The bass encroaches into the midrange, but I only noticed it a few days after changing pads. It's more noticeable with movies than music. The 840 pads were such a pain to put on that I'm loath to restore the stock pads to test. I'd like to get the bass back under control, but I'm loathe to give up the improved comfort.
With what are your covering the vents, mrspeakers? The stock felt is fully in place on my set.