What is this filter? I am not sure I understand what it is. A set EQ or something different? I went to the site but that doesn't clarify it for me, regarding what is actually done.
In practice, it is very much like EQ, but more powerful. It is called an audio convolution filter (they are also sometimes called finite impulse response filters or FIR filters), if you want to look it up. This covers the basics nicely: https://wiki.jriver.com/index.php/Convolution
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