Ultrasone 'the German headphone company' are well established in the premium headphone market. Today we're taking a look at one of their more affordable entries, the Ultrasone Pro 550 S-Logic natural surround sound over-ear headphones.

Ultrasone really deliver a full package straight out of the box. Included is a superb quality carry case bag. The case is specifically moulded to fit the Pro 550 headphones and additional storage for cables, adapters and literature is here too. The case features a handle and the shape is rather compact too, but doesn't skimp on protection.

The build of these headphones is nothing short of impressive, the entire construction is fanatically rugged. The guts are made from a very hard and dense metal reinforced grey plastic, the same plastic is used on the headband adjustment mechanism too. Two supplied 'screw in' cables are found in the box, one a regular 1/8" auxiliary cable and another ultra long 1/4" cable ideal for amp-like usage. Because they are screw in and of a high plastic outer quality, long jeopardy should be provided. But the length of the 1/8" is severely too short, an adapter should have been included so the 1/4" could be used as a 1/4" auxiliary jack. Each ear cup has an engraved in aluminium Ultrasone logo, giving them a very serious look. Admittedly though they're a more traditional design and are not as stylish as many other headphones on the market today.

They can quickly and easily be folded up to pop within a bag. The mechanism is tight and smooth, very different from other headphones that share a similar style of design. These feel as if they could take quite a beating.

Something we felt that was severely lacking with these is any kind of music control. No remote attached to the cable or on-headphone touch/ buttons controls are provided either. This does unarguably hinder the musical playback experience. Having to skip tracks, adjust volume, so on and so fourth via the device playing the audio is inconvenient when being on the move. It goes without saying that no microphone is bundled into these headphones either. Ultrasone appear to solely be focusing all attention on the audio performance and in today's headphone market this is of course still mandatory but the importance of a remote should definitely not be overlooked.

Comfort is a field where the Pro 550's excel. The thick airy padding coupled with the ability to finely adjust the angle of the cups and length they extrude to, makes for a lush fit. The leatherette ear pads (another spare set is included within the box too) cushion and glide on and off the head, they isolate exterior loud sounds well and also deter severe noise pollution. They allow for a roomy fit but the cups are firmly on the large size and those with smaller heads may find them just too large to wear. We found the large size frankly unnoticeable, however the ear pads could become irritable against the head with prolonged usage.

Ok, now moving onto the real centrepiece, the audio performance. As a mild disclaimer, these headphones are supposed to have a 'break in period'. We initially removed them from the box and immediately plugged them into an iPhone 5. For the sake of our review we left them idle playing shuffled music for 40 hours straight. We can't really say whether or not this is necessary but we felt we should allow them to break in if they needed to.

To sum up the audio performance, it's spectacular. The specifications of these are as follows: A frequency range of 10-22,000 Hz, an independence of 64 Ohm, a sound pressure of 102 dB and massive 50mm Mylar drivers are enclosed by an MU metal buffer-board. All this delivers a big and definite, but not over pressured bass. Audio is sustainably neutral, nothing is over emphasised. The mid frequencies are linear and the highs have a bit of airy crispness about them which we all rather enjoyed. Volume can get loud but doesn't become unbearable when fully cranked. Something worth noting is when the volume is low at around 20% of the possible output, the definition isn't lost.

The Ultrasone Pro 550 Headphones do an excellent job of dissecting musical tracks. Vocals and all instruments even up to different parts of a drum kit can distinctly be independently heard. The S-Logic natural surround sound is striking when listening to music but is outstanding when watching movies. Vocals have a genuine distance and sound travels around the head instead of into it, in a convincing manner. The sound stage is one of the 550 headphones killer features. Of course this must in addition prop up the stereo performance which is also very good.

To really chug out the maximum degree of performance these will have to be used in conjunction with an amp. However the performance presented from an iPhone, iPod, Mac, PC and so on using the 1/8th audio cable is still nothing short of brilliant. And not much of a quality gap lays between using an amp or not. We used these headphones primarily with the iPhone 5 and loved what we heard.

Overall the Ultrasone Pro 550 Headphones have an appealing and pleasurable clear and smooth sound signature. For $139 and £141 on Amazon, they are unbelievably good value.