This post is not to question your ability as a x-over designer but rather you can explain to me your design philosophy. This design philosophy permeates to other models in your current speaker range.
I guess I'd have to say a lean more towards accuracy and an even in room response. So I look to maintain an even response in the vertical and horizontal off axis ranges.
The on axis freq response seems has a peak around 4.5Khz and rising response from 8Khz upwards. Does it affect the perceived sound quality?
Peak? Rising response? If you draw a line through the middle of it then it varies less than about 2db up or down from end to end. The Neo's do have a smoother response in the 10 to 20 degrees off axis than they do on axis. So off axis response is even smoother than on axis.
This means you can face the speaker more straight out into the room and get a smooth response plus a wider sound stage.
Most rooms with carpet, padded furniture, and any room treatments really suck up the high frequency output levels. Check the room response of these two speakers.
This is an LS-6 and an A/V-1. Neither of them have a rolled off top end. In fact, the top end of the A/V-1 is not too unlike the Neo-2X.
Most speaker designs seem to opt for a "BBC dip" on rising frequency response.
I measure lots of different speakers all the time and I rarely see a BBC dip.
I think that if the recording engineer would have wanted a dipped out area in there then he would have created one. The speakers job is to reproduce the input signal as accurately as possible.
Does these rises give a perceived sound of a "sparkle" at the top?
Nope, no sparkle, no brightness. A little added sense of air? Maybe, but it still does not add as much as the room takes away.
Something else to keep in mind is where the music is.
