Originally Posted by homerdodge
As I read the manual, the 'large' setting pushes the entire audio spectrum to the fronts, even if LFE is on. The 'small' settings cuts the audio to the fronts off below 100 Hz.
Caution: The 5000's manual incorrectly uses "LFE" for the subwoofer on/off!!!
LFE (Low Frequency Effects) is a separate channel that provides the rumble for explosions, etc. It does NOT carry low frequency information for the main and surround channels.
The subwoofer is what is used to reproduce the LFE channel PLUS any bass from "small" channels.
When you set a speaker size to LARGE, the full bandwidth of that channel is sent to that speaker. No information is redirected to the sub output FROM THAT CHANNEL. If you set a speaker size to SMALL, that channel is split into highs and lows. Highs are sent to that output; lows are sent to the "bass mix" which is a sum of all channel lows and the LFE channel.
If the subwoofer is on ("LFE" on the 5000), the bass mix is sent to the sub output and not to any other output.
If the subwoofer is off, the LFE channel any lows from "small" channels are redirected to channels set to "large". If there are no "large" channels, all low frequency information is discarded.
That's the way it is supposed to work any way.
THX recommends setting all speakers to small so the lows are reproduced only by the sub. That eliminates multiple sources of LF energy in the listening space. With the sub as the only source for bass, coverage is theoretically much more consistent across all listening positions. There will always be peaks and nulls in bass frequencies (unless you're out doors) due to reflections. With only a single LF source, it's easier to minimize peaks/nulls in the room by moving the sub around. With multiple LF sources you'd need to move them all!