviation
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What it is: The average amount of deviation in frequency response of 5 re-seats, from the average frequency response.
When it matters: Shows how consistently the headphones perform after re-positioning them.
Good value: <0.5
Noticeable difference: 0.1
:
0.49 dB

Good consistency. The Bass Range of our Over-Ear and On-Ear headphones are measured on 5 different human subjects, 5 times each. In the graphs, each line represents an individual's average Bass response. The variance in the Bass range is very little, except for one of our test subjects who wears glasses, which gets about 3dB less Bass at 40Hz. In the Treble Range the variance is about +/-3dB is which is decent.

6.7 Soundstage
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What it is: Soundstage qualities are not inherent to the audio content, the headphones have to 'create' them rather than 'reproduce' them. They determine whether the sound is perceived to be coming from inside or in front of the head, how open and spacious the soundstage is, how much the headphones acoustically interact with the environment, and how strong the phantom center is.
When it matters: When an accurately produced, large and spacious soundstage, similar to that of a stereo loudspeaker setup is desired.
PRTF Error
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What it is: The average amount of deviation in Pinna-Related Transfer Function of the headphones, compared to that of a loudspeaker. Whether the soundstage is perceived to be unnatural, located inside or in front of the head, is dependent on this quality. The more the headphones activate the HRTF resonances of the ear (similar to what loudspeakers do), the more the soundstage will be pulled out from inside the listener's head. This quality affects both stereo and mono content.
When it matters: When a natural, in-the-front soundstage is desired, similar to that of a loudspeaker.
Good value: <5
Noticeable difference: 0.5
:
6.7 dB
Openness
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What it is: How open the headphones are, and how open and spacious they sound. This quality affects both stereo and mono content. This test differentiates between acoustically and electronically produced crosstalk and only takes the acoustically generated crosstalk into account. This value is the inverse of the Noise Isolation test score.
When it matters: When an open, wide and roomy sound is desired. A value of 10 indicates a fully open headphone, and a value of 0 indicates a fully closed headphone.
Good value: >7.5
Noticeable difference: 0.5
:
8.1
Acoustic Space Excitation
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What it is: How loud the headphones are, and how much they excite their environment acoustically. If the headphones are loud and open enough, the sound leaking from the headphones takes some of the characteristic of its environment (reflections/reverb) before reflecting back into the open headphones and to the listener's ears. This quality affects both stereo and mono content. This value is the inverse of the Leakage test score.
When it matters: When an open, wide and roomy sound is desired.
Good value: >7.5
Noticeable difference: 0.5
:
5.5
Correlated Crosstalk
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What it is: How strong and solid the phantom center is. This is mostly a stereo quality and its effects on mono content are minimal. This test is sensitive to the phase of the crosstalk and whether it is produced acoustically or electronically.
When it matters: When a true reproduction of the stereo image is desired. A value of 0 indicates no crosstalk, or that the existing crosstalk is not correlated enough to affect the phantom center. A negative score means the crosstalk is out of phase with the original signal, resulting in a slightly wider stereo image at the expense of creating a 'hole' at the center of the stereo field. A positive score means the crosstalk is in phase and positively affecting the phantom center.
Good value: >1dB
Noticeable difference: 0.3dB
:
0.0 dB

Decent Soundstage. The HD 668B have a semi-open design, so although their Soundstage is less isolating the closed-back headphones, it sounds noticeably less spacious than fully open headphones. Adding to that effect is the relatively small and shallow earcups of the HD 668B which means they don't interact with the pinna the way loudspeakers do.

7.5 Imaging
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What it is: 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.
When it matters: When accurate positioning of the objects in the stereo image, and clear and transparent imaging is desired.
Superlux HD 668B Phase Response
Phase Error
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What it is: The average amount of deviation in the phase, from the ideal flat response.
When it matters: When an accurate and transparent imaging is desired.
Good value: <60°
Noticeable difference: 10°
:
45.62 °
Driver Mismatch (Amplitude)
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What it is: The Left/Right balance of our test unit, that is, the amount of amplitude difference between the left and right drivers. This is not a design test, but a marker for manufacturing tolerance and ergonomics.
When it matters: When a properly balanced stereo image and low manufacturing tolerance is desired. A poor score indicates a noticeable difference in level between the left and right drivers.
Good value: <0.3dB
Noticeable difference: 0.1dB
:
0.31 dB
Driver Mismatch (Frequency)
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What it is: The amount of difference (Std. Err.) between the frequency response of the left and right drivers of our test unit. This is not a design test, but a marker for manufacturing tolerance and ergonomics.
When it matters: When an even and stable stereo image, as well as a low manufacturing tolerance, is desired. A poor score indicates there may be 'holes' in the stereo image at certain frequencies.
Good value: <2dB
Noticeable difference: 0.1dB
:
1.78 dB
Driver Mismatch (Phase)
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What it is: The amount of difference (Std. Err.) between the phase response of the left and right drivers of our test unit. This is not a design test, but a marker for manufacturing tolerance and ergonomics.
When it matters: When an even and stable stereo image, as well as a low manufacturing tolerance, is desired. A poor score indicates there may be inaccuracies in the stereo image reproduction at certain frequencies.
Good value: <90°
Noticeable difference: 30°
:
87.46 °

Good Imaging. Phase error is minimal in Bass and Mid Ranges and won't really affect the imaging. However, the phase shift, as well as mismatch in high-treble, will have a small but negative effect on the stereo image.

7.8 Total Harmonic Distortion
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What it is: The subtle, unwanted frequencies (harmonics) produced alongside the intended frequencies.
When it matters: When clean and pure sound reproduction is desired, though its effect is not as noticable as frequency response.
Score components:
Superlux HD 668B Distortion
Weighted THD @ 90
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What it is: The overall amount of harmonic distortion measured at 90dB SPL. To make the score more perceptually relevant, more weight is given to the higher frequencies.
When it matters: How pure the sound is at moderate listening levels.
Good value: <0.100
Noticeable difference: 0.1
:
0.522
Weighted THD @ 100
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What it is: The overall amount of harmonic distortion measured at 100dB SPL. To make the score more perceptually relevant, more weight is given to the higher frequencies.
When it matters: How pure the sound is at loud listening levels.
Good value: <0.300
Noticeable difference: 0.1
:
3.569

Good harmonic distortion performance. The overall level of harmonic distortion is low for the most part. However, high-bass shows a bit of excess distortion, especially under heavier loads. Additionally, peaks at 8KHz tend to make the sibilant frequencies a bit brittle and harsh, but at 1% of the test signal this effect will be subtle.

3.9

Isolation

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Score components:

The HD 668B  are not intended to block a lot of ambient noise. They have a semi-open design that gives them a more immersive Soundstage but also means they leak and let ambient noise seep into your audio. They're headphones best used in isolation where there isn't much noise to ruin what you're listening to and the leakage level won't bother anyone.

3.5 Noise Isolation
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What it is: How much outside noise is blocked out by putting the headphones on.
When it matters: If the headphones are going to be used in a noisy envinronment (airplane, subway, etc.)
Score components:
Superlux HD 668B Noise Isolation
Overall Attenuation
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What it is: The overall amount of environmental noise reduction in dB.
When it matters: In loud envinronments like planes, trains, offices, etc.
Good value: <-20dB
Noticeable difference: 1dB
:
-6.69 dB
Bass
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What it is: The overall amount of noise isolation in the bass range (20Hz-250Hz).
When it matters: When the outside noise is bass-heavy, like in airplanes.
Good value: <-15dB
Noticeable difference: 1dB
:
0.16 dB
Mid
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What it is: The overall amount of noise isolation in the mid-range (250Hz-2.5KHz).
When it matters: When the environment's noise is mid-heavy, like in an office.
Good value: <-15dB
Noticeable difference: 1dB
:
-0.23 dB
Treble
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What it is: The overall amount of noise isolation in the treble range (2.5KHz-20KHz).
When it matters: When the environment's noise is treble-heavy. Although uncommon, areas with sharp sounds fall under this category.
Good value: <-30dB
Noticeable difference: 1dB
:
-19.73 dB
Self-Noise
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What it is: The amount of noise created by the active electronics of the headphones (if applicable), measured from 300Hz-20KHz. Applies mostly to wireless and noise-cancelling headphones.
When it matters: If too loud, it could become distracting when listening to quiet material like podcasts and audiobooks.
Good value: <16dB
Noticeable difference: 1dB
:
0 dB

Poor Isolation. Given the semi-open design of these headphones, poor isolation is natural. These headphones don't block any noise below 1KHz. Above that, they achieve about 20dB of reduction which actually is above average.

4.5 Leakage
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What it is: The amount of sound bleeding out of the headphones.
When it matters: When the listener doesn't want people around them (in office, recording studio, etc.) to hear what is being listened to.
Score components:
Superlux HD 668B Leakage
Overall Leakage @ 1ft
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What it is: The amount of sound leakage heard 1 foot away from the user, while the user is listening to a 100dB SPL signal.
When it matters: When you don't want people hear what you are listening to.
Good value: <35dB
Noticeable difference: 1dB
:
51.95 dB

Poor Leakage performance. The semi-open HD 668B leak less than some fully open-back headphones, but more than the ones with a closed-back design. The significant portion of their leakage is between 400Hz and 10KHz which is a relatively broad range, and the overall level of the leakage is also fairly loud.

0

Microphone

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What it is: The microphone section shows the quality of speech capture and transmission by the mic, as well as how well the microphone under test handles noisy environments.
When it matters: For your speech to be transmitted to and understood properly by the listener, the microphone needs to have a good recording quality. If the environment the microphone is being used in is noisy, a microphone with a good noise handling performance would be needed as well.
Score components:
0 Recording Quality
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What it is: Microphone recording quality shows how natural, neutral, extended and intelligible speech would be with the device under test, in a quiet environment.
When it matters: A microphone with a good recording quality ensures that the person listening to you would hear a full, clear, and easily understandable speech. Therefore, it is important whenever a good quality of speech transmission and intelligibility is needed.
Score components:
LFE
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What it is: Low-frequency extension shows how deep the bass response of the microphone is, and therefore, how deep and full your voice would sound to the listener. It is the lowest frequency at which the frequency response reaches -3dB of the target response.
When it matters: LFE is not a big factor in speech intelligibility and even speech recorded with a mic that has an LFE of 500Hz could still be easily understood. Therefore, it is mostly important if you are concerned with how deep and full your voice would be heard.
Good value: <150Hz
Noticeable difference: 30Hz
:
N/A
FR Std. Dev.
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What it is: Frequency Response Standard Deviation shows how accurately and balanced sound is captured by the microphone at each frequency. FR Std. Dev. is calculated between LFE and HFE, and the rest of the spectrum is ignored.
When it matters: A good frequency response is desired when a natural and neutral speech quality is desired. As opposed to HFE which is more a metric for speech intelligibility, frequency response could be considered as a metric for a natural and neutral sound.
Good value: >3.5dB
Noticeable difference: 0.5dB
:
N/A
HFE
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What it is: High-frequency extension is the highest frequency at which the frequency response reaches -3dB of the target response. It shows how extended the treble response of the microphone is.
When it matters: HFE is one the most important factors in speech intelligibility. The higher the HFE, the brighter, more open, and more extended the speech quality will be which makes it a lot easier to understand by the listener.
Good value: >8KHz
Noticeable difference: 1KHz
:
N/A
Weighted THD
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What it is: The unwanted frequencies (harmonics) produced alongside the intended frequencies, which cause deformation of an output signal compared to its input.
When it matters: When clean and pure sound reproduction is desired, though its effect is not as noticable as frequency response.
Good value: <1.5
Noticeable difference: 1.0
:
N/A
Gain
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What it is: Shows how much louder the microphone can go above our reference loudness level. The gain value is reported relative to our reference level, which is 94dB at a distance of 5cm from the mouth.
When it matters: A microphone with a high gain is important when the input signal (speech) is very quiet. For example when whispering, or talking on the phone in a library.
Good value: >18dB
Noticeable difference: 3dB
:
N/A

0 Noise Handling
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What it is: How well the microphone is able to separate speech from background noise, so that the transmission would include more voice and less noise.
When it matters: When a clean and intelligible speech transmission is desired in a noisy situation like talking on the phone on a busy street or on the bus.
Score components:
SpNR
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What it is: Speech to Noise Ratio is the difference in level between speech and background noise as heard by the listener
When it matters: If the microphone is going to be used in a noisy environment, it is important for it to be able to separate the speech from background noise, so the voice would be easily audible and understandable.
Good value: >24dB
Noticeable difference: 3dB
:
N/A

2.7

Active Features

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What it is: Headphones with active components that require a battery. This includes noise cancelling and wireless headphones that actively reduce noise or transmit audio via a wireless connection.
When it matters: How suitable the power and wireless specifications of an active headphone will be, depending on your listening habits. The range and/or discharge time of the active headphone you select will be important if you're often on the move or have long uninterrupted listening sessions.
Score components:

No active features.

0 Wireless Range
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What it is: Headphones that offer a cable-free listening experience over a wireless network, typically via Bluetooth or radio frequency.
When it matters: If you don't want to be limited by the length of an audio cable. This means having the freedom to move around in your home or office with a much greater range than an audio cable could provide, especially, if the Bluetooth source is heavy or difficult to carry.
Score components:
Type
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What it is: The type and version of the wireless network, the headphones use to connect to the audio source. This could either be Bluetooth or radio frequency.
When it matters: The Bluetooth version will determine how compatible the headphones are with your Bluetooth enabled devices. Typically, newer Bluetooth versions are backward compatible with older ones but may lack the additional features that more recent Bluetooth protocols provide.
:
Wired Connection
Obstructed Range
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What it is: The range that the wireless headphones can reach before dropping any audio when the Bluetooth source was placed in another room.
When it matters: If you can't or prefer not to carry your Bluetooth source on you, while listening to your audio in an indoor environment. Although, the obstructed wireless range will slightly depend on your home or office layout.
Good value: >35ft
Noticeable difference: 5ft
:
N/A
Line of Sight Range
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What it is: The range that the wireless headphones can reach before dropping any audio when in direct line of sight of the Bluetooth device.
When it matters: If you can't or prefer not to carry your Bluetooth source on you, while listening to your audio in a large and open environment.
Good value: 170ft or more
Noticeable difference: 10ft
:
N/A
NFC
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What it is: Near Field Communication technology that allows you to quickly, pair your headphones with your Bluetooth and NFC-enabled device.
When it matters: This makes pairing with an NFC-enabled device a lot easier than the typical and often tedious hold-to-pair procedure that most wireless headphones have.
:
N/A

10 Latency
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What it is: The latency is how long it takes for audio to play through your headphones once the audio signal has been sent from a source.
When it matters: When gaming or watching movies. High latency means you will hear the audio much later than the images you see on screen.
Score components:
Base Latency
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What it is: The Base RF latency or the default sub-band coding (SBC) of most Bluetooth headphones.
When it matters: When watching videos a high latency can cause sync issues between the images you see and the audio you hear.
Good value: 50ms or less
Noticeable difference: 15ms
:
0 ms
aptX Latency
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What it is: An audio coding algorithm (Codec) that improves bit rate efficiency. It reduces latency and improves sound quality over Bluetooth.
When it matters: For better sound quality if your often streaming music over Bluetooth. Also it slightly improves latency when watching videos with wireless headphones.
Good value: 50ms or less
Noticeable difference: 15ms
:
N/A
aptX(LL) Latency
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What it is: Low latency variation of aptX that significantly reduces sync issues between video and sound when using Bluetooth headphones.
When it matters: When watching videos or gaming latency is a lot more noticeable than just listening to music.
Good value: 50ms or less
Noticeable difference: 5ms
:
N/A

N/A Battery
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What it is: The power source of your headphones. All headphones with active features have a battery that will deplete over time.
When it matters: To continue using the active features of your headphones. Some models lose features or switch off completely when the battery is drained, which limits what you can do with them until the next charge.
Score components:
Battery Type
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What it is: The type of battery that the headphones use. Usually AAA or embedded, Li-ion rechargeable batteries.
When it matters: When your headphones run out of power. Rechargeable batteries usually charge via the headphones Micro-USB port whereas AAA batteries have to be replaced or charged with an external device.
:
N/A
Battery Life
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What it is: The amount of time it takes for a headphones' battery to be completely drained. Battery life will vary depending on the active features used and volume level.
When it matters: For active headphones that connect wirelessly, have noise cancellation or other audio-enhancing features, that cease to work once the battery is dead.
Good value: >10hrs
Noticeable difference: 0.5hrs
:
N/A
Charge Time
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What it is: The amount of time your active headphones have to be connected to a power source to charge from 0 to a 100%. However, charging time will vary depending on your power source.
When it matters: To be able to use the active features of your headphones. Especially, wireless ones that completely switch off and need to be recharged when the battery is dead.
Good value: 2h or less
Noticeable difference: 0.25h
:
N/A
Auto-off
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What it is: A feature that turns off the headphones, after a set time, when they're not in use.
When it matters: To prolong battery life when the headphones are not being used, or if you forget to manually turn off your headphones.
:
N/A
Audio while charging
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What it is: Some active headphones remain usable while charging. They continue to stream audio and do not disable other active features.
When it matters: This makes sure that your headphones's battery are not being drained when your relatively close to a power source. However, this means wireless headphones will need a wired connection to the power source during the charging process.
:
N/A
Passive Playback
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What it is: Active headphones that still work when all their active features are turned off or out of power.
When it matters: If you run out of power and do not have spare AA/AAA batteries or access to a power source to recharge your headphones.
:
N/A

0 App Support
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What it is: The additional app provided to enhance your listening experience. They typically deliver a set of practical features that give you more control over the sound, noise cancelling and effects that the headphones produce.
When it matters: An app with a lot of features allows you to customize your listening experience to suit your taste and preferences. For example, additions like an equalizer can give you more bass or treble and room effects can simulate a bigger Soundstage in closed back headphones.
Score components: Subjectively assigned
App Name : N/A
iOS : N/A
Android : N/A
Mac OS : N/A
Windows : N/A
Equalizer
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What it is: Parametric, graphic or preset sound profiles that slightly alter the frequency response.
When it matters: If you want to tailor, your listening experience. Depending on what you're listening to you may want more or less bass for some tracks or more mid-range for vocals-heavy audio.
:
N/A
ANC control
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What it is: Control over the Active noise canceling technology. This could be either a simple on/off button, and adjustable slider or even adaptive self-regulating noise cancellation.
When it matters: If you're in an environment where you need to monitor your surroundings or completely isolate yourself from ambient noise.
:
N/A
Mic Control : N/A
Room effects
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What it is: Room effects that enhance the audio quality to make it more immersive.
When it matters: If you want to further tweak your listening experience. Adding room effects, can simulate a more spacious Soundstage or deliver a surround sound-like feel.
:
N/A
Playback control
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What it is: An in-app player that gives you access to play/stop, track skipping or volume controls directly with the app.
When it matters: It's a shortcut that allows you to control your audio without leaving the application.
:
N/A
Button Mapping : N/A
Surround Sound : N/A

No compatible app

In the box

Superlux HD 668B In the box Picture

  • Superlux HD 668B Headphones
  • 1/8" to 1/4" Adapter
  • Audio cable (x2)
  • Carrying pouch
  • Manual

Conclusion

5.8Mixed Usage
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What it is This is the combination of the different use cases to evaluate how versatile the headphones are. Therefore an everyday headphone should be well-rounded enough to adapt to most situations and environments without significant losses in sound quality, design ergonomics or isolation.
Score components:
Below-average for mixed usage. These headphones are for critical listening and aren't designed to be versatile in all environments. They won't block a lot of noise for your commutes, and they're too leaky to take to the office. They're also a bit bulky and cumbersome for sports, but they're an excellent-sounding and affordable pair of headphones for critical listening.
7.5Critical Listening
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What it is The level of audio fidelity a headphone can reproduce. Therefore a balanced and true representation of bass, mids, treble, soundstage and imaging, as well as a comfortable listening experience, is essential for critical listening.
Score components:
The Superlux HD 668B are a good, budget option for critical listening. They deliver a satisfying and tight bass that doesn't overpower the presence of instruments and vocals. They have a relatively flat mid-range but a slight bump in the high-mid /low-treble that makes them sound a bit sharp on some tracks especially with songs that are already a little bright. Sadly, they don't have a soundstage as immersive as some of the other fully open-back headphones, but overall the sound quality of the HD668 is sufficiently good for both casual and critical listeners.
4.8Commute/Travel
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What it is How well the headphones handle the loud environments involved in commuting or traveling. Therefore your listening experience should be comfortable, hassle-free and as isolated from noise as possible.
Subpar for commuting. They're not intended for this use case as they don't block a lot of ambient noise, they're not portable and do not have the most durable build quality.
5.3Sports/Fitness
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What it is How well-adapted the headphones are, to use while doing sports or strenuous exercise. Therefore the headphones should not be too cumbersome and deliver a stable and comfortable listening experience.
Not made for sports. They're bulky and impractical to use outdoors. They're also not stable enough to use while doing physical activities and will slide off your ears if used while running or working out. Also, they don't have any controls, which makes controlling your music source while exercising a bit more difficult.
5.2Office
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What it is How well the headphones can deliver a comfortable and isolated listening experience in an office-like environment. They should not leak much and should block the noise of a busy office.
Score components:
Below-average for office use. They let a lot of noise seep into your audio and also leak a lot which might be distracting to your colleagues.
Average for Home Theater use. They have a great sound for listening to music and watching movies. They also have no latency since they're wired. However, they won't have the best range unless you have an extension cord for the audio cable. They're also a bit uncomfortable and tight on the head.
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Questions & Answers

2 ANSWERED QUESTIONS
2
Alright, so i'm looking for some good, closed, portable, fullsize headphones. They would have to be under 250 and be stable enough to stay on when I run. I don't care if they're bulky or if they're ugly so long as it's comfortable. My previous headphones are the hd 598 and the ath 900x if you need to know. Thanks in advance!

Here are our suggestions: Bose SoundTrue Around-Ear II, Bose SoundLink Around-Ear II, and Plantronics BackBeat Pro 2.

Between the 3: SoundTrue is the cheapest, but wired. SoundLink sounds best, but doesn't have noise cancelling. Backbeat Pro 2 does have noise cancelling, but doesn't sound as good as the other two. The difference in sound is not huge between the 3, and all are good sounding, so it comes down to your preference and budget.

1
Curious why you picked these to review over the Samson SR850? Samson is easier to drive, more comfortable, better bass performance.
Thanks for your suggestion. We picked the Superlux because it was high on our suggestion list, and we weren't aware of the SR850 until now. You can submit and vote for your suggestions here.
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