I like to use my ears to calibrate and my own eyes. I have used calibration tools, but sometimes I only use them as a starting tool and then tweek from there. I voted good understanding. My dad and I have completely different listening tastes. I like very forward sounding speakers and he likes laid back. I am definitely not an expert and do not design my own crossovers, speakers and such, nor would I want to when others have done it already.
Dan