I guess I should run the math on this, but I'm thinking the height of the sub from ground, and the top-to-sub distance, and the relative ears of the audience are fine tuning things done at the venue, or maybe they are negligible in the context of room reflections, power alley,...

Out of curiousity I did the math. If A squared + B squared still = C squared in a right triangle, the difference between a groundplane measurement at 60' away and a groundplane measurement at 60' away but with the main speaker raised 6' would be neglible.

0 height squared 0

60 away on ground squared 3600

Square root of 3600 = 60' path length

6' height squared 36

60 away on ground squared

3600 3636

Square root of 3636 60.3'

The difference in path length is .3' = 4".

At 100 Hz, one full wavelength is 1130/100 = 11.3' So we're talking a comparatively small difference between the two measurements.

How many of these differences are there in a total wavelength? Approx 35. 4" * 35 = 140" 140" / 12" = 11.6' Close enough for this.

If you were predicting earthquakes I trust you were more scientifically exact than this.

Knowing there are 360 degrees of phase in a full rotation of a waveform we can see that 1/35th of a full rotation is a little more than 10 degrees of phase change.

There's enough slop factor to say your measurement with the top on the sub or raised up 6' vertically will be quite similar.

PT