This set of cans is Sony's bid to make its noise-cancelling technology affordable. They're pretty chunky, and they're right in the middle of our price range, with our other two pairs of headphones coming in either side. If you happen to be in the States, you can pick these up for under $50, making them something of a bargain.
The headphones are powered by a single AAA battery, the holder for which is integrated into the headband.
In terms of pure technical specifications, the headphones should be quite good, with a decent response bandwidth encompassing the middle-to-low end and a good top end. The impedence is also the lowest of any of the sets here.
Feel and fit: The NC6s are interesting because they're sort of comfortable, and sort of not. The first problem is that the headband has no cushioning, and is really quite flat and inflexible, meaning that it presses down fairly firmly on the top of your head. It's snug, but not particularly pleasant.
The second issue is that the earphones themselves are very flat with just a thin covering of foam - there's no cushioning whatsoever. They feel very flat and hard, and after a couple of hours of continuous use, they can hurt your ears pretty substantially. The lack of cushioning is also an issue if you happen to wear glasses, since they'll push the frames into the side of your head after a while.
On the other hand, neither of these problems are so large that you can't put up with them, and at least one other person in the office had absolutely no problems wearing these for a prolonged period.
The actual earphones rotate in one direction horizontally and both directions vertically, allowing them to fit to the exact shape of the side of your head very well. However, the rotation doesn't help when you're trying to pack these up to take on the road.
Noise cancelling: We found that the NC6s had the best noise cancelling of any of the units on test. Switching the cancelling on via the switch on the right headphone, we were knocked back by how well the ambient noise of the office and the air conditioning was blocked out.
We found that this pair was the best at blocking out voices, doing more than any other set to silence Tim's dulcet tones! This will no doubt be of interest to you if you are looking at these for a crowded office environment.
However, the cancelling did produce a fairly substantial hiss. It was not as bad as the Acoustic Authority set, but it was noticeable. In general, the hiss disappeared into the background once music started playing, but there were a couple of tracks where we found that the hiss interfered with our enjoyment of the music, as you'll see when you read on.