I am trying to equalise my SVS and picked up a BFD unit. The problem is there is no way of turning of the main speakers short of removing the cables. When I used the tones downloaded from the site sugested in the snapbug BFD pages it seems a lot of sound in the tones under 80 hz are still coming from the mains, even though the HK is set at 80 hz crossover. Adding filters to the BFD seemed to have no effect on the measured output. I tried having the BFD in both positions green light on and off. Anyone have any ideas ???