@herman but it is, and I’ve measured it. It’s not "real." It’s not the capability of the speaker so much as the resonance of the room.
I’ll try one more time and then leave you to it. I don’t care how much your room is adding to it, it is impossible you are getting the same level at 20 Hz that you are in the midband with a 6.5 inch speaker.. impossible.... your measurements are incorrect.
something is wrong with your measurements at the top end too when you turn up the midband by 10dB (red to yellow) but at 20KHz it goes up 20dB
if you play a 20 Hz tone do you hear it?