Introduction to designing crossovers without measurement

Hi AllenB,

I am putting up a crossover with RST28F-4 and RS180-8 drivers from Dayton, I have attached the crossover and simulation. I see a huge dip in impedance around 2K region can you suggest what is causing it? Or a better approach for this. These are the values from parts Express and I am yet to order the drivers 20210316_170502.jpg
 
I can't see the values but I'd begin by guessing resonance is playing a part in the tweeter response near 2k.

If you disconnect the woofer you can confirm which driver is causing the issue, if it is the tweeter then please show the raw tweeter response overlayed with the crossed tweeter response, as well as the circuit.
 
Your 2nd order high pass filter resonance is a little high at 1.7 which would account for a lower impedance. It shouldn't be necessary to use resonance that way to boost the knee, because the natural response is 8dB higher there. I'd begin by reducing the value of the capacitor and finding an alternate way of shaping the response.
 
Firstly, you can make your plot window look something like the attached image, this way you can see the phase for the two ways.

Next, enter the tweeter driver properties and set the offset. Now you have it as being 3.18 inches forward. Is that correct?

Then, watch for the need to change polarity as you change the responses.
 

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Your impedance dip is now at 5 ohms, very good.

Yes, I changed the polarity on both, they are the same, you can change them back. As long as they are the same it will work. The reason I did that was to make the graph more readable.