Although I don't think it has the class and refinement to compete with the HD600, Koss ESP950, K701, but perhaps the 668B strikes a wonderful synergy with your music and amplifier. Why, you ask? The answer is simple; Because they feel pretty good! They’re very light but not at all loose or flimsy. Everything feels pretty robust a solid. At the same time, I use the Ultimate Ears TF10 (IEM) everyday during commute. I am hoping to buy a pair headphone that sound better than that(or I am just looking for a different sound). I don’t really like the sharp treble on the TF10, since I listen to a lot of Cantonese music (jazz,blue,pop). I have done several things to modify the 668B and feel I have raised their performance level quite a bit. Now I listen to only two headphones – my HifiMan HE-5LE and Superlux HD 668B. The build is mainly based on plastic except for the metal headband. Despite this, they feel like solid headphones that won't break from a few falls to the floor. Also, this amount of plastic makes them extremely lightweight, which is a plus if they are going to be worn for several hours. Clearly, this build is similar to several AKG models, and the headband is very similar to the renowned Audio Technica R70x. The earcup and headband cushions are made of pleather.

Superlux HD668b review Reviving an old budget king: Superlux HD668b review

Treble: These headphones were extremely bright and harsh-sounding. It's strange that the review on Headfonia claimed the treble was excellent - granted, there's a lot of detail and when it behaves, the treble is quite sparkly. But as you can see in the FR graph there is a very sharp and pronounced peak between 5-6KHz, which is THE area that causes sibilance (overall the entire treble region is just way too pronounced to sound natural). I am not sure why Superlux tuned this headphone to accentuate this particular area, but I agree with Tyll's (from InnerFidelity) assessment on this one... it's like listening to a good headphone through razor blades. Comfort is better on the 661. Sound quality, the 661 is better suited for music, where the 668B has a dryer but more articulate sound that would be better for monitoring. The 661 is a little warmer on the mids and bass, and has a fuller mid section. The treble is similar in tone to the 668B, but less dry.

The build quality regarding the rest of the headphone can best be described with the words: "You usually get what you pay for" I always feel that the AKG K240 is quite flat and boring, even the Sextett version which I had for a while. I definitely prefer the HD668B to the K240. Inexpensive, well-tuned v-shaped fun sounding headphones with good technical performance and even midrange response. I just bought the Samson SR850 which is the clone of HD668B. Do you think the Soundmagic A1o will provide a good synergy to this headphone? Or will any in the list of your portable amps shoot out except for the JDSLabs (i already have this, adding a new one)?

Superlux HD-668 B – Thomann UK

I think at the moment the HD660 earns my strongest recommendation for music. Here is the review of them: http://www.headfonia.com/the-new-superluxes-are-good-the-hd330-hd440-and-the-hd660/ I would say that pairing the 668B with iPod or similar device will give you only 50% of their potential. The difference on a good amp is dramatic.The AD700 is quite special with its entry level Audio Technica signature, and although it's not my favorite phone, I think the AD700 is still superior to the HD668B. Goldenears.com graphs are wildly different from those of Headphone.com & I’m really confused about HD668B bass & sub bass response.

Review] Superlux HD668b - Head-Fi.org [Review] Superlux HD668b - Head-Fi.org

I hear an artificial "cavernous" quality to the K701 that overlays all recordings. The 668B is more chameleon-like in that it doesn't seem to add as much of its own signature. I think a strike against the 668B is its plastic housing does color the bass/lower mids to a small degree. This headphone will definitely lend itself to user modifications. The headband size is self-adjusting but the comfort or pressure distribution aren't great due to the split design. I’ve got a question, especially to you, Mike. How would these play paired with Yulong U100? I know its amp is not very bassy, and neither are the HD668, but I’m planning to use them mostly for classical music and some jazz abums, so I don’t mind that so much. Deep bass extension on my HD861 is minimally better by ca. 3 Hz, but not much and only audible when performing sine sweeps. I have listened to these headphones for roughly 24 hours accumulated over a month. I initially burned them in for half a day. The headphone still sounds the same, maybe just a very slight decrease in treble. Volume is quite soft, I need to turn my Xiaomi 4X volume up to around 30-40% to be as loud as my Sony MDR-ZX600 at 20%.Vocals are a touch more recessed on the DT990 Pro, however, it does have a slight edge in tonal accuracy. The DT990’s vocals are a little richer and vibrant, where the HD668B is somewhat dry. It’s really amazing how similar these headphones sound, the biggest differentiator is the treble. On the DT990 Pro, the treble has more sparkle but it’s also more strident and fatiguing. Pretty distanced and not too in-your-face. Electrical guitars sound amazingly smooth, acoustics sound clear as crystal. One peeve about this aspect is that it could be a little more forward. Not too much, but enough to hear the air in the strings At the heart of the build are the spring steel wires that form the headband. They run from the top of the headphones all the way down to where the earcups are attached. Partway down the wires is a plastic joint on each side which adds some rigidity and also holds an additional pair of wires that are attached to the self-adjusting “wings” that sit on the top of your head. The Superlux HD 668b where my first “non gamer” headphones as I always wanted to step up my audio gear and at the time (2020) it was the best over ear headphone I could afford. Highs sound... how to say... grainy. Not overly grainy, but with high frequencies the graininess is noticeable. A little honky and weird at times, and considered "unlistenable" to some people I know.