I have a 5.1 surround system. Won't bore you with the component details unless it becomes important to know. For ANY DVDs I have with the THX Optimizer menu: the test tones come out of all the channels (L, R, C, SL, SR) except the sub. Receiver Xover set @ 80Hz and volume is raised during the test. When I play the movie, I get sound out of the sub at expected levels. Can anyone tell me why? I guess everything seems to work ok but simple curiosity demands an answer why the sub test is silent.
I have no ready answer for you but you definitely have my attention! This sort of curiosity will be the death of me (us?) as there is no obvious answer but I do plan to spend some time with a disc that has the THX Optimizer just to see if I can recreate this oddity.