it means they have a lot of music in the 28-32htz range. Yeah you are right E but most of the new rap is upper bass in the 40's but if he has a subsonic cutoff he should be fine. He just might not get the SPL he is looking for if he tunes to 28 ya know? I guess it doesnt matter if you do listen to bass cd's and 3-6 mafia then tune lower but if not then tune a little higher.
Actually James Most hip hop is Using more lower bas then ever since lil jhon came.