In my experience with IEM's, both the quality and quantity of bass is related in some degree to the fit of the IEM in your ear. As good as mine fit, if I don't give a little extra push into the canal, the bass is not as deep as it is when I give that extra push into my ear. Everyone's "perfect fit" is different and so will everyones experience in terms of bass reseponse, at lieast that's my feeling. I don't feel the highs and to a lesser extent, the mids, are as affected by fit.