There was one time years ago that I had my PA system here for awhile. One day the downstairs neighbors were just blaring the bass BAD & I decided I'd show them. 1200 Watts of power cranking Death - Symbolic through two 2x15" w/ 2" radial horn cabinets -- SOOOO loud!!!
... in my puny little condo it was just ridiculous how loud it was! I think I dared two songs & then unplugged it & packed it all up in case someone called the cops. They didn't blare the bass for awhile.
The funny part is, I'm on pretty good terms with the downstairs neighbors... I never said anything about that incident & neither did they + I never say anything about the bass. They have three children from toddler to about 12 and anytime I see them they're nice/polite & so am I.
I really feel like I'm not doing anything wrong practicing with headphones. Like I said, I don't do any singing in my room so the "next door" neighbors should have no reason to be upset. I'm not changing what I'm doing unless they come & talk to me -- I'm not going over to talk to them because it may be absolutely nothing & that could be embarrassing! I might come off as some crazy person then & I don't want to create a problem that didn't exist in the first place.
That's about it.