No mention of a shock mount. That’s the white spider thing holding on to the sides of the Mic.
Those white strings are elastic bands. their job is to keep floor, desk and stand vibration from showing up in the microphone and the sound.
it pics up the AC at around -50db
For sure? You turned it off and the sound vanished?
Then you lose on Sports Call® because the audiobook spec is at least -60dB. Sound goes double every 6. So your AC is double louder than it should be…twice.
You got lucky. Many people have no idea what’s causing troubles. You can point to yours.
So now you can try exotic solutions. Before I found my hummy bass cabinet, I discovered that if I put the microphone in exactly one place next to the credenza, it wouldn’t pick up the hum. I recorded that way for a good long while until I got up enough time and gumption to go looking for the source of the noise. I would have put handsome money on it coming from the high tension wires going over the house.
Nope.
Koz