How tall should speakers be?

If you speakers sound better when your on floor then place something under front to pitch the tweeter up tp your ear at listening seat. As Kal said in general tho not always true the tweeter is most important to have around ear level.

Some speakers have a critcal vertical listening window. I owned a set of Spica TC-60s ten or so years ago and tweeter response was radically different if you were standing or sitting. The difference was even audible at about +/- 5 degrees. So, yeah, where your ears are verically in relation to the tweeteer is very important with some speakers.

Tweeter dispersion has alot to do with image size and location. As well as image "sweet" spot.

I'm trying to understand something here for myself.

I've spoken with a few others about this thing too and we all seem to agree for the most part, that the imaging of the sound stage improves and/or does change greatly from being in a standing position to a seated position. usually the standing position is better and this circumstance certianly has the Tweeters below ear level as the result.

Why is this, if others seem to desire the tweet be at ear level instead?

There was a thread here on decoupling speakers from the floor by setting them on plinths with an inert material between the speakers and plinths. I tried this and am amazed at the improvement in image and soundstage. My speakers are only 36 inches tall so I'm thinking some of the improvement comes from the extra two inches in height.
As the hawks are a fairly short speaker, this may work for you also. Before building the plinths and setting spikes in them I tried setting the speakers on thick phone books. Try this experiment and see if the results are positive. I'll bet they are.