i have a cheap adc equalizer/spectrum analyzer - it includes a 10-band equalizer, pink noise generator, and microphone. it has been helpful for tuning/placement of my system, which includes an active crossover & subwoofer system. i think i paid ~$150 for the thing brand-gnu, 15 years ago... there are several of these not-too-expensive devices on the market; i think audio control currently mfr's these. i can't recommend using the equalizers on a hi-rez system, tho, but for adjusting x-over settings, & for subwoofer/speaker placement, they can be wery helpful.
doug