Check to make sure you have the headphone/ jack plugged all the way into the headphones. I bought two pairs and both have tons of nice sparkly treble and seem very flat, no flabby bass as long as you leave ANC off. if you have another 3.5mm audio cable, try that and seat it really well just to be sure. if it is seating OK, then you may have a defective pair, read similar complaints your yours on some reviews that were for either the cable not in enough or defective units. good luck!
Headphone Reviews and Discussion - Head-Fi.org