What do mean by "can't seem to get any sound test frequency to measure the room response,"? Are you not hearing the test sine wave?. If not, how is auto calibration even working?. Is there something wrong with the dd18?. I might be misunderstanding here. Let's assume I am.
Went through something very similar a couple years ago, when adding my dd12. To make a very long story short, try the low pass and get comfy/familare with the software controls. I tried coutless adjustments while running all low frequencies to the dd12. Must have spent 20+ hours trying to get it right. Eventually got it to sound "ok" but not what I had hoped. Had always believed that letting a sub handle *all* the base was
the obvious/correct route. Turns out I was wrong for my setup and gear.
Just like you, i wanted minimal slam and zero noticablity. Using the
lowpass let my aerial 7b's jump back in down low. This changed
everything. Found that to a certain cutoff, the aerials sounded better
down low then the dd12. Especially mid bass as it was night and day. Below 50hz is where they needed a little help, so that's where i ended up.
Still had to spend many more hours getting it dialed in. Auto adjustment
didn't cut it for me. Software seems complex at first but really gets a lot
easier as you use it. Trick is to make single adjustments and listen before
moving on. Keep it simple regarding the eq part (shoot for a smooth line,
not straight). I kept the setup stuff out over a two week period and slowly
dialed it in. Ended up having 3 saved setups for different types of music.
Can easily switch between them with the remote. You could/should add a
movie specific setup as well (my ht system is completely separate). Am
currently running my dd12 cut off at 56hz with the volume set at 12.
Sounds great and you can barely tell it's there.
Again, try the low pass with full range to your mains. It could be the ticket
