phone apps are easy to get a sense of volume within the room, i.e. compare this to that
however, to refine anything, speaker location, toe-in, .... it is better to put a simple sound pressure meter on a tripod, set at seated ear level at listening position
then you can move about, move speakers, change level controls, use test tones to see if any tone adjustment(s) are indicated. Hear and see if room treatments work.
My speakers have two level controls each, and it takes a lot of work to adjust both frequency curve but also matching L to R.
My McIntosh MODE switch is also a big help refining L to R
These test tones (tracks 9-38) are individual 1/3 octave tracks: select, pause, adjust, play, pause, next ....
https://www.discogs.com/release/7290000-Various-Amazing-Bytes
I imagine I could locate a copy readily enough.
Most other test cds have far fewer test tones.
I don't use Test LP's, if any alignment is off a bit, it effects results.