IMO the DT1350 had over-controlled bass, very fine-grained and extended treble...and a pinched middle....also had a stiff, unwieldy metal headband that vice-gripped the bejeezus out of the average head....and you had to get the positioning just so or no bottom.
The T51p address and fix all of the shortcomings.....new flexible metal band, soft pads...and they are now just resting comfortably on the ears. Fit is similar to the KEF M500. The bass is present in the right quantity, slightly warm at times (probably recording dependent) midrange is now smooth, and the top has remained it's wonderful self....it all integrates seamlessly....oh, and they threw in lightning fast dynamics. Very rhythmic. That is the big thing I noticed.....the PRAT. I just grooved along to everything. The distinct character of each tune's recording seemed to ring true on the T51p. I think the wonderful treble extension is providing the grain-free timbre accuracy. The drivers must be perfectly matched because the imaging is perfectly focused and aligned. Yeah I like these
Thanks for the report Beagle. How is the soundstage?