Originally Posted by cwt
It reads like a non discrete sharing of the l/r signal between channels Deepsky; this is from an earlier pdf;
Quad Bypass Mode- Ideal for stereo-music playback and older stereo movies, the right channel information is sent to the right surround channel and the left channel information is sent to the left surround channel. The
centerchannel (if active, see System Setup in Pro Setup) is sent a mix of the right and left channels, with the mix lowered by 3db. All four right and
left speakers receive R/L information and the center gets a mix of the two.
That description makes perfect sense based on the name.
In AVR parlance this is sometimes called All Channel Stereo, or Party mode. These modes have no formal or rigid definitions, case in point being Classe's Party mode which is mono from every speaker.
Quad Bypass is a way different animal from Trifield. They are both passive (no logic steering) but the similarity ends there.