As with guitar strings the pads on you SH600 need to be changed when they are worn out to get the most out the sound. I bought my SH600 used and the pads were so worn out that they were thinner and no spongyness in the pads, this resulted that the cans tested on your ears inserted of hovering over them. This was completely fixed with these new pads, and now the sound is better since the speakers are at an appropriate hight over the ear. They lose one star since they are expensive and will not last very long.