Superlux HD-660

The sound signature on these can be described as almost "Grado"esque.  They have a mid/high forward sound that makes them great for guitar rock.  They don't have the harsh treble that is characteristic of most of the Grado line and a lot of the other Superlux models.   Soundstage is good for a closed can and better than the HM5.   Compared to the Brainwavz HM5, I find the 660 to be tighter and more controlled bass with slightly more exaggerated mids.  Compared to the ISK-2011 I find the sound more V shaped and more fun.   The ISK is a good monitoring headphone but is not nearly as musical for the genres I typically listen to.
 
For Rock music, I would rate them in this order:

Grado 325is
 
Superlux HD-660
 
Grado SR-60
 
ISK-2011
 
Superlux 668b
 
Monoprice 8320
 
It isn't really fair to include the 325 since the price is 5x that of the others in this list but the sound signature draws comparisons so I included it.  All of the rest of these phones fall into the sub-$50 range and draw comparison based on what is the best spend for $50.
 
I did find that the HD-660s say they are 150ohm drivers and they do require an amp that can really push a 300ohm phone to do their best work.  These are not the headphones for your iphone or Samsung.   Running a Fiio E07k or a Ibasso Dzero are both better but to really push them, the Asgard and the Fiio E09K docked with an E17 are better yet.   With the slightly bright sound to the HD-660, they make a good pairing with the Asgard.
 
Overall, these rank high on my list for most enjoyable.  I find myself wearing them more often than most of my open headphones because it allows me to listen in comfort while others watch TV etc.

Out of the 4 budget headphones I have picked up over the past year these contend just fine. 
 
My 4 budget headphones are as follows:
 
1.  Takstar Hi2050
2. Superlux HD668b
3. Takstar Pro80
4. Superlux HD660
 
1 Being my favorite, 4 being my least favorite of this list.
 
Do not hold my ranking against the Superlux HD660s, they are actually my everyday headphones at work because of their noise isolation and unique look.  However, they don't have anything unique in their sound to set them aside from the rest.  The Hi2050s and the HD668b's are both open (HD668b's "semi open") so it is not fair to pin them head to head with the very closed HD660s, so take the ordering with a grain of salt.. and my next paragraph since it compares the 668b's directly to the 660s..
 
If I were to listen to 8 hours straight of music, I would pick the 660s over the 668b's.  They are easier to listen to with a wider dependable range of frequencies, they have a more reliable bass thump (my 668b's give a little rattle in the left ear with a hard bass hit), and the stock pads on the 668b's would kill you before you got to the second hour (please put more comfortable pads on the 668b's if you have them..).  So now you ask, why are the 668b's ranked higher?  The 668b's have character, that is the sole reason (and the soul reason, the 668b's will touch your soul).  Those high as can be highs of the 668b's can make your spine shiver and put butterflies in your stomach with the right song.  The 660s just don't have anything like that.  Also, the 668b's are killer gaming headphones with a wide sound stage and natural frequency response.  The 660s lack of any characteristic sound signature is the only reason why they are ranked 4th.  Aside from their lack of a unique "fun" sound, they are solid and easy to listen to.
 
In terms of power needed to drive these things, they are pretty equivalent to the 668b's.  The Fiio E11k maxed out should produce enough noise for you.  Turn the gain to high and it is far more than enough.  You will need a portable amp if you are going to take them on the road, but keep in mind that they are not very compact.  If you are looking to buy budget headphones for travel, pick the Pro80s.
 
Overall I do not regret my purchase.  For under $50 you can get the best quality noise isolation headphones China has to offer, they look very unique, and you can live with the stock pads.  I would recommend them to a friend.
 
 
Bonus Advice:
 
If you have no noise isolation restaints and you aren't looking to use headphones soley for gaming, pick up the Hi2050s off of my list.  They are by far the most versatile out of these 4 headphones and you will not be dissapointed.  I also think they look the best too .  They are open, so please do not wear them at the office as everyone will hear you blasting Taylor Swift.. that would be tough to "Shake Off" in the break room gossip.  Oh, and they are almost as good for gaming as the 668b's, but the 668b's are clearly the best for gaming out of the list.  Hope you enjoyed all of this random advice from a stranger, take it as you like

*The soundstage is pretty good for the price but only so-so in a grand scheme of things.
It's very "listenable" or rather, enjoyable. It doesn't disappoint in any genres or even gaming although ... yeah. Don't want to do that.
 
At first it was rather harsh on mid-treble but after burning it in it is very smooth on the treble now. It does lack bass once you listen to a neutral headphone in comparison on the other hand which is strange given it's a closed headphone but the details are not perfect and it's not flat.
 
 
The best part is the price. I got these for 57$ SGD shipped. My next target is the HD-662. I bought the HD660 out of accident but i'm not even slightly mad.
 
I have now got the 668B and 662B and 681B.
 
The build quality on the 660 is ok on the headband with a leather wraparound but the rest of it is kinda bargain basement and the cable is coiled which I do not like and is actually old fashioned.

I like them. They are not ruler flat or reference grade but they are fun. Much better than my HD-681. I like them better than my HARX900 but not as well as my Senn HD-439 or HD-598. I'll be ordering DT770 velour pads. Got these on your want list? Go for it!

great value, nice sound, very detail, but makes my ear sweat when i use in a long term(2-3 hr)..