Sennheiser's MM 450-X is a headphone pair which retails at £300 and seemingly does it all. It's wired, it streams wireless Bluetooth audio, and has active noise cancellation circuitry. From an audio standpoint, the MM 450-X offers excellent performance whether it’s wired or in Bluetooth mode.
Unfortunately, the NoiseGard active cancellation feature is a bit less effective, bringing some audible hiss into the equation and, on some tracks with deep bass, adding in distortion at top volumes. If noise cancellation is your top priority, there are better options out there, but if you're primarily interested in Bluetooth and the noise cancellation is merely a convenient extra feature, the MM 450-X is worth your attention.
The MM 450-X has a lightweight, supra-aural (on-ear) design. The black plastic earcups swivel at joints just above the ear for a more precise fit, and the pads and headband are thoroughly cushioned. A metallic band with the Sennheiser logo etched on it runs through the middle of the black plastic headband. The fit is comfortable at first, but can feel like it's putting a bit too much pressure on the top of your head during longer listening sessions. The larger Sennheiser MM 550-X costs £50 more, but features larger earcups, earpads, and drivers, and also adds a switchable SRS WOW HD effect.
All of the MM 450-X's controls for wireless playback, track navigation, power, and volume are located on the outside panel of the right ear – memorising which button controls what function is fairly easy. (Your mobile device's volume controls work independently of the volume controls on the headphones).
The Bluetooth button (under-lit in blue) and the NoiseGard button (under-lit in red) are both located on the lower edge of the right ear, along with the jack for the audio cable (for wired listening). A USB connection for charging is located on the left ear, protected by a rubberised cover.
The MM 450-X folds down flat for easy stowing. A black zip-up carrying pouch is included to house the bevy of accessories the headphones ship with. A power adapter (with four slide-on wall socket plugs for various types of outlets) is included, but the USB cable can detach from it if you want to charge your headphones via your computer's USB port. An airline headphone jack adapter and a 0.25in headphone jack adapter are also included, as is an audio cable for wired playback – it terminates in a 3.5mm connection. A CD-based manual is also included.
Pairing the MM 450-X with a Bluetooth device is a simple and quick process, assuming the process is also straightforward on your streaming device – it took fewer than 10 seconds to connect to an iPhone 4S.
There's a built-in microphone for making mobile phone calls – audio quality is about as solid as it can get with cellular fidelity. The Bluetooth button can control more than just the pairing process, by the way – holding it down made it auto-dial the last person I called, and pressing it once when the headphones were already paired summoned Siri.
On deep bass tracks at top volumes when streaming wirelessly, the MM 450-X offers powerful audio for its size, and there's no distortion – until you enable the noise cancellation. At top volumes, the NoiseGard noise cancellation begins to distort on tracks with deep bass. At more reasonable volume levels, this isn't an issue, but it's still a bit surprising from a £300 pair. So, with no noise cancellation, we have a solid performance from the Bluetooth streaming MM 450-X, but with NoiseGard on, things can deteriorate a bit on more challenging tracks at high volumes.
You can also listen to the MM 450-X through the included audio cable. At top volumes, with no noise cancellation on, there is no distortion on deep bass tracks. Connecting the cable automatically disables Bluetooth, but you can still use the NoiseGard functionality – and yes, it still distorts at top volumes whether you're using a cable or not.
Getting back to the audio performance when streaming, the sound signature is typical Sennheiser – rich bass, but not overly boosted, paired with articulate, crisp high-mids. On Bill Callahan's "Drover", his vocals are lent a smooth, crisp treble edge that helps them stand front and centre in the mix. The constant drumming pattern receives a nice bit of low-end boost, but not too much. The result is a bright sounding track that gives priority to vocals and guitar strumming, but bass lovers might wish there was a little more oomph in the lower frequencies. Since the earpads are pretty small they can sit slightly off-centre. Adjusting them might bring a bit more bass response to the mix, but this is not a booming, deep low-end pair.
On Jay-Z and Kanye West's "No Church in the Wild", the kick drum loop has a nice crisp punch, again thanks to the MM 450-X's crisp high-mids. The sub-bass synth hits that punctuate the loop sound a bit less powerful than deep bass fans may wish, but it's the lows and low-mids that get most of the attention, not the sub-bass frequencies. Thus, an electric bass is likely to have a bit more presence than a super-low synth part.
On classical tracks like John Adams' "The Chairman Dances", the higher register strings, brass, and percussion stand out most in the mix, with the reserved bass response of the MM 450-X subtly gracing the lower register strings with a smidge of boost. However, compared with a booming bass headphone pair, the MM 450-X sounds almost like it has a flat response in comparison. The large drum hits at the end receive a nice amount of low-end presence, lending them a little extra power, but this is simply not a powerful, bass-heavy pair.
It's also worth noting that on quieter tracks, like this classical piece, the headphones don't get terribly loud, which isn't an issue if you're in an office or at home, but could be a bit problematic in a noisier environment like the subway or an airplane.
The overall audio performance of the MM 450-X is solid – a bit on the bright side, but with rich, if not overwhelming, bass response. The issues it has with distortion at high volumes when the NoiseGard is activated make its price seem a bit too high. It must be said that not many headphones offer both wireless audio and noise cancellation, however.
Generally speaking, the MM 450-X is a fantastic Bluetooth headphone pair and a decent, but not amazing, noise-cancelling pair. The inclusion of a cable for wired listening makes the headphones even more versatile, but it's hard to overlook the distortion. It shouldn't be viewed as a deal-breaker, as it won't occur with every genre of music, nor at regular listening levels, but it lessens the MM 450-X's value.
There are, quite simply, better options. If noise cancellation is your main priority, we love the great sounding, effective AKG K 490 NC, and the Bose QuietComfort 15 is an industry standard. As far as wireless headphones go, if that is all you need, you can save quite a bit – the Sennheiser MM 100 is a great sounding, relatively inexpensive option. If you really want both features and have a bit more money to spend, the Sennheiser MM 550-X is a more solid all-round product.
Manufacturer and Model
Sennheiser MM 450-X
Active Noise Cancellation