I be very pleased with these phone when plug into my ipod classic . compare to my to previously own hd595 the soundstage be larger and the music be more detailed . I then add a fiio e11 amp connect by a fiio l9 line out . the improvement be huge . the bass come alive . the low bass be deep and control ; you could actually feel it . the upper bass be mellow . the midrange be sweet and the high be pure . the soundstage expand and the imaging seem exact . on recording with a large dynamic range the sound go from I could hardly hear it to I can hardly stand it . I believe that to really get the best out of the hd 598 you need to add a adequate amp .