Some thoughts regarding speaker height -
Although the distance from the woofer to the floor has some relevance to the frequency content, its contribution is minor compared to the relative distance of each driver to the listener's ear. Those relative distances are critical to preserve the integrated sound composed of individual onset transients from each driver. The distances are established by the relative placement of the drivers along their baffle and the ear's relationship to those launch points. Higher frequency geometry is more critical due to their small wavelengths.
Thiel design assumptions are an ear at 36" from the floor and a distance of 3M (10') with a minimum of 2.5M (100") more or less. Moving the speaker higher or lower is quite similar to moving the ear higher or lower. The relative driver distances are distorted.
A fairly safe way to keep the geometry straight with very little compromise to the integrity of the composite wave is to vary the vertical angle of the speakers. I suggest marking a spot 36" from the speaker bottom, and making a target at your actual ear height. Hold a builders' square at the speaker height mark and tilt the speaker until your sight-line hits the ear target. If you raise the speaker by any means, the compensation is to tilt forward to bring the triangulated geometry back to focus at the ear. (And vice-versa for high seating.)
If you use REQ, FuzzMeasure, etc. the proper tilt, and a mic at ear position will produce the best-looking step response. Other tilts/heights will produce a hole or lump or offset between the early-arrival tweeter onset transient and later-arrival woofer onset transient. Later Thiel products with coax / coincident upper range drivers solve the tweeter x midrange issues, but the high vs bass timing issues still remain.
Thiel's design target for bass Q is .7 in an anechoic environment. That is on the articulate / lean side of the tracks. Room gain will augment and time-extend the bass to the extent that the room is large enough to support bass frequencies.
Here is a link to a relevant article by Robert Harley published in The Absolute Sound.
