Speaker height...should known better

You want limited vertical dispersion, to avoid too early floor and ceiling reflections of wider mid and low frequencies.

and tweeters high frequencies are narrow in all dimensions, horizontal and vertical, so you want your tweeters toe-in aimed at your listening position and raised/tilted back to project at seated ear height.

tilting back some is advantageous, as it alters the angles of reflection off both the floor and ceiling, and toe-in alters the angle of reflection off the side walls.

I put a 2x4 flat above the front two wheels, which raises the front of my speakers 1-1/2", just right for my listening distance

horn mouths are usually designed to give even and wider dispertion, limited vertical.

My tweeters are Electrovoice T350’s, when mounted vertically, they disperse horizontally

https://www.cieri.net/Documenti/Istruzioni/Electrovoice%20-%20Tweeter%20T35,%20T35B,%20T350.pdf

what amazes me is how, even though tilted, nothing vibrates off the tops, 

https://www.audiogon.com/systems/11516

@larryi You could also tilt the speaker back a little to angle the tweeter more to your liking.  That often does the trick and it is a cheap fix.

Good idea.  Exactly what I wanted to reply with after I read the posted thread.  And, its not some temporary hack-fix either, we can show tall speakers where the tweeters and small midrange drivers are in cabinet designs that actually point these units in a downward direction closer to listener ear levels.  Some of my low sitting floor standers had the tweeter midrange spacers angled to put tweeters "up" too. 

For example, rear lower cabinet spikes are adjustable to tilt the Wilson Sabrina Yvette speaker's tweeter downward towards the listener at ear level.  Adjust as necessary if its an option to test with a wood block and/or add taller adjustable spikes later vs buying new stands - as another viable option.  

In a way, it’s a free sonic upgrade.  Gotta take the wins in our costly hobby.

Good idea on the tilt. How would figure out how much tilt (in degrees) to accomplish a 2 to 3 in difference at the listening position? 

Not to long ago, I had a pair of Vandersteen 2ci and required certain amount of tilt for them only specifically for the Vandys. Can I apply the same concept to the Triangles?

Thanks in advance 

You could always put a ribbon tweeter on top.parts express 50$each .you can adjust it to your seating position. This is why I like line arrays cuz no matter where you are ,sit or stand there always there. Enjoy the hunt and the experience and the music