Firstly, there isn't a ribbon tweeter that I would use under 1.5 to 2 kHz. Most wouldn't be under 4k. At sixteen per side, let's assume Raal and Mundorf are financially impractical.
What makes you think 1kHz is out of the vocal range?
However, if that's what you want, consider planar magnetic instead of true ribbons and BG Neo8's ($80), perhaps with a 10 or 12K low pass and a single Neo3. Even the big Genesis', only had one tweeter of the array without the low pass. Look at GR Research's former line arrays.
What makes you think 1kHz is out of the vocal range?
However, if that's what you want, consider planar magnetic instead of true ribbons and BG Neo8's ($80), perhaps with a 10 or 12K low pass and a single Neo3. Even the big Genesis', only had one tweeter of the array without the low pass. Look at GR Research's former line arrays.