Steve, 60hz is considered the thump range, when you get down to around (50hz) or less than 45hz it sounds good and powerful. But when you get around or below that 38-35hz area and if got the power, and it's not rolling off down there (AKA the SPL flat down to 20hz) it takes on other dimensions, because the building AKA(Home construction stiffness) can come into play then.