With the exception of the sub, some people can do a good job of tweaking the other speakers without an SPL meter, while other people do a crappy job. The benefit of an SPL meter is that you get more consistency and you don't have to wonder.

I don't think it's possible to level-balance a sub without an SPL meter (unless you are just playing music etc... and going for the sound you want) because you are dealing with completely different frequency ranges between sub and everything else.


M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8