Mostly personal experiences here.
1. Removing all telephone books from the house.
In the corners of you room of some benefit. Other than that no effect.
2. Removing all plants and flowers from the listening room.
Small plants are okay, but a large rubber tree plant is a comb filter.
3. Removing all empty beer, etc. bottles from the listening room.
Nothing.
4. Removing unused speakers from the listening room.
Without shorting plugs remove them. Even with shorting plugs better get them out.
5. Removing all unused amps and other components and cables from the listening room.
No effect that I have heard unless piled around the speakers.
6. Removing all Sonex from the room.
Soft foam is death.
7. Removing speaker grills.
If you have them, experiment. Some speakers sound better without grills. Others sound no different.
1. Removing all telephone books from the house.
In the corners of you room of some benefit. Other than that no effect.
2. Removing all plants and flowers from the listening room.
Small plants are okay, but a large rubber tree plant is a comb filter.
3. Removing all empty beer, etc. bottles from the listening room.
Nothing.
4. Removing unused speakers from the listening room.
Without shorting plugs remove them. Even with shorting plugs better get them out.
5. Removing all unused amps and other components and cables from the listening room.
No effect that I have heard unless piled around the speakers.
6. Removing all Sonex from the room.
Soft foam is death.
7. Removing speaker grills.
If you have them, experiment. Some speakers sound better without grills. Others sound no different.