In my dedicated listening Space with Room Treatment added, all my Cabinet Speakers (Floor Standing and Stand Mount) and the ESL Speakers have been set to be as vertically Plumb as can be for the Front Baffles and Side Walls as their initial set up.
I have worked with orientation - Toe In / Toe Out to create the best sound staging, i.e, Imagery and Spacing for the Imagery.
When the imagery takes on what feels the most honest presentation, i.e, the spread of the performers and increase / decrease in depth to the setting. I then work with the Head Room that can be created.
The Front Baffle of the Speaker will be removed from being Plumb and leaned away with approx' a 10mm off set between Speaker Base and Head, this is then reduced to 5mm. Then back to Vertical Plumb and then leant forward to the point the Speaker is a little precarious.
I have got the very best from a Floor Standing Speaker design with the forward lean being near 40mm. Typically in my listening space 5mm - 20mm forward lean does the trick to increase the Headroom and create the effect there is a added volume to the listening space.
When tweaking the Baffles Plumb, always double check the side wall and keep it perfect as can be for being plumb.
I would only imagine a Seat Height Tweak is needed if the Speaker is best when precariously set forward, and a reduced lean is best with the listener a little elevated, or if a backward lean needs the listener a little elevated to feel the full benefits.
