It's a valid thought, but in this case I did my homework.  The sealed pads on the new 48E (the previous 48's weren't sealed - you could rotate them 360 degrees) make the difference in the bass.  Just put the 48E on and get a good seal, play some music with bass, then yawn really wide, which breaks the seal, and listen to the bass disappear.  The much better highs I can't account for yet.  Although I can tell you this - when I yawn to kill the bass, the highs also sound much more like the old DT-48's.  Currently my hearing goes flat to 10 khz and drops maybe 3 db at 12 khz, so with the DT-48 and my Sennheiser 800's I can make a pretty good judgement about the sound.  When I had the Soundcraftsmen equalizer I could equalize headphones to within 1 db of the Koss ESP9's.  I could do that now.  Piece 'o' cake.