Used Power Tools Test tone from my iPhones and a good old Radio Shack SPL meter on the standard audio system of my Model S. Bass response was surprisingly flat to just below 40Hz after below which it drops of a cliff. EQ was set flat at 0db. Will check with ful spectrum Room EQ from the laptop when I get some time, but sure doesn't look like the Ultra hi if sub is necessary at least from freq response standpoint.