I'll convey the theoretical and what I hear in this matter.
Theoretically, there is the design height of the crossover. This is the height where the reverse null is deepest. With the 1801 this happens on axis with the tweeter. This means that the theoretical tweeter height should be at ear level

- right???
Well, sure, but I don't hear the magic when being at the perfect height. There isn't a very narrow 1" window where things are just right, and the converse nasties when NOT within that window.

I suppose there is some possibility of hearing the most ideal phase position, but it escapes my ears.
The 1801 tweeter is about 16 1/2" from the base of the speaker. Measure your sitting ear height, then subtract 16 1/2" for the ideal. If you can't fid the perfect height stand, don't worry about it.
Dave