This is an experimental plugin, which implements biquad filter shown in Audio EQ Cookbook.
This plugin is implemented in Rust. You need Rust to build the plugin.
% git clone https://github.com/yoshinorisano/obs-biquad-filter-plugin.git
% cd obs-biquad-filter-plugin
% cargo build
After build successfully, copy biquadfilter.dll
to the OBS's plugin directory.