If the light remains red, it probably means that the sub isn't receiving a strong enough signal to turn it on. You might try entering your receiver's "speaker" menu, and turning up your receiver's output to the sub. Then, to keep the sub at the same volume you now have it, turn the volume knob on the back of the sub down a little. See if that makes a difference.
Balancing your speaker volumes by ear usually doesn't yield good results. If you have not already done so you should invest in a setup disk like
Avia, or
Digital Video Essentials, and the ever trusty
Radio Shack Sound Pressure Level Meter to calibrate your system. It would be money well spent, and can make all the difference in the world.
This will give you an idea of what I'm talking about. Don't let the technical aspect of this procedure scare you. It's not THAT complicated, and you're fully capable of doing this.
