Hello Danny and any O3 owners. This is more a theoretical question -- I don't have O3s, but built something "similar" awhile back, with Neo3 tweeters and some Peerless 5" midwoofers I got on sale. The Peerless have a rising HF response on-axis, but flatten out nicely at 90 degrees off axis (firing upward at the ceiling), with a -6dB point at 1780 Hz, before rolling off steeply. Thus I ran them full range (no lowpass filter), and highpassed the Neo 3s in 2nd order electrical, also -6dB at that frequency. I hear (and measure) a smooth, flat transition with an ear/mic axis exactly at the height of the upper cabinet edge, just above the tweeter and at precisely 90 degrees to the midwoofer. But because of the limited vertical dispersion of the Neo3, this axis is VERY critical. Much above it, and the treble drops off. Much below it, and there is a wide "sag" in the response from the midwoofer, due to being greater than 90 degrees off axis.
Even further back in the room, where late-arriving reflections (including from the ceiling) homogenize things a bit, I still hear notable shifts in tonal balance as I sit up straighter or slouch down. Do you notice similar phenomena with the O3s? If so, how do you address them?