Room mode: is it expected to have such a difference between dBA and dBC?-Acoustics Forum-Acoustic Fields Forum

I’m converting a spare room to a recording studio for voice over and youtube videos . I did some preliminary studies of the room’s acoustics based on the procedure explain by Denis on the video “Recording Room Mode, part II”

https://youtu.be/Z3dRzJ7eAgQ

If you look in the comment section at the bottom of the video, you will see I mistakenly set my audiometer to dBA instead of dBC (that latter being the same thing as dB SPL if I understood it well).
So, I took a second set of measurements with the right setting this time.

I took *great* cares to ensure all the devices were calibrated exactly the same as in my initial testing. I expected _some_ difference in the results. But they are indeed _very_ different. Here is a link to a graphical view of the results:

https://www.chicoree.fr/pub/ac…..s/mode.jpg

The room is 6.35m x 2.9m (x2.4m height at its max — but it’s an attic room)

That raises several questions to my mind.

(1) first, do both sets of measurements seem coherent to you? Or is this “obviously wrong”?
(2) for voice-only work, are low frequencies (<125Hz) as critical as they are for music?
(3) should I need to care about "room mode" for _recording_, knowing the talent will mic’d with a lavalier, and positioned were I put my speaker for the tests?