Setting up the phase inverter

Guys, hello everyone! Can you tell me how to properly configure the phase inverter, with or without a filter??? Why am I asking, because the resonant frequency of a low-frequency speaker in a closed box without a filter is 43 hertz, and with a filter of 38 hertz. What frequency should I start from in order to adjust the phase inverter? Sorry for my English.
 
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No, I don't need programs!!! I've measured everything a long time ago. I am interested in HOW the port is configured. The filter must be connected, or the port is configured without a filter. Or does the filter not hurt?