Crossovers for speakers with horns

[weltersys]

Maybe my description was bad, but I have 2 woofers. One over the horn and one under.

That was in the original post.
The time of flight distance between the woofers and tweeters still varies with distance as described.

Therefore I placed mic between the woofers at horn level. I do see some rather large differences in response when I move the mic up and down. I assume it's better to measure at a larger distance (outdoors), to minimize the difference in distance to the individual drivers?

Yes, a larger distance will reduce the path length difference.
What is the vertical scale of your measurement?
What is the center to center distance between the woofers?
What was the measurement distance?

 

[TroelsM]

5dB pr line. Cc on woofers are approx 35cm. Mic is approx 1m away