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I avoid loud people. 
The louder someone is, the less they have to say. 
I may be wrong, but it almost seems like the louder you are, the dumber you are.
Was gonna disagree, but those people sound like assholes >

I live behind an amphitheater that has concerts all summer long and those concerts are not even as loud as these parties. >

I had the same problem with the same kinds of awful neigjbors and neither the cops or property managers did a damn thing about it. The cops would show up an hour or two after the complaint and said "turn the music down" and the neighbors would just turn it back up 5 mins after they drove away. 
I don't even get why having music that loud can be any sort of appealing. It hurts. It makes it hard to hear each other. It lowers the sound quality of the songs. So why. WHY.
I guess we are, not necessarily bad guys, but the odd ones out by being bothered by this. Or everyone's been so horribly shaped by oppression they don't care how uncomfortable they are in their own home. >

Musician here. Turning music up loud doesn't degrade song quality. Either the songs are shit quality to begin with, so being loud makes all of that noticeable, or, the speakers and system is being overloaded. It is the speakers clipping that lowers the quality.
TL;DR The volume control will never directly affect the quality of a recording. It's either a bad recording, or an overloaded system.
Could be either these days, probably a combined effort of both things. People don't understand audio, and it really shows. Not a dig at you, personally. But if you wanna play music loud, you should really learn how it works first. The only thing worse than loud music, is shitty quality loud music.
Sincerely, someone who loves good quality, loud music, but also appreciates quiet enjoyment of my house. If I want loud, I go bush for the weekend with 15,000-30,000 watts of amps, subs and speakers, and a hundred odd mates. We get to have our fun, and our neighbours still like, well, tolerate us. >

Hear hear hear!!
Louder for the people at the back ! >

The people in the back, AND those with tinnitus.