hi streetsmart & lancito,
i tested 6 locations with the mic on a tripod. everything was followed from the manual. in fact i put the mic/tripod on the front part of the sofa so it will be away from the backrest.
what settings did u guys changed on the sub after the auto-test? 0db to me is still too low. my sub volume setting is at 12 o'clock and the crossover set to max as the AVR's sub crossover is set at 80hz. ok lang ba to? is it better to use the crossover of the 2308 rather than the DTX4.15's crossover? i haven't tried to increase the AVR x-over setting and control from the sub though. masubukan nga.
Two last points on the mic:
1) Make sure that the mic is at least 2 inches higher than the backrest of your sofa.
2) Don't select a mic position which is close to a wall.
If you can disable the crossover of the sub, do so. Otherwise, set the low-pass filter to the highest - 120 hz. Do the same with the AVR - low-pass filter to 120 hz.
Aside from increasing the gain of the sub, you can also use the LFE+Main option of the Denon, wherein the sub outputs not only the LFE channel but also the bass frequencies of the other channels. That should increase the overall bass volume, if that is what you wish.
By the way, it is pretty useless for us to compare settings on the sub because we have different subs and AVR's and rooms. Actually, Denon sets my sub volume to -12.0 and that is perfect for my system.