I like the sound of sine waves from 20 Hz and up. Billie Eilish is very good for this :-)
Bed aware not to set the level on your subs too high or you will only hear the "sound". And use dsp.
Bass- at what frequency does it change from sounding like a string to just a low tone?
I have two subs and speakers I like. I have little experience comparing them to anything else. As the frequency of a given note goes lower, at some point in my system it stops sounding like an instrument making the sound and instead it just sounds like the sound. I’m not crazy about this, but maybe that’s how it is for everyone?