Placement of Single Subwoofer Affecting Sound of Main Speakers

Due to a recent furniture arrangement in the room, the subwoofer that was sitting dormant for several years had been reluctantly reinstated in the main system. I have been experimenting with the placement of the sub in the room. Due to limited placement options, the sub can only be placed in these 3 spots ;

1. In one corner of the room, very close to the side and rear wall (1 or 2 inches from the walls)

2. Just behind the left speaker, 5 inches from the rear wall

3. In between the speakers but very close to the left speaker, not at the centre of speakers.

To cut to the chase, I’ve briefly tried all options. The 1st option with the sub placed in the corner of the room gave the worst result. Now, the interesting part. Even though the sub was turned off, the sound quality of the system degraded. It appears that the physical presence of the box in the corner of the room made the sound worse.

I am currently settled with the 2nd option and this configuration sounds much better than the 1st option irrespective of the sub powered up or down.

The sub is currently on spikes as I’m still waiting for some Nobsound springs to arrive before I can plonk the sub on these.

I’ll be trying the 3rd option again although the WAF is the worst on this one.

Has anyone here experienced a worse sound quality from the system with the placement of the sub in the room? A sub that’s switched off and not working.