all pass networks
Time domain equalization is done by using "all pass networks." These are a quad of two left half plane poles and two right hand plane zeros. (You can also use a real LHP pole and RHP zero pair for frequencies near DC.) These produce a time delay near the pole frequency without any amplitude changes. You adjust the real and imaginary parts of the pole-zeros to push up the minimum delay portions of your network. Thre is no easy way to select the optimum parameters. CAD programs do a trial and error method.