You most likely didn't get a bad pair... You just don't like the tonality... Same thing for those who may not like the Audio-Technicas and the Marshall you have if they demoed it... Different HRTF makes for differing opinions on headphones. Also the frequency response of both the KPH40 and the PortaPros are so close you might as well call them the same headphones but you getting enjoyment out of those and not the KPH40 is certainly eye brow raising.

Also yes return them