Here, they are.
Superlux is a taiwanese brand very well known (in the Internet) for manufacture awesome sound quality headphones at silly inexpensive prices. The HD 668B is the most popular (and best, because I've bought them) model they sell. This headphones are design for professional studio monitoring, so you can imagine what is the quality they have. What you can't imagine is the price they cost. This depends on your location but it will be surprising anyway. Let's start.
What really matters, the sound.
The sound is VERY GOOD. Let's talk about it.
When I first plugged them, I had read lots and lots, tones of good comments, so many that I hoped an orgy of sound waves, but obviously, it wasn't so. However, I say they sound INCREDIBLE, I can't imagine a better sound.
Technically, they have very good bass, very good middle and incredible treble. Although treble is better than bass or middle, I'm not saying at all they aren't good, because they are, very. The bass is not what you hear from the awful Dr. Dre's Beats, they are not too much, not exceeding, but they have great punch however. The middle is also very good, correct volume, you can hear everything in these frequencies very good and very clear. The treble is great, brilliant, twinkly, just how it has to be.
In the internet, lots of picky users who care about headphones say that these ones become different with 200 hours of life. It seems the bass becomes much better and louder, the middle becomes much better, and the treble becomes a bit softer and proper. Which is EVEN GREATER.
(Anyway I'm not going to plug them for hours when I'm not listening just to reach 200 hours of use).- Equalization
If there is anything in the sound that bothers you (improbable), it can be fixed simply with a bit of equalization. They are not difficult to equalize. But it isn't necessary really. You won't be at all disappoint with the 'default' sound.-Volume
The Superlux speakers have a resistance of 56 ohms, which is almost double the usual resistance in common headphones. One of the things you may doubt about is if you'll need a headphone amplifier or a good sound card in your computer. The answer is NO. They sound very good and loud in a normal PC with integrated sound card. The sound is also quite a lot loud either in my non-loud Philips MP4 player or my Nokia phone. I like listening to loud music and I am completely pleased with the volume. In fact, I would say they sound louder than my 32 ohms Philips!- Comparisons
The sound which comes out of this headphones is so good that you can check in the Internet which other headphones they are compared with. One of the most famous comparison alternatives (and one of the most cheap) is the Sennheiser HD555 which costs around $80 (Ebay). The Superlux turn out to be better by far, of course. They are often tested against AKG and Beyerdynamic models as well.
Packaging and box
sponge inside to protect the king of headphones. However it is simple, beautiful and it works very good, so why spending more money in a better box?
The system used by Superlux to hold the whole thing to your head looks strange but works. For someone it may be uncomfortable because of the pressure in your head (the manual says it is 3.5 newtons. Yes, it does). Anyway it is right so, otherwise, later on, it would be too weak.
The pads is by far the most popular trouble with these headphones. People say they are very bad quality, they produce too much heat and your ears sweat. Well, now it's summer and I haven't had any problem with them. I have to say that I've tried much much worse pads than these ones. Anyway, all the headphones are a bit hot.
If you can't deal with the default pads you can get a replacement. Most of people buy original AKG pads for the K240 which fit perfectly in the Superlux, but they are expensive. You can find these things in Ebay too, starting from a price of $9.
HOWEVER, it is known that the sound is modified by doing that. The new pads, which are not the same plastic don't get a seal between your head and the speaker so well as the original ones do. As a result the sound can escape and bass become lower.
Well, there is one thing that bothers me, but I have to accept it. The Superlux HD 668B are semi-opened headphones, which means that part of the sound can escape and part of the noise can come in. So, to my mind, the worst thing of these headphones is the isolation (any other semi-opened or opened headphones suffer from the same). It can become a problem if you like listening to music while travelling, like me.
If you don't buy one of these you are an idiot.