They're not being passive aggressive OP, they're scared of you.
You've had some insight in this thread as to how most people respond to "spontaneous" party people. I'm with the crowd here - I hate noise coming from next door, especially late into the night / early morning. But I find the idea of asking people to turn it down too intimidating to attempt (the only time I did it was during my finals week at university when I really needed to revise / sleep).
From our point of view, people who are inconsiderate enough to have a loud party with no notice in the first place are - in our heads - unlikely to be sympathetic to a complaining neighbour. We believe we will get laughed at and called a party pooper. That's why your neighbours are apparently giving you the cold shoulder. They don't know what to say to you, so you're going to have to do the leg work here.
I do realise, now, that most people who behave like this are not actually arseholes (and you don't seem to be either OP), they are just thoughtless. I remember having some friends round for drinks one evening, after a few in the pub. It wasn't a party, but it was spontaneous and as it got late, I asked everyone to keep it down and turned the music off (we lived in a flat and had up and downstairs neighbours). One of the friends was surprised that I'd even thought of the neighbours and said it was good of me, because she'd never think of it.
I realised then - the people who over the years have given me so many horrible, sleepless nights are not mean, they don't think of me as a dull square. They just don't think.
Grovel OP. Grovel.