hmm this one is certainly worth trying. sadly i will need to get hold of the minidsp once i get these pesky modes identified!The bass note on the downbeat at 0:49 is C2, which is 65.41 Hz. You might also be hearing the octave overtone at 130.82 Hz. Doesn't sound out of the ordinary to me so you may need to control your room at those frequencies. You could run a slow sweep with a SPL meter (or your phone with a SPL metering app) to get a rough idea. Plenty of sweep videos on YouTube and elsewhere.