Tonight, after work, and when the kids were asleep, I compared the ms01 to my akg 701Q using three different hp amps; Matrix mini I v2, GTA se40/can/opener and for giggles my portable fanmusic. The 701 is a semi open back design that is generally acknowledged to be a nice set of cans and an excellent monitoring system. They do require some juice and are not the most sensitive headphone to drive. They are not crazy difficult but do require power in order to come to life. Both the Matrix and GTA have that, with the GTA rigged as a hp amp having more than needed. The MS01 are of high sensitivity and can run on a whisper. That being said, they can bring to the surface tube amp hum......albeit, generally masked when the music kicks in. The 701 is stone quiet using the GTA. The MS01 sounds great using the fanmusic, with the fanmusic running out of gas when driving the 701. Which, really, wasn't difficult to predict.
Not surprising the GTA drove both pairs the best....offering a more refined and engaging presentation. The Matrix is a bit thinner and more hard sounding but highlighted the high end with both phones....sounding a hair more extended. Believe it or not, the fanmusic gave up very little to the GTA, adding a bit of a misty veil, when driving the MS01. The fanmusic works well for efficient cans and in this case a good match for the MS01.
Now for my general impressions when comparing both cans. IEM will always present a different soundstage than on ears, with the former generally placing the soundstage within your head, to a degree. It is not necessarily contained only within our head but generally not as wide, with less air than open cans. On ears provided the opportunity to extend the soundstage further outward. IMO, one is not better or worse, just different, I can enjoy both when listening to good recordings.
That aside, both cans present a timbrally accurate picture. However, no one would mistake one for the other. The MS01 delivery deep and accurate bass. You will never be wondering if you are missing low end and unless your speakers go low or you have a subwoofer, they will treat your ears to a bottom you may not experience outside of a live concert. The 701 is a bit MIA in comparison and do not provide the impact below 80 hz that a lot of recordings provide. MS01 advantage extends through the upper bass, too, which provides more punch and impact.
The MS01 have a mid-range peak, somewhere around 2200 hz and they present a more upfront picture but which is still nicely balanced. They just slightly highlight instruments and vocals within this range. The 701 is more laid back and may have a slight smiley type response curve. My preference goes to the MS01, which kept me engaged.....where the 701 sounding a bit less interesting.
The lower treble was good with both cans and that is a compliment to the MS01. They shouldn't sound this good for this price. Both cans are extended and you will not miss any high end detail with either. You won't get fatigue by hyped sound either. The 701 being a bit more refined and extended but you will hardly be left wanting more from the MS01. Unless you have ribbons in your open air speakers you most likely will get as good or better reproduction of the high end as you do from your home speakers.
The bottom line is that regardless of the price difference, IMO, the MS01 were preferred over the 701 with the amps and sources I used. That is saying a lot when comparing a hp that cost almost four times as much. If I had to pick between the two I would choose the MS01. Really!
In a few days I'll have a Melos Sha1 and will see if anything changes. I'll also try the Rogue M120 ' s on them when they arrive tomorrow but I'm not really expecting much to change.
Finally, I continue to be mightily impressed by these inexpensive IEM and now without reservation recommend them to others.