Multiple angled mid-tweeters?

[wesayso]

I'm hesitant to recommend doing this below about 7kHZ though, if you want the cleanest stereo imaging effects. The frequency range of about 800HZ to 6kHZ is where most stereo imaging effects happen without problems. Below about 1kHZ imaging gets blurred by the inter-aural crosstalk.

As far as I've been able to tell, I do see it a bit different.
Cross talk in a stereo setup, with the speakers about 3 meters apart, listening distance to those speakers also at 3 meter, will show cross talk effects hitting our ears for phantom sounds that create a dip at about 1850 Hz and again around 5500 Hz. It will affect the area below it too, in balance. Especially in a reflection free environment.
How big of an effect this will be depends on both the speaker and the room.

From a reputable source, see the bottom graph for an in room phantom signal as measured at the ear:

Scroll all the way up to see the title of the book . Interesting reading non the less.