MusicTechHelpGuy walks through Channel EQ moves for bass and doubled rhythm guitars in Logic Pro, keeping the low end intact while carving out space and width elsewhere.
For bass, he leaves the fundamental untouched since that's where the low end needs to live. Instead he boosts mids and mid-highs to bring out pick attack and transient detail.
On a simple crunch rhythm guitar, he thickens the bottom and midrange, then filters off the extreme low and high end to avoid boominess or rasp.
After copying that EQ to the second guitar track and panning it opposite, he shifts the midrange boost to a slightly different frequency on each side. That small offset keeps a doubled part from sounding phased or identical, giving the left and right channels natural variation and width.