In reply to:
If so, my guess is that the "set sub to both" setting is over-riding the "set mains to small" setting so the effect you are getting is the same as setting the mains to large.
The "sub:both" setting would seem to be meaningless when your mains are set to small. Note that I have not red the 2400 manual, I'm just extrapolating based on how my HK operates...
That's not quite exactly how the Yamaha receivers operate...
To clarify each... when you set MAIN to SMALL "The unit directs the low-frequency signals (90Hz and below - I have a fixed crossover) of the main channel to the speakers selected with "1E BASS"." (from my Yammie manual)
So you have full frequency info going to the MAINs channel... if you set the speaker set to SMALL for them, anything below 90Hz (in my case, YMMV) is sent to what you set BASS to:
SWFR - all that info goes to the sub (and if there is a specific LFE signal headed that way as well, it's mixed with that)
MAIN - sends both the low-end MAIN program audio (that sub 90Hz stuff) and the LFE channel to the mains.
BOTH - 'nuff said.
So since you've got M60s and an EP500, the "correct" settings would be LARGE mains (they get full range), and BASS set to SWFR (so LFE channel only goes to the sub).
-If you set MAINs to LARGE and BASS to BOTH, you're sending full range AND the LFE channel to the mains and the LFE channel to the sub.
-If you set the MAINs to SMALL and BASS to BOTH, you're sending that sub 80-90Hz info that it's rejecting from the mains back to the mains and to the sub, and the LFE channel to the sub mixed with the cast-offs from the mains.
Maybe a flowchart would help of what everything is and where it can be shunted to. the confusion comes from the fact there are two sources of the low-end... that low stuff from the mains and the specifically mixed .1 LFE channel.
Now repeat that with all the speakers in the system... if your REAR CT is set to small, the low end stuff from its signal is also mixed to the sub if BASS is set to SWFR or to the sub and mains if set to BOTH, etc, etc...
Did I clarify or make this worse?!?
Bren R.