Yeah, too bad all frequencies weren't easily contained using the same methods. Also keep in mind that knocking on a speaker cabinet box isn't exactly real world either, it would take systematic frequencies played through the installed speaker and measured upstairs to get the actual best effect, thus the reason that I trust the experts and people from multiple trusted companies that say that fluffy insulation is good, packed insulation is bad (for in wall/ceiling absorption) and you want to disconnect as much as possible from inside the room to outside.

That is where the gap comes in. My guess is that you are compressing the insulation just the right amount to impact certain frequencies only instead of having it fluffy and being able to grab a wider frequency range.

Farewell - June 4, 2020