Hey Canali, thought I'd respond to you in the forum as this info could be of benefit to others looking into the 7520.
You had asked how these might stand up to the HD800 as well as discussed getting the Fiio X5.
I have had a couple occasions to listen to the HD800 and it is an incredible headphone. It is superior to the 7520 overall, but they are designed for quite a different purpose than the 7520. You will find on this page http://www.amazon.com/Sony-MDR7520-Professional-Studio-Headphones/product-reviews/B004Z58VZ2, a review from an owner of an HD800 who compares the 7520 very favorably. I've read the same on head-fi as well, with another HD800 user praising the detail retrieval of the 7520. As far as amp requirements go, if you have a decent smartphone, you will have no problem powering the 7520.
As far as myself getting the HD800, I have a pair of LCD-2s, and as much as I would like the HD800, I can't rationalize having two open sets of cans. In my opinion, the LCD2 is still world class. Right now, I just want to enjoy them rather than looking for the next best thing - which from my experience would likely just be a side-grade unless I was spending thousands which I'm not prepared to spend.
You will find a number of comments of those who are involved in studio production as engineers who regard the MDR-7520 very favourably to even their high-end studio monitors. Typically, this isn't a sound signature most people would particularly like, as consumers have become used a to a 'sweetened' or exaggerated frequency tonality in speakers and headphones. The studio sound can be described as flat. It is a bit dry sounding, but it allows you to hear deviations in all of the frequency areas. It gives you a baseline. It is akin to having a color calibrated monitor for design or photographic work.
Even with studio monitors, the lower bass range can be under emphasized. This is remedied by active sub-woofers or the design of the speakers and enclosure. The idea of neutrality in headphones is still up for debate. What needs to be considered is that bass, in a room space, is magnified - and felt. So even the very flat line frequency response of my LCD2 are not quite natural to what would be heard. That would go for many headphones, including the HD800. Now, its not a huge deal, as your brain acclimates to the sound and it is a bit recording dependent (as there are a range of tastes in the mastering of audio).
The MDR-7520 is a headphone, that I feel gets bass properly represented in balance. In my review I discuss this, and even as a I write this I'm listening to an impeccable classical recording that the bass does not interfere. If I was to play something that required that lower range, such as electronic music, the bass would be well represented and enjoyed.
As far as DACs go, you will find so many opinions, but you will also read in the Sound Science area of Head-fi, that some of these super expensive DACs, don't audibly (and this is the key word here) perform better than the cheap $8 chips found in a smartphone. It isn't what most audiophiles want to hear. Same with cables. So you may not even need the Fiio X5, but get it if you like the idea of having a separate system from your phone. What is important are transducers. Spend your money on that first, then amp, then dac, and maybe cables (for utility). Dynamic headphones like the HD800 and HD650 are going to require amps to sound their best. But the amp requirements, again in my opinion and some others on head-fi, are dramatically overstated.
File format is also important and first part of the 'chain', and I primarily listen to FLAC, but not because they sound better than a 320kpbs MP3. With MP3, just make sure you are using LAME encoder for best quality. I use FLAC as it allows easy translation to a compressed format in the future if needed. Also, while I have some 24bit files at 96khz or higher I honestly think the whole hi-res music format is one of the biggest jokes in the history of audio. There is no discernible audible difference and 16bit and 44.1 is more than adequate for our human ears. What is important is the recording quality of the actual music. This will depend on many factors. To this end, this is where my LCD2 will shine over the 7520, in reproducing the best dynamic recordings (ie. not pop music that has no quiet parts thanks to heavy dynamic compression and limiting).
Ultimately, the 7520 can compete with some top-of-the-line cans, just because of its presentation. While in some technical aspects the 7520 will be beaten, the overall tonal signature of the 7520 is one that find is near-perfect for pro use while still being very enjoyable. I've also listened to the Focal Studio Pro, which are excellent, but a different take on the studio sound. They are also not designed so much for large ears. The Oppo PM3 are another recommendation, though the bass impact was a little light, you may want to look at these. 7520 + DAP is the price of the PM3. PM3 is more comfortable, spacious sounding and more laid back while remaining neutralish. PM3 also doesn't require any additional amp or fancy DAC. It is designed to sound great right out of a portable.
My recommendation for the 7520, is when you get them, take a couple weeks to get used to them. Listen to a wide range of music, even stuff you are unfamiliar with. Research what are some of the best recordings out there and take a listen. My only other recommendation is that if you don't need a closed headphone for home use, consider a headphone like the Fidelio X2 or Sennheiser HD650. I owned the HD650 and I'd say it is one of the best introductions to audiophile sound. For some on head-fi, it is still their top of the line headphone after all these years, again because of their presentation and not necessarily their technical specifications. The Fidelio X2 may be a match for it in many ways and it produces a bit more bass quantity, which is good as the 650 is a bit rolled off, and the X2 is very easy to drive. It also is a bit more comfy and the build is more premium. They could be your second cans to the 7520 as an open headphone will always sound different than a closed can.
Looking forward to your impressions!
