I’ve noticed that it’s ok to listen to subs at a lower volume (around 30% on my mp3 player) at night when your mind is drifting away into the sleep and if the volume is too high it can disturb your sleep or even deprive you of it. On the other hand, when listening during the day the volume must be higher since you’re distracted doing something or thinking about something else than listening to the sub, you’re not focused on it. I gauged it since I’m very sensitive to subs and I feel when it’s working for me, I feel its energy in my chest. I’m especially sensitive to Elixir and it served me to gauge the thing I mentioned in here.