Hello Krikor,
Looking at the picture, you can barely see 2 wooden boxes (on each side of the Pi 4s). These boxes housed a 1uf cap and an L-pad. The T90 are coming in at 18k. It is also helpful when you integrate the T90 that the voice coil of the tweeters be at the same plane as the voice coil of the horn driver to avoid phase errors. Godspeed.