HD800 - O2 and ODAC vs. Eddie Current Balancing Act (TRS jack) and Modwright Sony XA5400ES
The HD800’s best trait is its soundstage and imaging. It has just the right amount of width and plenty of depth to the soundstage and does out of head projection quite well. The BA/Modwright combo imparted a reverb-like effect which the Objective combo lacked. It increased the perceived space a bit but it also blurred the imaging a bit.
The HD800’s FR OTOH could use some work. It peaks in the upper bass and slowly rolls off in each direction which IMO emphasizes the wrong frequencies reducing its perceived tightness and even bordering on bloated with the BA (presumably because of its extra output impedance) and messing up the imaging when the music gets busy. The O2 had tighter bass and kept the imaging together better but the HD800 lagged behind the HE-6/EF-6 in those areas either way.
The midrange was liquid smooth on both setups but the BA imparted a bit more viscosity.
I found the upper mids a bit too sucked out as women hitting the high notes in Jpop faded into the distance. The O2 may have been ahead by a hair here but I’m not really sure.
The treble remains strong and is quite well behaved except for a hint of grain and the rough spot around ~6khz which only stands out as troublesome in comparison because the rest of it is so good. Something will excite it occasionally but it more annoying than outright painful. The BA took some of the edge off the treble and the treble didn’t make a nuisance of itself known as quite as often.
Overall I’d take the Objective combo since I prefer its tighter bass, better separation, and sharper imaging over the BA/Modwright’s slightly bigger soundstage and I could probably mod away just as much, if not more, of the HD800’s treble issue as the BA fixed.