How to place speakers at the optimum height

The height of the speaker has a lot to do with how close your listening position is.
If you listen at near feild like I do, then it's much more critical on the hieght.
I prefer my ear to be between the mid driver and the tweeter. Some like the tweeter to be ear level.
If you listen at 8-12 ft. away the hieght is not as crucial.
You can also leanthe speaker forward or back to aim a certain driver or tweeter more to your ear hieght to help in what you think sounds the best.
I like my tweeters to be a little off axis instead of ear hieght. But then, some speakers call for critical hieght on the tweeter.
Try different hieghts and judge for yourself what you think sound the best.
Hope this helps.
John

IME, it is more important that the speaker(tweeter) be aimed to your ear than at ear level.

I agree with Zman but... make sure you level the speakers and make sure they do not rock side to side or back and forth. You can also try toeing them in some. Ex. 15'' from the back wall outside corner 16'' and inside corner 14''(middle of speaker 15'') then take 1 or 2 laser pointers (stand behind the speakers and aim them (from the outside corners) toward the wall behind where you sit) and have the lines crisscross about 1 foot behind your head. You may need to try several attempts or adjustments, but maybe it'll work for you. Lots of luck.

You can also read John Atkinson's measurements in Stereophile, provided the speaker you're interested in has been reviewed there. He measures and discusses the vertical dispersion of speakers and usually gives you hints on optimum listening height (unless it's not critical).

You could also listen to the speakers while squatting (sorry!) and standing to try to focus in on the height that sounds best.
-Bob