The tweeters are fixed in height by the speaker.-floorstanders- Nothing more to do then, but choose a chair of suitable height! Well wife deceided on the furniture so am sitting with 2 degrees above the tweeter axis.. do not notice any difference if I lower my head 3inches to match tweeter height , 104 inches listening distance
Same problem the Meridian DSP5200 are really to short for my sofa , no wonder that pro speakers are rarely floor standing even if they are huge your supposed to buy correct high stands or flush mounts them into the wall or place them on your mixing desk .
Had a pair of snell E3 when I was young and bought an aftermarket short stand to get them higher the mid and treble got more balanced but they lost some bass