Piezo horn crossover

Counting from the tweeter, I added a 8 ohm serial resisor, this does not affect the resistance in the working range 2-20 kHz but protects the amplfier against low impedance way higher up in frequency. I then added a 8 ohm resostor across the driver to get a 8 ohm resistance. With this setup I could try different capacitors to see if I could equilize the the lift arount 4 kHz and get a flatter frequency response. I tried the horn with no crossover at all, then adding a 3.3 µF cap, a 2.2µF and finaly a 1.65µF.
This is how the responses turned out

If

If I normalize it to the  level at 10 kHz it looks like this

Both graphs show that the smallest cap is overdoing the eqalization, It appears that 2-3µF will give the flattest response. Compared to no filter I get about 4 dB reduction of level below 4 kHz. I get a -6dB point somewere between 3 and 3.5 kHz so this might work out with my Peerless drivers. With a bit of luck I can run them flat out otherwise I will fiddle with a 6 dB filter and Zobel to tweak the low pass filter. I will only use second hand electrolytic caps, fancy plastic film are wasted on this setup especially the tweeter.