I just received Eris 4.5 and T10. The Sub is connected to the computer by RCA. Sub to Monitors are connected by TRS. The sound system is working fine. However, I find the sub too loud despite the sub volume/gain has ben decreased to the minimum. HPF is on, Crossover is at 80Hz, Sub is in-phase, It's in Ground mode.
What can I do to reduce the loudness of the sub while keeping the monitor volume the same? Reduce master volume from the computer? Do I need an interface?