That's really good price, I got mine for more or less that on ebay one time and love them for piano use.
I would sum them up as follows personally, FWIW, for anyone thinking whether they may like to buy them blind without trying and wonder what they sound like.The good:
Very comfortable, light on the head, there is none of the getting warm under the pads very quickly, for me anyway
Very flat response, in that sense they surpass the more costly HD 650 and are more on level of the HD600.
Easy to drive, no concerns for whatever piano whatever you plug them into, it will drive them just fine.
Very spacious sound and good projection and sense of mental imaging, as is the advantage of open back designs, you really get a sense where sounds are coming from.
on the whole the sound signature is very laid back and relaxing, trebles are not in any way piercing for those that tend to get ear fatique easily, these are perfect I would say for that, because of that you can actually turn them up without getting that feeling you ears are being hammered, for pianos and large dynamics range sounds this makes them very comfortable on the ears for long term use I find.
For me I find it a great combo for pianoteq, it take the somewhat metallic harshness out of it an make it sound a bit more natural overall.The perhaps not so good:
Due to the laid back sound signature, and the recessed upper range they do not come across as terribly detailed sounding or forwards. I'd actually put these more in the circle of nice to listen to headphones, not reference headphones, even though they are very flat in response.
If you want to pick up every nuance or pick out a bad recordings and do mixing. I'd use something else, they are actually rather flattering to the sound and smooth I think, not in any way harsh. To my ears that is just right, it sounds very natural to like how sounds come across in the open air in nature, but nothing is overstated with these headphones, but at the same time everything is there just enough.
Related to this I would say some may find this sound a bit recessed and boring, not exciting enough for some. As someone once put once it remember well, and IMHO, he hit the nail on the head:
When you listen to classical music like an orchestra, it is like sitting in the audience as a spectator, there is this slightly distant quality to the sound stage. If you want to experience what it sounds like to sit on the stage amongst other instruments, then look at something like grado territory, AKG etc then that would be more for you. I agree totally with this.
bass extension is good enough for me, enough for piano for sure, but there is better in the same price range, you'll not get the very deepest of bass. It is quite common for many headphones to have a bit of a lift around 100 HZ and below by about 2 to 3 dB. Many closed backs do too, and if you are used to that type of bass, you may find them a bit lacking at first, but can easily get used to it when you listen to them a while.
Stereo imaging is not the most accurate, it sounds really good an spacious and natural due to wide soundstage, but must not be confused with stereo width and space. There is actually a little bit of mistiming an phase issues due coordination issues between left and right. Once you have heard a phone with more accurate timing you would hear that difference straight away, but if you never heard anything different you'd never know. To me it just doesn't sound the most accurate in that regard compared others I used on and off.
Some frequencies and areas for vocals in particular,there are some problems areas with distortions too. Also, not the fastest drivers. If you like rapid beats and bass stuff, again these may be a little lacking for that, still very respectable though for that type of use.
Overall these are not the tidiest cleanest sounding headphones in this price range if you were to buy them at stock price in terms of sound perfection, if there is such a thing, but overall they just sound lovely ... to me, a sound signature you can cuddle to with some warmth like a Xmas evening by the open fire
In this case it is true however that the more you pay in this range the HD600 and HD650 are better in that regard ( but note, amps often needed for the latter too ) still my can of choice is the hd598, I had the other two briefly and they have come and gone because of the convenience factor. Also the HD 598 surpasses both of these more expensive brethren in terms of soundstage IMO.
For the elderly and if you are ears are beginning to struggle a bit, again you may find them sounding somewhat recessed and looking for that bit of a mids to treble boost, then look elsewhere perhaps.
They let in external sound as do all open backs, if you want isolation from external sounds, this is not for you.
cable is a bit thin and flimsy, for example if you tap it you can hear it through the phones. If you walk around a bit and the cable is moving and touching things you can hear those knocks transmitted through the phones. To me that is no issue, I don't do that.
Hope that helps