Hopefully this will be a short review packed with some worthwhile information.
This is my first pair of "high-end" headphones. I have not owned any other Sennheiser products, nor did I have much experience in high end headphones. I do have experience with higher end home audio on the other hand. I spent a lot of time researching this product and noticed some debates about what people think of the HD700. Some people seem to love it, and some seem to hate it. Most recommended trying before buying, but I understand that many people are unable to do so. Hopefully I can clear things up and give a bigger picture to what your are purchasing.
What you need:
These headphones are rated at 150 Ohms and only come with a 1/4" jack so they are not necessarily meant to be portable. They will need an amplifier, and optionally a DAC (for less noise, and better sound quality).
http://www.schiit.com/products/modi-2 (I went with the Multibit Version)
After reading what to expect out of the headphones, I found that they have a little bit harsher treble than other Sennheiser products. Many people recommended getting a tube amp to help suppress some of the harshness. I have read that mulitbit DACs also can provide a difference in sound for the headphones. Most were described as "meatier, or fuller sound." If you don't plan to spend extra on multibit, then the modi 2/modi 2U will be very good as well. Another thing to note, I decided to use higher quality cables due to better shielding and lower interference with other equipment that I have near my computer.
Sound out of the Box:
When I first opened them and fired them up they sounded good, not great. The sound seemed a little off in my opinion. It had an amazing sound stage, but seemed that it was lacking bass, and the treble did seem a little harsh. After previously reading about this, I came to almost expect it. Luckily, I found a solution to this issue.
After changing the EQ and adjusting it to what I wanted, I love these headphones. They are everything that I expected and more. I would definitely know what to expect when you are looking into them. If you have some patience, then it will be worth the investment.
Other things to mention:
Comfort is top notch. Very lightweight, premium materials used, and breathable. These are open back headphones, so sound will leak out, and you will hear things around you. Cable is 10' long. No 1/4" to 1/8" adapter in box. Box is also the case for them, good quality with a hinge.
Awesome purchase, but if you are starting from scratch, then you need to invest in other equipment to get the most out of these. You may also need to mess around with these for a little bit to get them to sound how you want them to. Overall, I am very happy with them, and plan to use them for many years to come. Would definitely recommend if you are looking to get serious about your audio.