Hi, first time posting here, but thought I would post my findings since this site helped make my decision to buy both of these headphones, especially the threads where dsnuts had some input - I got the 681's because they supposedly are the Samson SR850, just rebranded.
This is my uneducated/uninformed in the headphone/professional sound world review, I'm a pro guitarist but I leave all that stuff to the engineers and sound guys to make it sound like I want :p These are just my findings from playing competitive FPS games, which I do quite a lot.
Just let me say straight off for anyone torn between these two and not sure which to buy like I was, you will be satisfied with either if your main focus is FPS competitive gaming - you won't really regret one over the other. It is kind of cool to have both though, I just use one for a week or so then switch to the other just for a little change. I started out with the 681's but just had to find out about the AD700X's.
I got the 681's for $30, the AD700X's for $130.
First the audio settings - I followed these instructions exactly to set up Windows 7 and Battlefield 3 audio:
Next my sound card: Asus Xonar DX, with settings on the Main menu in the Xonar DX Audio Center (software that comes with the Xonar cards) as
Sample Rate PCM 48 KHz
Analog Out Headphone
SPDIF Out not selected
7.1 Virtual Speaker Shifter selected (and just arrange the speaker icons as you like)
Dolby Headphone selected
For the 681's, on the Effect menu (EQ), I leave it as default (all sliders in the middle)
For the AD700X's, I kind of do the upside-down smiley face, all the mids all the way up, with the lows and highs from the ends, the sliders at the middle and rising towards the center.
Sound wise, the 681's sound kind of "tighter" and "thicker" with maybe a little more low, and footsteps sounded louder in BF3 before the EQ'ing for the AD700X's.
The sound difference in all other games before EQ'ing the AD700X's (COD BO2, Crysis 2 and 3 etc) was nowhere near as apparent as in BF3, they were much closer in any other game.
Also, after EQ'ing the AD700X's, I can distinctly remember examples with both headphones, in BF3 where I heard people coming up behind me where I turned around and shot them first just from the positional and directional sound.
AD700X's sounded "brighter", more "highs" and very echo-ey with gunfire in BF3 TDM just sounding like one big echo-ey firefight off in the distance before the EQ'ing, I couldn't really hear the footsteps in BF3 as well as the 681's, but the EQ'ing definitely fixed that. They sound a little more open also maybe, and maybe also a little higher class - kind of hard to describe.
These clips also helped talked me into the AD700X's:
They're supposedly the improved version of the AD700's with better bass but still a lot of brightness - I didn't try out the AD700's but I would say this is probably true from dsnuts' reviews of them - I don't really find the 700X's "outclassed" by the 681's for positional and directional accuracy (after EQ'ing) the way he describes the regular 700's to be.
The AD700X's are definitely a little louder than the 681's.
Comfortwise - my head probably wouldn't be considered larger than normal, the 681's were pretty tight to start out with, I keep them mounted on my pc tower as if the tower is wearing them when not in use so they stretch, it seems to have worked pretty good because they were a little uncomfortable at the beginning, and the way they fit on the ears is a little tighter so your ears may get sorer faster than the 700X's.
The 700X's are not too loose like the 700's supposedly are, they definitely are looser than the 681's, the pads are the softer cloth material compared to the 681's leather-like material, and the pads go around your ears more than the 681's as well as the drivers not touching your ears as much as the 681's, so that could help with the comfort level and soreness, but it still helps to take them off between rounds while waiting for the next round to start.
So any other questions just ask, and thanks for helping me to decide on these!
Edited by BujinStudent - 11/19/13 at 1:38am