Apartment Drama

Does your complex have rules about noise? Usually there are rules limiting noise to certain hours. You should be within your rights to play music at moderate volume at 3pm. It's up to you. Does the neighbor own guns?

Headphones usually have capabilities to provide better definition and imaging and the best piecefull solution.
My other solution would be to advice neighbors to appear next time knocking at your door with presence of police officer(s) only. Cops less-likely will open the case or even will care to arrive for minor neighbor troubles thus leaving your neighbor 'grouchy' and somewhat 'upset' and probably seeking some mental help. Had similar neighbor by myself always knocking at my door and complaining about my noisy kids playing in the middle of the day.
While you being PIA to your neighbors you can always place your speakers on cardboard boxes as Elizabeth suggested. I found Egg boxes work best and somewhat as good as dedicated speaker stands.

What was the decibel level you were listening at?

Talk to your neighbor. Find out if there's a real problem with the sound or if it's something else. A few people are totally unreasonable nearly all the time, but most people are kinda' nice if you're nice to them.

BTW, when I rented I would always tell the landlord that I play music often and loudly. I don't think I ever lost out on an apartment because of it, but the landlords were thankful and sometimes made special arrangements for me.

I lived in apts my whole life and hated those neighbors with the thumping coming thru the building. Now that I have a house I can be lord of the manor.
Elizabeth has it right, it's the bass, you'll never be able to use cabinet spkrs in that apt. Maybe some small monitors on strands like totems. But she has a proven solution...why not give some Maggies a try. And a good set of headphones for late night listening.

But you will never be able to crank it up again in this current apt.