dcaudio OP74 posts03-17-2020 6:33pm"Is there a CD that has good frequency tracks and use a sound meter on my iPhone to measure to get a flat response?"
I gave up trying to adjust the various sub settings by ear and used a test CD (Stereophile STPH 002-2) with 1/3-octave warble test tones and the Decibel X app on my iPhone.