they exist to support the engineered design. your amp input should (mostly never is ) be flat. The output is equalized to account for"roll off" towards the end of the line or the next active. Your higher freqs. drop off much quicker over distance than your lower so you balance the output with a (normally) 6 to 10 db tilt, depending on design, so you end up flat at the next amp or end of line! you're using that eq. to obtain that tilt and ,yes, it effects mostly the low end in the perfect world but can slightly lower the top as well! I'm sure our more elite "Sweepers" will chime in with more info than you can handle! Later, Mike M.
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