Once my ears get accustomed to the NH's with stock pads, I can (and want to) listen to them forever. But I am forced to switch to closed headphones and earbuds now and then, and sometimes when switching back to the NH's, the bass seemed a bit boomy resulting in a somewhat muddy sense through the lower mids. I heard this a few times when switching back to them but thought I must be imagining things because I had been previously listening to them very happily for weeks straight (power of ears/brain to adapt). Anyway, I read
this post, and that prompted me to try the HM5 hybrids. He felt more negatively about the stock pad sound than I do, but some of what he said resonated so I got the HM5's. With them the bass and muddyness issues are completely gone but all of the NH's goodness is retained, so simply put they sound just about perfect to me. Love them.