Good question. My measurement software is anechoic from about 300 Hz on up. That is, what you see is the inherent response of the speaker, not the room. Unless you have a mega-buck, mega-size anechoic chamber, you can't do anechoic measurements much below 300 Hz. The sampling window is to short, and the wave lengths start getting too long (two few cycles per second) to be captured accurately by the software. You run out of resolution. My software has a feature that lets you transition to a room response below 300 Hz, and in that region you start to see room effects. The sharp dip at 220 Hz is a floor bounce cancellation, where the sound waves hit the floor and rebound out of phase. Where exactly that occurs, and to what degree depends on the location of the woofer to the floor, and the mic to the speaker. The only way to avoid cancellations like that is to place the woofer right next to the floor, which causes other problems. It's very controversial whether you can hear floor bounce cancellations.
Now, if I were dumb enough to show you the full measured response down to 20 Hz, you would see even more prominent cancellations, and a room mode bass peak around 70 Hz. That's just the nature of speakers in rooms. I used to publish the full response, but it was a nightmare explaining all of the ups and downs you see below 300 Hz. So I cut it at 200 Hz, which shows the beginning of the room response region.
