One way to find if your system is improving is live-recording. I have >200 live-recordings of my systems over last 10 years in my YT channel. I can watch/hear the history (10 years) of my systems in YT.
Human ears are easily biased and get tired with different sounds. Also, human ears trick us too. But microphones are never tired and recordings always let me hear consistent sounds. I compare a recording of my speaker sound and the original music after the each fine tune of my speakers. And I adjust my speaker’s balance, tone, brightness, sound depth, forwardness, pressure of vocal, image height, musicality, openness, details of woofer and tweeter, naturalness, clarity, cleanness, etc. One can’t remember all these information by aural memory. Live-recording is only way to perform fine-tune of sounds in reproduction audio.
The ability to hear those delicate information can be acquired with experience and training. The capability (adjustability) of speaker and ability to fine-tune the speaker according to those information are a different topic. Alex/WTA