The answer is the filters in the 6X provide maximum effectiveness when placed as close as possible to the power line they are filtering.
The BC86 Mark 5, 6X, 12X, and 18X filters are designed to ‘dam’ noise in the AC power in your home circuit. Noise can come from outside the home from many miles away or from appliances in your home. Even the AC lines in the walls of your home radiate noise that can interfere with your audio equipment.
Plugging the filter into the outlet just prior to where you plug in your equipment will block or ‘dam’ the unwanted noise from traveling to your gear letting all your components enjoy clean power. Our customers are now plugging in filters in outlets in the same vicinity as the listening room to clean the radiating energy from the AC lines in the walls. The BC86 Mark 5 is a great filter for this purpose.
Blue Circle and Mystic Audio teamed up to make this simple but very informative video to demonstrate the optimum application of a filter.