Reviewed on May 26, 2017

Superlux HD 668B HEADPHONES REVIEW

Usage Ratings - Version 1.3.1
5.5
Mixed Usage
8.1
Neutral Sound
4.5
Commute/Travel
5.3
Sports/Fitness
5.3
Office
4.4
Wireless Gaming
6.2
Wired Gaming
1.8
Phone Call
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.

Test Results
Design 5.6
Isolation 3.1
Microphone 0
Active Features 0
Connectivity 4.0
Pros
  • Great sound quality.
  • Lightweight design.
Cons
  • Sensitive to noisy environments, by design.
  • Plasticky build quality.
  • Uncomfortably tight for some listeners.
  1. Update 11/21/2019: Converted to Test Bench 1.3.1.
  2. Update 11/6/2019: Converted to Test Bench 1.3.
  3. Update 2/16/2018: Converted to Test Bench 1.2.
  4. 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

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

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
Weight : 0.51 lbs
Clamping Force
:
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
OS Compatibility
:
Not OS specific
Ease of use : N/A
Feedback : N/A
Call/Music Control : No
Volume Control : No
Microphone Control : N/A
Channel Mixing
:
N/A
Noise Canceling Control : N/A
Talk-Through
:
N/A
Additional Buttons : N/A
6.7 Breathability
Avg.Temp.Difference : 4.8 C
5.2 Portability
L : 9 "
W : 7.1 "
H : 4.1 "
Volume : 262 Cu. Inches
Transmitter 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
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

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.

6.5 Stability

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

Headshots 1
Headshots 2
Top

Sound

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.

Sound Profile
Bass Amount
:
-2.16 db
Treble Amount
:
1.27 db
7.5 Frequency Response Consistency
Avg. Std. Deviation
:
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.

8.6 Bass Accuracy
Std. Err.
:
1.89 dB
Low-Frequency Extension
:
33.15 Hz
Low-Bass
:
-3.09 dB
Mid-Bass
:
1.49 dB
High-Bass
:
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 Accuracy
Std. Err.
:
1.38 dB
Low-Mid
:
0.03 dB
Mid-Mid
:
-1.31 dB
High-Mid
:
-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 Accuracy
Std. Err.
:
3.64 dB
Low-Treble
:
-0.68 dB
Mid-Treble
:
3.48 dB
High-Treble
:
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.

7.1 Peaks/Dips
Peaks
:
1.87 db
Dips
:
1.37 db
8.4 Imaging
Weighted Group Delay
:
0.33
Weighted Amplitude Mismatch
:
0.31
Weighted Frequency Mismatch
:
1.78
Weighted Phase Mismatch
:
10.12
7.7 Soundstage
PRTF Accuracy (Std. Dev.)
:
1.64 dB
PRTF Size (Avg.)
:
7.04 dB
PRTF Distance
:
11.79 dB
Openness
:
9.1
Acoustic Space Excitation
:
6.4
8.0 Weighted Harmonic Distortion
WHD @ 90
:
0.100
WHD @ 100
:
0.189
3.1

Isolation

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.

2.5 Noise Isolation
Isolation Audio
:
Overall Attenuation
:
-6.69 dB
Bass
:
0.16 dB
Mid
:
-0.23 dB
Treble
:
-19.73 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
Leakage Audio
:
Overall Leakage @ 1ft
:
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

Integrated
:
N/A
In-line
:
N/A
Boom
:
N/A
Detachable Boom
:
N/A
0 Recording Quality
Recorded Speech
:
N/A
LFE
:
N/A
FR Std. Dev.
:
N/A
HFE
:
N/A
Weighted THD
:
N/A
Gain
:
N/A
0 Noise Handling
Speech + Pink Noise : N/A
Speech + Subway Noise : N/A
SpNR
:
N/A
0

Active Features

No active features.

N/A Battery
Battery Type
:
N/A
Continuous Battery Life
:
N/A
Additional Charges
:
N/A
Total Battery Life
:
N/A
Charge Time
:
N/A
Power Saving Feature
:
N/A
Audio while charging
:
N/A
Passive Playback
:
N/A
Charging Port : N/A
0 App Support
App Name : N/A
iOS : N/A
Android : N/A
macOS : N/A
Windows : N/A
Equalizer
:
N/A
ANC control
:
N/A
Mic Control : N/A
Room effects
:
N/A
Playback control
:
N/A
Button Mapping : N/A
Surround Sound : N/A

No compatible app

4.0

Connectivity

0 Bluetooth
Bluetooth Version
:
N/A
Multi-Device Pairing
:
N/A
NFC Pairing
:
N/A
Line of Sight Range
:
N/A
Default Latency
:
N/A
aptX Latency
:
N/A
aptX(LL) Latency
:
N/A
0 Non-Bluetooth Wireless
Non-BT Line of Sight Range
:
N/A
Non-BT Latency
:
N/A
10 Wired
Analog Audio
:
Yes
USB Audio
:
Yes
Detachable : Yes
Length : 10 ft
Connection : 1/8" TRS
Wired Latency
:
0 ms
PC / PS4 Compatibility
PC / PS4 Analog
:
Audio Only
PC / PS4 Wired USB
:
No
PC / PS4 Non-BT Wireless
:
No
Xbox One Compatibility
Xbox One Analog
:
Audio Only
Xbox One Wired USB
:
No
Xbox One Wireless
:
No
0 Base/Dock
Type
:
N/A
USB Input
:
N/A
Line In
:
N/A
Line Out
:
N/A
Optical Input
:
N/A
RCA Input
:
N/A
Dock Charging
:
N/A
Power Supply
:
N/A

In the box

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

Compared to other Headphones

5.5 Mixed Usage

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.

8.1 Neutral Sound

The Superlux HD 668B are a good, budget option for neutral 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 neutral listeners.

4.5 Commute/Travel

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.

5.3 Sports/Fitness

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.

5.3 Office

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.

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