I'm not an audiophile, but i have taken a small step in that direction with the purchase of an external AMP/DAC combo and the $350 HIFIMAN Sundara headphones. If it's a detailed review from a true audiophile you're wanting, i'd suggest listening to both the review and the update by Joshua Valour. If you want to view all the fancy frequency graphs and charts and stuff, see: Sundara | DIY-Audio-Heaven.
Except for the Sundara, the only other cans i have is the open-back QPAD QH-85 headset which caters to gamers (it's got a mic) and so i have nothing else to compare them to.
The Sundara is an open-back, planar magnetic headphone with very thin and responsive diaphragms which produce a fairly well-rounded sound, though it is a bit weak in the bass department. The mids and highs are well defined in my amateur opinion and the sound stage is roomy enough to not feel too cramped, though it isn't as wide as i'd like (i use a bit of 'extra stereo' effect in Audacious to compensate). I paired the Sundara's with a MOTU M2 Audio Interface and, overall, this combo sounds pretty great to my ears with a bit of EQ to boost the lows.
Very much contrary to what Joshua stated regarding the build quality, i find the Sundara to be really solid. They don't feel cheap at all. Yes, there is some play in the frame, however that is completely irrelevant when wearing them. Compared to my $94 QPAD's however, the Sundara is not all honeysuckle and lollypops. The QPAD QH-85 is significantly lighter and more comfortable than the Sundara, though it is also less robust. While the QPAD has a somewhat short and wimpy cable, at least it acts like a normal cable that actually obeys conventional laws of physics whereas the cable that ships with the Sundara is like a damned slinky. It may be adequate as far as conductivity, but the sheathing, which feels like a somewhat stiff and cheap vinyl, is like a coiled rattlesnake poised to strike at any moment and that's only a modest exaggeration. Simply put, the cable is Crap with a capital C. I tried running it through my hands while exerting some pressure to warm it and get it to straighten out, but that didn't help much at all. In the end i purchased an aftermarket cable from Audiophile Ninja for 60-some bucks and, though way overpriced, as is everything in the audiophile market, it is an infinitely better cable and it is actually a lot cheaper than many other custom headphone cables. It did not come with a clothing clip however and, given its weight, it should have. I solved that problem by sticking a piece of the hook portion of hook and loop tape (Velcro) around the barrel of the cable where it splits to feed the drivers. The hook will attach itself to your clothing, at least if it's cotton or wool.
I thought that the Sundara frame design, with its suspended headband that molds to your head, would be more comfortable than the QPAD design, however due to the extra heft of the unit, it isn't. I can wear the phones for about 1 or 2 hours before it starts getting uncomfortable after which i need to reposition the headband just slightly. The same is true of the QPAD, though i could wear it much longer. Also the clamp pressure of the Sundara frame is a bit too tight for my taste. I was surprised to hear Josh rave about how comfortable he thought the headphone was given my experience.
The Sundara ear pads are shallow which is nice because it positions the drivers close to the ears, but they are so close that, with the added clamp pressure, the top of my ears were getting a bit sore from contact with the material that covers the drivers. I wanted to stretch out the frame a bit to reduce the clamp pressure, but the head band makes that difficult because it prevents flexing the frame far enough to open it up. It is doable however and the phones do feel better after i figured out how to accomplish this (hold the unit in both hands near the drivers and open the headband as far as it will go, then with your index and middle fingers, press down on the top of the frame). While i'm very happy with the sound, i expected more in the comfort department for $350 clams, and a better cable too!
Another niggle i have with the Sundara is that the pivot points for the driver housings isn't loose enough which causes the ear pads to not conform to the sides of your bean as easily as they should. I put a tiny bit of lubricant on the hinge points but it didn't really help. I've had the Sundara's for
roughly a year and a half almost 3 years now and the pivot points feel nearly the same as when they were new.
In the end, the question is whether the substantial difference in price between the QPAD's and the Sundara's equates to $256 dollars worth of better sound and, from my perspective, the answer is no, it doesn't, but such is the case in the audiophile world where one can spend thousands on a set of cans to get an incrementally better sound. That said, they certainly do sound better than the QPAD's for sure and i'm not sorry i bought them.