Each time I listen to the T1.3, it just sounds wonderful. Big dynamic presentation, nicely filled out and natural bottom end when it's in the recording, rather than being omnipresent. I'd also note the dynamics sound as if they are physically hitting your eardrums, rather than being present without "thump" as with most headphones.
The latter really struck me on first listen.
I've toyed with selling them numerous times, but their sound, effeiciency and generally natural presentation has me keeping them and listening through them very regularly. Despite many people thinking Beyerdynamic made a poor decision releasing such a supposedly dark headphone, I say it's actually balanced more to what one actually hears live compared with the usual bass light, treble bright signature of many TOTL headphones.
Trying to EQ these just sounds wrong - I've tried Oratory1990 and Crinacle and neither sounds even close to right (although they both do a great job with my other phones). Take a longer listen to these - the initial "UGGHH" will turn to a smile in time.
They are also beautifully constructed - IMHO, even better than the T1.2 or T1.1.