This is a Review of Beyerdynamic T51i premium portable on-ear headphones with in-line remote/mic. T51i is the same in design and sound as their T51p model (beyerdynamic T 51 p: Portable Tesla Hi-Fi headphones, closed) with an additional of in-line remote/mic. Though at the moment of writing this review iT51i wasn't listed yet on Beyerdynamic webpage or Amazon, it should be available very soon. If you don't care about in-line remote/mic, T51p is an identical model for your consideration. As you have noticed from my previous write-ups, I review more in-ear than full size headphones. Though I enjoy a comfort of big over-ear headphones, those are not always practical on the go with your portable audio setup of either smartphone or DAP. As a compromise, using on-ear headphones (sitting on top of your ears, rather than around 'over' them) makes it more portable, but at an expense of worse sound isolation, poor fitment, and reduction in sound quality. Sounds like a challenge? Not for Beyerdynamic and their team of German engineers! Introduced originally under T50p, which derived from their flagship DT1350, T51p was an updated version followed by soon to be released T51i. Here is what I found. On-ear or over-ear, these a still considered to be full size headphones with two earcups connected by a headband, so it was a pleasant surprise to see a slim compact box T51i arrived in. It also included a lot of detailed info and specifications to give you an idea about the product even before you take it out of the box. Inside of the box, there was a slim nylon protective case where T51i was stored flat thanks to it's swivel earcups. Out of the case, I found these headphones to be very lightweight at only 174g despite predominantly metal design. The brushed metal design, everything from the headband to adjustment pieces, y-fork, and back and edges of earcups, was definitely a sign of high quality with a modern retro look. With each earcup having individual cable connection, unfortunately non-removable, the headband design was very minimalistic including two split metal bands with slim memory foam strips on the inside. The headband adjustment had a nice click mechanism and the attached y-fork connected to earcup had a full 180-degree fluid rotation. In addition to rotation adjustment, earcups also have a decent angle of tilt to meet demanding needs for any shape of the head. The round soft memory earpads were just an icing on the cake and I found the fitment to be among some of the best I have tested with all on-/over-ear headphones I reviewed in the past. I know its a bold statement to make, but between a perfect clamping force and the comfort of how these earcups adjust to my ears - I was able to find a sweet spot instantaneously and as a bonus was rewarded with a fantastic passive noise isolation on a level of some of the over-ear headphones. Following a short strain relief on each earcup, the right side of the cable (cables are thin rubberized, yet durable) had a built in-line remote/mic surrounded by the same metal material as the rest of the design. I do have to note that all 3 buttons were cramped together, multi-function button in the middle with volume up/down around it, but the recessed opening of the remote actually guided in placement of your thumb right in the middle to hit the center button. Although volume up/down were designated for Apple devices, the multifunction button worked flawlessly with single click for Play/Pause/Call, double/triple click for Skip next/prev, and long press for Google NOW. Call quality was decent, and thanks to a close proximity of remote/mic to your face, it picked up voice crystal clear. Following the cable after remote, the y-splitter had a small rounded design with strain relief on all 3 ends, and the cable was terminated with gold plated right angle 3.5mm connector. As part of the accessory package, included were 1/4" jack adapter, airline flight adapter, and as I mentioned before - a premium nylon flat case with a few storage pockets and form fitting foam partitioning to secure headphones and cable inside. As impressive as it looks, the next step was to examine it's sound quality to see what these TESLA drivers can deliver. Advertised with having a strong magnet, these dynamic drivers supposed to have highest efficiency and minimal distortion. I did start with about 8 hours of burn in to make sure these T51 would "warm up" for the job! I found the sound quality to be top notch with a warm sound extended down to a textured sub-bass level and fast punch of mid-bass to detailed rich mids and extended clear highs. Without getting into a typical deeply v-shaped sound, Beyerdynamic engineers were able to bring out a perfect balance of a powerful and clear bass without making it too bloated. Looking at some of the frequency response data measured on T51p, you can clearly see a mid-bass hump around 100Hz which is going to satisfy anybody's low-end craving, even for those who consider themselves bassheads (though I would not categorize these headphones of having a basshead sound signature). And if other-than-neutral bass is not your cup of tea, this can always be tamed by an EQ adjustment. The mids sound warm and intimate, especially when it comes to vocals though their presentation felt a little bit pushed back, probably due to extra bass quantity. Highs were extended enough to provide clear details, but not too bright and were easy on your ears for extended listening. Soundstage/imaging is probably average, which I consider to be pretty good for closed design. Also, there was absolutely no microphonics effect coming from the cables. My sound testing was done driving T51i directly from X5 and Note 2 which wasn't a problem thanks to their 32ohm mobile-friendly impedance. I also used Beyerdynamic A200p usb DAC/amp in my testing. I know it's probably sounds cliche, but I honestly think that pair up took T51i sound to the next level. It opened up details and made sound more dynamic, including a tighter bass and adding more clarity and sparkle to upper mids and treble. Whats great about A200p is that if you are using T51p without in-line remote, that little usb DAC actually adds a transport control to play/pause and skip tracks. Obviously, with T51i while connected through A200p you will not be able to use headphone's in-line remote/mic. Another thing I wanted to mention, I couldn't help but to be curios how T51i will compare to my recently reviewed pair of on-ear V-Moda XS. Though XS has an advantage of a removable cable and super compact cliqfold storage, in terms of the wear comfort, sound isolation, and sound quality - I found T51i to be superior. As a matter of fact, I took it even one step further comparing to M-100 (and it's popular bass response), and found T51i to dominate in that comparison with a similar bass quantity and a higher quality. Overall, this was another very pleasant surprise where I didn't expect performance of on-ear headphones to reach such a high level! For my taste these headphones are almost perfect, with an exception of non-removable cable and slightly recessed mids where the vocals sounded a bit withdrawn to my taste. But this sound signature is easily fixable with EQ, and considering fantastic "made in Germany" design, rich full body sound, super comfortable fitment, and the bass to make everybody happy - these deserve a very serious consideration for anybody in a market for on-ear or over-ear headphones. Here are the pictures.