It would be easy to dismiss the Denon AH-NC800 noise-cancelling headphones out of hand. At £250, they are £30 more expensive than the excellent AH-D2000 headphones, and it's hard to imagine that the AH-NC800s could be £30 better, as active noise-cancelling headphones rarely exceed the capabilities of their passive brethren. However, descended as they are from the AH-NC732 noise-cancelling headphones, which left us far from unimpressed, we'd be remiss not to at least give the AH-NC800s a chance to prove their worth.
With noise-cancelling headphones generally being used out and about, it's unsurprising that the AH-NC800s are pretty solidly built, if a little utilitarian feeling as a result. The thin, flimsy cable is the likeliest break-point, so it's nice to see that Denon has made this replaceable, as it connects to a 3.5mm jack socket on the left earcup. We wouldn't expect the AH-NC800s to break in what you could consider normal use, but they won't take a beating, and the only less-than-solid parts are the articulated joints which make the AH-NC800s foldable, and thus particularly portable, so it's a fair trade-off.
Fortunately for those worried about the structural integrity of the AH-NC800s, Denon supplies a semi-rigid case with them, so there's no reason to worry about placing these headphones in a bag. This case is also home to the AH-NC800's accessories, which comprise two cables of different lengths and an aeroplane adaptor. We'd have liked a volume attenuator as well, having been nearly deafened by inconsistent volume by more that one airline, but it's not the worst omission Denon could have made.
One addition we're slightly curious about is the three-position power switch on the right earcup. Off and On we had no problem with, but the Restorer option left us a little confused. Denon says that this: "improves the fidelity from your portable audio player," but leaves it to the user to figure out quite how. We have our theories, but aren’t sure because, at least with the music we use to test (ranging from The Beta Band to Wagner), we couldn't discern any improvement from using this Restorer setting.
We chalk that up to two things: first, that we always use as high bit-rate encodes as we possibly can so any supposed enhancements have little room for improvement and, second, that the AH-NC800s sound good enough so adding an 'audio restorer' into the mix is completely unnecessary. The one caveat to that is the need to have the AH-NC800s turned on for them to sound any good - un-powered they need a lot of volume from the player to get any volume from the earpiece. However, this is hardly a criticism - anyone who buys active noise-cancelling headphones and is then surprised at needing to power them clearly has a screw or two loose.