I do not think this is a fair assessment. The dt1770 opens the sound up considerably, providing significant more detail, clarity and spectrum balance. Bass on the dt770 is powerful, but to my ears pretty one notey and missing detail and texture compared to the dt1770. Bass also comes from around you (like a sub in a room) on the dt1770, where as the dt770 just hits you in the face with it. The dt1770 comes across to me as more euphoric than the dt770. To me, the dt770 is a great buy at it prices for rock and pop, but I find it not great at more detail orientated music like electronic, prog, classical and jazz. The dt770 v-sig makes classical and jazz not great, but the dt1770 is much more balanced and open sounding in the top end, allowing jazz and classical to shine to my ears.
Dt770 was my first nice closed headphone. It is a great starting point, but to me the dt1770 is a VERY BIG increase in quality of sound.