The first thing might be to find out who is the real complainant. If the sound is getting to them via the building structure, rather than through/around the door, you have few practical solutions. If it is via the door, sealing it helps but a double structure like an additional door, a drape or, at best, building a vestibule around it will be even more effective.
My experience was that sealing the door was an entirely adequate solution except for those times that I intentionally blasted the system. But that was only briefly and at a reasonable hour. OTOH, my listening room abuts no other apartments, except above and below, and my building is solid, reinforced concrete. That really helps (except when you want to do any inwall wiring!).
My experience was that sealing the door was an entirely adequate solution except for those times that I intentionally blasted the system. But that was only briefly and at a reasonable hour. OTOH, my listening room abuts no other apartments, except above and below, and my building is solid, reinforced concrete. That really helps (except when you want to do any inwall wiring!).