S1 Pro system Auto EQ
The S1 Pro System uses an accelerometer to determine if it is in the tilt-back, horizontal or vertical position. It also has a switch inside the pole cup to determine if it is mounted on a speaker stand. Based on the orientation and the switch, the S1 Pro System automatically applies the correct EQ.
If you take a loudspeaker and put it on a speaker stand, then a tabletop, and then on the floor, the sound will change[1]. When the speaker is on a tabletop or the floor, it is interacting with the boundaries (tabletop, floor, walls, and ceiling too). This means if you want great sound in all situations you have to EQ the loudspeaker.
Bose tuned the S1 Pro to sound great in all four positions (speaker stand, tabletop, floor (both tilt-back and horizontal)) taking into account the boundaries. And the engineers carefully considered how you would be using the S1 Pro. That's why there are two settings for the floor (tilt-back and monitor).
I encourage you not to second-guess the automatic EQ. To use them in ways other than Bose intended you'd have to put the loudspeaker in a free field (a room without reflections).
But if you could put the S1 Pro in a free field[2] here's what might hear.
Using the speaker stand position as a reference:
- Tabletop: a little less bass than speaker stand
- Tilt-back: a little less bass than Tabletop.
- Horizontal: about the same as Tilt-back except there's some EQ treatment to support use as a monitor.