Background

Build/Fit

Sound

In conclusion

Let me get out of the way up-front: Ion-ear headphones. They're invariably a compromise - sacrificing either comfort, performance, or both(!) to achieve portability. I've tried, and wanted to enjoy many. I've had extensive testing time with the Audeze from Sine, for example. There was so much to love about them: the build, oh, the build; the practicality; andplanar speed and low-end in a package that can be used everyday. But god-dammit, I just can't get a good seal on these. Now I'm primarily an open-backed guy, but when I use closed-cans I want two things: some decent isolation (for both myself and the people around me), and comfort. Hence the reason why I own (and love) a pair of Beyerdynamic DT770 870ohm, which I'll compare these to mostly, for obvious reasons.For transit/OTG, I use IEMS. I have a pair of Zero Audio's Carbo Tenores, which I use every day. I've never wanted to spend good money on portable on/over ears, as I've never found anything worth spending money on, and if I did, they invariably had one/two fatal flaws that I couldn't get past. So when my next-door neighbour at my office was looking to buy some new portable cans, I went with him to my local personal audio store to help him compare a few different cans:1. Audeze Sine2. Oppo PM-33. Meze 99 Classics4. Beyerdynamic T51pSpoiler-alert: (if you haven't guessed it from the title of this review) - he chose the Beyers. Audeze - bad seal. Oppo - supremely comfortable, but less portable and didn't had a huge advantage in perceived sound quality. Meze 99 Classics (which I also own): killer sound; but too bulky to be truly portable. So he bought the T51p's, and he's kindly let me spend a day or two with them to give them a road-test (in exchange for their DT770 stable-mates, of course).Came in the usual mid-range Beyer cardboard box, but inside an awesome padded transit case - nice. The cans themselves are made of a nice high-quality brushed aluminium with soft-touch black-plastic around the drivers, and faux-leather memory foam pads/padding. Being someone else's brand-new cans I'm not even going to see if they're removable! The (non-removable!) cable is an appropriate length for portable cans, but feels a little cheap and toy-like for a $300+ (AU) pair of headphones, portable or no. It's terminated in a 90-degree 3.5mm jack that feels sturdy enough to inspire confidence for throwing what ever you plug it into into pockets, bags and the like. Overall a nice presentation, but more on the utilitarian side than out-and-out premium/luxury.Being smallish, they're obviously light-weight and barely noticeable in terms of heft when carried/stowed. Onto the make-or-break test - Putting them on, they're...well, comfy! Very comfy. Enough clamping force to stay on and roll your head around, and the padding under the skeletonised headband does what it's supposed to. And the earpads fit nicely on my (admittedly) small ears! The material is plush, creates VERY decent passive isolation. Having given it a 2+ hour wearing test, I'm pleased to say I didn't get any hot-spots or sore points like I get with every other on-ear. Overall - supremely comfortable. Big tick.So onto the business-end of the review - how does it sound? In a word - excellent. For the review, I used solely lossless (FLAC/ALAC) files from both a Samsung Galaxy S7 using USB Audio Player Pro, and a Macbook 15-inch Pro (yes the one with actual holes for connecting things like cards, cords, and USBs...but that's another story). Digital > Analogue conversion and amplification was handled off-board, in this case by an Audioquest Dragonfly Black.Test albums:- Radiohead, A Moon Shaped Pool- Smashing Pumpkins, Siamese Dream- Daft Punk, Random Access Memories- Elvis Costello & The Attractions, This Year's Model- Tool, Undertow- Hiatus Kaiyote, Choose Your WeaponI literally A/B'd these at first with the DT770's, which immediately felt strange - I didn't like themfor the first track or two. Things sounded congested, lacking in impact and separation. Ok, some mental burn-in is obviously required, like with any new equipment. It became clear this was more a symptom of the difference in format between the two Beyers. The DT770's literally surround your ears with big, boomy housings which give more of a 'cavernous' type sound/feel. Owners of these will remark, rightly, that they have decent sound-stage for closed cans. The (relatively) tiny earpads of the T51's feel...small. The sound is more focusedyour ears, but after a short while you start to hear things - headstage; left/right separation; and imaging.Then, you realise that these have good detail. Like, really good. The busy cacophony of "Burn the Witch" on Radiohead's latest album is handled with aplomb, managing the transients and attack very deftly indeed. Not sure if this is an inherent feature of Tesla-drivers, but I like it.The overall colouration is ever so slightly dark, or warm, depending on how you like to describe it. It's absolutely non-fatiguing and inherently musical. It's what I'd describe as an enjoyable/'fun' voicing, that made me simply listen to albums start-to-finish. Which is a Good Thing.is remarkable and present, with surprising extension. Daft Punk's "Lose Yourself to Dance" has appropriate levels of "WHUMP", but not quite as deep or tight as the DT770s - which truly are bass-Kings as many rightly say.are thick, detailed, but I'd have to say a little veiled to be honest. The aggressive guitar "crunch" in "Hummer" by Smashing Pumpkins isn't as forward or exciting as I'd like it to be, and I like it that way - owning two pairs of Grados, and being a guitarist I guess you could say I'm a bit of a Mid-junky.are sweet, detailed, but not overly intimate or transparent. Elvis Costello singing "Little Triggers", and "Fingerprints" by Hiatus Kaiyote (if you haven't heard them, do yourselves a favour) are enjoyable but don't have that "live"/immediate feel like they do in more transparent headphones.is every so slightly veiled to my ears, moving back to the DT770's, the treble's noticeably "hotter". Listening the awesome drum-work of Danny Carey on Tool's "Ticks and Leeches", there's not quite as much sizzle in the high-hats, and equates to the T51's having a a little less drama, or "WOW" for me. But we're only talking degrees here for the sake of comparison.These were a genuine surprise for me - I'd always balked at considering the T51p's because of a) the face that they're on-ear, and b) the price, or more accurately their price considering the fact that they're on-ear, and it looks like you're getting so much less headphone for the price compared to, say, the DT770s.The best thing I can so about them is that they truly aren't a compromise. They are, to my ears, a genuine audiophile experience, and one you can take with you/experience on-the-go. Hard for me to comment on the value-equation, as I'd rather spend that amount on a new pair of full-sized cans, but think that price/performance-wise they represent very good value compared to some of the company they're in, and that I tested them against.Oh, and my work-mate loves them. Then again, he did come from a pair of Boses...fair to say he's now caught the bug.Cheers, and thanks for reading.Mightygrey.