Sierra Tower w/RAAL in room response question

[jimlucci]

I have 2.1 setup (music only) with Sierra Towers w/RAAL + Rythmik L12.

Audio chain: PC w/Streaming service -> usb attached Schiit Modi 3+ Dac -> HK3490 Receiver -> Sierra Towers + Rythmik L12

I have been running numerous Room EQ's (w/miniDSP Umik) for baselines and speaker positioning and am getting a pretty steep LF rolloff starting at around 100Hz. It is at about 80 spl at 112Hz and falls to 43 spl at 50Hz. From 100Hz up to 20K it is pretty flat (between 70 spl and 80 spl). Readings that include the subwoofer in the test add some spl to that region (+10db) but the slope downward stays pretty much the same.

I expected to see a flatter response further into the lower frequencies and am wondering if my room has a lot to do with that (pretty big area) and/or that I might be pretty subwoofer deficient. Just wondering what other people have experienced with their in room responses with and without subwoofer.

Rough schematic of my room:
roomdiag3.png