4308, audessey and crossovers ?

Look up the -3dB point of your speakers and add about 20Hz to that (though with a 24db/octave crossover, you may get away with only adding about 10Hz). That crossover setting will give the speaker enough time to transition to the sub before its natural rolloff occurs, ensuring that you don't lose any bass in the crossover range.

the -3db spec is the DIN

Uhm... but from what he posted the +/-2dB point is 44Hz, meaning it is already rolling off at that point. I would go 50Hz for that speaker, possibly even 60 if you listen at higher levels and have a capable sub.

As far as what to set the sub to, if it's anything like the Onkyos with Audyssey, you're setting the LFE cutoff, not an additional filter on the subwoofer as a whole (because what would be the purpose in that?). Setting it to its max of 120 lets the LFE channel pass through unadulterated, though 80 is the THX recommendation. Another thing to make sure of is if your sub has a crossover dial, turn it up to its maximum to prevent the crossover circuitry from causing a delay. Crossovers on the sub can change the delay time detected by Audyssey.

I'm a bit confused by Denon's terminology. I'm reading the manual... and it would seem like LFE+Main would be the preferred option, meaning the subwoofer reproduces sound from both the LFE channel and redirected bass from the main channels. The Denon manual says "Select LFE+Main if you want the bass signals to always be produced by the subwoofer." I would think you'd want that.

Not necessarily. It simply means that from 44 to 22kHz, the response is no more than +2dB or -2dB from reference. It could, theoretically, be up below that depending on the tuning.

Good call. Hadn't thought of that.

I would still use the 50 or 60 hz Xo point unless the user listening at modearte volume levels, then I would use the 40hz, but I wouldn't run it "large" in any case for movies.

The Sub's crossover gets selected based on what you have slected on the other speakers automatically. There might be a separate setting for the "LFE" set that to 80hz or above, other wise you could loose LFE content.

Have you had a chance to look at it in REW? My audessey set itself much like yours did but after a little looking at REW it seems setting the speakers to small all the way around and all speakers crossed at 40 hz and sub set to lfe and main at 80 hz worked out the smoothest curve in my room at least.

REW = Room EQ Wizard free software you can down load at hometheatershack.com they also have a nice forum area on its use. Just follow its included help files and its easy. you will also need a SPL meter or a decent mic setup it will explain the hookup and setup stuff.