If all players control the same cube, then you probably don’t want to do that logic in the cube BP. The cube would have to continuously track when new characters are created in the world, and track each character for changes in their MicLoudness variable. That is not practical.
Instead, since there is a single cube, you can easily fetch it from the character BP, and update it. So the simplest way would be to use Tick from character BP, find the cube using “Get Actor From Class”, and update the cube using MicLoudness.
Once that works you should consider optimizing a bit :
- Move the GetActorFromClass into BeginPlay instead of tick, store the result in a variable
- Use RepNotify (from MicLoudness) instead of Tick, and update the cube from the notify event. If you need overtime update, start a timeline from the notify event.