Thanks to all those responding. I have been a bit too focused on this, but do not want to be. It's just when another is invading your space, it can be overwhelming.
I know it is likely best for tenants to discuss things face-to-face, and though I thought I would prior, his odd schedule inhibited me from doing so and also, do not want to go upstairs. Then I began thinking that I did not want to speak to him, feeling that if he does not
know better in his 50's, it tells me something.
I had contacted the Management Co.
supervisor, which was a big mistake, but did so impulsively, being reminded of how she is. I had spoken to her
assistant the day prior, who had kindly listened to me and appeared understanding. She said if "not hearing from them, to call again the next day". When I did, was told to call back in 30 min., but got a call from the supervisor a few minutes later, who was not only in a huff, but misconstruing things and just became intimidating. She did tell me to call the
manager again when hearing the bass noise, though telling her it is
usually late when this occurs. This woman is just hostile and overbearing (of course, the newer tenant is paying more $$ in rent, so the established, more respectful tenant is not considered or supported).
I have lived here for a
long while, but since having had some different noise issues from a few others in recent years, it is now being seen by the manager that I am just being "oversensitive" (without
her experiencing what I have in each instance). Her attitude has been nonchalant now, negating the situation. It's so frustrating, I know another would be disturbed by it, too. I moved here
so long ago, that since then, being some 50 page agreement for incoming tenants to sign. My feeling is, if a tenant would just
not do what they signed an agreement to
not do in the first place, this behavior wouldn't occur. If a person is actually considerate and respectful as many are, this would not come up.
I recently prepared a well-thought out letter explaining and asking for cooperation, to place on the neighbor's door, when he was gone. (I have read that this can appear as "passive aggressive", but I did not know what else to do, not having assistance). I don't know if it has had much impact. When I heard the bass noise again, I turned on my own stereo, finding it can drown out the
thumping noise, not even at a loud level, but soon hearing some conflicting, LOUDER volume from his system.

I have not run into him and don't want to.
This is not how I want to waste my energy. I'm tired. I'm older. I want to enjoy my space. It's not like when I could just go find an apartment anywhere, now having specific housing considerations, I am stuck until having an opportunity. It was suggested that I could take another unit when available, yet I am not climbing stairs with bad knees and if downstairs again, the
same thing could occur. (When speaking to that younger assistant in the office, she mentioned that another mgmt. company she had worked for "did things differently", which tells me they do not all operate in the same way). Anyway, that's it for now.