gene said:
You probably need to spend more time on optomizing your subwoofer placement and finding the right crossover frequency for your system. None of the speakers in your system are full range and by setting them large you are likely smoothing out a null but at the expense of doubling up bass at certain frequencies below the xover frequency. Check all of your primary seating areas to see if setting your speakers to large really did improve your systems bass response or if it was just limited to the money seat.
At loud listening levels you can suffer some dynamic range loss from your speakers if they are tasked to produce frequencies below 80Hz they aren't well suited for.
You may wish to consider adding a second sub to smooth out room modal response and again work on finding the right location for your sub, shifting your listening position away from the null, and using some passive room treatments to help out.
Gene,
You make some good points but I do not have other sub placement options in my family room HT. I have moved the sub as much as I can in the rear corner placement and the current location is the best compromise. My speakers are capable of significant output in the upper 20Hz region so an 80Hz Xover hardly seems too low. My original question that has not been answered is do I defeat this Xover by setting the speakers to large on the 3805?
Actually my goal all along has been to optimize the sound throughout the room, not just a sweet spot. Setting the speakers to large has given me the best FR across several seating positions in the room. I have considered adding another sub or upgrading but I am pretty near the top of the sub food chain with the DD-18. I believe adding another collocated sub would only provide more SPL and not do much re the rooms FR.
These are the compromises we make with our multi-use HT rooms. Overall I'm very happy with the current setup and just added a projector (AE900U from Visual Apex being a good site citizen

) and that is an interesting story that I will tell here once I'm finished with the install. Thanks again for your comments.