positioning of a horn speaker

I agree with Neville. Move them closer together. This same issue plagued me until I moved my horns a little closer together than the distance to my listening position. For instance, I sit about 11' from the mouth of both horns and they are now about 8' apart from each other. I believe this is due to the more direct radiation of horns.

The toe-in may work for you. It didn't for me. Probably some room interaction here. I find mine sound best when aimed just outside of my position, over each shoulder but not crossed. I'm not one to make a big deal of imaging so I happened upon this setup through experiments to remove other artifacts I was hearing at the time.

try the long wall and further apart and play with toe-in until you have it. Every half of inch will be different....

I design horn speakers with the expectation that they will be toed in severely, as Morningstaraudio describes, so that may work with the Tylers. If not, then I suggest moving them closer to one another.

Duke

I thought the attractiveness of horns disappeared with stereo, because corner placement extends the horn and few stereo setups lend themselves to dual corner placement.

db

The shape of the horn figures heavily in this matter. Mine are only 40 degrees dispersion pattern. This is pretty narrow but necessary in this design so that the horn unloads at the proper rate. Mine, therefore behave better with toe-in and I am better off being back some twelve feet or more. If your horn has a much wider dispersion, you might wish to spread them further.
If, as I suspect, you are dealing with an off-the-shelf horn, there may not be any right way to perfect it and you'll have to just experiment until you get something you can live with.

Vertical dispersion is very narrow in tractrix designs and limitation in that area may be contributing to your problem.