There aren't too many headphones out there that offer both noise cancelling and built-in Bluetooth. Out of those select few, fewer again are actually worth your time and effort and attention. Sennheiser's HD 4.50 do a very good job of being wireless, and a very good job of noise cancelling -- with only a few small trade-offs.
What Is It?
Sennheiser's HD 4.50 BTNC headphones sit at the top of its Bluetooth headphone range, but interestingly don't sit under the 'noise cancelling' umbrella category on Sennheiser's website. That should give you some indication as to how Sennheiser sees the HD 4.50 -- as a wireless headset with noise cancelling, rather than a noise cancelling headset with wireless. If you like your music to be the highest quality possible, this is a good thing: noise cancelling headphones generally make some serious compromises in audio quality to achieve maximum silence.
The $329.95 Sennheiser HD 4.50 use a closed-back, over-the-ear design, so will block out a fair amount of external noise purely by virtue of their design. Soft leatherette-wrapped memory foam earpads conform to the wearer's head for an even closer seal. And then, on top of that, Sennheiser's active noise cancellation uses a microphone on each earcup to detect external noise and internal circuitry to create an inverse sine wave from the headset's speaker drivers to cancel it out. The internal, microUSB-rechargeable battery lasts for 19 hours with noise cancelling enabled and 25 with it turned off, all the while with music playing at a moderate volume.
The HD 4.50's plain-Jane design is reminiscent of Sony's $699.95 MDR-1000X, but at a much reduced price. You don't get a fancy hard-shell carry case with the HD 4.50 as you do with competitors like the Bose QuietComfort 35, but it's still serviceable enough. You get a two-prong travel adaptor for your airplane in-set IFE, a microUSB cable and a bundled 3.5mm adapter cable -- with a nifty screw-in connector that'll keep it locked into the headphones themselves. There's no companion app like you'll get with the Bose headphones, though.
What's It Good At?
Despite being noise cancelling, and despite being Bluetooth, Sennheiser's HD 4.50 BTNC headphones actually sound really good. Bluetooth hooks up first try, just as you'd like it to -- and if it doesn't, it's a problem -- and there's no huge lag in between pressing play and hearing your music, generally an indication of a poor connection or too much audio processing going on behind the scenes. There's only a very faint baseline hiss from Sennheiser's NoiseGard active noise cancellation, too, so you're not trading away the hum of an office air conditioner for the scratchy hiss of a record player like some noise-cancelling cans do.
If you want a pair of headphones with powerful bass, the HD 4.50 has you covered -- if there was a signature to these headphones' sound, I'd say that would be it: the presence of deep and thumping and tight low frequencies. That's not to say that mid-range notes are drowned out or lacking detail, because they are too; it's only at the absolute top of the generally crisp and clear treble frequencies that the HD 4.50 is missing a little of that X-factor that makes some competing Bluetooth -- but not noise cancelling, notably -- cans great. All noise cancelling headphones sound closed-in and very inside your ears, but the HD 4.50 is less so than most.
Battery life is excellent for a pair of wireless and noise cancelling cans -- I hit close to the 19 hour claim that Sennheiser makes on a full battery charge, which is long enough for any flight around the world with time to spare for boarding and waiting at the airport. The earcup-mounted controls for the HD 4.50 are intuitive, too. Volume and a multi-function skip/play/pause jog switch are arranged on the silver ring around the matte black earcup itself, alongside the power/noise cancelling/Bluetooth toggle, and all three are easy to find and operate with your thumb while you're wearing the headphones and listening to music -- important when an unexpected call comes in, for example.
What's It Not Good At?
The HD 4.50 sounds good and seals very well against outside noise, but the trade-off that you necessarily have to make here is that these headphones can get a little bit uncomfortable after extended wear. The headband is quite tight-fitting, and your ears will get quite warm due to the tight seal. If you're the kind of wearer that isn't going to have them on for extended periods of time, you'll be completely fine, but don't expect to wear them happily for an entire 12-hour flight.
The accessories bundled with the HD 4.50 and the all-plastic design of the headphones themselves leaves a little bit to desired: while it's still fine, the QuietComfort 35's carry case and overall construction is significantly superior. If you plan on keeping these headphones for a long time -- like, until they fall to bits -- you might find Bose's option worth that extra $70 upfront. And, of course, the design is up to your personal taste, but I like the Bose a little more.
Sennheiser's noise cancellation in the HD 4.50 is on the lighter side, which is a good thing for the quality of the headphones' sound reproduction, but at the same time if you're searching for that silent, hiss- and hum-free silent bliss of ultra-powerful noise cancelling, look to Bose or even Sennheiser's gutsier -- but twice as expensive -- PXC 550, which have longer battery life and more powerful cancellation of outside noise. But, unless you're flying a lot, the HD 4.50 is, in my opinion, a better compromise for the everyday commuter.
Should You Buy It?
Sennheiser's $329.95 HD 4.50 BTNC Bluetooth noise cancelling headphones definitely sit on the cheaper side of the spectrum when it comes to that one-two punch of wireless and ambient noise reduction. That makes them attractive in the first place. But then you add their pretty good sound quality -- better than competitors with stronger noise cancelling -- on top of that, and the proposition becomes even more attractive. Unless you need that super-strong noise cancelling, or if you plan to wear your headphones for several hours at a time, you'll be happy with the HD 4.50.