Since senior jazzy is outstation last night so I'm the one who tested it I was surprised by amount of bass the HD 668B pumps out, more surprising that the bass is not annoying at all. If there is any bass line, at any frequency you WILL hear it on this headphone, the bass extension is amazing, which suits jazzy very, very well

I'm not a basshead but after hearing it, the bass isn't overwhelming and like most say, its neutral so you won't feel lightheaded because too much bass is in your system, but just enough and shows every single bit of it. If there is a bass line that follows behind the vocal, you will hear it as well so sound separation is quite good as well! Other part of sound spectrum is pretty neutral and sounds pleasing, despite the deep bass the high is not compromised but its not bright enough for detail freak. You will hear the percussion detail as well without being muddled by the bass. This headphone is good enough to reveal flaws in mp3s compression so be warned.

Standard HD 681 sounds a bit rough and shrill on some female vocal, there is report saying there is spike at 9KHz and the high is a bit recessed as compared to HD 668B.

But nontheless both are great for each price bracket, I have heard nothing better for their cheap prices. My friend bought some headphone called 'earpollution', I only heard if for like .2 sec before I take it off, guess the name really tells what is it sounds like