Been a busy month lately, non the less in short the HE 4 is really an upgraded Dt 880 in all respects! And to help demonstrate this, instead of posting my subjective review I'm going to post some Objective measurements of both headphones.
A big thanks to HeadFi /ChangStar Member Purin/Marvey
The top picture is the DT 880 and the bottom is the HE 4. On the Bottom picture look at the Green line closest to the top. Notice that each headphone has a relative peak around 10k hrz and a dip at about 5k.
Additionally there is a relative shelf from 200-1000 hrz before the major dip in the central and upper mids.
Also notice that the HE 4 Demonstrates a more linear Bass Response from 20 hrz up to 200.
As well as the slight roll off after 10khrz, what this amounts to for the HE 4, when compared to the DT 880 the HE 4 has a tighter bass, and a touch more mid presentation. And what's seen in the graphs is discernible through listening.
It should also be noted the Bottom Lines, colored Grey Yellow and Magenta are objective readings, although of what I don't know.
For the sake of simplicity let us focus on the Green line at the top of the graph!
But my ears and objective data confirm that, both the HE 4 and DT 880 sound much alike! With the HE 4 in my opinion being a clear upgrade to the latter. It should be noted though, that the HE 4 requires an amp just as the DT 880 does.