Superlux HD-668 B

Introduction
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.

If you wish to read this review in spanish, click here

First Impressions (2020)
My last “gamer” headphones were the Steelseries Arctis 3. Both headphones feature a V-shaped signature where the bass and treble are a little bit boosted. However, when I switched from the SteelSeries to the Superlux, I instantly noticed that the sound opened. This is because in the Arctis 3, the mids seemed so lost beneath the rest of the frequencies that any voice or instrument in this range sounded lacking in body. Unfortunately, I sold the Arctis 3 several years ago, so I cannot make a direct comparison, but trust me, the improvement was significant.

Unboxing, Build and Comfort
For $35, the unboxing experience is very good. The headphones come in a decent cardboard box and come with a good variety of accessories: 2 cables (a 1 and 3 meters long), a 3.5mm to 6.35mm adapter and a carrying bag.

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.

A particular thing about the 668b is a 3.5mm connector hanging from the left earcup to connect the headphones cable. Many people mention that this is a clear weak point in the construction and can break at any time. In my 4/5 years of use (not continuous but regular), they have not suffered any problems in this area, but I thought it was good to mention it so it is taken into account.

Comfortwise, this is the worst aspect of these headphones objectively. If you are a person who is used to the low clamping force headphones that float on your head, you will have a bad time with this pair. One piece of good news is that after two weeks of use and letting them rest with the headband open in some box or support, the clamping loosens considerably.


The earpads are also a problematic point for these headphones. They are very shallow, so it is very likely that the ears will touch the fabric covering the driver. However, according to what I searched (but have not yet tried), the earpads compatible with AKG K240 can fit in the 668b earcups, relieving the discomfort that the pleather and shallow earpads may cause.

Frequency response description

Credits: DIY-Audio-Heaven

• V shaped sound signature but sounds well balanced with bass notes not bleeding into other frequencies.
• Boosted mid bass but with good control avoiding interference with midrange sounds.
• Neutral midrange which makes female and male vocals sound natural and articulate.
• Boosted highs that are sibilant most of the times (problematic for mid and higher volume level listeners). However, they provide great clarity.
• Great extension in the treble giving a sense of "air" and spaciousness in music.

Subjective sound description


Bass
There is an early sub-bass roll-off, so these headphones do not extend that well in that range. However, there is a good amount of mid bass, it has punch shown on sounds like drums and on EDM song basslines. In "Vivere" in particular, the large number of instruments in the song can be heard clearly, with a very pleasant bass guitar which is always present behind the vocals without interfering.

"7th Dimension" (Koan Sound) has good bass rumble. The good quantity and quality of bass highlights electronic music, giving it a "fun" character. The 668b handles passages with a wide variety of synthetic sounds very well.

Mids
"Luck Be a Lady" (Sinatra live at Carnage Hall), his voice is immaculate and it seems like you are in the same theater listening him sing. The rest of the instruments sound well separated from each other and with a high level of detail.

With classical and melodic music, the voices and instruments sound organic and with a hint of forwardness. This also shows a well controlled bass execution that does not muddy the mids.

The midrange frequencies in general have a character approaching neutral, accentuating a bit in the upper midrange registers. Vocals in general are presented with great naturalness and have good clarity and presence in their reproduction thanks to the slight elevation between 1.5 to 2.5 kHz.

Treble
Sibilance is very noticeable in "Come rain or come shine" (Sinatra live at Carnage Hall) when the trumpets and cymbals sound together. This also happens in "Teach me tonight."

"Black Magic" (Slayer live) the cymbals at the beginning of the song are piercing at medium and high volumes. The lead singer has good focus sounding clear and prominent.

"No retreat" (Destructo) the bass is again well-presented, and the bells at 1:52 are quite sharp and overly bright, even at what are considered low volumes.

"S" sounds in "Strangers by nature" (Adele) have an exaggerated character.

Soundstage & imaging
Being a semi-open design, these headphones allow for better sense of spaciousness than IEMs or closed-back headphones. Its soundstage is not huge but it does expand a bit around the head. More wide than tall, but with good depth.

For the price, the imaging and separation that the 668b offers are incredible. Instruments can be differentiated from each other with clarity, their location and the distance between them on the stage can be perceived. There is also excellent articulation between voices and instruments.

I always test these two items with "Rime of the Ancient Mariner" (Live at Long Beach Arena). It's spectacular at minute 1:20 how you can tell with these headphones that the bassist and one of the two guitars are on the right side of the stage and the other guitar is a little to the left with the singer at the center. I can't always capture this detail, and the Superlux surprised me for the better.

Also in "Hydrogen" (M.O.O.N.), a song where the left to right movement of the bass notes is excellent, it covers the three important positions as it should (left-center-right).

Personal note
Its resolving character can become fatiguing at higher volumes and for genres that have many string instruments (rock or classical music with violins).

Conclusion
At the beginning of this review, it might sound like these headphones have more cons than pros. Ultimately, as someone who reviews audio products, I have to be as objective as possible, and yes, their comfort will leave something to be desired for some individuals (I don't mention it in the review, but it's not my case). Setting that aspect aside, the price to performance offered by the 668b is one of the best that can be found for over-ear headphones under $50: spectacular resolution, punchy yet well-controlled bass, organic-sounding vocals and instruments. If you're not afraid of treble or listen at low to moderate volumes, I am 100% recommending these Superlux headphones for budget-conscious audio enthusiasts.

Link to my review and measurement index thread where one can also find a full review overview, more information about myself as well as my general-ish audio and review manifesto: https://www.head-fi.org/threads/956208/

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I only give full stars. My ranking/scoring system does not necessarily follow the norm and is about as follows:

5 stars: The product is very good and received the "highly recommended" award from me.

4 stars: The product is very good and received the "recommended" award from me.

3 stars: The product is good/very good, but not outstanding/special enough to get any of my two awards. ["Thumbs Up"]

2 stars: The product is only about average or even somewhat below that and somewhat flawed/flawed in some areas. [neither "Thumbs Up" nor "Thumbs Down"]

1 star: The product is bad/severely flawed to outright bad. ["Thumbs Down"]

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Superlux HD668B


Source:

Review sample.


Miscellaneous:

Pretty inexpensive.

Unlike my Superlux HD681 that came packed in a cheap see-through plastic packaging, the 668B arrived in a proper packaging.

Included are a storage bag (feels quite cheap, but it's much better than nothing at this price point) that I already know from my HD668B as well as a similar 3.5 to 6.3 mm adapter, but in addition, there are also two cables and a clip that secures/locks the cable joint. I'm using the shorter 1 m cable.

It's obvious that the HD668B have adopted design elements from several AKG and Audio Technica headphones.

The plastic used on the headphones feels quite cheap but rather sturdy.

Proper strain relief on the cable and good flexibility. Cable attached to the left ear cup, which is the industry standard. I like the clip that secures/locks the extension cable in place.
Cable extension is a standard 3.5 mm TRS plug, so any regular headphone extension cable could be used in theory.
Cable microphonics are fairly low, which is nice.

Comfort is decent but not great.
The pleather ear pads are rather shallow but the case is not as bad as on my Fostex T50RP Mk3.
The headband size is self-adjusting but the comfort or pressure distribution aren't great due to the split design.

Clamping force is on the higher side.

There is a bit of passive noise isolation, but not to the degree of most fully closed-back over-ear headphones.




Sound:

I have the shorter (1 m) of the two extension cables attached.

Tonality:

V-shaped with elevated mid- and upper bass ass well as upper middle and upper treble.

The midrange is definitely nicely tuned and follows a flat, diffuse-field oriented tuning wherefore voices sound natural and realistic – something that is especially nice to hear on headphones this inexpensive.
As the bass and highs are elevated, though, the midrange is perceptively ultimately pushed further into the background of the mix.

The lows stay nicely out of the mids and don't start to climb before about 550 Hz; they then reach their climax somewhere around 100 Hz with an elevation of around 8 dB of what would be neutral to my ears, with a subjectively perceived strong, bassy impact. Level stays there down to 60 Hz; below that, the bass starts to roll off.
Therefore, the midbass and upper bass are the most elevated areas, however the sub-bass isn't lacking at all and definitely present with similar quantity as the central mids, however probably not fully down to the very lowest registers where it is perhaps a bit below the mids’ level.

The upper middle and upper highs as well as super treble are then elevated, with surprisingly high evenness wherefore the highs are bright but fairly (but not fully) realistic, although undeniably tuned more towards the “fun” side.

Resolution:

Very decent – even more so considering how little these headphone cost.

Pretty clean sounding bass that is only a bit on the softer side. Details are good, but not the most separated (sounds a bit blunt), despite being fairly tight and fast.

Decent midrange resolution and speech intelligibility – nothing sounds grainy here.

Treble resolution is good, but fast attacks could be rendered a bit cleaner.

Soundstage:

On the smaller to average side with almost just as much spatial depth as width.
Reaches about from the left from the right ear cup and about to where my eyes are located.

Imaging and separation aren't as clean as on some of my more expensive headphones, but the imaging is anything but blurry and remains decently precise and distinguishable even when more complex music is played.

- - - - - - - - - - - -

Comparisons:

Superlux HD681:

The HD668B sound bassier to me.
Deep bass extension on my HD861 is minimally better by ca. 3 Hz, but not much and only audible when performing sine sweeps.
The HD681 are brighter, leaner (and therefore less realistic) in the mids.
The same goes for the treble where the HD681 are brighter and peakier – out of the two, the HD668B are definitely the better-tuned headphones.

The HD681s’ bass sounds a bit cleaner and tighter in comparison.
Both are similarly resolving in the mids and highs, with the HD861 appearing airier in comparison (but most likely only because of their tuning).

The two headphones’ soundstages are nearly identical to my ears, with the HD681s’ being perhaps just a tiny bit wider.

Fostex x Massdrop TH-X00 Mahogany:

Way different price league, but several similarities.

Both sound v-shaped.

The bass boost starts about similarly on both headphones until 100 Hz, with my Fostex being a bit less full in the root, however below 100 Hz, the TH-X00 continue to climb further and further, and start to roll off much lower than the Superlux that are already really good in this regard, wherefore they have got considerably more sub- and midbass quantity than the cheaper headphones, with an overall more sub-bass-driven sound signature. Due to this more sub-bass-driven signature, they are the even more engaging and fun sounding headphones in the lowest registers.
The Fostex’ upper mids are more in the background, but not subdued.
The upper middle highs are clearly brighter on the Superlux, whereas the TH-X00 are tuned brighter in the starting super treble.
Out of the two, the Fostex’ highs sound more realistic and natural.

In terms of resolution, the Fostex are ahead, but the gap towards the Superlux is not as gigantic as one may thing. Not at all, in fact, as the latter still perform very reasonably when compared to the former that are ultimately however superior by a good bit in about every aspect regarding resolution.
Therefore, the Fostex’ bass rendering is cleaner, tighter, faster, better controlled as well as better layered; in the mids, they are more layered and detailed as well as refined sounding, which also applies to the highs.

The soundstage size is comparable with the TH-X00s’ appearing overall just a bit larger in terms of spatial width and depth.
In terms of imaging, though, the soundstage is cleaner and better focused on the Fostex, with superior instrument separation, a better portrayal of “emptiness” around tonal elements, and an overall more authentic imaginary room. Directly compared, the Fostex’ soundstage also collapses less when fast and busy music tracks are played, even though the Superlux do a good job at this as well.




Conclusion:

Recommended.

Inexpensive, well-tuned v-shaped fun sounding headphones with good technical performance and even midrange response.


Photos:

This headphone could give you an excellent sound stage without high- piercing treble and thin bass with one condition - you need a dedicated amp for this one to shine.

Although this headphone stated about 56 ohms for each side, 112 in total and should be easy to drive with just any setting, it is not. I have tested with Asus Xonar Essence STX. At first, I used a low-gain in headphone amp setting and experiences all negatives everyone found in this headphone. However, after switching to a high gain amp setting, everything was changed for the much better.

This one is by far the best value headphones for its price if you have a dedicated headphone amp for it.

I have written a review in danish at the danish head-fi-forum, which is called Hoved-fi.dk, and I'll now do my best to translate it into english:

I have on a few occasions heard of Superlux, and that their headphones, despite being low cost, aren't the worst one can buy.

A few days ago, I had the opportunity to buy a pair of HD 668 B's for what equates to roughly 21.50$, including the cost of shipping and a pair of velour earpads.

Naturally, before recieving the headphones, I had seen quite a few written and video reviews of the HD 668 B, but since I do not seem to share sound preferences with a whole lot of reviewers, I am never quite sure what to expect from a headphone.

Finally: The arrival of the HD 668 B's! I removed the stock "leather" pads without even trying them with the headphones, as all of the reviewers mentioned that the stock pads were awful. The velour pads are very comfortable, and because the headphones weigh next to nothing, they are also comfortable for longer listening sessions.

The build quality regarding the rest of the headphone can best be described with the words: "You usually get what you pay for"

Except for the headband and the holders for the "wings" that rest on your head, the headphones are made of plastic. They dont squeak or rattle when handled, but apart from that, there aren't many more nice things to say about the build quality.

Not that they are going to fall apart with everyday use, but on the "nice-materials-scale", I'd give them a 2 out of 10 - because there at least is some metal included in the construction.

The headphones are sold with (I believe) a 10 foot and a 3 foot cable. I got mine secondhand, and only got the longer of the two cables.

The cable is rather thin, but is at least detachable, so if you happen to step over the cable, it should just come right off - if not, the cable can be replaced as described.

The 668 B's make use of what I'd describe as "wings", that rest off the top of your head, and prevents the headphones from sliding down. The concept is fine, but you might have to bend the wings (carefully!) a bit, in order to adjust the clamping pressure on your head.

The sound:

I have owned a pair of Hifiman He-350, that I'd - before owning the 668 B's - describe as being bright. HD668 B is, however, even brighter, and a bit more aggressive.

If you'd like a bit more lowend, you can try adding more layers of foam in front of the drivers.

If you one day find yourself with 30$ you don't know what to do with, I'd recommend you try out the 668 B's - If my description of the sound seems like something you'd like.

I am not going to go more in-depth about the sound, as I do not consider myself to be experienced enough to properly describe other sound characteristics - and I do not want people to be mislead by improper descriptions

First, off the Superlux HD-668 B are a great value for what you get. I recommend modding them for better listening sound and comfort.

Mods:

• Added electrical table inside the cups covering the holes. This lowers the sound stage but not too much and helps control the sound.
• Removed paper inserts in the cups because not needed with 1st mod
• Removed foam inserts. Clears up the sound, helps to tame the treble somewhat, and also, bringing the mids forward.
• Replaced stock earpads with Tranesca leather Angled big overear earpads. This gives comfort over the cheap stock pads
• Resoldered the poorly done wires for better lasting connection.

Fixed the clamping by stretching the headphones out.

Testing:
Equipment Used: SMSL sApII headphone amp running through an SMSL M2 USB DAC using Digital Output mode in Linux with PulseAudio.
Method: I listen to a wide variety of genres from Jazz, Rock, Metal, Electronic, and Classical/Orchestra. So I tested a bunch of songs from each different genre and they all sounded great without anything missing from them.

Sound:

• Treble is way too hot and has a harsh sound. To fix this is to trim back the 4khz - 10khz rage in an equalizer but I have fixed this somewhat by modding these cans, but some EDM songs not all can have hot/harsh treble if mids/lows aren't playing at the same time.
• Mids are not pronounced and are covered up by the harsh sounding Treble. This can be fixed with an equalizer or mods.
• Bass is punchy and not overpowering that it will blast your head off.
• Lows are not missing anything in their range. They sound accurate and are very responsive.
• Vocals are very clear and natural.

Build Quality

Intro (important)
Before you continue reading, you can and should read my ‘about author’ page on head-fi to get a taste of my sound preference and test tracks. I bought these for $42 AUD ($30 USD) on sale at Gearbest. I bought these after reading all the raving reviews, even some comparing it to the Sennheiser hd600 but I guess they were all hype.

Listening and tests were mainly done with my Xiaomi 4X phone using Spotify's extreme quality (320Kbps, 24bit, 48Khz?). Note, my Xiaomi 4x output is slightly warm sounding and bassy (a solid 3-5dB more bass) compared to audio from my Ipod 5th gen and my computer (I5 core). The 4X output also sounds noticeably clearer and has better imaging than both my ipod and computer.
I usually listen at a low to very low volume. When using my Xiaomi 4X I listen at 20% of max volume (3 notches). Thus why I prefer a slight L or V shaped sound signature as bass output decreases with lower volumes. This also means my evaluation of the bass might not be as accurate.



Sound

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%.



- Treble is way to Hot, particularly the highs. This could be attributed to the multiple relatively large peaks which are present at around 2k, 6k, 10k, and 15k (thanks to Rtings.com frequency chart). The biggest peaks are present at 10k and 15k. As a result the headphone sounds very unnatural and harsh. I would not consider myself a treble sensitive person but the super boosted highs just make it sound so unnatural. Like Tyll from Innerfidelity said, I have to admit these do sound pretty decent IF you EQ everything from around 1.5kHz gradually down to 5dB or even more.

I see some people being shot down (even comments being hidden What?!!) for saying the highs are too hot as though there’s some kind of cult following thanks to the headphones hype. Believe the hype if you want but just take a moment to think about it. Tyll from Innerfidelity is at his retirement age meaning his ability to hear highs is hampered, yet he says the highs are way to hot, like “razor blades”. Doesn’t that ring any bells? Maybe at very high volumes the bass might come out more thus balancing out the treble but even then I did not find the bass to be strong enough to mask the treble. Regardless, you shouldn’t be listening at high volumes, unless you enjoy accelerating your hearing loss.

Anyways, below is my EQ setting. Even with my EQ setting treble may still be hot for some. I’ve also attached a picture of a frequency curve versus age graph for those who do not know about age-related hearing loss (Presbycusis).






Otherwise like I said, these will sound very unnatural and extremely harsh. Although mids are already quite forward, I experimented with removing the foam screen in front of the driver to further boost the mids. Mids did become even more forward but it also lifted the already super elevated highs. I have even swapped the stock pads with Velour pads which only reduced the isolation. Thus the bass was reduced which brought forth the hot highs even more.


- Mids are a bit forward but nowhere near as much as the highs. I find it okay, some may say it is a bit recessed which could be attributed to the relatively more prominent sub-bass and super elevated highs.Personally i did prefer a little more of the mids hence why i experimented with taking out the dampening foam positioned in front of the driver.


- Bass is okay or a little bad with stock pads and very bad with Velour pads. With stock pads (plastic pads) I have to say bass gave more than what I first expected given that it is a semi-open back design. Sub bass is quite decent, nearing the amount that my Sony MDR-ZX600 puts out though doesn’t go as deep. Mid-bass is tight and has good quality but is a bit soft especially when compared to the mdr-zx600. Overall, I’d say bass is quite coherent and neutral besides the elevated sub-bass.

With Velour pads, bass was pretty much non-existent as the velour pad could not create a seal since it is made of fabric. As I said before, this brought forth the mids and already elevated highs even more.



Soundstage and imaging

I hear quite a few people say that these have a very wide sound stage but I do not think so. There is a difference between having a big soundstage and sounding diffused. I don’t know if it’s because the bad implementation of the semi-open design and/or the bad tuning but the 668 sounds quite diffused like listening to a concert from 100+ metres away. Good soundstage should sound like being surrounded by musicians a few metres away. If you want to know what very good soundstage and imaging is like then try the Sony mdr1A, you will tell from comparing that the 668B is diffused. Imaging on the 668B is pretty much on par with my mdr-zx600 if not a little worse due to the diffused soundstage.

Isolation

Pretty much non-existent due to the semi-open back design.

Design and comfort

It is mainly made of cheap feeling plastic with visible joint gaps. The headband consists of a rigid metal wire structure and has two probes with pads that rest against the top of your head. The plastic pads made me sweat quite a bit and was uncomfortable since the two small head pads could not distribute the weight of the headphone sufficiently. As expected from a semi-open headphone, there are holes at the back of the housing which act as vents. The worst thing about the 668B was the stock pads which I just could not describe as pleather but rather as plastic. The plastic pad was very rigid and made my ears sweat quite a lot. It was so uncomfortable that I had to make a permanent switch to velour pads even though that meant near non-existent bass. Apart from all the negatives, I must commend Superlux for implementing detachable cables on such a cheap headphone and providing a 3m cable.
Below is a picture of the headphone with velour pads on.





Summary

The 668B is just not worth it. You could have better headphones for roughly the same amount of money (such as the Sony mdr-zx600) or even better to invest in a slightly more expensive headphones under $100, that way you don’t need to think about upgrading for a while. There is no excuse for EQ, any headphone put through a good EQ software can sound decent. It’s like strapping a jet engine on a Toyota Prius, of course it would out speed a Ferrari, but will it perform and drive as coherently? No. Plus I do not want to waste time switching my EQ pre-set every time I want to listen to the 668.

I could only recommend the 668B to the elderly or anyone else who has hearing loss. Or for anyone who is on an extremely tight budget, want a neutral sound, does not mind spending time switching EQ pre-sets, and are willing to spend extra on better ear pads. Even then you’d still have its diffused soundstage and near non-existent isolation.

I’m way late to this party but you know what? I’m glad I came. Have you been looking for a super affordable headphone but are overwhelmed by all the choices out there? Let me simplify it for you; The Superlux HD668B is exactly what you’ve been looking for.

Superlux was started in an apartment building in Taiwan over 30 years ago. They have continued to grow and now have a huge facility in the industrial zone at Lan-Yuan port, China, where they make headphones, speakers, microphones and a bunch of other electronic gear.

At the time of writing, the Superlux HD668B is listed at $34.99 and is available at Gearbest here.

This product was provided for the purpose of an honest review. I’m not affiliated with the company and all observations and opinions here are my own.

Pros

• Punchy, articulate bass
• Clear and detailed sound
• 2 cable extensions included
• Price!

Cons

• Stock earpads are a bit thin

SPECIFICATIONS

• Drive Type: Semi Open Back
• Frequency Response: 10-30kHrz
• Sensitivity: 98 dB SPL/1mW
• Maximum Power Input 300mW
• Impedance: 56 Ohm
• Weight 7.8oz (222 grams)
• Cable: Removable 1M & 3M
• Plug Adapter: 3.5mm to 6.5mm (1/4 inch)

Package and Accessories
The Superlux HD668B comes in a large but simple box with an image of the headphones and model number on the front. On the back and sides are some features and details of the included accessories.

When you open the box you see the provided cloth carrying/storage bag. The headphones are secured in a cardboard cutout which holds them in place. It’s a simple presentation but it’s practical and the basic materials used help to keep the cost down.

Included in the box are:

• 1x Superlux HD668B headphones
• 3.5mm to 6.35mm adapter
• 1x 3 metre female to male 3.5mm cable
• 1x 1 metre female to male 3.5mm cable
• Carry bag
• Cable clip
• Instruction manual

That’s not too shabby considering the price you’re paying. Having the two cables provided is really something I wasn’t expecting but it’s very appreciated and also a very practical addition. At this point, just seeing my first glimpse of the headphones and the two cables, I was already thinking what great value this is.



Build Quality and Design
To be honest, I wasn’t expecting much in terms of build quality. I mean, heck, I consider $35 cheap for earphones but for a full-sized over-ear headphone? C’mon! As I lifted the headphones out of the box my anticipation grew.

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 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 earcups are large and made from a light but robust plastic. There is a series of concentric circular holes, covered with a metal grill, place around the centre of the earcups. These give the headphones their semi-open back characteristic.

The inner part of the earcups pivots slightly in and out, while the spring steel wires twist back and forth, so the headphones naturally find the right position on your ears.

Looking at the earpads, they’re quite large and easily fit right around my big ears. The pads are made from a PU leather with a foam interior. There’s also a sheet of foam covering the drivers so there’s some padding between your ears and the driver covers.

These pads are easily removable, so you can replace them if they get worn or you can get some third-party alternatives for added comfort.



Comfort and Noise Isolation
I find the Superlux HD668B extremely comfortable to wear. The clamping force is sufficient to hold the headphones securely on your head and you can move about easily without fear of them falling off.

Thanks to the large diameter of the earpads, any pressure is spread over a large surface area so they don’t cause any discomfort at all. The only thing that might be an issue is the earpads becoming quite warm, due to the firm pleather covers. I imagine if I were to upgrade to some third-party replacement pads, the HD668B would be every bit as comfortable as my Beyerdynamic DT990 Pro.

Being a semi-open back, the HD668B does not have much passive noise isolation. I can still easily hear the clacking of my mechanical keyboard as I type this, as well as the television in the background. This is normal for this type of headphone and if you’ve had open or semi-open back headphones in the past you’ll know exactly what to expect.



Cables
Finally, there is the external cable connector that differs from the usual female jack type on most headphones. The HD668B has an external 3.5mm plug, onto which you connect a female 3.5mm cable extension.

Both the 1-metre and 3-metre extensions terminate in a straight 3.5mm plug which is perfect for connecting to a mobile phone, portable DAP or computer. There’s also the included 6.35mm adapter if required to plug into a desktop amplifier.

As for the cables, they have a smooth, black rubberized sheath. They’re fairly supple and don’t have any kinks or unruly bounciness. Another bonus with the cables is that there is almost no microphonics at all, even when walking around. In fact, holding the cables in your hand you might wonder again – how can they provide all this for so little cost?



Sound
Any scepticism I had vanished as soon as I heard the first notes coming from the HD668’s transducers. These things sound ridiculously good (in the context of their price). I was greeted with a mildly V-shaped signature with a touch of warmth, along with clarity and detail.

The tonality is superb, the balance is just right – not analytically boring, nor overly fun coloured. There’s a healthy dose of bass impact, clear and intelligible midrange (albeit a touch recessed) and airy, crisp treble.

GEAR USED FOR TESTING

• ATC HDA-DP20
• Acoustic Research AR-M20
• PC/MusicBee > Topping DX7
• Samsung Galaxy Note 5

BASS
This is one of the most surprising aspects of the HD668B. The bass is well articulated, textured and doesn’t show any sign of bloat or woolliness. Mid-bass has nice impact with a fairly fast but natural decay. There’s no noticeable bleed into the midrange. I love the quantity of the bass in relation to the mids and highs. Clearly, the person who added the B (for balanced) to the model number knew what he was talking about.

Sub-bass also has a satisfying goodness. There’s a nice weight to it and a fast, controlled rumble which, similar to the mid-bass, does not intrude over the midrange. The HD668B revels in its control here, bringing the party without the associated hangover.

MIDS
The midrange has great tonality throughout. Lower mids are a hint lean but still have enough body so as not to sound hollow or too distant. The upper midrange is a little more upfront and can be a little edgy on occasion but having said that, it’s an area my ears are particularly sensitive to.

Vocals sound natural and come through with clear intelligibility. The HD668B renders voices with just enough warmth that they sound organic but maintain clarity and texture.

TREBLE
The treble is light and airy with a hint of sparkle. Detail retrieval is very good and for the most part, the treble is non-fatiguing. On brighter tracks, some sharpness can be detected but that’s mainly due to the HD668B’s transparency; it doesn’t try to smooth over the treble but rather aims to faithfully reproduce the recording.

SOUNDSTAGE
The Superlux HD668B presents a soundstage with above average width and plenty of height, accentuated by its airy characteristic. While the depth is fairly ordinary, instrument separation is still good and maintains some space between various elements.

Comparisons
BEYERDYNAMIC DT990 PRO – 250 OHMS ($160)
The DT990 Pro is more heavily V-shaped, with more accentuation in the treble. The Superlux HD668B has just a little more weight in the mid and sub-bass areas. Both share a similar width in the soundstage but the DT990 Pro has more depth and roundness to its stage.

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.

In terms of comfort, the DT990 Pro is superior. It has slightly less clamping force and of course, has those lovely velour earpads that are thicker and softer. I’m fairly certain though, that if I were to put the Beyerdynamic pads on the Superlux, the comfort level would be near identical.

MSUR N650 ($90 – $100)
A bit of a hidden gem, the MSUR N650 has a warm and inviting sound. It’s got more mid and sub-bass than the HD668B but doesn’t have the same masterful control. Bass on the N650 carries more weight and has greater impact, giving the overall signature warmer overtones.

The N650’s midrange has denser notes, making vocals more intimate and closer to the listener, even though the N650’s midrange is more recessed.

The N650 shares a similar treble to the HD668B, which is crisp and airy. Its soundstage is not as wide but it does have more depth and superior imaging.

Comfort-wise, the N650 has softer earpads but they sit more on the ears rather than around the ears like on the HD668B. Both headphones are initially comfortable but I find my ears need a rest with either one after 1 – 2 hours.



Superlux HD668B Conclusion
The Superlux HD668B is simply brilliant for such a low-priced headphone. Even today, it still holds its own against products costing double or triple the price. The balanced, airy and transparent sound will surely surprise you and likely exceed your expectations.

In light of all this, I’m stumped as to why there are so many 4 star reviews for this headphone. Sure, that might be accurate if you were looking at it purely based on sound quality alone. But when the cost is taken into consideration it’s a no-brainer. Add to that the comfort, build quality and the fact that you get 2 cables as well, the HD668B is easily worth full points, IMO.

So, if you’ve been looking for a really inexpensive headphone to start your audiophile journey, look no further. Get yourself some of these today.

*This review was originally posted on my blog. You can see my other reviews over at Prime Audio.

It's hard to review products that are at either end of the pricing spectrum. It's hard not to be critical of products who's high price makes you expect the best. By the same token, it's human nature to root for the underdog.

So please take it with a huge grain of salt when I say: "These are the best monitoring headphones ever".

First, see above. The low price makes it hard to find fault with something that costs so little and yet delivers so much.

Second, if you like bass, you won't like these. It's all about a clean and even clinical sound. Sound that makes you dissect music instead of listening to it. The B in the name of the HD 668B's stands for balanced, but they are not balanced at all. There is a clear preference for highs that gives the headphones a "live" sound in audiophile lingo. Most audio engineers I know would probably call this kind of balance: "good for analytical monitoring".

Any small mistake will be exaggerated and you will wince at any off note. Sound compression comes through loud and clear as well, and your favorite mp3 will sound broken.

Switch to a better sound source (high bit-rate or lossless files) and this particular problem goes away instantly. Instead, you will be surprised to find that despite their elevated highs they are not overly sibilant.

Apart from being cold in their presentation they do have one more definitive trait to the sound: Open. The box proudly proclaims a "Semi-Open" design, but don't believe that for one second. There is no stopping air from getting in or out of these particular cans. However, that does give them a wide sound-stage, and one that I have never heard at this price-point.

You don't get enveloping sound with them. Imagine sound laid out inside an infinity symbol rather then a circle. Any sounds that are far in front sound like they are either above you or in your brain though things that are slightly off to the sides are well positioned.

Before starting the review, I had plans to compare them to AKG 240's, ATH M50x's and other such studio or DJ headphones. They don't compare. The sound is wide, it's open, it's clear, but they lack refinement both in the low end and the boosted treble.

This raw sound will not make all music sound heavenly through them, but listening to live and especially orchestral performances from a good source makes you feel like you're in the pit with the rest of the orchestra.

Bottom line, if you want to listen for errors in music, these will help you find them. If that doesn't sound appealing to you, I'm not surprised. I do think that's what they're made for though, and they do a damned good job of it.

NOTES:
1) Testing was done on both laptop/desktop/portable devices and an Onkyo T8020. Sound sources were mp3, flac, vinyl.
2) About 50 hours of active burn-in were done, and the low end did loosen up a bit in this time, so they do benefit from it.
3) They are almost identical to the Superlux HD 668B and on a blind test you cannot tell the difference between the two reliably.

Available for right around $40, the Superlux HD668B is hands down my favorite entry level open back headphone. As some one who started out with a Beyerdynamic DT 990, my cost of entry to the world of audiophile headphones ran me right around $250. That was for both my headphone and the little amplifier I needed to power it properly. What makes the Superlux HD668B so amazing, is that it offers a similar sound as the DT 990, clean, clear and wonderfully detailed without sacrificing bass, for significantly less money AND without the need for an amplifier! 
 

Following the HD600s, I had simply obtained the Superlux 668b as a point of comparison and reference, as it is a well know and popular budget Headphone. My brother also uses a pair that he swears by (unless he is borrowing my SHP9500). The simple truth is that the Superlux 668b cuts through detail like a knife. Rough and tumble sound, like a cowboy; he gets the job done well with only 6 bullets, or 50 bucks, then tips his hat while he walks off into the sunset. Superlux went full high-noon and checked off all the boxes for a compelling sound without robbing the evening coach. The Superlux 668b follows suit of the KSC75 in being an incredible value in sound quality. Better still, the Superlux has some very well though out design features.
 
The tiny little 3.5mm cable (i dont know what else to call it) that is used to attach various lengths of auxiliary extension cable is fantastic.
As I am sure a few of you thought to do....

 
or better still.....
 

 
To be honest, this could perhaps be used with a bluetooth adapter (though you would look goofy to say the least.)
 
The sound signature strikes me as V- shaped with treble emphasis. I find this quite nice as a contrast to my Sennheisers and Philips. My warning label for this headphone is that they can be harsh. They can be very harsh. This also adds an extra sense of clarity at times. Going from the 668b to HD558s is like going to bight sun to a damp cave. 
I find the sound of the Superlux 668b good enough that I would consider mixing with them.
 
As I have found with pretty much every headphone (except IEMs) more clean power adds to the extension and balance. The Bass got some more growl from the Project Polaris as well.
 
The soundstage is there, but often times I felt as if they were trying to be a tad closed by shoving treble into my skull, while others they seemed almost distant. I have not pinned down exactly what causes this, but it is likely to do with signature. 
 
The fit is another point on which the Superlux 668b can go wither way. The stock pads are quite large and there is foam inside (not big enough for my dumbo ears though.) The wing things on top are meh at best, and honestly I would prefer a real headband, something like the AKG style that the Samson SR850 has. The good news is that the wire frame can simply be stretched or bent to whatever headshape you want. Tight or loose is all up to you. I only loosened mine a bit, but kept it tight enough that I could try to muster out some more bass.
 
The pads are fine. Honestly sub-par compared to many other headphones, but for the price they are fine. I got some velours for $8 on amazon. I do not like them as they were a little smaller than the stock pads in inner height, so I went back to the stock pads. I also noticed that the velours leaked more bass, but also seemed to add a little to the mids.
 
Song recommendation: Gunslinger – Avenged Sevenfold (fits the cowboy theme)
I quite like what these to with metal in particular.
 
Comparisons will be here:
 
Superlux 668b vs HD600:
 
The Superlux is much less forgiving and harsh, more treble, and gives excellent detail. The Superlux strikes me as a bit V shaped with emphasis on the treble comparatively. Strangely enough, I find the Superlux to be more forward, yet somehow less intimate. The 668b is definitely leaner than the HD600. Some people will likely find the HD600 to be relatively veiled in comparison. Some frequencies are a bit under-represented on the Superlux while the HD600 is more neutral. The real difference for me is that it sounds like you are monitoring a recording on the Superlux, While listening to music on the Senneheiser.
 
Superlux 668b vs HD700
 
Wile the Superlux can sound more inside your head at times; the HD700 is very 3 dimensional. The HD700 also carries more warmth and has more body. They both have similar treble spikes as well. I also get less splash from the HD700, as well as more resolve. I find the bass to roughly the same in texture, and tightness. The 700 again carries a level of warmth in the bass, which can make the 668b bass seem better to those who want raw visceral bass. The Superlux can be sibilant sometimes, while this rarely happens with the HD700. I also find the HD700 to be smoother (minus the treble spike) in typical Sennheiser fashion. Price/performance: Superlux wins by a landslide.
 
Superlux 668b vs Koss KSC75
 
These two sounded surprisingly similar. The Superlux is more detailed for sure, as the KSC75 gets more bass texture. The price increase over the Koss is clearly all going to the build. This shows as I am not afraid to be a little rough with the 668B. I also found the sound of the 668b to be more analytical than the KSC. In fact, I would even mix with the Superlux.
 
Superlux 668b vs SHP9500
 
Well. This is where the rubber meets the road. The SHP9500 is much more natural, smoother, and, to me, far more comfortable. The Superlux fights back by having more aggressiveness and is undoubtedly more crisp. The SHP9500 seems a relaxed compared to the 668b and The SHP9500 won in the intimacy battle.
 
Superlux 668b vs HD558
 
I found the Superlux to be far cleaner, and far less mid-bass heavy. The treble more rolled off with HD558. They are in many ways opposites. I think the Superlux is the more capable headphone, but I still find the HD558 to have that special something many headphones simply do not. The Superlux is a much better value for money, but it would not surprise me if more people prefer the HD558.
 
Conclusion: Like many, I have been in the tight budget category, and many see no reason to spend more on headphones. For those people, this should be a banner to fly. The price/performance is unquestioned in my mind. This is a genuine steal at the asking price. I will recommend the Superlux 668b without question.

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The product was provided to me free of charge by Gearbest (thank you @George-gearbest) for the review purpose in exchange for my honest opinion.
Manufacturer website: Superlux, Available from Gearbest.
* click on images to expand.

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Intro.
 
Even so I have been focusing lately on testing and reviewing flagship IEMs and CIEMs, majority of which cost north of $1k, in this write-up I’m going back to my roots and will talk about sone of the cheapest pairs of headphones I’ve tested to date.  Keep in mind these are full size semi-open cans, not another budget pair of in-ears or earbuds where I have seen even lower prices ($5 Monk being the prime example).  But still, at $35 or sometime even down to $30, I haven’t heard full size headphones that cheap with a sound that good!  Don’t mistake this level of excitement for “OMG, this kills any $500-$1k pair of headphones”, let’s be realistic.  But I have no problem saying these $30-$35 headphones have a build quality of other $60-$70 pairs and sound quality that can go head-to-head with a number of full size cans up to $200.
 
3+ years ago when I started writing my audio gear reviews, my focus was solely on budget earphones, trying to find the next Giant Killer.  But you can’t judge something to be a “giant killer” without experience of testing more expensive mid-tier and flagship “giants”.  Now, I made a full circle which gives me a more objective point of reference for comparison.  I also made an interesting observation about this HD668B model while reading various impressions since its release in 2011.  Many of the negative comments I read about it are no longer applicable to this 2016 version, which makes me wonder if Superlux already implemented some of the fixes and improvements based on the received feedback.
 
The ironic part of this write-up is that I wasn’t even planning to review these headphones and was asked to take a listen to them in addition to something else I requested to review from Gearbest.  I probably would have dismissed them just on the basis of how much they cost, expecting the usual of “you get what you paid for”.  But I was proven wrong, and now would like to share with you about my experience with Superlux HD668B after spending the last few weeks testing them.
 
Unboxing and accessories.
 
Unboxing experience of HD668B didn’t feel at all like I was dealing with a cheap pair of budget headphones.  A sturdy cardboard box with a nice cover image, a very detailed spec and a description of the design, and a complete list of accessories with corresponding pictures – the packaging box exterior already carried a message of the product being too good to be true for $35 price tag.  But as you know, the writing on the box could be just a part of the overhyped marketing, so without further hesitation I proceeded to lift the cover.
 
 
 

 
I was greeted with a set of full size cans neatly packed inside of a cardboard insert and other accessories around it.  With everything out, I was looking at a generous size soft nylon carrying pouch/bag, two extension cables, 6.3mm adapter, a peculiar cable clip, and a printed manual/guide.  The nylon pouch felt neat and durable, branded with Superlux name.  I consider adapter to be a filler, but it could come handy with full size headphones when used in a desktop setup.  The clip made sense once I attached the cable to HD668B, realizing it does a great job securing the joint if you pull on the wires.
 
 
 
 
 
Regarding the cable, it was actually an extension cord.  First of all, the whole idea of a removable cable in $35 pair of full size headphones is impressive.  But it’s not a traditional cable with 3.5mm male plug on each side.  To keep HD668B earcups slim, Superlux brought out the connector to the outside with a male 3.5mm plug and a very short extension cable.  As a result, you attach the provided “extension” cable to this external connector.  Included was 1m short cable, perfect for a portable use, and 3m long cable for other applications. You can also combine them together to form 4m extra long cable to give you more traveling room around the desk.
 
This "extension" cable idea was quite unique, though it would not be easy to find an extension cable with in-line remote if you need to.  But you can also argue that majority of people would prefer not to carry a phone conversation with these on.  With connector placed on outside, the earcup housing was definitely slimmer.  Also, the attached earcup connector cable is very short with a heavy duty shielding and impressive strain relief.  Not 100% sure if the cable clip was really necessary since the mating of the cable was already secure, but it never hurts to add another level of protection.
 
 
 
Design & build.
 
The first look at HD668B brought back the memory of my recent review of ATH-A2000Z with a similar wire-headband design and 3D-wings.  Honestly, I was expecting a flimsy plastic construction, but surprisingly found it to be not bad at all.  Starting with a headband, you have minimalistic design with a support of 2 steel spring-wires, assuming one carries a cable going to the connector on the left side.  I have an average size head, and it was a bit tight at first but loosened up after a short time of being stretched over the soccer ball.
 
There is no height adjustment like in traditional full size headphones, and instead you have soft foam “wings” on a spring metal wire which self-adjusts as you put headphones on.  This could be hit-or-miss with some people who have big head or curly hair (the last comment actually came from my wife).  For me personally, it works quite well since I’m already accustomed to ATH-R70x and ATH-A2000Z, both of which have a similar “wings” headband support.
 

HD668B next to ATH-A2000Z
 
Though the headband spring-wire felt solid, these wings felt a bit flimsy in comparison, especially a thinner wire attachment - just have to be more careful when taking these headphones off you head.  Closer to earcups, the headband wires are held together with a plastic joint piece on each side, kind of reminding me of “y-splitter”.  These pieces look to be replaceable, if needed, and made of a solid plastic material.  I found HD668B to be relatively comfortable to wear, and with evenly distributed 220g of weight it felt feather light.
 
Moving on to earcups, here Superlux took a page right out of AKG240.  I have no doubt that Superlux engineers were inspired by AKG design, even bringing the connector to outside, though keeping a standard 3.5mm TRS plug for “extension” cable attachment.  The back of earcups also has a similar to AKG circular vents, intended for a semi-open back performance.  The inner middle part of earcups does pivots to adjust around your head, and it works quite well.  The pleather earpads are easy to remove and to replace, especially if you want something softer.  Since the earpads look universal and stretch over the top of earcups, I’m sure replacement alternatives won’t be hard to find.
 
The included original pleather pads are OK, but they do get a little hot after extended use.  It definitely makes sense to experiment with different earpads to hear how they affect the sound.  Just like eartips of in-ear monitors, you can fine tune the level of low end extension and impact as well as being able to control the top end.  In addition, once you remove the earpads, you can also experiment with different dampening foam materials to figure out how it affects the sound.  Here you will find plenty of room for modding experiments.
 
 
 
 
 
 
 

 
The fit.
 

 
Sound analysis.
 
Before jumping into sound analysis, I left HD668B on burn in for about 100hrs, making sure their dynamic drivers are properly conditioned.  Honestly, I didn’t have too high expectations for these, still being a bit skeptical due to the low price.  As a result, my surprise was more shocking when I discovered HD668B to be tuned with a tasteful V-shaped full body sound signature and warm detailed tonality.
 
In more details, I hear a deep low end impact, down to a textured sub-bass rumble and a tight mid-bass which has a bit of a hollow punch.  The bass is rather well controlled, articulate, and there is no spillage into lower mids.  The lower mids have a nice full body, but there is no muddiness or congestion, while upper mids are clear and detailed with an organic presentation of vocals - not too much upfront, just pushed a little back due to an elevated low end.  Treble is surprisingly crisp and detailed, with a good extension, and some nice airiness which helps with layering and separation of instruments and vocals and contributes to higher resolution of the sound.  If I have to nitpick, perhaps upper frequencies have a little shade of metallic sheen, but it wasn’t that bad especially when you pair up with different sources.
 
Soundstage has a good expansion in width, not super wide but definitely way above the average.  The depth is not too far out, but you still feel like a few rows in front of the stage, giving a soundstage perception of spreading left/right around you without going too deep.  Layering and separation was surprisingly good due to well controlled low end which keeps the sound clean from muddiness without spilling into mids and extra sparkle in treble which adds some air between the layers of the sound.
 
If you are looking for a good isolation, these are definitely not the best for listening on the bus or in the library, after all - this is a semi-open design.  But it wasn’t leaking as bad when you step away 2-3ft.  I’m sure some will find this semi-open design even beneficial since it could raise the surround awareness without losing too much of the sound details.
 
Sound comparison.
 
Considering 98dB sensitivity and 56 ohm impedance, I found HD668B to be a little less efficient in comparison to my other headphones, and as a result I had to push the volume a little higher.  Also, it’s clear that more expensive headphones have an edge in build quality and material selection.
 
HD668B vs ATH-MSR7 - HD soundstage is wider, while MSR7 has more depth.  HD has a deeper sub-bass and a little stronger mid-bass, while MSR7 has a more balanced low end.  I also noticed that HD has a little faster attack of the mid-bass while MSR7 is a tad slower.  Lower mids are similar, while MSR7 upper mids are more forward, balanced, and a little brighter in comparison to HD.  I hear treble as being similarly crisp and well defined, though MSR7 has a little more airiness and a better extension.  Overall, the biggest difference here is a more balanced signature of MSR7 versus lifted low end and slightly recessed mids of HD.
 
HD668B vs ATH-M50x - HD soundstage is wider, while M50x has more depth.  HD has a deeper sub-bass while mid-bass is similar, perhaps with HD having a bit stronger impact.  Mid-bass speed is also similar.  Lower mids are very similar, while upper mids in M50x are more balanced and more forward in comparison.  Also, M50x upper mids are a little smoother and a touch warmer.  HD treble is crispier and has more airiness in comparison to a smoother M50x treble.  While I enjoy M50x comfortable fit for extended listening on my laptop, here I actually preferred the sound of HD.
 
HD668B vs SoundMagic HP150 - HP150 soundstage comes closer to HD width, but not quite there, and HP150 has a little more depth.  Also, HP150 sub-bass reaches deeper to the same level as HD, but a little shy of HD quantity, and mid-bass in HP150 is a bit lower in quantity as well.  HP150 lower mids are leaner and upper mids are a little more upfront and brighter with an advantage of slightly improved retrieval of details.  Treble is rather similar, being crisp, bright, snappy, and with enough extension and airiness to make the sound more resolving and layered.  Actually, after closer listening I hear HP150 being a little brighter in upper mids/treble.
 
HD668B vs Oppo PM3 - HD has more width and both have a similar depth.  HD has a deeper sub-bass extension and faster mid-bass punch with more impact.  PM3 mids sound more congested in comparison to HD, though they are more forward in presentation.  Actually HD upper mids are brighter and more detailed and the treble is crisper, better defined, and with more airiness.  PM3 has a very smooth laid back sound while HD has a faster punchier brighter and more detailed sound.
 
 

 
Pair up.
 
Note 4 – Pretty good pair up, though have to push volume closer to the max.  The sound becomes more balanced with a little less impact in mid-bass and a softer sub-bass.  But mids are still detailed and treble still has a great extension.  I also found upper mids/treble to sound a little brighter.  Good soundstage expansion.
 
LPG – here you will find a great transparent sound, deep extended sub-bass, punchy mid-bass, clear and detailed mids, crisp and airy treble.  Soundstage had an impressive width.  It was a great pair up, and I enjoyed the sound quite a bit, definitely giving HD668B giant killer stamp of approval while driving this pair of $35 headphones from this $2k source.
 
DX80 – I found a surprisingly balanced sound with mids a little more forward instead of pushed back, but I think this balanced sound sig change was due to sub-bass and mid-bass being scaled back a bit.  Very clear and detailed sound, upper mids are a bit thinner and vocals were not as organic anymore, treble is crisp, clear, and airy.  Soundstage was wide.
 
X7 w/AM2 – in this pair up I found sub-bass and mid-bass scaled down a bit, making the sound more balanced.  But it also felt like upper mids came a little more forward.  In addition, the bass was tight and punchy, clear detailed mids with plenty of body, and crisp airy treble.  Soundstage was wide.
 
L3 Pro – here the signature was back to v-shaped, with a good sub-bass extension and a nice rumble, and tight punchy mid-bass with a decent impact.  Lower mids have plenty of body, and uppers mids are clear and detailed but also a little harsh with a metallic texture and a touch of sibilance.  Treble is crisp, airy, extended.  Soundstage was wide.
 
AK120ii – in this pair up I found a little bit less sub-bass, still tight punchy mid-bass with a bit of a polite quantity, lower mids had natural full body and upper mids were a little thin, bright, and quite detailed. Treble is crisp, airy, extended.  Upper frequencies have a bit of a metallic sheen.  Soundstage expansion was pretty good.
 
Conclusion.
 
I’m starting to notice a pattern where many of my “giant killer” discoveries happen by accident, when I’m not even looking for another budget pair of headphones and instead just asked to try something new for fun.  Did I get spoiled by flagships?  It’s hard not to, and I’m being honest about it.  But sometime it’s refreshing to take a step back and to listen to these amazing gems that cost so little.  From $5 Monks to $10 KZs and now $35 HD668B – these are all amazing discoveries that show you how creative a manufacture can get by challenging themselves to squeeze every ounce of performance and sound tuning on such a small budget.  HD668B is a real deal Giant Killer, and either if you are on a budget or just want to humor yourself with another budget discovery – I have no problem recommending these semi-open full size headphones because they don’t just look cool and ready for modding, but they also sound great!

 

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Preamble:

Superlux – the Chinese/Taiwanese company really doesn’t need any further instruction for anyone who is at least just a little into audio and headphones. Being in the business for over 30 years, the company is manufacturing microphones, portable PA systems, conference gear, monitoring systems and of course headphones.
Especially their headphones and also in-ears were very positively received by the audiophile community and headphone lovers for delivering exceptionally good value for the money and sounding good despite being so inexpensive. A large part of this “secret” is the abandonment of large (or any at all?) marketing and ad campaigns and re-using the design of existing products.
Less commonly known, Superlux also acts as OEM manufacturer from time to time.

I jumped on the Superlux train quite late – it must have been around spring of 2013 or 2014. That’s when I thought it could be fun trying such an inexpensive circumaural headphone and therefore bought the Superlux HD681.
Not expecting much, the ~ €20 headphone surprised me a lot and delivered anything but a cheap and unrefined sound – yeah, it was actually quite enjoyable and sounded like it cost considerably more. Based on what I heard, I wouldn’t have hesitated to spend ~ €70 for the sound and likely even more if the treble was somewhat less forward and more even.

I also shamelessly admit that I reached out to Superlux not too long ago, asking if I could test some of their other headphones, but didn’t hear back from them at all.
So when George from GearBest recently reached out to me and asked whether I was interesting in getting a sample of the Superlux HD668B (http://www.gearbest.com/headsets/pp_279992.html) free of charge for the purpose of an honest, unbiased review, I didn’t turn down the offer but actually happily accepted it.


Technical Specifications:

Price: $25.99 (http://www.gearbest.com/headsets/pp_279992.html)
Type: circumaural, full-sized, (semi-) open
Drivers: 50 mm, dynamic
Frequency Range: 10 Hz – 30 kHz
Impedance: 56 Ohms
Sensitivity: 98 dB


Delivery Content:

Oh man!
Unlike the HD681 series, the HD668B arrives in an actual cardboard package that is even quite nicely designed and carries information about the delivery content, technical specifications and has got a couple of nice pictures of the headphone and its accessories.
Opening the package, I was even more surprised to find a manual, 3.5 to 6.35 mm adapter, the typical Superlux carrying sleeve, the headphone, no less than two cables (a short 1 m and a long 3 m one) and a clip to safely lock the cable.
At less than $/€30, that’s definitely not what I would have expected but extremely nice to see.
 

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Looks, Feels, Build Quality:

The HD668B looks like some other Superlux headphones and also features an automatically adjusting headband that is definitely inspired by some of Audio Technica’s models.
There are side markers and the cable is attached to the left side which is pretty much the industry standard for one-sided cables.
The small piece that protrudes is a 3.5 mm jack, so instead of the included cables, one could also use any other cable extension with a 3.5 mm socket.
Strain relief is good on the cable itself and sufficient on the protruding piece and feels relatively sturdy and is adequately flexible.
 

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The idea of the small clip that guarantees for a secure connection between the cable and the protruding piece is a quite clever idea in my opinion.
 

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As expected and known from other Superlux headphones, the entirely black headphone is made of plastic but isn’t too badly built at all and appears sturdy. Only the pleather pads’ stitching looks a bit cheap, but that’s what likely most of Superlux’s headphones have in common (including my HD681).
 

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Comfort, Isolation:

The circular ear cups swivel and therefore adjust to one’s individual head shape. The idea of the self-adjusting headband is also quite nice but I personally somewhat prefer the even pressure distribution of the HD681’s headband to the HD668B’s which distributes the pressure mainly to the sides of the top of one’s head.
Talking about clamping force, due to the headband but also in general, clamping force is on the stronger side and the HD668B sits definitely tighter on my head than my HD681. I don’t have a problem with that and also don’t mind my Sennheiser Amperior’s clamping force, but those who are sensitive to this might find the HD668B a little uncomfortable or tightly fitting after extended wearing periods although the pads are actually quite soft.
Microphonics are by the way pleasantly low even when using the headphone when walking.
 

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With my HD681, I was quite surprised that it had something that could be called slight noise isolation, and with the HD668B, I can also report that there is a little bit of isolation, but it is not much at all and doesn’t mask my keyboard’s or the fan’s noise although noise isolation is very slightly more present with the HD668B than with my HD681, probably because of the stronger clamping force.


Sound:

In case anyone of you is wondering about the last letter of the naming scheme of Superlux’s products, it is quite simple: of each product type, there are three iterations that differ in bass quantity. The one without any additional letter has got the most amount of bass, the one with a “B” at the end is right in the middle (“Balanced”) and the one with an “F” at the end is the one with the least amount of low-end emphasis (“Flat”).
So the HD668B sits right in between the HD668F and HD668 when it comes to bass quantity.

Just for your information, I am wearing rather bushy mutton chops at the time of writing these impressions (actually even a full beard at the moment), so the perception of treble might slightly vary for you if you are either mutton-chop-less or bald.
That facial and scalp hair has some effect on the treble is what I once found out in an experiment on myself when I shaved my entire head and face (I’m not sure about my moustache though, but of course it doesn’t matter for that) in order to find out whether my perception of my Sennheiser HD 800’s treble changed – but that’s an entirely different story.

Tonality:

The HD668B is a v-shaped headphone with a present upper bass punch, somewhat recessed but not sucked-out however slightly bright mids and a forward middle as well as upper and super treble.

The bass stays out of the mids and starts climbing from around 500 down to 100 Hz where the climax is reached with ca. 7.5 dB north of neutral and has a subjectively perceived strong impact. It doesn’t start rolling off until 60 Hz, so there is still a good amount of midbass and even some sub-bass although there isn’t that much going on anymore below 35 Hz.
As mentioned, the lows stay out of the mids really nicely. Speaking of the latter, they are a bit in the background and somewhat on the leaner, brighter side wherefore vocals sound a little brighter than what would be neutral.
Above 1500 Hz, the treble starts climbing, takes a small dip between 4 and 5 kHz and then rises even more, reaching its brightest point around 11 kHz although the rest below is definitely on the bright side, too. Above that, the highs don’t take a step back at all and maintain this amount of treble sparkle even past 17 kHz.

Overall, instruments and vocals don’t sound coloured by much besides the upper treble that makes cymbals sound somewhat metallic and unrealistic. Instruments like trumpets that play in the lower treble do however sound realistic. Vocals can sound a slight bit sibilant from time to time but it is nothing striking and I think the small dip in the middle treble around 4.5 kHz helps with that a bit, as the HD668B sounds a little less sibilant than my HD681.

Resolution:

No hype here, as you definitely shouldn’t expect a headphone that can fully compete with decent models above $150 or even $100 in every discipline, but to come very close.
However, for the little money the HD668B costs, you get a really good overall package, and just as with the HD681, I wouldn’t mind paying more than $70 for the sound quality alone, but just as with the HD681, the treble can be too forward and edgy at times and/or could be more detailed/better layered in order to keep the emphasis but not to sound somewhat obtrusive.

The bass isn’t slow at all but feels a bit soft and is not the most detailed or cleanest and sounds a little blunt, however I have a hard time realising that a headphone this inexpensive is producing a bass that has got definitely better speed and control than I would expect at the price point.
The mids don’t sound grainy or lack details at all and are pretty nice considering the price.
And while the treble doesn’t reach the separation and details of more expensive headphones, there is really nothing wrong with it at all although it would have probably sounded even more pleasant if either the upper-end resolution was a little higher or if it was less forward.

If you are familiar with some of the trash that you can buy for less than $30, you should easily hear that the HD668B is nothing like those models but sounds really decent for costing so little.

Soundstage:

The soundstage is on the smaller to average side with almost as much spatial depth as width. Regarding size, it is circa as wide as the space between the ear cups and stops around where my eyes are located.
It is not the airiest soundstage but good overall and while instruments aren’t as cleanly separated as with more expensive headphones, they aren’t too blurry and don’t blend into each other by too much.
Regarding price, the soundstage is even quite good when it comes to precision although I couldn’t precisely make out two instruments that are very close to each other.

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In Comparison with other headphones:

Superlux HD681:
The HD681 does definitely not really appear weak on the bass at all but the HD668B is the audibly bassier headphone. The HD681 extends slightly better by ca. 3 Hz which is not much and only audible when doing sine sweeps.
In the mids, the HD668B is slightly less bright than the HD681.
The HD681’s treble is more forward, brighter and more obtrusive and has got no slight dip in the middle highs, hence the HD668B is easier tolerable in the highs out of the two.

Regarding bass, the HD681 appears a little cleaner, less grainy and more detailed, but really not by much.
In the mids and treble, both are more or less on the same level with the HD681 only sounding airier because of its tonal tuning. The HD681’s treble is probably a slight bit cleaner however it is more aggressive as well as edgy.
Overall I would say both are pretty much on the same level with just a different tuning.

When it comes to soundstage, both headphones sound almost identical to me. The HD681’s might be a little wider but if this is really the case, it would be less than 0.5 cm.

Overall, it’s pretty much a draw with the HD681 having the slightly cleaner bass and the HD668B sounding more tolerable and less edgy in the highs.

Fostex x Massdrop TH-X00 (Mahogany):

Although both headphones are playing in a (totally) different price and sound league and one is (semi-) open and the other is (semi-) closed, they still have some things in common.
For once, the Fostex doesn’t isolate well at all for a closed-back headphone whereas the Superlux has got some isolation although it is open. Besides that, both sound v-shaped, are using dynamic drivers and offer really good value, both at their respective price points.

The bass starts about similarly extending on both headphones until 100 Hz with the Fostex being a little less full in the root, but below, the TH-X00 continues to climb and starts rolling off much later, so it has got considerably more sub-bass and midbass, making it more engaging and fun sounding in the low registers.
In the mids, the Superlux is the somewhat brighter and leaner sounding headphone.
In the lower and middle treble, the Fostex is less present and even slightly recessed in the presence range, hence vocals don’t sound sibilant or bright at all but tonally right to the point. And while the Superlux is the brighter and thinner sounding headphone in the highs, the TH-X00 has got the somewhat more present area around 12 kHz to my ears but sounds overall considerably more natural and realistic.
Overall, the TH-X00 has got the better made and more realistic v-shape so to speak.

You definitely won’t see me ever writing that both are playing even slightly in the same league but you also won’t see me writing that the TH-X00 totally smashes the HD668B and runs circles around it although the Fostex is better in about everything by a good bit and has also got a much more premium build quality. In fact though and realistically speaking, on the sound side, the TH-X00 is definitely even far away from being five times better than the Superlux but is still playing in an easily audible higher league.
When it comes to the bass, the Fostex is cleaner, more arid, tighter, better controlled as well as better layered and reaches deeper without softening towards the sub-bass. In the mids, it sounds more realistic and layered, and its treble is more detailed and refined as well.
In terms of soundstage size, both are about comparable although the TH-X00 feels a bit wider and deeper. When it comes to spatiality though, the TH-X00 is audibly better separated, generates more air and empty space arounds instruments and creates the more authentic imaginary room. It also doesn’t collapse with fast and busy music.

In my opinion, if you cannot/don’t want to buy the TH-X00, want a cheap backup or really cheap alternative that doesn’t sound like total crap but relatively decent for the respective price, the HD668B could be a really solid choice if you can let go things the Fostex’s deep bass extension or resolution and if you can live with a forward, sometimes somewhat overly-bright and edgy treble. Switching from the Fostex to the Superlux, while the latter is inferior in about everything, I however don’t screw up my face or want to throw up, which is a really good sign.


Conclusion:


Less than $30? Indeed. For this little money, one gets a really decent headphone that could easily cost twice or three times as much based on the pure sound, but please don’t expect the HD668B to blow away some of the better headphones costing more than $100/150 or to be on-par.
And even though the headphone is strong on the technical side and still so cheap price-wise, it comes with a nice selection of accessories and a really nice package design.

The sound is more on the fun and v-shaped side with mids that are just slightly brighter than neutral and a treble that might be somewhat too edgy, forward and bright for some, however this bright treble is the only thing the HD668B does “bad” when it comes to tonal tuning. Besides the ambitious highs, it sounds overall remarkably natural for the price and above.
And in terms of resolution, while it is not perfect and sounds a little grainy in the bass, the HD668B plays definitely in a higher class than what you pay for.

On the bad side, we have the bright and sometimes too edgy treble that is definitely nothing at all for people who like to listen at rather high volume levels (not me) and the clamping force that might also be a little too tight for some.
On the good side however, there are so many things sound-wise for the price and even without knowing the price tag.


I am not 100% sure whether I should make this a 4 or 4.5 star review, as the HD668B is sitting somewhere in-between. Neglecting price and value, it would be a 4+ star product in my book, but including the value as I always do in my ratings, this headphone scores easy 4.5 out of 5 possible stars.

Yep, it is quite remarkable that Superlux has created a couple of headphones that don’t sound like the usual trash you would probably expect for such little money.

I have to start this review out by saying I'm no audiophile and not a native English speaker. But I do listen to a lot of music (just recently I had finished upgrading my collection to FLAC), and have experience with a few headphones and low-end speakers. That said, some head-fi has rubbed off on me and I've learned to express my audio thoughts more fluently by reading head-fi threads and reviews. Now, we can get into the meat of this review, the Superlux HD-668B.
 
You need to understand that if you already have a good set of cans, this isn't the headphone you need. This headphone can be (and indeed is) amazing, but only in the right hands! The ideal user of these would be somebody who has been using cheap earbuds they got with their phone all their life. And coincidentally, that is who I was when I purchased these. From that perspective, these are amazing. The bass is finally audible, the mids are clearer, and the treble more defined. But once you're used to headphones, these are a different beast.
 
Very early on, you start noticing the design, and especially the comfort. It's bad. The stock pads feel like they're made of cardboard and not sweating with them on is impossible. They push on your ears and honestly just get painful after a while. You can fix that with velour pads. I didn't have the money for AKG pads, so I went for some generic unbranded ones from eBay for $10. And sure enough, they're softer. You don't sweat as much and while they still sit on your ears, they are much less noticeable than the cold harsh cardboard stock ones. This does change the sound quality however! The bass loss is even greater, and the sound isolation gets worse (but we'll get to sound quality in a bit). What you can't improve easily is the clamp. Part of the reason the comfort with these is bad is because the top "band" is made of metal wires, and they do not bend easily. You can try, but you'll most likely just deform or break them. Also, the earcups can be shallow, and the plastic underneath the pads is not comfortable. There are mods online that fix this, but I just stuck a piece of toilet paper under the pads. It improves the padding and negates the effects of the hard plastic covering the driver, but it again has effects on the sound (mainly reduced treble). The top AT-like wing system doesn't really work until you adjust the wings properly (something I only found out almost a year after getting them -- it's extremely difficult to adjust these things, but it pays off). They can't be too low or they'll push on your head, and they can't be too high or they'll make no difference anyways. You need to set them up so that the clamp of the headphone carries about half of their weight, or they'll be another annoyance.
What I do have to commend, however, is the great cabling system. You get one ~1m and one 3m cable. Male to female 3.5mm. I think I speak for everyone when I say more manufacturers should implement this into their designs -- it's saved me about a hundred times now, because any pulls that happen just pull the cable out. No damage to the headphone in the slightest, and replacing the cable is a piece of cake.
 
"But what about the sound?" Well here is my take on it, comparing them to HD518 and DT770 80 Ohm: Objectively, the bass is lacking. It's detailed (more so than with my HD518s), but you'll have to push the volume up pretty high for it to actually sound like it should. But compare them to your average crappy phone earbuds, and the bass is just incredible, especially with this detail. The mids are there but because the low-end is a bit recessed they sound a bit hollow, especially where choirs and orchestras come into play. The treble is where it's at. These cans are bright, and the treble here can get sibilant at high frequencies. The only cure here is burn-in, burn-in, and again, burn-in! And even then, the treble is so pronounced that, especially if your hearing is still preserved well, the high freuqnencies will get to you. While these Superlux cans bring out the guitar shredding and the vocals in rock and metal, they get very tiring -- with the kind of music they're exceptionally good at, and that's saddening.
Orchestral music clearly lacks the bass. Even cellos and tubas sometimes have to take a back seat to violins and singers or pianists, and the male singers in choirs need to be loud to defeat sopranos, trumpets, and violins. Benny Goodman's orchestra is mainly just the clarinet and trumpets, but that's what's important anyways. In recordings where the boomier bass and warm mids should step back and let the high mids and treble prevail, these are incredible. But again, they can get tiring, at least to some people.
They are pretty easy to drive at 56 Ohms, though my old Android phone (Xperia S, 2012) does have to be set to nearly max volume for these to shine. My newer phone (Xperia Z3 Compact; 2014) has no issue driving these, and the same goes for my PC (with the Realtek ALC892 chip responsible for te audio).
 
All that said about the comfort and sound, I'd still recommend them. The bass is an upgrade from earbuds and isn't overwhelming (this is why the lack of bass is also listed as a pro above), and the rest of the 668B is miles ahead of any phone-bundled accessory. After a while you really will feel the urge to go for something better. Just don't go for something with boosted bass; Instead, find something more neutral and work your way up from there if you still fe. They're also a great place to start if you don't know if you'd rather get open or closed headphones -- because they're semi-open, the sound leakage isn't that big, so if somebody is disturbing you (or vice versa) with these cans on, you know you need to go closed. Otherwise, you're free to go with open sets.
And if you're somebody who already has a dozen headphones? If you don't have the money but want something fun and Beyer 880-sounding, go with these. They're not as good, obviously, they cost $50 shipped with velour pads, but they do their job pretty well. Once you get tired of them, they're a great gift for anyone who has not yet experienced the awesomness of "better-end" audio (as opposed to high-end or mid-range), especially for older people who aren't as sensitive to high frequencies.
 
I hope my short-ish review here adds to the myriad of similar reviews in some way. Happy listening!

Bought used at $30 (Pretty burnt in). Auditted for 1 day. Pads were changed to Hifiman Velour pads and A/B'ed with the original pads, and the cable was a cheap one from KableDirekt.
And now, I can't help sharing my thoughts. They sound pretty good. My initial impression is: such meaty sound! It really gives you the whole of the music.
 
Bass is strong and well-extended.
 
Mids are mediocre and veiled.
 
Treble is good. Refined but can be too bright to people who are used to Senn HD600 type of sound or headphones that are even darker. 
Don't use the velour pads, they make the headphones too bright for long listening sessions.
 
Overall clear sound. Sound stage is fine, somewhere between Grado L cush and G cush, but the veiled mids don't give it a good quality in spatial separation.
 
Build quality is only acceptable. Comfort is fine as over-ears generally should.
 
A review written by s1rrah, link here: http://www.head-fi.org/t/793934/superlux-hd668b-lordy, it claims that the HD668B delivers 80% the performance of a Grado PS1000. I had not auditted PS1000 before, but I agree they sound similar to some Grados, especially considering the refined treble they have. And the extended and punchy bass also should give a PS1000 sound signature. But still the tonality is slightly different from the typical SR series of Grado, maybe the treble is carry out differently when you look at frequency response data but to my ears, HD668b has a good treble, but can be quite fatiguing. Sticking to the original pads, which gives a higher bass compound, sort of remedies the fatigue issue.
 
I would say I favor them over the Grado SR225i that I owned and loved for a long time. They of course should sound inferior overall to my PS500's that I really love... wait a minute, are PS500's really better? 
 
I just picked up my PS500 again and find that it's really hard to say it's all the way better to the HD668b.
 
The superlux HD668b presents music of most genres very nicely. At $40 bucks on Massdrop, you should do yourself a favor and grab one of them 
 
First review on head-fi, please forgive mistakes I must have made.

I got the Superlux HD668B as a gift from my brother. These were my first better than average headphones, and boy, they are good!
 
The build quality is quite good. It is sturdy and flexible, with a removable cable.
They come with a short cable and a longer cable, a quarter inch adapter and a nylon (feels like nylon) carrying pouch.
 
As for comfort, it isn't that good at first, as it has quite a strong clamping force, but it does get better with time. After a while, you can't even notice you're wearing them.
 
The sound: The first time I listened to them I was shocked how transparent and clear the sound is, with somewhat piercing highs, but good punchy bass and neutral mids. I let them burn-in for about 130 hours, and noticed that the sound opened up a little. The highs became less piercing, but still very prominent. The bass acquired more punch and depth. As for the soundstage, I can say they have excellent imaging for a sub 50$ pair of headphones.
 
Superlux must have mistyped the price on them. Must be that, because they are an amazing bang for the buck.
 
I do highly recommend these if your are looking for budget headphones with great sound quality, soundstage and imaging.

This review is based in my experience of almost 6 months with them, running 24/96 Flacs > Foobar2K > Wasapi > Asus Realtek ALC1150 + 4580 Op-amp > HD668B I decided to reboot my interest in audio gear and I was looking for affordable cans that could show me what I've been missing all this time, whitout breaking the bank and with enough SQ to make the next steps really worth it.
 
After much reading around it was clear that the best option was the HD668B's, lucky me I found a local dealer of Superlux so I didn't have to wait for them, went to the store and got them for a steal. I must admit that upon first listening I almost regretted my decision, the detail and articulation promised was there, but they sounded "weird", non natural and the comfort was kinda bad. I didn't test further than a couple days and let them alone for a couple months. After upgrading/rebuilding my workstation I decided to tame that weird sound into something likeable and I managed to do it while the sound burned in (I believe is not HPs that burn in but our ear is what burns-in to them ) I didn't mind much about the "monitor" wording, I thought it was just marketing but now that I have them I can say that an audio engineer in a studio would like them, they are clear, analytical and cold if you like, I like that on a HPs but I'd like warm and bass definition also.
 
Highs: Without EQing the highs can be harsh and piercing with some records, bad mastered or low quality mp3s can be tiring to hear, taming the highs reveal very decent and detailed heights.
 
Mids: Sound like a valley between the cold highs and the loose bass. It's adequate, detailed and enjoyable, I wish it was more "present" but is ok.
 
Bass: It always have confused me, I don't know if it lacks extension or definition, they can go low but there's no punch and when there is punch it does not feel natural. Luckily I'm not a basshead nor I listen to bass heavy music so bass, with its weirdness, end up being fine for my needs, with a little EQ.
 
I have ordered a PA2V2 Amp and all the parts needed to fix my beloved iPod Classic 4G, the Amp should be arriving soon and the parts in a month, then I'll have time to test several combinations and update this review.
 
As conclusion: I'd say go for them, with the price you can't go wrong, if anything they will teach you what  you need and what to look for your next pair of cans, all that while allowing you to enjoy music with a quality hardly available for the price range with other brands.

I apologize if I duplicate the findings of others. I read the other reviews, and I'm trying to address the things I thought haven't been talked about yet.
 
 
The current (it changes, it has too I guess) price (HD7 version) is 29.00 USD w/free shipping.  (Musician's Friend, and a few other "musician" websites.  NO CONNECTION.)
 
I had to wait quite a while to get them.  The Presonus HD7 option would've been faster, cheaper and less hazardous to the merchandise.  At least potentially.....
 
I used the center "pads" from the Velour aftermarket cups in addition to the Super Lux's own pads, and that made a perceptible difference in taming an EXTREMELY DETAILED (and clean) top octave (above 10,000 or so)  My experience was that I couldn't wear them for extended periods of time until I let them run for several days.  The bass is well controlled, and it has improved in dynamics (slam, if you will) over time.  It's no Ultrasone Pro 900 (It's not even a Senn 600 or 650 either at either frequency extreme) however the mids are quite full and (this word's a little annoying to objectivists, but it's not totally out of place) lush.
 
 
The trip from Taiwan was apparently fraught with hazards.  I'm going to contact the seller (Amazon) and look into what happened to the box (it took a HARD lick to its upper left hand side, the phones and accessories were fine though).  I feel certain they'll have no explanation.  I wouldn't if I'd sent something to Taiwan from here.  The 668B is a bargain at twice the price, but don't pay that much if you don't have to.
 
The driver reminds me (more than anything) of the driver from my first "high fidelity" headphones from the early '80's (I'd owned junk headphones before that) the Koss HV/XLC.  There was also a RS version of the same headphone, but without volume sliders on each cup.  (I owned both, until I bought my Senn HD-600's in the late '90's.)  The highs are more extended on the 668B, the Bass is about the same, but doesn't overdrive as easily as the Koss phones did.  (You could make the diaphragms of the HV/XLC "kack" with too much bass in the program material).
 
It's my first choice for "away from the house" needs, because if it gets trashed, it's not a $300.00 catastrophe.   That alone makes a strong case for its inclusion in your collection! 

Brilliant performers. Very detailed, I can spot imperfections instantly now. Great value for money. Definitely the best headphones under €100. Never even look at my hd 598's anymore.

First that all. Im gonna say to all who wanna buy these that these headphones need Burn In, You will notice too much highs the first time. And yes, that was my first impresion of these, Too much highs and sibilances, but after a week I started to notice a improve in the highs and they started to sound awesome.
 
So lets start with the Sound:
 
Bass: Punchy/Fast Midbass, Sub-bass is weak, but overall they give enough bass energy.

Mids: Nothing special here. They´re OK. (Even after this edit I cant still say something bad/good about their mids, they are OK.)
 
Highs: They are bright, These highs are amazing, they give them more energy, trumpets, Saxos, Cymbals sounds amazing. I dont understand why some people say that these are too harsh or they have too much sibilances, yeah they have sibilances but I dont feel them excessive or annoying.
 
Also, their timbre isnt the best, somewhat dry,
 
Gaming: Very detailed and relly good soundstage, I remember my first COD 4 match with these, I even heard enemies across the COD 4 Map Showdown. That was awesome and since that day. I cannot play without them. (Edit: This is no longer the case xD).
 
Edit: I recently posted my review of the Superlux 681 Evo where I compare them a lot against these headphones: http://www.head-fi.org/products/superlux-hd-681-evo-black-professional-monitor-headphones/reviews/14340