Sennheiser's PXC 450 noise-cancelling headphones claim to offer outstanding sound quality and optimum protection against ambient noise. At AU$799, they're aimed at a high-end consumer who's after terrific sound accuracy primarily when on the move, such as a business traveller — and those who are comfortable wearing enormous 'phones in public. They're built to compete with the popular Bose QuietComfort range.

Design
These are certainly among the most comfortable headphones we've seen in months. The luxury earcups are very comfortable to wear during long listening sessions and certainly feel less clammy than others of similar design. A little experimentation is required to get the best seal between the cups and your head, but your listening experience will be better as a result.

The single AAA battery resides inside the right-hand cup, and Sennheiser has done an excellent job of positioning the headphones' volume and noise-cancelling control buttons in an accessible place.

With the traveller in mind, the PXC 450s are foldable in two ingenious ways, the easiest of which makes it possible to flat-pack the headphones into the supplied hard case, which is about the size of three DVD cases.

Overall build quality is excellent. The attention to detail is also admirable, such as a small amount of rubber padding between the earcups and the brackets they're attached to. The well-padded headband has a spine of tough aluminium, meaning it's incredibly comfortable but resilient to accidental damage.

Features
The PXC 450s' useful TalkThrough feature can be activated with the touch of a button on the right-hand earcup. Automatically, music volume is lowered and voices around you are channelled into the headphones, allowing you to talk comfortably without removing them.

Should the battery powering the noise-cancellation expire, the bypass switch can be flicked, converting the headphones into a standard mode. This is handy, but we'd prefer this to be done automatically rather than having to flick a switch, especially as it's located in a difficult-to-get-at position behind the left earcup.

Performance
Sound quality from the PXC 450s is impeccable. Neither bass nor treble is favoured too heavily, and both are beautifully clear, well defined and far from any distortion. The Dire Straits classic Brothers In Arms sounded incredible. The deeply recorded bass was clear and noticeably separate from the low vocals. The high-pitched hi-hat and cymbals were crystalline in their crispness and Mark Knopfler's guitar solos flowed beautifully.

To really push the headphones' breaking point, we lined up a powerful song from American thrash metallers Unearth. The distorted twin guitars were accurately defined, vocals were powerful and drums were clear. The PXC 450s demonstrated their ability at accurately reproducing a range of genres, although dance fans may demand more bass. Due to their closed-back design, the PXC 450s are almost inaudible to anyone but the listener, even at high volume.

Audio quality aside, the noise cancelling is superb. Our office became all but silent and our oft-frustrating air conditioner was vanquished entirely. On a train journey, deep ambient noise is effectively neutralised.

Conclusion
Given the high cost, those planning to buy headphones for home use would be better off with a open-backed design for a more detailed and natural sound. But travellers will see the PXC 450s as superb high-end headphones. Exceptional audio quality, combined with effective noise-cancellation and a pocketable design make them perfect for the frequent flyer — although given the price, they're more likely to be found in business class.