Dolby TrueHD, DTS-HD Master Audio & THX certified queries

Hi sifu and all hifikaki... I just want to ask about this 3 super software decode on high end av receiver. I have Onkyo avr model tx-sr 705 which i bought last month. Its decode of this 3 super software. I follow all the rules to how to show up the Dolby trueHD and DTS-HD Master Audio format at the display on my avr and i found it.. Sure the sound quality from both audio format is very powerful. but... when i push THX button on remote to activate THX format on avr, why the sound suddenly poor and lack. Any one can help me. Is that problem come from my setting or my avr or my bd player or from bluray disc?

powerful but is it natural


lacking in what sense?

I read THX setting must use with THX certified item such as speaker, cable & etc (also the disc must support THX). Normally I never use THX setting with my Onkyo 905.