With good subwoofer placement, after calibration you will not be able to locate it. It will seem like all the bass is coming from every speaker but the subwoofer.
If you get a SPL meter to help you calibrate, get the Avia or Digital Video Essentials or Rives Audio CD disc to help your cause.
If you use your ears, play some bass heavy tracks, Godzilla menu is good and there are several listed
here.