Confused about subwoofer testing results chart

[paul8]

Hey there,
I run some tests against my REL HT/1205 sub-woofer using REW's built-in CEA-2010 burst tones, on the chart attached it appears the sub can hit 10 Hz at 70 SPL - this seems impossible, the sub is rated 22 Hz at -6 Db.
Do I misread the chart then?
My test setup is like this: REW on Macbook with Samson Go mic attached via USB, my PC which also runs REW sends the burst tones to my Yamaha 3080 receiver via HDMI. I know this is not an ideal mic for testing, but it seems sufficient for a start, it's flat and omni directional.

 

[IWC Doppel]

My understand is microphones are less accurate below 20Hz, but leaving that aside you will have significant room gain below 20Hz and this helps measured db. Might be easier to do sweeps say 10-300 Hz and keep lifting the volume by 6 or 3 db you will start to see compression when the next line up doesn't follow with the same shape, you will then better understand where the limits are.

I normally sweep from 5 Hz, but I know my subs can cope with the Xmax required for that excursion