If my subwoofer has no LFE input...

If I remember correctly the Denon AVR receivers have in the speaker, subwoofer menu (when set to on) THX and THX + Mains. So if a subwoofer is not connected to the sub pre out you could still get the LFE info to your Left and Right Main speakers when set to THX + Mains.
Regards
Rich

In the above post the correct nomenclature is LFE, so subsitute LFE for THX (in the speaker configuration, sub menu on the on screen display). ie. LFE and LFE + Mains. Sorry for the confusion.

Rich, the only way to get the LFE content in the mains is to select the no subwoofer option. The LFE, LFE+main is what goes to the sub, not the fronts. I've tried both, and greatly prefer the LFE only going to the sub. LFE+main causes some weird phase cancellations between the sub and full-range mains. However, this can be a good way to use the sub to extend the range of nearly full-range (40Hz) mains set to large. You set the sub output to LFE+main and set the sub's crossover to a very low frequency, such as 30Hz, to provide bottom fill only. This works better for audio than HT.

Nighthawk, according to my DENON AVR-4800 manual and the on screen display you have to set the subwoofer to "On" to get to subwoofer mode screen: "LFE -THX-" or "LFE + Main".
That is you have the flexibility to choose how the bass information is distributed to your speakers if you have large front left and right speakers and a subwoofer as part of your home theater speaker system.
By selecting the "LFE + Main" option, you will be sending the same bass frequencies to both the front left and front right, AND to the subwoofer speakers simultaneously.
If the "LFE -THX-" option is selected, bass for the large front left and front right goes ONLY to the front left and front right speakers. Bass going to the subwoofer comes from the LFE signal and any speakers which you have designated as "Small".
I believe this is the only way for DENON receivers to get an LFE signal to the front speaker outputs so that a subwoofer with no LFE RCA input could ultilize it's high level speaker inputs.

http://www.usa.denon.com/catalog/pdfs/avr4800dfu.pdf

Rich, I certainly see how you could interpret it that way. My 5800 manual words it a little differently. It says "When the LFE+Main playback mode is selected, the low frequency signal range of channels set to large are produced simultaneously from this channels and the subwoofer channel." It doesn't say the LFE info is also present in the mains. However, if you set the fronts to large, the surrounds to small, and the sub to off, the fronts will get the bass content of the sub channel and the surrounds mixed in with the bass content of the fronts.